Showing papers in "Journal of the American Society for Horticultural Science in 1996"

Influence of Light on Grape Berry Growth and Composition Varies during Fruit Development

Abstract: Potted 'Cabernet Sauvignon' and 'Pinot noir' grapevines ( Vitis vinifera L.) grown in a sunlit phytotron were used to study the influence of cluster light exposure during various stages of fruit development on berry growth and composition. Clusters grown without light during berry development stages I and II, stage III, or stages I, II, and III, were compared to clusters exposed to light throughout fruit development (control). The temperature of light-exposed and nonexposed fruit was similar. The weights and diameters of berries grown without light during stages I and II, or stages I, II, and III, were similar and significantly lower than those of the control. Fruit softening in both cultivars, as well as the initiation of berry coloration, was delayed when berries were grown without light during stages I and II. Following fruit softening, berries grown without light during stages I, II, and III were lower in sugar than the control. On the final sample date, 'Cabernet Sauvignon' berries grown without light during stages I, II, and III were higher in malate compared to the control. 'Pinot noir' berries grown without light during stages I and II, or stages I, II, and III, were lower in malate before fruit softening, and higher in malate following fruit softening, than the control. Control berries had greater skin anthocyanins and phenolics compared to the remaining treatments. Berries grown without light during stages I and II, or stage III, were greater in anthocyanins and phenolics than fruit grown without light during stages I, II, and III. Light had no effect on fruit tartrate concentration or juice pH. Light had its greatest impact on fruit development during the initial stages of berry growth. Berry growth was reduced and ripening delayed when fruit were grown without light during stages I and II. Normal fruit development was not fully restored when these fruit were exposed to light during stage III.

Chemical Composition of Lowbush Blueberry Cultivars

Abstract: The chemical composition of the lowbush blueberry (Vaccinium angustifolium Aiton) cultivars Blomidon, Cumberland, and Fundy were examined at three stages of fruit maturity, before and after refrigerated storage, in a 2-year study. There were differences (P< 0.001) related to maturity and cultivar in berry fresh weight, percentage dry matter, fruit firmness, percentage soluble solids, titratable acidity, and the concentration of sugar, acids, and anthocyanins. Among the nine organic and phenolic acids measured, seven acids varied among the maturity groups and eight varied among the cultivars. Between the 2 years of study there was a 60% difference in total fruit acid content as well as in the relative amounts of each acid. The 2-year mean profile of lowbush blueberry acids was distinctly different from that recently reported for highbush (Vaccinium corymbosum L.) and rabbiteye blueberries (Vaccinium ashei Reade). The level of certain acids as well as the concentration of anthocyanins increased during cold storage. Estimation of sugar concentration by percentage soluble solids overestimated sugar concentration by 3070. Acid measurement by titration underestimated acid content as measured by HPLC by 61%. Results of this study illustrate the variation in the chemical composition of lowbush blueberry fruit among cultivars, maturities, and seasons, and can be used to compare lowbush blueberries with other Vaccinium species. Lowbush blueberries (Vaccinium angustifolium) are native to Eastern Canada and the Northeast United States, where wild stands are commercially managed and harvested. Lowbush fruit is small compared to highbush (Vaccinium corymbosum) or rabbiteye blueberries (Vaccinium ashei). Since stands of lowbush blueber- ries are made up of numerous wild clones, the commercial lowbush product is more heterogeneous than commercial highbush or rabbiteye blueberries. The mineral and vitamin content of lowbush blueberries was reported by Bushway et al. (1983) and the total N, amino acid, anthocyanin, flavanol, and sugar content was exam- ined by Goueli(1976). Lowbush blueberries contain equal amounts of glucose and fructose but do not contain sucrose (Barker et al., 1963, Goueli, 1976) while highbush blueberries contain fructose, glucose, and small amounts of sucrose (Eck, 1988). Ehlenfeldt et al. (1994) recently reported the organic acid composition of highbush and rabbiteye blueberries and suggest that these two Vaccinium species are distinguishable based on their acid profiles. The purpose of this study was to examine the chemical profile of lowbush blueberry cultivars with emphasis on fruit components that influence sensory quality. The study examines fruit at three stages of maturity, before and after storage, and during two harvest seasons.

Sugar Accumulation Enhanced by Osmoregulation in Satsuma Mandarin Fruit

Abstract: The effect of water stress induced to enhance sugar accumulation in Satsuma mandarin ( Citrus unshiu Marc.) fruit was investigated. Satsuma mandarin trees were subjected to water stress using mulch cultivation from late August to early December. In mulch treatment, soil was covered with double-layered plastic sheets that prevented rainfall from permeating the soil, but allowed water from soil to evaporate. The water status of soil, fine roots, pericarps, and juice vesicles was determined using the isopiestic psychrometer. As the severity of water stress increased, both water potential and osmotic potential of fine roots and pericarps significantly decreased in plants grown under mulch cultivation compared to well-watered trees. Although water potential and osmotic potential decreased, turgor of both roots and pericarps of the water stressed trees did not decrease under water stress conditions. Because turgor was maintained, osmoregulation occurred in Satsuma mandarin trees in response to water stress. The osmotic potential of juice vesicles in water-stressed fruit gradually decreased, and sugars accumulated in vesicle cells. Concentrations of sucrose, fructose, and glucose increased in fruit sap under water stress, and the acidity in the fruit juice increased. Furthermore, the total sugar content per fruit of water stressed trees was significantly higher than in fruit of well-watered trees. These results suggest that sugar accumulation in Satsuma mandarin fruit was not caused by dehydration under water stress but rather that sugars were accumulated by active osmoregulation in response to water stress. When sugar components in osmoregulated fruit were analyzed, it was found that monosaccharides, i.e., glucose and fructose, were largely responsible for active osmoregulation in fruit under water stress conditions.

Founding Clones, Inbreeding, Coancestry, and Status Number of Modern Apple Cultivars

Abstract: Pedigrees of apple (Malus ×domestica Borkh.) cultivars were used to study worldwide genetic diversity among clones used in modern apple breeding. The most frequent founding clones were 'Cox's Orange Pippin', 'Golden Delicious', 'Red Delicious', 'Jonathan', and 'McIntosh'. Coefficients of coancestry between 50 mainstream cultivars and these clones averaged 0.03, 0.12, 0.07, 0.06, and 0.02, respectively, but they were frequently as high as 0.25 with certain pairings. Among a group of 27 cultivars carrying the Vf gene for scab resistance, coefficients of coancestry with the five founding clones were of the same order. Although few of the cultivars sampled were substantially inbred, inbreeding could reach serious levels in their future offspring if current breeding practices are continued. The status effective number was 8 for the mainstream group and 7 for the Vf-carrier clones. This indicates clearly that apple breeders are operating with a population of greatly reduced genetic diversity. Careful consideration of pedigrees and increased size of the genetic base are needed in future apple breeding strategies.

