Showing papers in "Journal of the American Society for Horticultural Science in 1994"

Novel Gaseous Ethylene Binding Inhibitor Prevents Ethylene Effects in Potted Flowering Plants

Abstract: A 6-hour fumigation of flowering Begonia ×elatior hybrida Fotsch. 'Najada' and ' Rosa', B. ×tuberhybrida Voss. 'Non-Stop', Kalanchoe blossfeldiana Poelln. 'Tropicana', and Rosa hybrida L. 'Victory Parade' plants with 1-MCP, (formerly designated as SIS-X), a gaseous nonreversible ethylene binding inhibitor, strongly inhibited exogenous ethylene effects such as bud and flower drop, leaf abscission, and accelerated flower senescence. The inhibitory effects of 1-MCP increased linearly with concentration, and at 20 nl·liter -1 this compound gave equal protection to that afforded by spraying the plants with a 0.5 STS mM solution. Chemical names used: 1-methylcyclopropene (1-MCP), silver thiosulfate (STS). here the results of tests of the efficacy of 1-MCP in preventing ethylene effects on the display quality and shelf life of potted flowering plants.

Salinity Tolerance Mechanisms of Six C4 Turfgrasses

Abstract: Physiological responses to salinity and relative salt tolerance of six C 4 turfgrasses were investigated. Grasses were grown in solution culture containing 1, 100, 200, 300, and 400 m M NaCl. Salinity tolerance was assessed according to reduction in relative shoot growth and turf quality with increased salinity. Manilagrass cv. Matrella (FC13521) ( Zoysia matrella (L.) Merr.), seashore paspalum (Hawaii selection) ( Paspalum vaginatum Swartz), and St. Augustinegrass (Hawaii selection) (Stenotaphrum secundatum Walt.) were tolerant, shoot growth being reduced 50% at ≈400 mM salinity. Bermudagrass cv. Tifway (Cynodon dactylon × C. transvaalensis Burtt-Davey) was intermediate in tolerance, shoot growth being reduced 50% at ≈270 mM salinity. Japanese lawngrass cv. Korean common (Zoysia japonica Steud) was salt- sensitive, while centipedegrass (common) (Eremochloa ophiuroides (Munro) Hack.) was very salt-sensitive, with total shoot mortality occurring at ≈230 and 170 mM salinity, respectively. Salinity tolerance was associated with exclusion of Na + and Cl - from shoots, a process aided by leaf salt glands in manilagrass and bermudagrass. Shoot Na + and Cl - levels were high at low (100 to 200 mM) salinity in centipedegrass and Japanese lawngrass resulting in leaf burn and shoot die- back. Levels of glycinebetaine and proline, proposed cytoplasmic compatible solutes, increased with increased salinity in the shoots of all grasses except centipedegrass, with tissue water levels reaching 107 and 96 m M at 400 mM salinity in bermudagrass and manilagrass, respectively. Glycinebetaine and proline may make a significant contribution to cytoplasmic osmotic adjustment under salinity in all grasses except centipedegrass.

Effect of ozone and storage temperature on postharvest diseases and physiology of carrots (Daucus carota L)

Abstract: Effects of ozone and storage temperature on carrots and two postharvest pathogens— Botrytis cinerea Pers. and Sclerotinia sclerotiorum de Bary—were investigated. Pathogen-inoculated and uninoculated whole carrots were exposed to an ozone concentration of 0 (control), 7.5, 15, 30, or 60 μl·liter -1 . Treatment chambers were flushed with a total flow rate of 0.5 liters·min -1 (air and ozone) for 8 h daily for 28 days. The experiment was repeated twice at storage temperatures of 2, 8, and 16C. The residual ozone concentration (ozone supplied-exhausted and reacted ozone) increased with ozone supply concentration but was less at higher storage temperatures. A 50% reduction of daily growth rates of both fungi at the highest ozone concentration indicated that ozone was fungistatic. Carrot respiration rate, electrolyte leakage, and total color differences increased with ozone concentration. Ozone-treated carrots were lighter (higher L* values) and less intense (lower chroma values) in color than control carrots. Postharvest physiologist. Watery soft rot (Sclerotinia sclerotiorum) and gray mold (Bot- rytis cinerea) are common postharvest diseases of carrots. Until recently, growers used the fungicide benomyl to control these storage rots. The manufacturer's withdrawal of benomyl as a postharvest fungicidal dip on carrots has necessitated a search for alternatives; ozone is one potential candidate. Ozone is the tri-atomic form of oxygen that is unstable and decomposes either spontaneously or after it comes in contact with oxidizable surfaces. Ozone's high oxidation potential (Lide, 1991) makes it an effective disinfectant for poultry hatcheries, poultry chill water, water treatment plants, soft-drink bottling plants, and aquaria water (Guinvarch, 1959; Rosenthal and Wilson, 1987; Sheldon and Brown, 1986; Torricelli, 1959; Whistler and Sheldon, 1989; Yang and Chen, 1979). Since ozone can be easily and economically generated on site, transportation and storage costs are not incurred. Unlike CO 2 and N, which are two gases com- monly used in storage, ozone has a characteristic odor. For this reason, harmful levels of ozone can be instantly detected and avoided by workers. Ozone can be applied as a gas or as ozonated water. Reported differences on the effectiveness of ozone as a storage disinfectant may be due to differing application methods or measurements of ozone concentration, treatment period, and pathogen and product sensitivity to ozone. Gibson et al. (1960) and Rice et al. (1983) concluded that ozone is an effective agent for controlling microbial and fungal pathogens in stored produce such as cheese, strawber- ries, raspberries, currants, bananas, and potatoes. Continuous exposure to 0.05 ppm ozone (gas) effectively killed Escherichia

Ethanolic Fermentation of `Bartlett' Pears as Influenced by Ripening Stage and Atmospheric Composition

Abstract: Changes in fermentation volatiles and enzymes were studied in preclimacteric and postclimacteric 'Bartlett' pears (Pyrus communis L.) kept in air, 0.25% O 2 , 20% O 2 + 80% CO 2 , or 0.25% O 2 + 80% CO 2 at 20C for 1, 2, or 3 days. All three atmospheres resulted in accumulation of acetaldehyde, ethanol, and ethyl acetate. The postclimacteric pears had higher activity of pyruvate decarboxylase (PDC) and higher concentrations of fermentation volatiles than those of the preclimacteric fruit. For the preclimacteric pears, the 0.25% O 2 treatment dramatically increased alcohol dehydrogenase (ADH) activity, which was largely due to the enhancement of one ADH isozyme. Exposure to 20% O 2 + 80% CO 2 slightly increased ADH activity, but the combination of 0.25% O 2 + 80% CO 2 resulted in lower ADH activity than 0.25% O 2 alone. For the postclimacteric pears, the three atmospheres resulted in higher PDC and ADH activities than those of air control fruit. Ethanolic fermentation in 'Bartlett' pears could be induced by low O 2 and/or high CO 2 via 1) increased amounts of PDC and ADH; 2) PDC and ADH activation caused by decreased cytoplasmic pH; or 3) PDC and ADH activation or more rapid fermentation due to increased concentrations of their substrates (pyruvate, acetaldehyde, or NADH).

