Showing papers in "Hortscience in 2010"

Blue Light-emitting Diode Light Irradiation of Seedlings Improves Seedling Quality and Growth after Transplanting in Red Leaf Lettuce

Abstract: In this study, we determined the effects of raising seedlings with different light spectra such as with blue, red, and blue + red light-emitting diode (LED) lights on seedling quality and yield of red leaf lettuce plants. The light treatments we used were applied for a period of 1 week and consisted of 100 μmol·m -2 ·s -1 of blue light, simultaneous irradiation with 50 μmol·m -2 ·s 1 of blue light and 50 μmol·m -2 ·s -1 of red light, and 100 μmol·m -2 ·s -1 of red light. At the end of the light treatment, that is 17 days after sowing (DAS), the leaf area and shoot fresh weight (FW) of the lettuce seedlings treated with red light increased by 33% and 25%, respectively, and the dry weight of the shoots and roots of the lettuce seedlings treated with blue-containing LED lights increased by greater than 29% and greater than 83% compared with seedlings grown under a white fluorescent lamp (FL). The shoot/root ratio and specific leaf area of plants irradiated with blue-containing LED lights decreased. At 45 DAS, higher leaf areas and FWs were obtained in lettuce plants treated with blue-containing LED lights. The total chlorophyll (Chl) contents in lettuce plants treated with blue-containing and red lights were less than that of lettuce plants treated with FL, but the Chl a/b ratio and carotenoid content increased under blue-containing LED lights. Polyphenol contents and the total antioxidant status (TAS) were greater in lettuce seedlings treated with blue-containing LED lights than in those treated with FL at 17 DAS. The higher polyphenol contents and TAS in lettuce seedlings at 17 DAS decreased in lettuce plants at 45 DAS. In conclusion, our results indicate that raising seedlings treated with blue light promoted the growth of lettuce plants after transplanting. This is likely because of high shoot and root biomasses, a high content of photosynthetic pigments, and high antioxidant activities in the lettuce seedlings before transplanting. The compact morphology of lettuce seedlings treated with blue LED light would be also useful for transplanting.

Cooling effect of shade trees with different characteristics in a subtropical urban park.

Abstract: The effect of shade trees on the air and surface-soil temperature reduction under the canopy was studied in a park in subtropical Taipei City, Taiwan. Ten species of trees and two species of bamboo, which had tightly clustered tall stems and spreading branches resembling trees in shape, were chosen for the study. In the summer of 2007, we measured leaf and canopy characteristics of each species. The microclimate conditions under the tree canopies and an unshaded open space were measured repeatedly at middays without precipitation. In comparison with the nearby unshaded open space, air temperatures under the canopies were 0.64 to 2.52 °C lower, whereas the surface-soil temperatures were 3.28 to 8.07 °C lower. Regression analysis revealed the relative contributions to air cooling effect by the plant's leaf color lightness, foliage density, leaf thickness, and leaf texture (surface roughness) in decreasing order. Foliage density had the greatest contribution to surface-soil cooling followed by leaf thickness, leaf texture, and leaf color lightness in that order. Regression analysis also revealed that solar radiation, wind velocity, and vapor pressure at the site had significant effects on temperature reduction attributable to shade trees or bamboo.

Enzymatic Browning, Polyphenol Oxidase Activity, and Polyphenols in Four Apple Cultivars: Dynamics during Fruit Development

Abstract: Additional index words. Malus ·sylvestris var. domestica, fruit maturation, polyphenols- polyphenol oxidase complex, chlorogenic acid, catechins, procyanidin B2, low browning apple Abstract. Enzymatic browning is one of the most important reactions that occur in fruits and vegetables, usually resulting in negative effects on color, taste, flavor, and nutritional value. The reaction is a consequence of phenolic compounds' oxidation by polyphenol oxidase (PPO), which triggers the generation of dark pigments. This is particularly relevant for apples, which are rich in polyphenols and highly susceptible to enzymatic browning. The objective of the present work was to quantify enzymatic browning and PPO activity and identify and quantify target polyphenols in apple (Malus ·sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.) pulp in the cultivars (cvs.) Aori27, Elstar, Fuji, and Mellow at three fruit developmental stages (FDS). The enzymatic browning was quantified by tristimulus colorimetry; PPO activity was quantified by an enzyme- substratespectrophotometricassay;phenoliccompoundsweredeterminedandquantified by reverse-phase high-performance liquid chromatography-ultraviolet/visible-mass spectrometry. Enzymatic browning showed significant difference among cvs. and FDSs and interaction between both factors. PPO activity showed significant difference among cultivars and FDSs. A significant difference was evidenced for polyphenol content among cultivars and FDSs with interaction between both factors. Chlorogenic acid was the major phenolic compound in 'Aori27' and 'Mellow'. In 'Fuji', chlorogenic acid and (-)-epicatechin were the major phenolics and in 'Elstar' (-)-epicatechin and procyanidin B2 were the major phenolics at different FDSs. The enzymatic browning showed high correlation to polyphenol content in all cultivars and high correlation was observed between browning and PPO activity in 'Aori27' and 'Elstar'. The magnitude of the correlation between browning and polyphenols and PPO activity is genotype-specific. At the commer- cial harvest, 'Fuji' showed the highest polyphenol content and 'Aori27' showed the low- est level for enzymatic browning. Chemical names used: 3-(3,4-dihydroxycinnamoyl) quinic acid (chlorogenic acid), (-)-cis-3,3#,4#,5,7-pentahydroxyflavane (epicatechin), and cis,cis$-4,8$-Bi(3,3#,4#,5,7-pentahydroxyflavane) (procyanidin B2).