Molecular markers associated with plant architecture and resistance to common blight, web blight, and rust in common beans

Abstract: Random amplified polymorphic DNA (RAPD) markers were used to construct a partial linkage map in a recombinant inbred population derived from the common bean (Phaseolus vulgaris L.) cross BAC 6 x HT 7719 for studying the genetics of disease resistance in common bean. The linkage map spanned 545 cM and included 75 of 84 markers used in this study. The population of 128 recombinant inbred lines was evaluated for resistance to common bacterial blight, foliar resistance to web blight (WB; Thanatephorus cucumeris (Frank) Donk), and resistance to rust ( Uromyces appendiculatus var. appendiculatus (Pers.:Pers) Unger). Common bacterial blight (CBB; Xanthomonas campestris pv. phaseoli (Smith) Dye) resistance was evaluated for CBB strain Epif-IV in later-developed trifoliolate leaves and for CBB strain EK-11 in seeds, first trifoliolate leaves, later-developed trifoliolate leaves, and pods. In addition, lines were rated for plant uprightness and branch density. Two to six markers accounted for 14% to 34% of the phenotypic variation for each trait. Significant marker locus- trait associations were found for 14 mapped loci and 7 of the 9 unmapped markers. The distribution of detected QTL appeared to be nonrandom with most significant markers associated with more than one trait or closely linked to markers significantly associated with variation for a different trait. One marker, BC409 1250 , was significantly associated with WB resistance, resistance for CBB strain Epif-IV in later-developed trifoliolate leaves, and resistance for CBB strain EK-11 in first trifoliolate leaves, later-developed trifoliolate leaves, and pods. A rust resistance gene was mapped in an interval 14.6 cM from RAPD marker H19 1050 and 12.5 cM from marker AJ16 250 . Common bacterial blight (CBB; Xanthomonas campestris pv. phaseoli), web blight (WB; Thanatephorus cucumeris), and rust (Uromyces appendiculatus var. appendiculatus) are important diseases of common bean (Harter and Zaumeyer, 1944). These diseases cause economic losses due to a reduction in seed yield and seed quality in dry bean producing regions worldwide (Galvez et al., 1989; Saettler, 1989; Stavely and Pastor-Corrales, 1989). The most reliable and effective control strategy for these diseases is the

Phenylalanine Ammonia-lyase (PAL) Activity and its Relationship to Anthocyanin and Flavonoid Levels in New Zealand-grown Apple Cultivars

Abstract: Phenylalanine ammonia-lyase (PAL) activity was measured in a range of New Zealand-grown apple ( Malus domestica Borkh.) cultivars at three stages of fruit development. Anthocyanin and total flavonoid levels were also measured (by HPLC) in the same fruit. There was wide variation in the level of PAL activity, anthocyanin and total flavonoid levels in different apple cultivars and at different stages of development. There was no apparent correlation between average PAL activity over the three developmental stages and final anthocyanin concentration ( r = 0.34, P > 0.1), but there was significant correlation between average PAL activity over the three developmental stages and the final concentration of total flavonoids ( r = 0.75, P 0.1) or total flavonoid levels ( r = 0.15, P > 0.1). These results suggest that PAL activity has an influence on total flavonoid levels in the fruit but that PAL-IS does not. Anthocyanin levels are likely controlled at a point in the flavonoid pathway other than PAL or PAL-IS.

The Bases of Productivity in Apple Production Systems: The Role of Light Interception by Different Shoot Types

Abstract: Although apple (Malus domestica Borkh.) system yield differences are generally related to whole-canopy light interception, this study tested the hypothesis that these orchard yields are related primarily to total light intercepted by the spur canopy. Seasonal leaf area development of different shoot types, exposed bourse shoot leaf net photosynthesis, fruit growth, whole canopy light interception (by image analysis of fisheye photographs) and relative light interception by different shoot types (by a laser assisted canopy scanning device) were estimated within four 14-year-old 'Empire' apple production systems (slender spindle/M.9, central leader/M.7, central leader/M.9/MM.111 and Y-trellis/M.26). The final LAI values were CL/M.7 = 1.8, CL/9/111 = 2.3, SS/M.9 = 2.6 and Y/M.26 = 3.6. Exposed leaf net photosynthesis showed few differences and was not dependent upon the production system. Yields of the pyramidal shaped tree forms were 40 to 42 t·ha -1 while Y-trellis produced 59 t·ha -1 , with similar fruit sizes. Again, yields were primarily related to the percentage of light intercepted by the whole canopy, 48% to 53% for conic forms versus 62% for the Y-trellis system. Laser analyses showed that the Y-trellis system intercepted about 20% to 30% more light with the spur canopy than the conic tree forms, supporting the hypothesis. Yields were better correlated with spur canopy LAI and spur canopy light interception than with extension shoot canopy LAI and light interception.

Developing a Slow-release Nitrogen Fertilizer from Organic Sources: II. Using Poultry Feathers

Abstract: The structure of feather keratin protein was modified in attempts to develop a slow-release N fertilizer of 12 weeks duration or longer by steam hydrolysis to break disulfide bonds, enzymatic hydrolysis with Bacillus licheniformis (Weigmann) to break polypeptide bonds, and steam hydrolysis (autoclaving) to hasten mineralization followed by cross- linking of the protein by a formaldehyde reaction to control the increased rate of mineralization. Release of N in potting substrate within elution columns from ground, but otherwise untreated, raw feathers occurred mainly during the first 5 weeks with a much smaller release occurring from weeks 8 to 12. Steam hydrolysis resulted in an increase of N during the first 5 weeks and a decrease during weeks 8 to 11. Cumulative N release over 11 weeks increased from 12% in raw feathers to 52% for feathers steam hydrolyzed for 90 minutes. This favored an immediately available fertilizer but not a slow- release fertilizer. Microbial hydrolysis with B. licheniformis resulted in a modest reduction of N release during the first 5 weeks and a small increase during weeks 8 to 11. Both shifts, while not desirable for an immediately available fertilizer, enhanced the slow-release fertilizer potential of feathers but not sufficiently to result in a useful product. Steam hydrolyzed feathers cross-linked with quantities of formaldehyde equal to 5% and 10% of the feather weight released less N during the first 5 weeks, more during weeks 6 and 7, and less during weeks 9 to 12 compared to raw feathers. The first two shifts were favorable for a slow-release fertilizer while the third was not.