Modified-atmosphere Packaging of Blueberry Fruit: Modeling Respiration and Package Oxygen Partial Pressures as a Function of Temperature.

Abstract: A mathematical model was developed to characterize the interaction of fruit O 2 uptake, steady-state O2 partial pressures in modified-atmosphere (MA) packages ((O2)pkg), and film permeability to O 2 (PO2) from previously published data for highbush blueberry (Vaccinium corymbosum L. 'Bluecrop') fruit held between 0 and 25C. O2 uptake in nonlimiting O2 (RO2 max,T ) and the (O2)pkg at which O2 uptake was half-maximal (K½ T ) were both exponentially related to temperature. The activation energy of 0 2 uptake was less at lower (O2)pkg and temperature. The predicted activation energy for permeation of O2 through the film kJ·mol -1 ) required to maintain close-to-optimum (O2)pkg across the range of temperatures between 0 and 25C was ≈ 60 kJ·mol -1 . Packages in which diffusion was mediated through polypropylene or polyethylene would have values of ≈ 50 and 40 kJ·mol -l , respectively, and would have correspondingly greater tendencies for (O 2) pkg to decrease to excessively low levels with an increase in temperature. Packages that depend on pores for permeation would have an of <5 kJ·mol -l . Our procedure predicted that, if allowed to attain steady-state conditions, packages with pores and optimized to 2 kPa O2 at 0C would become anaerobic with as little as a 5C increase in temperature. The results are discussed in relation to the risk of temperature abuse during handling and marketing of MA packaged fruit and strategies to avoid induction of anaerobiosis. Shelf-life of blueberries (Vaccinium spp.) can be extended by controlled-atmosphere (CA) storage (Smittle and Miller, 1988) and modified-atmosphere (MA) packaging (Dostal-Lange et al., unpublished data). Current conditions used in CA storage for highbush blueberry range from 1.5 to 2.5 kpa O2 and 5 to 12 kPa CO2 at 0C (1 % O2 = 1.013 kpa O2 at sea level). MA packaging has the potential to provide low O 2/high CO2 regimes similar to CA storage. The traditional approach for designing an MA package is to generate a physiologically effective package O 2 partial pressure ((O2)pkg, kpa, see Table 1) by matching total respiratory O 2 uptake of the packaged product to the total O 2 permeation through the film (Kader et al., 1989). Ideally, an MA package should maintain safe and effective partial pressures of O 2 and CO2 over a range of temperatures because there is a distinct risk of temperature abuse during shipping, handling, and marketing. Fruits held in MA may go anaerobic if temperatures increase (Kader et al., 1989), but little has been published on the extent of this problem or possible solutions. Empirical approaches have not identified MA package designs that can cope with large increases in temperature. Mathematical models have been used widely for predicting steady-state partial pressures of (O 2)pkg and (CO2)pkg in MA systems

A role for ethylene in the yellowing of broccoli after harvest

Abstract: Ethylene production from florets of 'Shogun' harvested broccoli ( Brassica oleracea L.var. italica) held at 20C in darkness increased as the sepal tissues yellowed. The pattern of respiration rate and ethylene production from branchlets or entire heads was similar, although the magnitude of ethylene and carbon dioxide production appeared to be diluted by the other fleshy stem tissues. The reproductive structures, stamens and pistil, may have a role in determining the rate of sepal degreening, since removing them from florets reduced the yellowing rate. The pistil and stamens also had 7-fold higher levels of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase activity and more than double the ethylene production of other tissues within the floret. Stamen ACC oxidase activity was high on the first day after harvest, before yellowing became obvious. Changes in ACC oxidase activity of the pistil and stamens mirrored changes in ACC content in these tissues. The climacteric status of harvested broccoli was confirmed by exposure to 0.5% propylene. Propylene stimulated respiration and ethylene production and accelerated yellowing (measured as chlorophyll and hue-angle decline). Broccoli tissues did not respond to propylene immediately after harvest. In tissues aged in air before treatment, the time for response to propylene was shorter, a result suggesting a change in tissue sensitivity. Ethylene exposure induced a dose-dependent decline in hue angle, with 1 ppm ethylene giving the maximum response.

Mode of Oxygen and Carbon Dioxide Action on Strawberry Ester Biosynthesis

Abstract: Chandler' strawberries ( Fragaria ananassa Duck.) were kept in air, 0.25% O 2 , 21% O 2 + 50% CO 2 , or 0.25 O 2 + 50% CO 2 (balance N 2 ) at 5C for 1 to 7 days to study the effects of controlled atmospheres (CAs) on volatiles and fermentation enzymes. Concentrations of acetaldehyde, ethanol, ethyl acetate, and ethyl butyrate were greatly increased, while concentrations of isopropyl acetate, propyl acetate, and butyl acetate were reduced by the three CA treatments compared to those of air-control fruit. The CA treatments enhanced activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) but slightly decreased activity of alcohol acetyltransferase (AAT). The results indicate that the enhanced PDC and ADH activities by CA treatments cause ethanol accumulation, which in turn drives the biosynthesis of ethyl esters. The increased ethanol concentration also competes with other alcohols for carboxyl groups for esterification reactions. The reduced AAT activity and limited availability of carboxyl groups due to ethanol competition decrease production of other acetate esters. butyrate was increased by exposing strawberries to 20% CO 2 for 2 days at 1C. Applying ethanol postharvest caused accumulation of ethyl esters and decreased concentrations of butyl esters and hexyl esters in apples (Berger and Drawert, 1984). Exposing feijoa fruit to acetaldehyde vapor enhanced taste and volatile concentrations; however, the same treatment caused off-flavor and too-high con- centrations of ethanol, ethyl acetate, and ethyl butyrate in straw- berries (Pesis et al., 1989). In this research, we studied the regulation of ester biosynthesis in strawberries kept in 0.25% O 2 and/or 50% CO 2 , with emphasis on the mode of CA action on acetate ester production.