Improving Nitrogen Use Efficiency in Melon by Grafting

Abstract: Identification of rootstocks capable of improving the nitrogen use efficiency (NUE) of the scion could reduce N fertilization and nitrate leaching; however, screening different graft combinations under field conditions can be costly and time-consuming. This study evaluated a rapid and economical methodology for screening of melon rootstocks for NUE. Two experiments were designed. In the first, melon plants (Cucumis melo L. cv. Proteo) either ungrafted or grafted onto four commercial rootstocks: 'Dinero' and 'Jador' (Cucumis melo L.), 'P360', and 'PS1313' (Cucurbita maxima Duchesne x Cucurbita moschata Duchesne) grown in hydroponics were compared in terms of shoot dry biomass, leaf area, root-to-shoot ratio, SPAD index, shoot N uptake, and nitrate reductase (NR) activity at the early developmental stage in response to nitrate availability (0.5, 2.5, 5, 10, or 15 mM of NO 3 - ). The second experiment was aimed to confirm whether the use of a selected rootstock with high NUE ('P360') could improve crop performance and NUE of grafted melon plants under field conditions. In the first experiment, carried out under greenhouse conditions, melon plants grafted onto 'Dinero', 'Jador', and 'P360' rootstocks needed 5.7, 5.2, and 6.1 mM of NO 3 - , respectively, to reach half-maximum shoot dry weight, whereas plants grafted onto 'PS1313' rootstock and the control treatment (ungrafted plants) needed 9.1 and 13.1 mM of NO 3 - , respectively. Total leaf area, SPAD index, and shoot N uptake increased linearly and quadratically in response to an increase of the N concentration in the nutrient solution. At 2.5 m M of NO 3 - ; melon plants grafted onto both C. melo and Cucurbita maxima x Cucurbita moschata rootstocks had the highest NR activity, whereas no significant difference was observed at 10 mM of NO 3 - . In the second experiment, carried out under open field conditions, increasing the N fertilization rates from 0 to 120 kg·ha -1 increased the total and marketable yields of melon plants, whereas the NUE decreased. When averaged over N levels, the marketable yield, NUE, and N uptake efficiency were higher by 9%, 11.8%, and 16.3%, respectively, in 'Proteo' grafted onto 'P360' than in ungrafted 'Proteo' plants.

A career perspective on citrus rootstocks, their development, and commercialization.

Abstract: Professor Hume was right: rootstocks are critical and much is still to be learned. Rootstocks and scions are the foundation of many tree fruit industries of the world. Together, those components establish profitability, but it can be argued that the rootstock is the critical component; otherwise, scions would be grown on their own roots everywhere. There is no precedent for the failure of a citrus industry because of an inadequate scion variety, but serious problems have occurred because of a less than satisfactory rootstock. Therefore, after 35 years in the field conducting rootstock and scion evaluation research and working with our University of Florida citrus plant improvement team, here is an historical perspective on citrus rootstocks along with some observations and reflections on the human or social side of research and grower cooperation. It is well established from decades of experience that citrus rootstocks bring many advantages and profitability to commercial enterprise. In some instances, citrus rootstocks are the sole determining element that allows citrus to be grown in particular circumstances. Yet, despite their popularity and necessity, every rootstock has one or more undesirable traits that preclude its universal use. Those limitations have sometimes been discovered during research and development; at other times, they have not been revealed until after significant commercial use. Until the mid-1800s, citrus was grown primarily as seedlings. Commercial operations were limited in scope and size as compared with today and certainly were not operated with the same level of technical knowledge or experience. It is generally known that two grand disease events were apparently responsible for creating the initial interest in citrus rootstocks and changing the direction of citriculture; first, the damaging effects of Phytophthora foot rot when ownrooted sweet orange trees were common. Many of those trees were actually seedlings with their own inherent disadvantages. The second disease problem was citrus tristeza virus, which devastated trees of sweet orange and other varieties on the highly susceptible sour orange, the most popular rootstock in many parts of the world before the spread of the virus. As these problems spread and were encountered by citrus growers worldwide, budding, i.e., using a rootstock, became the accepted practice. Grafting or budding is actually a centuries old horticultural technique but one not widely practiced in citriculture until the late 1800s or the early 1900s. It was not until the 1940s, however, that the cause of tree decline on sour orange came to be associated with a graft-transmissible entity later shown to be a virus. The ‘‘modern’’ era of citrus rootstock use and subsequent history could be described as beginning in the early part of the 20th century in response to the diseases mentioned (Webber, 1967). Field trials with usually a small number of rootstocks were initiated and eventually followed with ones of larger scale (Batchelor and Rounds, 1948; Gardner et al., 1967; Moreira and Salibe, 1969). Those early trials also revealed the importance of other unknown virus and viroid diseases that affected the rootstocks being evaluated. However, they were conducted under considerable constraints, in retrospect, given the genetic and breeding tools available in 2009. Formal breeding programs have emerged and use new technologies such as somatic hybridization and molecular markers that are altering and expanding the range of possibilities for genetic manipulation leading to improved rootstocks (Kahn, 2007). As a result, there is a new era of citrus rootstock research and development underway that is linked to different ways of thinking about rootstocks and their role in future citrus orchards. It is conceivable that genetic advances might eventually eliminate the need for rootstocks as rootstock traits are incorporated into the scion variety.