Growth, Productivity, and Mineral Composition of Hydroponically Cultivated Greenhouse Tomatoes, with or without Nutrient Solution Recycling

Abstract: Tomato plants (Lycopersicon esculentum Mill. cv. Capello) were grown in the three most promising and used hydroponic cultivation systems using rockwool and peatmoss substrates and nutrient film technique (NFT), either with or without recovery and recycling of the drainage solutions. Prolonged recycling of nutrient solutions in NFT caused a reduction in fresh weight, dry weight, and yield compared to plants grown in NFT with regular renewal of the nutrient solution. There were no differences in growth, productivity, and leaf mineral composition between plants grown in rockwool and peatmoss systems, with or without recycling, and in the NFT system without recycling. These results suggest that recycling drainage solutions is an economically and environmentally sound horticultural practice that when used correctly does not cause a reduction in yield of tomatoes cultivated in rockwool or peatmoss. However, prolonged use of the same solution in the NFT cultivation system can negatively affect growth and yield. This is most likely due to an accumulation of sulfate ions in the fertigation solutions.

Water Relations, Growth, and the Composition of `Braeburn' Apple Fruit under Deficit Irrigation

Abstract: Three-year-old 'Braeburn' apple trees ( Malus domestica Borkh.) on MM106 rootstock were studied in a glasshouse to assess the effects of deficit irrigation on fruit growth, water relations, composition, and the vegetative growth of the trees. Trees were assigned to one of three treatments. The control (C) was fully watered. The first deficit treatment (D1) was deficit-irrigated from 55 days after full bloom (DAFB) until final harvest at 183 DAFB. The second deficit treatment (D2) was deficit-irrigated from 105 to 183 DAFB. Compared to C, the D1 and D2 trees developed a lower photosynthetic rate, leaf water potential ( Ψ l ), and stomatal conductance (g s ) during the stress period. Trunk-circumference growth was reduced in both D1 and D2 trees, but leaf area and shoot length were reduced in D1 only. Total soluble solids increased in both D1 and D2 fruit. Fructose, sorbitol, and total soluble sugar concentrations were higher in D1 fruit than in C and D2. Titratable acidity and K + levels were higher in D1 fruit than C and D2. For D1, lowering of fruit water potential (Ψ w ) was accompanied by a decrease in osmotic potential ( Ψ s ), and therefore turgor potential ( Ψ p ) was maintained throughout the sampling period. Regardless of fruit turgor maintenance, the weight of D1 fruit was reduced from 135 DAFB. Weight, sugar concentration, and water relations of D2 fruit were not affected by deficit irrigation. This indicates that fruit water relations and sugar concentration are modified if water deficit is imposed from early in the season. However, if water deficit is imposed later in the season it has less impact on the composition and water relations of the fruit.

Penetrometer Measurement of Apple and Kiwifruit Firmness: Operator and Instrument Differences

Abstract: Additional index words. Instron, puncture, twist test, Malus domestica, Actinidia deliciosa Abstract. Flesh firmness is a characteristic used to indicate fruit quality. Experimental design and data analysis are important when comparing devices that measure fruit firmness. We compared the Effegi penetrometer operated by hand, mounted in a drill press and then operated by hand, and mounted on a motorized drive and operated remotely; the hand- operated EPT pressure tester; the Instron with an Effegi probe; and a hand-operated prototype of the twist tester. Devices varied in operator differences and precision. Comparisons between devices were at the within-fruit level of variability and, therefore, more precise than comparisons where different device-operators used different fruit. We demonstrate statistical methods that are appropriate for making the comparisons of interest and discuss the possible cause of differences between operators and between devices. We also discuss how the mechanical properties of the devices may affect results and consider implications for their practical use. In this study, we found the precision of discrimination between soft and hard apples was best using the Instron in 1992, while the Instron and hand-held Effegi penetrometer were comparable in 1991. For kiwifruit, the hand-held Effegi penetrometer consistently gave the most precise measurements of softening in 1991, while the twist test was the most precise in 1992. Fruit quality assessments usually involve measuring flesh firm- ness using a penetrometer. Generally, a probe, with either a flat or convex tip, is driven into the flesh, and the maximum force is recorded. Early hand-held penetrometers were developed by Magness and Taylor (1925), and from these devices, a range of devices have been developed by different companies (reviewed by Bourne, 1982). A number of studies have examined the mechanics of puncture testing (Voisey, 1977, and references therein) and recommendations on using penetrometers include those of Blanpied et al. (1978), Smith (1985), and Watkins and Harman (1981). The wide use of firmness measurements has led to the periodic development of new devices for measuring firmness (e.g., Studman and Yuwana, 1992). Any adequate evaluation of their performance relative to existing equipment must consider operator differences, precision, and ability to detect texture change, as well as differ- ences in measurement of absolute firmness. Effective experimen- tal design is critical for comparing devices and comparing different ways of using the devices. Previous studies have compared different types of penetrom- eters (e.g., Abbott et al., 1976; Bongers, 1992) and investigated how experimental design (replicate number and sample size) affects detection of firmness differences (Saltveit, 1978; Worthington and Yeatman, 1968). In our study, we used a bal- anced, incomplete blocks (paired comparison) experimental de- sign together with modern statistical analysis approaches to compare different methods of measuring firmness. For relatively modest effort, our approach has provided information on differences associated with different operators and different methods and information on precision with which methods discriminate be- tween soft and hard fruit. The usefulness of the design was evaluated by assessing the factor by which the number of measure- ments would need to be increased to achieve similar precision with a less controlled design. Further design gains are possible. With large fruit, such as apples, as many as eight measurements per fruit may be possible without interference between results (Abbott et al., 1976). These multiple measurements would allow one pair of measurements for each of four device-operator combinations on each fruit. Biases that affect a particular device can, in principle, be corrected by a suitable calibration. Inherent lack of precision can be cured only by redesign of the device.