Orchard Groundcover Management Impacts on Apple Tree Growth and Yield, and Nutrient Availability and Uptake

Abstract: This study compared various conventional and alternative orchard groundcover management systems (GMSs)— including a crownvetch "living mulch" (CNVCH), close-mowed (MWSOD) and chemically growth-regulated (GRSOD) sodgrasses, pre-emergence (NDPQT) and two widths of postemergence (GLY1.5 and GLY2.5) herbicides, hay-straw mulch (STMCH), and monthly rototillage (tilled)—during 6 years in a newly established apple ( Malus domestica Borkh.) planting. Trunk cross-sectional area and fruit yield were higher in STMCH, GLY, and NDPQT, intermediate in tilled, and lower in GRSOD, MWSOD, and CNVCH treatments after 5 years. Despite N and K fertilizer applications, extractable soil N and leaf N concentrations were reduced under MWSOD and GRSOD, and soil K, P, and B concentrations were greater under STMCH. Leaf K concentrations were usually highest in STMCH trees, even when heavily cropped; leaf K declined below the sufficiency range in GLY, NDPQT, and tilled trees as they began to bear fruit. Leaf Ca was marginally deficient in all trees and was unaffected by GMS. Foliar Mn, Zn, and B concentrations declined rapidly in all treatments during 2 years without micronutrient fertilizers. Leaf Cu was higher in herbicide and tilled treatments where seasonal soil water content was intermediate (22% to 27%) and lower where soil was very wet or dry for most of the 1988 growing season. Multiple regression analysis indicated that leaf N and B and soil organic matter in 1990, and mean soil water content during the unusually dry Summer 1988, were the best predictors of fruit yield in 1990. Phytophthora root rot and meadow vole depredation were serious problems in STMCH and CNVCH trees. GMSs greatly affected tree establishment, nutrition, and yield; each system involves tradeoffs among important short- and long-term impacts on the orchard agroecosystem. Increasing attention is being paid to orchard floor management in order to minimize weed competition and bring today's highly capitalized plantings into full production more quickly. In the humid regions of North America and Europe, herbicided tree rows with mowed-grass drive lanes have become the most common orchard groundcover management system (GMS). Past studies have demonstrated that tree growth, productivity, and nutrient uptake during orchard establishment are maximized at least cost by herbicide GMSs (Haynes, 1980; Hogue and Neilsen, 1987). Currently, serious questions are being asked about the long-term sustainability of herbicide usage (National Research Council, 1989) and the possibility that alternative systems using different groundcover species or management strategies might provide some of the soil conservation benefits of vegetative ground cover- age without excessive weed-crop competition (Skroch and Shribbs, 1986). Several studies of orchard floor management have also indicated the need for more information about specific effects of GMSs on critical factors such as micronutrient availability and uptake by fruit trees (Atkinson and White, 1981; Haynes, 1980; Hogue and Neilsen, 1987). In 1985, we initiated a long-term field experiment to evaluate the relative impacts of alternative orchard GMSs on apple tree growth, nutrient uptake and yield, soil physical conditions and fertility, and the apple pest complex. The effects of

The Relative Tolerance of Six Prunus Rootstocks to Boron and Salinity

Abstract: The influence of B and salinity (3 Na 2 SO 4 : 1 CaCl 2 , (molar ratio)) on B toxicity and the accumulation of B, sodium, and SO 4 in six Prunus rootstocks was evaluated. High salinity reduced B uptake, stem B concentrations, and the severity of toxicity symptoms in five of the six rootstocks. Forward and backward stepwise regression analyses suggested that stem death (the major symptom observed) was related solely to the accumulation of B in the stem tissue in all rootstocks. The accumulation of B and the expression of toxicity symptoms increased with time and affected rootstock survival. No symptoms of B toxicity were observed in leaf tissue. The Prunus rootstocks studied differed greatly in stem B accumulation and sensitivity to B. The plum rootstock 'Myrobalan' and the peach-almond hybrid 'Bright's Hybrid' were the most tolerant of high B and salinity, whereas the peach rootstock 'Nemared' was very sensitive to high B and salinity. In all rootstocks, adding B to the growth medium greatly depressed stem SO 4 concentrations. In every rootstock except 'Nemared' peach, adding salt significantly depressed tissue B concentrations. A strong negative correlation between tissue SO 4 and B was observed. Grafting experiments, in which almond was grafted onto 'Nemared' peach or 'Bright's Hybrid', demonstrated the ability of rootstocks to influence B accumulation and scion survival.

Modified-atmosphere Packaging of 'Heritage' Red Raspberry Fruit: Respiratory Response to Reduced Oxygen, Enhanced Carbon Dioxide, and Temperature

Abstract: Heritage' raspberries ( Rubus idaeus L. ) were sealed in low-density polyethylene packages and stored at 0, 10, and 20C during Fall 1990 and 1991 to study respiratory responses under modified atmospheres. A range of steady-state O 2 and CO 2 partial pressures were achieved by varying fruit weight in packages of a specific surface area and film thickness. Film permeability to O 2 and CO 2 was measured and combined with surface area and film thickness to estimate total package permeability. Rates of O 2 uptake and CO 2 production and respiratory quotient (RQ) were calculated using steady-state O 2 and CO 2 partial pressures, total package permeability, and fruit weight. The O 2 uptake rate decreased with decreasing O 2 partial pressure over the range of partial pressure studied. The Michaelis-Menten equation was used to model O 2 uptake as a function of O 2 partial pressure and temperature. The apparent K m (K 1/2 ) remained constant (5.6 kPa O 2 ) with temperature, while Q 10 was estimated to be 1.9. RQ was modeled as a function of O 2 partial pressure and temperature. Headspace ethanol increased at RQs >1.3 to 1.5. Based on RQ, ethanol production, and flavor, we recommend that raspberries be stored at O 2 levels above 4 kPa at 0C, 6 kPa at 10C, and 8 kPa at 20C. Steady-state CO 2 partial pressures of 3 to 17 kPa had little or no effect on O 2 uptake or headspace ethanol partial pressures at 20C.

Orchard Groundcover Management Impacts on Soil Physical Properties

Abstract: This study was conducted to compare various orchard groundcover management systems (GMSs)—including a crownvetch "living mulch" (CNVCH), close-mowed (MWSOD) and chemically growth-regulated (GRSOD) sodgrasses, pre-emergence (NDPQT) and two widths of post-emergence (GLY1.5 and GLY2.5) herbicides, hay-straw mulch (STMCH), and monthly rototillage (tilled)—during the first 6 years in a newly established apple ( Malus domestica Borkh.) planting. Mean soil water potential at 5 to 35 cm deep varied substantially among treatments each summer, and treatment × year interactions were observed. During most growing seasons from 1986 to 1991, soil water availability trends were STMCH > NDPQT > GLY2.5 > GLY1.5 > tilled > GRSOD > MWSOD > CNVCH. Soil organic matter content increased under STMCH, CNVCH, and MWSOD and decreased under NDPQT and tilled treatments. Water infiltration and saturated hydraulic conductivity after 4 years were lower under NDPQT and tilled, and soil under STMCH and GRSOD retained more water per unit volume at applied pressures approximating field water capacity. Mid-summer soil temperatures at 5 cm deep were highest (25 to 28C) in tilled and NDPQT plots, intermediate (22 to 24C) under GRSOD, and lowest (16 to 20C) under CNVCH and STMCH. These observations indicate that long-term soil fertility and orchard productivity may be diminished under pre-emergence herbicides and mechanical cultivation in comparison with certain other GMSs. water retention and availability, bulk density, pore size distribu- tion, temperatures, soil organic matter content, groundcover bio- mass, and apple root distribution.