Hexanal Vapor Is a Natural, Metabolizable Fungicide: Inhibition of Fungal Activity and Enhancement of Aroma Biosynthesis in Apple Slices

Abstract: Hexanal vapor inhibited hyphae growth of Penicillium expansum and Botrytis cinerea on potato dextrose agar (PDA) and on apple (Malus domestica Borkh.) slices. After 48 hours exposure to 4.1 μmol·L -1 (100 ppm) hexanal, the hyphae growth of both fungi was about 50% that of untreated controls. At a concentration of 10.3 μmol·L -1 (250 ppm), neither fungus grew during the treatment period, however, some growth of both fungi occurred 120 hours after treatment. At concentrations of hexanal vapor of 18.6 μmol·L -1 (450 ppm) or more, the growth of both fungi ceased and the organisms were apparently killed, neither showing regrowth when moved to air. When fungi were allowed to germinate and grow for 48 hours in hexanal-free air, a subsequent 48-hour exposure to 10.3 μmol·L -1 hexanal slowed colony growth relative to controls for several days and a 48-hour exposure to 18.6 μmol·L -1 stopped growth completely. Concentrations of hexanal that inhibited fungal growth on PDA also retarded decay lesion development on 'Golden Delicious' and on 'Jonagold' apple slices. Hexanal was actively converted to aroma volatiles in 'Jonagold' and 'Golden Delicious' apple slices, with hexanol and hexylacetate production strongly enhanced after 20 to 30 hours treatment. A small amount of butylhexanoate and hexylhexanoate production was also noted. Within 16 hours after treatment, no hexanal could be detected emanating from treated fruit. Since hexanal was metabolized to aroma-related volatiles by the fruit slices, the possibility of hexanal being an essentially residue-less antifungal agent seems likely. The possibility of developing a system for treating apple slices with hexanal in modified-atmosphere packages was also examined. The permeability of low-density polyethylene (LDPE) film to hexanal and hexylacetate was, respectively, about 500- and 1000-fold higher than LDPE permeability to O 2 . The permeability of both compounds increased exponentially with temperature, with hexanal permeability increased 6-fold while hexylacetate increased only 2.5-fold between 0 and 30 °C.

A Comparison of Four Processing Tomato Production Systems Differing in Cover Crop and Chemical Inputs

Abstract: Four tomato production systems were compared at Columbus and Fremont, Ohio: 1) a conventional system; 2) an integrated system [a fall-planted cover-crop mixture of hairy vetch (Vicia villosa Roth.), rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and barley (Hordeum vulgare L.) killed before tomato planting and left as mulch, and reduced chemical inputs]; 3) an organic system (with cover-crop mixture and no synthetic chemical inputs); and (4) a noinput system (with cover-crop mixture and no additional management or inputs). Nitrogen in the cover-crop mixture above-ground biomass was 220 kg·ha–1 in Columbus and 360 kg·ha in Fremont. Mulch systems (with cover-crop mixture on the bed surface) had higher soil moisture levels and reduced soil maximum temperatures relative to the conventional system. Overall, the cover-crop mulch suppressed weeds as well as herbicide plots, and no additional weed control was needed during the season. There were no differences in the frequency of scouted insect pests or diseases among the treatments. The number of tomato fruit and flower clusters for the conventional system was higher early in the season. In Fremont, the plants in the conventional system had accumulated more dry matter 5 weeks after transplanting. Yield of red fruit was similar for all systems at Columbus, but the conventional system yielded higher than the other three systems in Fremont. In Columbus, there were no differences in economic return above variable costs among systems. In Fremont, the conventional systems had the highest return above variable costs. Ecological problems associated with conventional agricultural practices include soil erosion, contamination of water and soil resources with pesticides and nitrates, and an overdependence on fossil fuel (National Research Council, 1989). Thus, there is interest in developing agricultural systems that rely less on fossilfuel based inputs and more on biological processes to achieve similar productivity. Winter annual cover crops can enhance biological processes and potentially reduce fossil-fuel based inputs. They are seeded in late summer or early fall, overwinter, and then resume rapid growth in the spring. Winter annual cover crops can be an important source of biologically fixed nitrogen (Hoyt and Hargrove, 1986), help control soil erosion (Flach, 1990), improve soil physical properties (McVay et al., 1989), reduce nitrate leaching losses (Stivers and Shennan, 1989), add organic matter to the soil (Blevins et al., 1977), influence pest life cycles (Phatak et al., 1990), and suppress weeds (Teasdale, 1993). One method of managing winter cover crops in the spring is to kill them and leave their residue as a surface mulch. The subseOC. HORT. SCI. 121(3):559–568. 1996. or publication 12 July 1995. Accepted for publication 19 Jan. 1996. icle no. 185-95, Ohio Agricultural Research and Development Center, Univ. This paper is a portion of a thesis submitted by Nancy Creamer ulfillment of PhD requirements at Ohio State Univ. This research was in part by grants from the USDA Sustainable Agriculture Research and Program, the Mid-America Food Processors Association, and Virginia We extend our appreciation to Mac Riedel and Debbie Hamner, who th disease assessment, and to Barry Plassman, Randall Wood, and the Univ. Agricultural Engineering Dept. for contributing to the design and n of the undercutter. Mention of a trademark, proprietary product, or s not constitute a product guarantee or warranty by Ohio State Univ. and ply its approval to the exclusion of other products or vendors. The cost ng this paper was defrayed in part by the payment of page charges. Under lations, this paper therefore must be hereby marked advertisement solely

Endopolygalacturonase and the Melting Flesh (M) Locus in Peach

Abstract: Southern analysis of two ripening-related polygalacturonase (PG) genes of peach ( Prunus persica (L.) Batsch) detected a restriction fragment length polymorphism (RFLP) in one that had been previously identified as encoding the endoPG enzyme of melting flesh fruit. This RFLP distinguished the melting flesh cultivars Flavorcrest and Flordaking from the nonmelting flesh cultivars Carolyn, Early Gold Queen, Fla. 86-28C, and Fla. 9-26C. Complete deletion of endoPG-related genomic sequences was demonstrated in the nonmelting flesh variety Fla. 9-20C. In a blind trial, segregation of the endoPG RFLP was followed in relation to the melting flesh trait in a population of 20 trees from 'Fla. 86-28C' x 'Springcrest' in which the trait was segregating 1:1. Cosegregation of the RFLP with the trait occurred for 17 out of 20 trees. Practical aspects of scoring the melting flesh trait in a genetically variable population may account for incomplete segregation. EndoPG protein was detected by western blotting in fruit of the melting flesh cultivars Flavorcrest and Fragar, but not in fruit of the nonmelting flesh cultivar Carolyn. Results from this study and earlier work are used to discuss the hypothesis that the endoPG gene corresponds to the melting flesh (M) locus of peach.