Early compositional changes during postharvest senescence of Broccoli

Abstract: Compositional changes during the postharvest senescence of broccoli branchlets held at 20C in the dark were investigated, particularly during the first 24 hours. Major losses of sugars, organic acids, and proteins from floral, middle, and base sections of branchlets were detected during the first 6 hours. Between 12 and 96 hours, free amino acid pools increased (especially the amides glutamine and asparagine) for all sections of branchlets, while ammonia accumulated only in floral sections. Results are discussed in relation to the nature of the processes that set the tissues on the pathways leading to postharvest senescence. Studies of postharvest senescence in horticultural crops have usually concentrated on mature tissue (e.g., fruit pericarp tissue) in which changes occur relatively slowly. In contrast, organs contain- ing immature tissue that is actively growing at harvest (e.g., asparagus and broccoli) senesce rapidly. Major physiological, biochemical, and molecular changes have been demonstrated within 3 h after harvesting asparagus spears (Davies and King, 1993; Hurst et al., 1993b; King et al., 1990; Lill et al., 1990). Since all crops initially spend a period at ambient temperature after harvest (while the crop is graded and packed), and then frequently during display and sale, an understanding of early changes follow- ing harvest is essential for accurate interpretation of subsequent changes, which may include storage at other temperatures. Fresh broccoli is highly perishable with a storage life of 3 to 4 weeks in air at 0C (Makhlouf et al., 1989; Smith, 1940) and 2 to 3 days in air at 20C (Wang, 1977). As broccoli deteriorates, the head yellows due to degradation of chlorophyll (Wang, 1977). Decay is common on florets during advanced stages of senes- cence (Aharoni et al., 1985). Ethylene plays an important role in regulating the yellowing of broccoli florets. Application of exogenous ethylene or propy- lene hastens yellowing (Aharoni et al., 1985; Tian et al., 1994). Conversely, application of anti-ethylene agents (aminoethoxyvinyl- glycine, CO 2 , silver ions, rhizobitoxine, sodium benzoate, benzyladenine, and gibberellic acid) retards yellowing (Aharoni et al., 1985; Wang, 1977). The sensitivity of broccoli florets to exogenous propylene may also increase after harvest (Tian et al., 1993). However, the relationship between ethylene and other physiological changes during postharvest senescence of broccoli has not been characterized. We have previously described physiological changes occurring early after harvest of broccoli, including decreased CO 2 produc- tion and a reduced respiratory quotient (RQ) (King and Morris, 1994). In this paper, we detail compositional changes during the senescence of broccoli held at 20C in the dark for up to 96 h, particularly those changes occurring during the first 24 h. Branchlets were used as they are a useful model system for investigating changes during senescence of broccoli (King and Morris, 1993). Materials and Methods Plant material and holding conditions. 'Green Belt' broccoli (Brassica oleracea L. var. italica ) heads were harvested at maturity from a commercial field at dawn, stripped of remaining leaves, and transported to the laboratory within 1.5 h of harvest. Heads were surface-sterilized with 100 ppm sodium hypochlorite (Rushing, 1990). Three branchlets (≈40 g each; Fig. 1) were excised from each head using a sterile scalpel. The branchlets were obtained from the second layer above the head base. These were considered to represent branchlets of an average size and developmental age on the head. Branchlets were placed in sterilized glass jars (550-ml capacity) and held at 20C in the dark, except for brief periods of light when measurements were being taken. The containers were aerated continuously with humidified, ethylene-free air at a flow rate of ≈1.5 liters·h -1 . Containers were equilibrated for 1 h before initial measurements.

'Evergreen' peach, its inheritance and dormant behavior

Abstract: The evergreen (EVG) peach, first described in Mexico, was used as a parent with deciduous (DE) peaches to develop F 1 and F 2 hybrid populations in Mexico, Florida, Georgia, and West Virginia. F 1 trees were DE and F 2 plants segregated 3 DE : 1 EVG. In West Virginia, the most temperate location, the heterozygous class could be distinguished in the first few years of growth by late leaf abscission in the fall. Segregation ratios suggest that the EVG trait is controll ed by a single gene, evg, the EVG state being homozygous recessive. Evergreen trees were characterized by insensitivity of shoot tips to daylength and failure of terminal growth to cease growth until killed by low temperature. Lateral buds of EVG trees went dormant in the fall. Deep supercooling occurred in both EVG and DE trees, but it appeared later in EVG trees, was of shorter duration, and occurred to a lesser extent. Evergreen germplasm may be useful in developing peach cultivars for frost-free subtropic and tropical areas. It also presents a useful system for studying dormancy and cold hardiness. develop in EVG trees except in climates where they were partially or fully defoliated by stress or leaf diseases. The objective of this study was to test the hypothesis (Lammerts, 1945) that expression of the EVG habit is under control of a single recessive gene and to develop comparative information on the ability of EVG trees to acclimate in different locations.

Skin Color in Apples—Influence of Copigmentation and Plastid Pigments on Shade and Darkness of Red Color in Five Genotypes

Abstract: The biochemical and cytological mechanisms responsible for the differences in red color quality of apple s (Malus domestics Borkh.) were investigated. Copigmentation, the increase in absorbance maxima ( λmax) from anthocyanin and flavonoid interactions, is known to be a mechanism for producing variation in shade of red in flowers. In intact apple skin cells, the mean λmax was 550 nm, with no significant difference between genotypes. Furthermore, the ratio of flavonols and proanthocyanidins to anthocyanins was similar for all genotypes. Therefore, copigmentation is not a mechanism producing different shades of red in apples. Darkness of red skin was positively related to the proportion of red cells in the skin and the size of the vacuoles containing anthocyanins. Measurements of plastid pigments, chlorophyll, and carotenoids, compared with L*, a*, b* measurements, indicated that the visual blending of plastid pigments and anthocyanins has an important influence on red coloration of apple skin. Apple skin color is caused by the pigments chlorophyll and carotenoids located in plastids and the phenolic pigments (antho- cyanin, flavonols, and proanthocyanidins) located in the vacuole. The flavonols and proanthocyanidins do not contribute signifi- cantly to overall coloration but may be important in enhancing anthocyanin coloration by copigmentation. Color is traditionally measured by destructive techniques, such as isolation and quantitation of pigments, or by nondestructive measurements based on determination of the characteristics of light, transmitted or reflected, by the fruit. The relationships between pigment composition, color measurement, and percep- tion of color by the eye are complex, and evidence is lacking on the extent to which differences in pigment composition are apparent to the eye as color differences (Knee, 1980). In apples, red coloration is commercially desirable. Variation exists in the shade of red and the pattern of reddening (e.g., solid block or striping). This varia- tion depends on the genotype and on developmental and environ-

Estimating Nuclear DNA Content in Peach and Related Diploid Species Using Laser Flow Cytometry and DNA Hybridization

Abstract: Using laser flow cytometry, nuclear DNA amounts were estimated for 12 Prunus species, representing three subgenera (Prunophora (Prunus), Amygdalus, and Cerasus (Lithocerasus)), two interspecific hybrids, four cultivars, and a synthetic polyploid series of peach consisting of haploids, diploids, triploids, and tetraploids (periclinal cytochimeras). Peach nuclear DNA content ranged from 0.30 pg for the haploid nuclei to 1.23 pg for the tetraploid nuclei. The diploid genome of peach is relatively small and was estimated to be 0.60 ± 0.03 pg (or 5.8 × 10 8 nucleotide base pairs). The polyploid series represented the expected arithmetic progression, as genome size positively correlated with ploidy level (i.e., DNA content was proportional to chromosome number). The DNA content for the 12 diploid species and two interspecific diploid hybrids ranged from 0.57 to 0.79 pg. Genome size estimates were verified independently by Southern blot analysis, using restriction fragment length polymorphism clones as gene-copy equivalents. Thus, a relatively small and stable nuclear genome typifies the Prunus species investigated, consistent with their low, basic chromosome number (x = 8).

Predicting Tomato Seedling Morphology by X-ray Analysis of Seeds

Abstract: Studies based on X-ray photographs were conducted to predict the morphology of tomato ( Lycopersicon esculentum Mill.) seedlings at transplanting stage. Currently, seed-lot quality of tomato seeds for growing commercial transplants is determined with grow-out tests in the greenhouse because the standard germination test fails to predict the percentage of normal or usable transplants (UTs). These grow-out tests, however, are difficult to standardize. An X-ray evaluation procedure is presented as an alternative. X-ray images nondestructively provide information on embryo size and morphology and the amount of endosperm and the area of free space. These parameters correlate well with the morphology of 14-day old seedlings. Cotyledon morphology has the highest correlation with the percentage of UTs. A test based on the evaluation of X-ray images, classifying the cotyledon morphology and seed free space, predicts the percentage of UTs more accurately than the currently used germination test. A second method based on an equation that uses the probabilities of all X-ray categories proportionally predicts the percentage of UTs of primed seeds more accurately than the first method. Selecting individual seeds based on X-ray images has the potential to raise the percentage of UTs of seed lots. On the average, the percentage of UTs of control seeds was 22% higher after hand selection based on X-ray evaluation. Primed seeds gave 12% higher results. Hence, X-ray analysis can predict seedling performance and enable the selection of high-quality seeds.

Physiological Changes of Broccoli during Early Postharvest Senescence and through the Preharvest-Postharvest Continuum

Abstract: Additional index words. Brassica oleracea Italica group, color, ethylene, quality, respiration Abstract. The postharvest senescence of broccoli ( Brassica oleracea L. Italica group) was studied immediately after harvest until senescence was essentially completed at 20C. Changes in respiration, ethylene production, and color were determined for florets, branchlets, and heads of three cultivars of field-harvested 'Green Beauty', 'Dominator', and 'Shogun' broccoli. Changes in respiration and ethylene production were also determined for 3 hours of preharvest and 24 hours of postharvest storage using broccoli grown in containers. Carbon dioxide produced from heads of container-grown broccoli and from heads, branchlets, and florets of field-harvested broccoli decreased markedly during the first 12 hours of postharvest storage before stabilizing. The respiratory quotient shifted toward a more oxidative metabolism in parallel with the respiratory decline. Ethylene production during storage showed no consistent relationship to yellowing. However, time until onset of yellowing was broadly related to the basal levels of ethylene production. The maximum storage life at 20C is ≈72 hours. Branchlets are useful model systems for investigating broccoli senescence.

Nuclear DNA Content and Ploidy Levels in the Genus Ipomoea

Abstract: The nuclear DNA content of 53 accessions from 24 Ipomoea (Convolvulaceae) species, including four sweetpotato cultivars, was determined by flow cytometry of DAPI-stained nuclei. Ploidy level and DNA content were significantly correlated within the genus, but more highly so within species that contained multiple cytotypes. DNA content of cultivated Z. batatas (L.) Lam. (4.8 to 5.3 pg/2C nucleus) and feral tetraploid I. batatas (3.0 to 3.5 pg/2C nucleus) was estimated from the known DNA content of chicken erythrocytes (2.33 pg), which were used as an internal standard. Tetraploid forms of Z. cordato-triloba Dennstedt also were identified. Ploidy analysis using flow cytometry is rapid and suitable for large-scale experiments such as studying the genetic structure of populations of Z. batatas and related species. Chemical name used: 4´,6-diamidino-2-phenylindole (DAPI). Nuclear DNA content can be used to estimate ploidy level, provided that there has been sufficient cytological investigation to base the study on known chromosome numbers and ploidy ranges. The quantitation of DNA content often has been based on mi- crospectrophotometry of Feulgen-stained nuclei in squashed tis- sues (Bennett and Smith, 1976; Bennett et al., 1982). This method requires careful standardization of tissue samples and fixation, reaction, and spectrophotometer conditions (Price, 1988). More recently, flow cytometry of nuclei stained with DNA fluoro- chromes has been recognized as a fast, accurate alternative to microspectrophotometry (Dolezel, 1991; Galbraith, 1989). A strong correlation between DNA values determined by Feulgen mi- crospectrophotometry and flow cytometry has been shown (Michelson et al., 1991). The flow cytometer uses a laser beam that is focused on a small sample stream containing suspended nuclei. The nuclei can be stained with DNA fluorochromes such as ethidium bromide or propidium iodide (intercalating dyes), DAPI (specific for A-T base pairs), and mithramycin (specific for G-C base pairs). Computer-assisted measurements of fluorescence emission per fluorescent particle allow the generation of a histo- gram reflecting the distribution of fluorescence intensity among a fixed number of particles. Several thousand particles can be measured within minutes by flow cytometry, which has a capacity of at least two orders of magnitude greater than that of mi- crospectrophotometry. The genus Ipomoea (Convolvulaceae) is thought to contain >500 species with known ploidy levels of 2x,4x, and 6x and a basic chromosome number of x = 15 (Jones, 1964, 1968). The high basic chromosome number and small chromosome size in species of this genus make cytological studies laborious and time consuming. Morphological plasticity within the genus has led to considerable