Changes in Color and Chlorophyll Fluorescence of Broccoli Florets following Hot Water Treatment

Abstract: Hot water treatments (HWTs), at a range of temperatures (43 to 55C) and durations (10 sec to 30 min), were applied to floret groups of 'Shogun' broccoli ( Brassica oleracea L. var italica) directly after harvest. Floret groups were then stored at 20C in the dark for 3 days. A range of optimal treatments was found in which yellowing was markedly reduced, and heat damage (water soaking and decay) did not occur. Chlorophyll fluorescence measurements indicated that in the optimum treatment that prevented yellowing the F v /F m ratio following HWT decreased immediately and was maintained at a constant level for the next 3 days. A further experiment examined the effect of HWT durations up to 20 min at 47C on fluorescence and yellowing. Longer durations of HWTs (>5 min) progressively reduced yellowing and the F v /F m ratio. From these three experiments a HWT of 47C for 7.5 min was selected as the best treatment. This treatment consistently reduced yellowing for up to 5 days. A decrease in the F v /F m ratio may be a useful indicator of broccoli florets response to hot water treatments. The shelf life and market potential of cut broccoli heads is limited by rapid yellowing of the florets (King and Morris, 1994; Rushing, 1990; Tian et al., 1994). Postharvest heat treatments are known to delay chlorophyll loss in green tissue (Klein and Lurie, 1991; Paull, 1990). One recent study showed that broccoli (cv. Dominator) treated at 45C for 14 min retained 81% of its chlorophyll for 5 days postharvest (Kazami et al., 1991a). Previous work with New Zealand broccoli showed that cultivars such as Shogun, Green Beauty, and Green Belt differ in their postharvest behavior, particularly in respi- ration rate, ethylene production, and yellowing rate (King and Morris, 1994; Tian et al., 1995). Measurement of chlorophyll fluorescence provides a nondestruc- tive assessment of loss of chloroplast function, and has been used as an indicator of stress response and senescence in a range of harvested plant tissues and organs (Krause and Weis, 1984; Smillie et al., 1987). Toivonen (1992) showed that a decrease in variable fluorescence (F v ) in broccoli florets is highly correlated with a reduction in respiration rate and ascorbic acid content during 4 to 24 days of storage at 1C, suggesting that fluorescence may be a reliable indicator of broccoli senescence at low temperature. In the present work, we studied the effects of HWTs on yellowing of 'Shogun' broccoli florets. We used an extensive range of HWTs to define the optimum heat treatments for reducing broccoli yellow- ing. We followed this with studies of the relationship between color maintenance and fluorescence measurement.

Controlled-atmosphere Suppression of ACC Synthase and ACC Oxidase in 'Golden Delicious' Apples during Long-term Cold Storage

Abstract: Additional index words. reduced O 2 , elevated CO 2 , ethylene biosynthesis, CA Abstract. Preclimacteric 'Golden Delicious' apples ( Malus domestica Borkh.) were stored at 0 °C in: air; air + 5% CO 2 ; 2% O 2 + 98% N 2 ; or 2% O 2 + 5% CO 2 + 93% N 2 , and sampled monthly for 4 months to investigate the mechanism(s) by which reduced O 2 and/or elevated CO 2 atmospheres inhibit C 2 H 4 biosynthesis. Ethylene biosynthesis rates and in vitro ACS activity were closely correlated in all treatments, while in vitro ACO activity significantly increased over time regardless of the treatment. Only a small amount of C 2 H 4 biosynthesis inhibition by lowered O 2 and/or elevated CO 2 atmospheres could be accounted for by suppressed induction of ACO activity. Western blot analysis demonstrated that apples held for 2 months in lowered O 2 and/or elevated CO 2 atmospheres had significantly reduced abundance of ACO protein, compared to fruit held in air. Northern blot analysis of ACS and ACO transcript abundance revealed that reduced O 2 and/or elevated CO 2 atmospheres delay induction and reduce the abundance of both transcripts. Reduced O 2 and/or elevated CO 2 atmospheres reduce C 2 H 4 biosynthesis by delaying and suppressing expression of ACS at the transcriptional level and by reducing the abundance of active ACO protein. Chemical names used: 1-aminocyclopropane-1-carboxylic acid (ACC), ACC synthase (ACS), ACC oxidase (ACO), ethylene (C 2 H 4 ), S-adenosylmethionine (AdoMet). direct (i.e ., reduction in enzyme specific activity) and indirect (i.e ., blocking System II upregulation of C 2 H 4 biosynthesis).

Modeling the peach sugar contents in relation to fruit growth

Abstract: The edible quality of peaches (Prunus persica L. Batsch) to a great extent depends on their sweetness, which is related to sugar composition. Our objective was to develop a model to predict carbon partitioning within fruit flesh and to predict the sucrose, sorbitol, glucose, and fructose contents. The model is dynamic and deterministic and was designed to be driven by the flesh dry-weight growth curve, flesh water content, and temperature data. It uses differential equations where the state of the system is defined by variables that describe how much carbon is present as each form of sugar and as other compounds (acids and structural carbohydrates). The rates of change of these amounts of carbon depend on the current values of corresponding variables and on the transfer functions between them. These functions are defined by rate constants or by functions of degree-days after full bloom. The model was calibrated and tested using data sets from treatments that covered several leaf : fruit ratios. The predictions of the model were in fairly good agreement with experimental data. A sensitivity analysis was performed to identify the most influential transfer function parameters. Carbon flows between sugar forms were analyzed. Sucrose, which was the most abundant sugar, and fructose, which is the sweetest, contributed most to fruit sweetness. Simulations were performed to study the effects of changes in fruit growth-curve parameters on sugar contents and concentrations.

Genetic Diversity in Peach (Prunus persica L. Batch) Revealed by Randomly Amplified Polymorphic DNA (RAPD) Markers and Compared to Inbreeding Coefficients

Abstract: Previous studies of peach germplasm using pedigree information and isozyme polymorphism data have shown limited diversity in the U.S. gene pool. To further investigate the genetic diversity among peach cultivars grown in different regions of the United States, 94 RAPD markers were used to estimate the genetic distances among 136 cultivars. Of the 12 clusters formed in a dendrogram, the 90 U.S. cultivars and breeding lines and most of those from Europe and Latin America grouped to only three clusters, while the 23 peach entries from India, Pakistan, Russia, Okinawa, and China, as well as the almond cultivar used as an outgroup, were distributed among the other nine clusters. Therefore, the genetic diversity within temperate U.S. peach germplasm is quite limited, and to expand the variability, additional germplasm should be obtained, especially from Asia. Comparison of genetic similarity based on inbreeding coefficients with similarity coefficients based on the RAPD data produced a correlation of 0.395, which is comparable to values in similar investigations in other crops. Thus, similar conclusions can be drawn from these two sources of information. RAPD data are useful particularly when pedigree information is incomplete, there has been substantial selection within breeding populations, and a high proportion of alleles are identical in state but not by descent.