Additive effects of postharvest calcium and heat treatment on reducing decay and maintaining quality in apples

Abstract: . . Additional index words. CaCl2, Malus domestics, Botrytis cinerea, pressure infiltration Abstract. 'Golden Delicious' apples (Malus domestics Borkh.) were treated with heat or CaCl2 solutions or a combination thereof to determine the effects of these treatments on decay and quality of fruit in storage. Heat treatment at 38C for 4 days, pressure infiltration with 2% or 4% solutions of CaCl 2, or a combination of both, with heat following CaCl 2 treatment affected decay and firmness during 6 months of storage at 0C. The heat treatment alone reduced decay caused by Botrytis cinerea (Pers.:Fr.) by 30%, while heat in combination with a 2% CaC12 solution reduced decay by 60 %. Calcium chloride solutions of 2% or 4% alone reduced decay by 40 % and 60 %, respectively. Heat treatments, either alone or in combination with CaC1 2 treatments, maintained firmness (80 N) best, followed by fruit infiltrated with 2% or 4% solutions of CaClz alone (70 N) and the nontreated controls (66 N). Instron Magness-Taylor and Instron compression test curves show that heat- treated fruit differed qualitatively and quantitatively from nonheated fruit. Heat treatment did not increase the amount of infiltrated Ca bound to the cell wall significantly, and a combination of heat treatment after CaCl 2 infiltration increased surface injury over those fruit heated or infiltrated with CaCl 2 solutions alone.

Early Season Patterns of Carbohydrate Partitioning in Exposed and Shaded Apple Branches

Abstract: 14 CO 2 , light, Malus domestica, photosynthesis, translocation, fruiting Abstract. The partitioning of photosynthates labeled by 14 CO 2 in exposed and shaded 'Empire' apple ( Malus domestica Borkh.) branches was examined at 1, 3, 5, and 10 weeks after bloom. Extension shoots, nonfruiting spurs, or fruiting spurs were labeled separately to examine which shoot types exported to the fruit at each time. The general partitioning patterns were observed with autoradiography, while label accumulation in fruit was determined by oxidation and scintillation counting. At each treatment time, half of the branches was preconditioned with artificial shade (to 35% full light) for 48 hours before labeling and returned to the shade for a 2-day translocation period. One and 3 weeks after bloom, extension shoots showed little export to fruit; nonfruiting and vigorous fruiting spurs exported label to weak spurs and extension shoot tips. Shade had no major effect on partitioning patterns at 1 and 10 weeks, but essentially eliminated export from extension shoots at 3 weeks and greatly reduced export to fruit 5 weeks after bloom, as observed on the autoradiograms. At 5 weeks after bloom, the shading effect was equal to a 2-week delay in export. By 10 weeks after bloom, all shoot types were exporting most of the 14 C fixed to fruit. The photosynthate support of the fruit before fruit set seemed to strongly depend on the spur canopy, especially when the extension shoots were exposed to low light.

Water Use, Growth, and Fruit Yield of `Hosui' Asian Pears under Deficit Irrigation

Abstract: Five-year old 'Hosui' Asian pear ( Pyrus serotina Rehder) trees growing in drainage lysimeters and trained onto a Tatura trellis were subjected to three different irrigation regimes. Weekly water use (WU) was calculated using the mass- balance approach. Soil-water content of control lysimeters was kept at pot capacity, while deficit irrigation was applied before (regulated deficit irrigation (RDI)) and during the period of rapid fruit growth (late deficit irrigation (LDI)). Soil-water content was maintained at ≈50% and 75% of pot capacity for RDI and LDI, respectively. Deficit irrigation reduced mean WU during RDI and LDI by 20%. The reduced WU was caused by lower stomatal conductance (g s ) on deficit-irrigated trees. RDI trees had more-negative diurnal leaf water potentials ( ψ l ). The ψ l , g s , and WU remained lower for 2 weeks after RDI was discontinued. RDI reduced shoot extension and summer pruning weights, whereas winter pruning weights were not different between treatments. Except for the final week of RDI, fruit growth was not reduced, and fruit from RDI grew faster than the control during the first week after RDI. In contrast, fruit volume measurements showed that fruit growth was clearly inhibited by LDI. Final fruit size and yield, however, were not different between treatments. Return bloom was reduced by RDI but was not affected by LDI.

Random Amplified Polymorphic DNA (RAPD) Marker Variability between and within Gene Pools of Common Bean

Abstract: The objective of this study was to evaluate the degree of RAPD marker variability between and within commercially productive market classes representative of the Andean and Middle American gene pools of common bean (Phaseolus vulgaris L.). Six sets of near-isogenic lines were screened with oligonucleotide primers in the polymerase chain reaction-based RAPD assay. Simultaneous analyses with at least three sets of lines enabled us to score RAPD markers between the two major gene pools, races within the same gene pool, and different genotypes of the same race (within race). A "three-tiered" pattern of polymorphism was observed: between gene pools> between races> within races. The overall level of polymorphism between the Andean and Middle American gene pools was 83.4%. The overall level of polymor- phism between races within the same gene pool was similar forAndean races (60.4%) and Middle American races (61.7%). The level of polymorphism between related commercial navy bean lines was 39.2% and between related commercial snap bean lines was 53.6 %. The inherent simplicity and efficiency of RAPD analyses, coupled with the number of polymor- phisms detectable between related commercial genotypes, should facilitate the construction of RAPD-based genetic linkage maps in the context of populations representative of most bean breeding programs.

Transferring Cucumber Mosaic Virus-White Leaf Strain Coat Protein Gene into Cucumis melo L. and Evaluating Transgenic Plants for Protection against Infections

Abstract: A single regeneration procedure using cotyledon explants effectively regenerated five commercially grown muskmelon cultivars. This regeneration scheme was used to facilitate gene transfers using either Agrobacterium tumefaciens (using 'Burpee Hybrid' and 'Hales Best Jumbo') or microprojectile bombardment (using 'Topmark') methods. In both cases, the transferred genes were from the T-DNA region of the binary vector plasmid pGA482GG/cp cucumber mosaic virus-white leaf strain (CMV-WL), which contains genes that encode neomycin phosphotransferase II (NPT II), β-glucuronidase (GUS), and the CMV-WL coat protein (CP). Explants treated with pGA482GG/cpCMV-WL regenerated shoots on Murashige and Skoog medium containing 4.4 μM 6-benzylaminopurine (BA), kanamycin (Km) at 150 mg·liter -1 and carbenicillin (Cb) at 500 mg·liter -1 . Our comparison of A. tumefaciens- and microprojectile-mediated gene transfer procedures shows that both methods effectively produce nearly the same percentage of transgenic plants. R 0 plants were first tested for GUS or NPT II expression, then the polymerase chain reaction (PCR) and other tests were used to verify the transfer of the NPT II, GUS, and CMV-WL CP genes. This analysis showed that plants transformed by A. tumefaciens contained all three genes, although co- transferring the genes into bombarded plants was not always successful. R 1 plants were challenge inoculated with CMV-FNY, a destructive strain of CMV found in New York. Resistance levels varied according to the different transformed genotypes. Somaclonal variation was observed in a significant number of R 0 transgenic plants. Flow cytometry analysis of leaf tissue revealed that a significant number of transgenic plants were tetraploid or mixoploid, whereas the commercial nontransformed cultivars were diploid. In a study of young, germinated cotyledons, however, a mixture of diploid, tetraploid, and octoploid cells were found at the shoot regeneration sites.

Identifying Pollen Incompatibility Groups in California Almond Cultivars

Abstract: Six cross-incompatibility groups, which contain most of commercially important California almond cultivars (Prunus dulcis (Mill.) D.A. Webb, syn. Prunus amygdalus Batch), and their self-incompatibility (S) allele genotypes are identified. Incompatibility groups include 'Mission' (S aSb), 'Nonpareil' (ScSd), and the four groups resulting from the 'Mission' x 'Nonpareil' cross: (SaSc), (SaSd), (SbSc), and (SbSd), as represented by 'Thompson', 'Carmel', 'Merced' and 'Monterey', respectively. All seedlings from the 'Mission' x 'Nonpareil' cross were compatible with both parents, a result indicating that these two cultivars have no alleles in common. Crossing studies support a full-sib relationship for these progeny groups and the origin of both parents from common germplasm. Cultivars in these six groups account for ≈ 93% of present California production, a result demonstrating a limited genetic base for this vegetatively propagated tree crop. About 65% of the world almond production is in California, with >166,500 ha in production in 1990 (California Agricultural Statistics Service, 1990). The interplanting of cross-compati ble pollinizer cultivars in what previously were often single-cultivar orchards led to dramatic improvements in productivity and production consis- tency (Tufts, 1919; Tufts and Philp, 1922). Self-incompatibility in almond, a diploid tree crop (2n = 16), seems to be of the monogenic, gametophytic type (Socias i Company, 1991 ) as are other self-incompatible crops in the Rosaceae (Crane and Brown, 1937; Crowe, 1964). The self-incompatibility (S) locus controls self- and intra-specific cross-incompatibility (CI), and a series of many distinct alleles seems to exist (Socias i Company, 1991). Crossa-Raynaud and Grasselly (1985) have assigned the genotypes (S 1S2), (S3S4), and (S7S8) to 'Cristomorto', ' Ai', and 'Tardy Nonpareil', respectively. Tufts and Philp (1922), in their analysis of 23 early almond cultivars, established two CI groups (CIGs): a) 'Nonpareil' and 'I.X.L.' and b) 'Mission' (also known as 'Texas Prolific'), the main pollinizer for 'Nonpareil' at that time, and 'Languedoc' (different from the French cultivar of the same name). 'Long I.X.L.' and 'Profuse' have been added to the 'Nonpareil' CIG and 'Ballico' has been added to the 'Mission' CIG (Kester, 1963). Other early cultivars proposed by Kester and Asay, (1975) to be cross-incompatible include 'Jordanolo' and 'Harpareil', produced from a 'Nonpareil' × 'Harriott' cross; 'Reams' and 'Jubilee'; 'Kutsch', 'Rivers Nonpareil', 'Sultana', and 'Bigelow'; and 'Smith X.L.' and 'Drake', although crossing data no longer are available. Of these cultivars, only 'Mission' and 'Nonpareil' remain exten- sively planted. Newer cultivars, selected for improved horticul- tural performance and pollinizer efficacy, are being planted in- creasingly. Most of these new cultivars seem to be chance seed- lings from 'Nonpareil' × 'Mission' crosses (Hauagge et al., 1987). Four CIGs would be expected in the progeny of a 'Nonpareil' × 'Mission' cross if parents shared no common S alleles.

Growth and Gas Exchange by Lettuce Stands in a Closed, Controlled Environment

Abstract: Two studies were conducted in which 'Waldmann's Green' lettuce (Lactuca sativa L.) was grown hydroponically from seed to harvest in a large (20-m 2 ), atmospherically closed growth chamber for the National Aeronautics and Space Administration's controlled ecological life support system (CELSS) program. The first study used metal-halide (MH) lamps (280 μmol·m -2 ·s -1 photosynthetic photon flux (PPF)), whereas the second used high-pressure sodium (HPS) lamps (293 μmol·m -2 ·s -1 ). Both studies used a 16-hour photoperiod, a constant air temperature (22 to 23C), and 1000 μmol·mol - 1 CO 2 during the light period. In each study, canopy photosynthesis and evapotranspiration (ET) rates were highly correlated to canopy cover, with absolute rates peaking at harvest (28 days after planting) at 17 μmol CO 2 /m 2 per sec and 4 liters·m -2 ·day -1 , respectively. When normalized for actual canopy cover, photosynthesis and ET rates per unit canopy area decreased with age (between 15 and 28 days after planting). Canopy cover increased earlier during the study with HPS lamps, and final shoot yields averaged 183 g fresh mass (FM)/plant and 8.8 g dry mass (DM)/plant. Shoot yields in the first study with MH lamps averaged 129 g FM/plant and 6.8 g DM/plant. Analysis of leaf tissue showed that ash levels from both studies averaged 22% and K levels ranged from 15% to 17% of tissue DM. Results suggest that lettuce should be easily adaptable to a CELSS with moderate lighting and that plant spacing or transplant schemes are needed to maximize canopy light interception and sustain efficient CO 2 removal and water production.

Water Loss: A Nondestructive Indicator of Enhanced Cell Membrane Permeability of Chilling-injured Citrus Fruit

Abstract: , intermittent warming, grapefruit, lemon, shelf life Abstract. Water loss was found to be a nondestructive indicator before visible symptoms of chilling injury (CI) in cold- stored grapefruit (Citrus paradisi Macf.) and lemon (C. limon L. Burm. f.). The water-loss rate increased significantly after removing the fruit from cold storage and holding at 20C. Scanning electron microscopy revealed large cracks around the stomata. Changes in electrical conductivity of the flavedo tissues, total electrolyte leakage, and K + or Ca 2+ leakage were all inadequate predictors of CI, appearing only after CI was evident.