Root Restriction and Potassium and Calcium Solution Concentrations Affect Dry-matter Production, Cation Uptake, and Blossom-end Rot in Greenhouse Tomato

Abstract: Root restriction has been reported to reduce fruit yield, the incidence of blossom end rot (BER) and K concentration in tomato (Lycopersicon esculentum L. 'F121') plant organs. The objectives of the present work were to study the effect of root restriction, and combination of K and Ca solution concentrations, on greenhouse tomato fruit yield, quality and cation uptake. Root restriction reduced total yield but improved fruit quality by increasing the dry matter concentration and reducing the incidence of BER. Increasing the K concentration from 5.0 to 10 mmol·L-1 reduced the marketable yield, due to increased incidence of BER. Root restriction decreased K concentration and K/Ca ratio in tomato plant organs, but had no effect on K uptake rate per unit root fresh weight. Increasing K concentration from 2.5 to 10 mmol·L -1 increased the K concentration in plant organs and K uptake rate, but reduced that of Ca. In contrast, increasing Ca concentration in the solution had no effect on K concentration in plant organs and K uptake rate. The incidence of BER correlated well with K/Ca concentration ratio in the leaves, whereas a poor correlation was obtained with K/Ca concentration ratio in ripe fruit. solution (the lowest K and Ca concentrations) was (mmol·L -1 ): 2.5 KNO 3 , 1.5 NH 4 NO 3 , 0.7 H 3 PO 4 , 0.5 MgSO 4 ; to the higher K treatments 2.5 or 7.5 mmol·L -1 KCl was added; the high-Ca treatment was obtained by adding 2 mmol·L -1 CaCl 2 . Micronutri- ents were applied with synthetic chelate ( μmol·L -1 ): Fe, 27.9 as Fe- EDDHA; and Mn, 10.5; Zn, 4.4; Mo, 0.3; and Cu, 0.7 as EDTA. The solution also contained 40 μmol·L -1 H 3 BO 4 . The solutions were made up using tap water containing (mmol·L -1 ): Na, 3-4; Ca, 1.5; Mg, 0.5; Cl, 4-5; NO 3 , 0.1-0.2; SO 4 , 0.5-1.0. The initial pH of the solution was about 6.5. The pH was monitored daily and when it increased above 7.0 sulfuric acid was added to reduce it to 6.5. The electrical conductivity (EC) was in the range of 1.7-2.3 mS·cm -1 (the addition of sulfuric acid for pH adjustment did not change EC significantly). The solution was renewed every 2 weeks and the concentrations of K and Ca in the solution were determined before and after replacement. In that period of time C Ca decreased to minimum values of 1 and 2.5 mmol·L -1 , in the low- and high-Ca treatments, respectively, while C K decreased to minimum values of 1.0, 3.0, and 7.5 mmol·L -1 , for the 2.5, 5.0, and 10.0 mmol·L -1 treatments, respectively. Nutrient uptake was determined from the change in the solution volume and concentration. The experiment was arranged in five randomized blocks, each replicate contained twelve plants per plot which were transplanted

Producing transgenic 'Thompson Seedless' grape (Vitis vinifera L.) plants. [Erratum: Sept 1996, v. 121 (5), p. 980.]

Abstract: Transgenic grape plants were regenerated from somatic embryos derived from leaves of in vitro-grown plants of 'Thompson Seedless' grape ( Vitis vinifera L.) plants. Somatic embryos were either exposed directly to engineered Agrobacterium tumefaciens or they were bombarded twice with 1-μm gold particles and then exposed to A. tumefaciens. Somatic embryos were transformed with either the lytic peptide Shiva-1 gene or the tomato ringspot virus (TomRSV) coat protein (CP) gene. After cocultivation, secondary embryos proliferated on Emershad/Ramming proliferation (ERP) medium for 6 weeks before selection on ERP medium containing 40 μg·mL -1 kanamycin (kan). Transgenic embryos were identified after 3 to 5 months under selection and allowed to germinate and develop into rooted plants on woody plant medium containing 1 μM 6-benzylaminopurine, 1.5% sucrose, 0.3% activated charcoal, and 0.75% agar. Integration of the foreign genes into these grapevines was verified by growth in the presence of kanamycin (kan), positive β- glucuronidase (GUS) and polymerase chain-reaction (PCR) assays, and Southern analysis.

Micronutrient Toxicity in Seed Geranium (Pelargonium × hortorum Bailey)

Abstract: Seed geranium (Pelargonium × hortorum) micronutrient toxicity symptoms were induced by applying elevated levels of B, Cu, Fe, Mn, Mo, and Zn in fertilizer solution. Beginning at the 3-4 true leaf stage, seedling plants established in 11-cm (0.67-liter) pots containing peat-lite growing medium were fertilized at each irrigation for 5 weeks with solutions containing 0.25, 0.5, 1, 2, 3, 4, 5, and 6 m M plus the standard concentration of each micronutrient. The standard solution contained 20 µM B, 0.5 µM Cu, 10 µM Fe, 10 µM Mn, 0.5 µM Mo, and 4 µM Zn. All treatment solutions contained a fixed level of macronutrients. Visible foliar toxicity symptoms were produced when the nutrient solution contained 0.5 m M B, 0.5 mM Cu, 5 mM Fe, 1 mM Mn, 0.25 mM Mo, or 0.5 mM Zn. Reduction in dry matter yield was evident when 1 mM B, 2 mM Cu, 3 mM Fe, 2 mM Mn, 0.5 mM Mo, or 1 mM Zn was used in the fertilizer solution. Leaf chlorophyll contents decreased as Cu and Mn levels in the concentration range tested increased. Elevated levels of Fe increased tissue chlorophyll contents. The relationship between the nutrient solution and tissue concentrations of each of the six micronutrients was determined. A soil medium high in nutrient holding capacity does not usually require additional supply of micronutrient s when used for short-term crops such as bedding plants. Micronutrient fertiliza- tion, however, is essential for bedding plants grown in the soil-less root media , which are now extensively used in greenhouse crop production. Growers formulate micronutrients based on the Hoagland solution (Hoagland and Arnon, 1950), or use commer- cial fertilizers containing both macro- and micronutrients. Since plants require only minute quantities of these elements, a nutrient imbalance may occur when commercial fertilizers are used with water containing high levels of some micronutrients. Micronutri- ent deficiencies and toxicities have been reported for boron in chrysanthemum (Gogue and Sanderson, 1973), Easter lily (Marousky, 1981) and begonia (Elliot and Nelson, 1981; Nelson et al., 1979), for molybdenum in poinsettia (Hammer and Bailey, 1987), for manganese in Spathiphyllum (Broschat and Donselman, 1986), and for iron in Tolmiea (Smith, 1985). Such investigations are largely lacking in bedding plants. The objective of this study was to induce and characterize micronutrient toxicity symptoms of seed geraniums grown in a peat-lite mix.

Producing Transgenic `Thompson Seedless' Grape (Vitis vinifera L.) Plants

Abstract: Transgenic grape plants were regenerated from somatic embryos derived from leaves of in vitro-grown plants of 'Thompson Seedless' grape ( Vitis vinifera L.) plants. Somatic embryos were either exposed directly to engineered Agrobacterium tumefaciens or they were bombarded twice with 1-μm gold particles and then exposed to A. tumefaciens. Somatic embryos were transformed with either the lytic peptide Shiva-1 gene or the tomato ringspot virus (TomRSV) coat protein (CP) gene. After cocultivation, secondary embryos proliferated on Emershad/Ramming proliferation (ERP) medium for 6 weeks before selection on ERP medium containing 40 μg·mL -1 kanamycin (kan). Transgenic embryos were identified after 3 to 5 months under selection and allowed to germinate and develop into rooted plants on woody plant medium containing 1 μM 6-benzylaminopurine, 1.5% sucrose, 0.3% activated charcoal, and 0.75% agar. Integration of the foreign genes into these grapevines was verified by growth in the presence of kanamycin (kan), positive β- glucuronidase (GUS) and polymerase chain-reaction (PCR) assays, and Southern analysis.

Prestorage Heat Treatments Influence Free Sterols and Flavor Volatiles of Tomatoes Stored at Chilling Temperature

Abstract: The objective of this study was to determine the effects of prestorage heat treatments on chilling tolerance of tomatoes. Mature-green 'Agriset' tomato fruit ( Lycopersicon esculentum Mill.), either C 2 H 4 -treated or not, were immersed in 42C water for 60 min, held in 38C air for 48 hours, or not treated, and then stored at either 2C (chilled) or 13C (nonchilled) for 14 days before ripening at 20C. Heat-treated fruit stored at 2C and transferred to 20C ripened normally while nonheated fruit decayed before reaching red ripe. Color (a*/b* ratio), lycopene content, and internal quality characteristics of fruit were similar at the red-ripe stage irrespective of method of heat treatment. In red-ripe heat- treated fruit, free sterol levels were significantly higher in chilled fruit than in nonchilled fruit. Heating fruit in 38C air resulted in significantly higher levels of some free sterols compared with heating fruit in 42C water. Of the 15 flavor volatiles analyzed, six showed significantly decreased concentrations as a result of C 2 H 4 -treatment and seven showed decreased concentrations when stored at 2C before ripening. Some volatiles were decreased by the heat treatments. Prestorage short- and long-term heat treatments could allow for storage of mature-green tomatoes at lower temperatures with little loss of their ability to ripen normally.

Optimum O2 or CO2 Atmosphere for Storing Broccoli Florets at Various Temperatures

Abstract: Marathon' broccoli (Brassica oleracea L. var. italica) florets were stored in air, low O 2 (0.25%, 0.5%, and 1 %) or high CO2 (3%,6%, and 10%) at 0, 5, and 10C. Oxygen consumption and CO2 production were reduced under low O2 or high CO2 atmosphere, the reduction being greater at lower O 2 and higher CO2 levels. NO differences were found in ethylene production among the different atmospheres. Low O 2 and high CO2 retained color of broccoli florets to about the same extent at 10C but had no effect at 0 and 5C. Development of soft rot and browning was suppressed by low O 2 or high CO2, but offensive off-odor occurred in 0.25%02 at all temperatures and 0.5% O 2 at 10C. These results indicate that the best O2 and CO2 levels seem to be 0.5% O2 and 10% CO2 at 0 and 5C, and 1% O2 and 10% CO2 at 10C.

ß-Galactosidase II Activity in Relation to Changes in Cell Wall Galactosyl Composition during Tomato Ripening

Abstract: Activity of s-galactosidase II (EC 3.2.1.23), which can hydrolyze s-galactan from tomato cell walls, increased markedly during ripening of 'Roma' and 'Rutgers' tomatoes (Lycopersicon esculentum Mill.). Activity of two other s- galactosidase isozymes, incapable of galactan hydrolysis, was present in green fruit and remained unchanged throughout ripening. s-Galactosidase II activity was not detectable in green fruit of either cultivar, appearing first at the breaker stage of 'Roma' fruit and not until the pink stage of 'Rutgers' fruit. Consistent with this, galactose loss from Na 2CO3-soluble pectin (NSP) was detectable at an earlier stage in 'Roma' vs. 'Rutgers' fruit. A greater decline in NSP galactose was evident in 'Roma' fruit compared to 'Rutgers' fruit, in keeping with the higher levels and longer period of s-galactosidase II expression in the former. Significant galactose loss from trans -1,2-diaminocyclohexane- N,N,N',N' -tetraacetic acid- soluble pectin, in contrast, was not seen until the last stage of ripening. These results indicate that the long-reported, net galactosyl loss from the cell walls of ripening tomatoes correlates with s-galactosidase II activity. Nonetheless, the observation that softening commenced before s-galactosidase II activity or galactose loss was detectable suggests some other basis for the earliest stages of ripening-related fruit softening in tomato.