Irrigation Regimes Affect Yield and Water Use by Bell Pepper

Abstract: Keystone Resistant Giant' bell pepper ( Capsicum annuum L.) was grown in drainage lysimeters under controlled soil water regimes during 1982, 1984, and 1985. Three irrigation regimes were imposed on bell pepper grown on two soil types during spring and fall growing seasons. Irrigation regimes consisted of applying water when the soil water tension at 10 cm exceeded 25, 50, or 75 kPa during crop growth. Yields and water use were greatest when irrigation was applied at 25 kPa. Regression equations are presented to describe the relationships of water use to plant age and to compute the ratios of daily evapotranspiration to pan evaporation (crop factors) for bell pepper grown under the three irrigation regimes. ET/E p values used to estimate ET during the growth of several vegetables (Stansell and Smittle, 1980, 1989; Smittle et al., 1990a, 1992b) and have incorporated these equations into irrigation scheduling models (Smittle and Dickens, 1992; Smittle et al., 1990b, 1992a). In this research, we determined the yield and water use re- sponses of bell pepper to different irrigation regimes. We also developed regression equations to calculate ET/E p during the growth of bell pepper grown under the different irrigation regimes.

Role of Ethylene in Opening and Senescence of Gladiolus sp. Flowers

Abstract: The opening and senescence of gladiolus ( Gladiolus sp.) florets was accompanied by climacteric or nonclimacteric patterns of respiration and ethylene production, depending on variety, and whether data were expressed on a fresh-weight or floret basis. A climacteric pattern of ethylene production by the youngest buds on the spike (which never opened) was stimulated by cool storage, and was not affected by holding the spikes in a preservative solution containing sucrose. Ethylene treatment had no effect on senescence of the florets of any of the cultivars tested. Pulse treatment of the spikes with silver thiosulfate (STS) improved floret opening but not the life of individual florets. Sucrose and STS had similar but not synergistic effects on floret opening, suggesting that STS improves flower opening in gladiolus by overcoming the effects of carbohydrate depletion. Gladiolus are prized by florists for their showy flower spikes, and by growers for their relative ease of production. Like other flowers with spike inflorescences, gladiolus are normally har- vested with relatively few open florets, and the life of the flower is a function both of the life of individual florets, and of the postharvest expansion and opening of the buds remaining on the spike. Ideally, many of the florets on the spike should open before the senescence of the bottom florets. Because the dead florets are unattractive, senescence of the bottom florets marks the end of the flower spike's commercial display life. The typical life of these florets on a spike placed in water is 4 to 6 days (Marousky, 1968; Mayak et al., 1973). Modest increases in the life of gladiolus flowers have been gained by pulsing with sucrose, or using vase preservatives containing sucrose (Marousky, 1971). Little has been done to examine the physiological basis of senescence in gladiolus, and no work has been reported on the physiology of individual florets. This is surprising, since gladiolus flower spikes offer an interesting model system for studies of flower senescence. Individual florets provide a graded series of stages of development and senescence in an identical genetic and environmental background. Many studies have examined the possible role of ethylene in gladiolus senescence. Woltering and van Doorn (1988) reported that treatment with ethylene (3 μl·liter - 1 ) for 24 h revealed little to no sensitivity as indicated by slight acceleration of petal wilting in only some cultivars. Pulse treat- ments with the silver thiosulfate anionic complex (STS) have likewise provided little (Farhoomand, 1978) or no (Mor et al., 1981) benefit. In contrast, Merodio and de la Plaza (1989) reported that ethylene removal during storage improved the subsequent vase life of 'pink' and 'white' gladiolus cultivars. Ethylene re- moval also resulted in reduced water and color loss, and improved stem 'rigidity'. Murali and Reddy (1993) used a range of metal salts (in combination with sucrose) and found a positive correla tion between the effects of their treatments on ethylene production and vase life of the flower spikes. Thus, the role of ethylene in senescence of gladiolus petals and the life of the flower spikes is unclear. In this study, we examined the role of ethylene in floret senescence of gladiolus flowers by determining ethylene produc- tion and respiration of individual florets during development and senescence, and by exploring the effects of exogenous ethylene, STS, and sucrose treatments on opening and senescence of florets in a range of commercial cultivars.

Accumulation of Antioxidants in Apple Peel as Related to Preharvest Factors and Superficial Scald Susceptibility of the Fruit

Abstract: Antioxidants are believed to protect against the oxidation of α-farnesene to conjugated trienes in apple ( Malus domestica, Borkh.) peel, thus providing resistance against superficial scald development. We conducted three experiments in which apples were a) harvested weekly, during which they were exposed to increasing hours at <10C during ripening; b) induced to ripen with no hours at <10C by applying ethephon; and c) enclosed in paper bags as they ripened. Inducing ripening with ethephon increased total water-soluble reducing compounds and percentage inhibition of lipid oxidation of peel extracts, increased concentrations of α-tocopherol, carotenoids, and ascorbic acid in peel, but only slightly reduced scald. Delayed harvests increased all of these antioxidants except ascorbic acid and greatly reduced scald development. Bagging fruit before ripening decreased α-tocopherol, carotenoid, and ascorbic acid concentrations, decreased total water-soluble reducing compounds, and increased scald development. We conclude that changes in these antioxidants probably are affected more by ripening and light intensity than by low temperature before harvest. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).

Fertilizer Nitrogen and Boron Uptake, Storage, and Allocation Vary during the Alternate-bearing Cycle in Pistachio Trees

Abstract: 10 B, carbohydrate reserves, fruit tree nutrition, 15 N, Pistacia vera, uptake efficiancy Abstract. The effects of alternate bearing on recovery and loss of isotonically labeled fertilizer N and B and on the accumulation of carbohydrate and N reserves were assessed in mature 'Kerman' pistachio (Pistacia vera L.) trees. Total recovery of labeled fertilizer N applied once (in late January) was ≈ 60% greater if applied to trees entering an "off' than an "on" year, with respect to fruiting. Eleven percent more labeled B was recovered in off- than on-year trees. Five times more N (1 vs. 0.2 kg N) was lost from the tree in fruit and senescent leaflets from on- than off-year trees. In dormant trees, 144% and 22% more starch and N reserves, respectively, were present after off than on years. Thus, on-year trees were characterized by a greater reproductive demand for N and carbohydrates, reduced accumulation of C and N (i.e., storage) reserves in perennial tree parts, and reduced recovery of January-applied labeled fertilizer N than off-year trees. As B is absorbed passively, the higher transpiration that may accompany the 43% larger leaf area per tree and the probability of increased root growth probably contributes to its increased uptake during off years. The enhanced labeled N recovery in early spring by trees entering their off year preceded fruit and seed development in on-year trees. The differential tree capacity for nutrient uptake in spring may have been conditioned the previous rather than the current year. The increased uptake of labeled N by trees entering an off year (i.e., emerging from an on year) was associated with lower levels of carbohydrate and N reserves than for on-year trees that had just completed an off year. Future experimentation should assess the comparative capacity for nutrient uptake by on-and off-year trees at other stages of phenology, e.g., during seed development and postharvest. Alternate bearing-the alternation of high and low crop years—