RAPD Markers Flanking the Are Gene for Anthracnose Resistance in Common Bean

Abstract: Incorporation of the dominant gene Are, of Middle American origin, into commercial cultivars of Phaseolus vulgaris L., has been the main disease control strategy of plant breeders to limit the potential damage of Colletotrichum lindemuthianum (Sacc. & Magnus.) Lams.-Scrib. A random amplified polymorphic DNA (RAPD) marker designated OQ41440, generated by a 5'-AGTGCGCTGA-3' decamer primer, was found tightly linked in coupling with the Are gene. OQ41440 mapped at 2.0 ± 1.4 centimorgans (cM) from the Are allele in the Andean genetic background and at 5.5 ± 2.3 CM in the Middle American background. A second coupling phase RAPD marker B3551000, generated by the 5'-GTATGGGGCT 3' primer mapped at 5.4 ± 2.3 cM from the Are allele in the Andean genetic background and at 7.7 ± 2.7 CM in the Middle American background. Based on a recombination distance of 7.0 ± 1.9 cM between the two markers, OQ4 1440 and B3551000 RAPDs appear to flank the Are gene. The bracketing molecular markers allowed tagging of the Are allele with a selection fidelity of 99%. Use of the OQ41440 and B3551000RAPD markers for marker-based selection will afford the opportunity to retain the Are anthracnose resistance gene in bean germplasm, as other epistatic resistance genes are characterized, and incorporated into contemporary bean cultivars. Anthracnose, caused by Colletotrichum lindemuthianum, is a serious seedborne fungus capable of inducing complete yield loss in susceptible bean genotypes. Surveys in a wide range of produc- tion areas have identified several distinct races, suggesting exten- sive pathogenic variation on all continents (Pastor-Corrales and Tu, 1989). In North America, reported races include alpha, alpha Brazil, beta, gamma, delta, epsilon, and lambda in Canada (Tu, 1992, 1994). Recently, Kelly et al. ( 1994) identified two new races of C. lindemuthianu m in the United States, which are pathogenic on resistance genes currently deployed. The dominant allele at the Are locus, which confers resistance to alpha, beta, gamma, delta, epsilon, and lambda races of the fungus, was first found in a black bean from Venezuela, Cornell 49-242 (Mastenbroek, 1960) and has been used widely in North America and Europe as the main source of resistance against anthracnose (Fouilloux, 1979; Tu,

Air-filled Porosity, Gas Relative Diffusivity, and Tortuosity: Indices of Prunus ×cistena sp. Growth in Peat Substrates

Abstract: A 2-year experiment with Prunus ×cistena sp. was conducted in pots using seven substrates composed of various proportions of primarily peat, compost and bark. Peat substrates significantly affected root and shoot dry weight. Water desorption characteristics and saturated hydraulic conductivity were measured in situ to estimate the pore tortuosity factor and the relative gas diffusion coefficient. The pH, electrical conductivity, C/N ratio, total and hydrolyzable N, as well as NO 3 - -N and NH 4 + -N in solution were also measured. Estimates of the physical properties suggest that a lack of aeration limited plant growth. Plant growth was significantly correlated with both the gas relative diffusivity and the pore tortuosity factor. Among the chemical factors, pH and soil nitrate level were also correlated with plant growth. No significant correlation was found between plant growth and air-filled porosity or any other measured chemical properties. This study indicates that an index of gas-exchange dynamics could be a useful complementary diagnostic tool to guide substrate manufacturing.

Nitrogen Nutrition of New Guinea Impatiens `Barbados' and Spathiphyllum `Petite' in a Subirrigation System

Abstract: Greenhouse cultural methods must minimize runoff to keep pace with environmental regulation aimed a protecting water resources. Two experiments were designed to investigate the effect of N fertilization rate on New Guin impatiens (Impatiens ×hawkeri) and peace lily (Spathiphyllum Schott) in an ebb-and-flow subirrigation system. Maximum growth response for impatiens was centered around 8 m M N levels as measured by root and shoot fresh and dry weigh height, leaf number, leaf area, and chlorophyll concentration. For peace lily, growth peaked at about 10 m M N. Growing medium was divided into three equal layers: top, middle, and bottom. Root distribution favored the middle and bottom layers, and the relative distribution of roots was consistent as N level increased. EC remained low in middle and botto layers at N concentrations below 10 mM, but increased significantly for all layers at levels above 10 m M. The EC for the top layer was 2 to 5 times higher than in the middle or bottom layers at all N levels. Increased nitrate concentratio paralleled increased EC, while pH decreased as N concentration increased for impatiens and peace lily. c. lless nc., ix 059 r pH ted ater n a 609

Factors Influencing Ethylene-induced Isocoumarin Formation and Increased Respiration in Carrots

Abstract: Ethylene-induced formation of isocoumarin was characterized in relation to ethylene-enhanced respiration in whole or cut carrots (Daucus carota L.). Ethylene concentrations (0.1 to 5 ppm) and temperatures (1 to 15C) that increased respiration also favored a more rapid formation of isocoumarin (8-hydroxy-3-methyl-6-methoxy-3,4-dihydro-isocoumarin). Exposing mature carrots to 0.5 ppm C 2 H 4 for 14 days at 1 or 5C resulted in isocoumarin contents of 20 and 40 mg/100 g peel, respectively. These levels were easily detected as a bitter flavor in the intact carrot roots. Immature carrots formed higher levels of isocoumarin than mature carrots; 180 mg/100 g peel were detected in young carrots stored 14 days at 5C in air containing 0.5 ppm C 2 H 4 . Freshly harvested carrots exposed to 5 ppm C 2 H 4 accumulated 4-fold higher isocoumarin levels than those formed by carrots stored 30 days at 5C before exposure to C 2 H 4 . An atmosphere of 100% O 2 potentiated the effect of C 2 H 4 on isocoumarin formation, resulting in a 5-fold increase over that found in carrots treated with C 2 H 4 in air. A storage atmosphere of 0.5 ppm C 2 H 4 in 1% O 2 resulted in isocoumarin levels about one-half those attained in 0.5 ppm C 2 H 4 in air. Sliced, cut, or dropped carrots exposed to C 2 H 4 showed greater isocoumarin accumulation rates than intact uninjured carrots. Peeled baby carrots, however, had little capacity to form isocoumarin. In general, the more rapid the respiratory rise in response to C 2 H 4 , the more rapidly isocoumarin accumulated. The greater the respiratory response to ethylene, the higher the level of isocoumarin formed.

Effects of Matric and Osmotic Priming Treatments on Broccoli Seed Germination

Abstract: Priming, a controlled-hydration treatment followed by redrying, improves the germination and emergence of seeds from many species We compared osmotic and matric priming to determine which was the most effective treatment for improving broccoli seed germination and to gain a greater understanding of how seed vigor is enhanced by priming Broccoli (Brassica oleracea L var italica) seeds were osmotically primed in polyethylene glycol (PEG 8000) at -11 MPa or matrically primed in a ratio of 10 g seed:08 g synthetic calcium silicate (Micro-Cel E):18 ml water at -12 MPa In the laboratory, germination rates and root lengths were recorded from 5 to 42C and 10 to 35C, respectively Broccoli seeds germinated poorly at >35C Root growth after germination was more sensitive to temperatures >30C and 35% The greater germination performance of matrically primed seeds was most likely the result of increased oxygen availability during priming, increased seed Ca content, or improved membrane integrity