Evaluating Quality Attributes of Four Fresh Fig (Ficus carica L.) Cultivars Harvested at Two Maturity Stages

Abstract: The effect of two fruit maturity stages on the quality attributes of four fresh fig cultivars was examined, including consumer acceptance and antioxidant capacity. Fig quality attributes such as weight, soluble solids concentration (SSC), titratable acidity (TA), SSC:TA, firmness, antioxidant capacity, and consumer acceptance varied by cultivar. Fig cultivars harvested at the advanced maturity stage ("tree ripe") had lower TA and firmness but higher weight, SSC, and SSC:TA than figs harvested at "commercial maturity." Fig maturity did not affect antioxidant capacity, but tree ripe figs had higher consumer acceptance than commercial maturity figs. SSC was more highly correlated with consumer acceptance than TA or SSC:TA, but other factors may also be important in controlling this relationship. Cultivars with high SSC and firmness, at a maturity stage high enough to tolerate harvesting and postharvest handling, should be selected to develop the fresh fig industry. Because fig firmness is a concern, changes to packaging should be evaluated to protect the flavor of advanced maturity figs during postharvest handling.

Growth and Physiological Responses of Landscape Plants to Saline Water Irrigation: A Review

Abstract: Water shortages and poor water quality are critical issues in many areas of the world. With rapid increases in population and shortage of water supplies in urban areas, use of alternative water sources such as municipal reclaimed water and other sources of non-potable waters for irrigating landscapes is inevitable. A potential concern is the elevated salt levels in these alternative waters. This article briefly summarizes general information regarding alternative water sources and general responses of landscape plants to salinity stress. Methodology of screening and evaluating salt tolerance of landscape plants are discussed. Recent research results on salt tolerance of landscape plants and their physiological responses to salinity stress are reviewed. Like agricultural crops, a wide range of salt tolerance among landscape plants has been found. In addition to plant species, dominant salt type, substrate, irrigation method and management, and environmental conditions also affect plant responses to salinity stress. A number of mechanisms of salinity tolerance have been observed among landscape species, including restriction of ion uptake, selective ion uptake, and tolerance to high internal concentrations of sodium and/or chloride.

Variation in Formaldehyde Removal Efficiency among Indoor Plant Species

Abstract: The efficiency of volatile formaldehyde removal was assessed in 86 species of plants representing five general classes (ferns, woody foliage plants, herbaceous foliage plants, Korean native plants, and herbs). Phytoremediation potential was assessed by exposing the plants to gaseous formaldehyde (2.0 mLL -1 ) in airtight chambers (1.0 m 3 ) constructed of inert materials and measuring the rate of removal. Osmunda japonica, Selaginella tamariscina, Davallia mariesii, Polypodium formosanum, Psidium guajava, Lavandula spp., Pteris dispar, Pteris multifida, and Pelargonium spp. were the most effective species tested, removing more than 1.87 mgm -3 � cm -2 over 5 h. Ferns had the highest formaldehyde removal efficiency of the classes of plants tested with O. japonica the most effective of the 86 species (i.e., 6.64 mgm -3 � cm -2 leaf area over 5 h). The most effective species in individual classes were: ferns—Osmunda japonica, Selaginella tamariscina, and Davallia mariesii; woody foliage plants—Psidium guajava, Rhapis excels, and Zamia pumila; herbaceous foliage plants—Chlorophytum bichetii, Dieffen- bachia 'Marianne', Tillandsia cyanea, and Anthurium andraeanum; Korean native plants—Nandina domestica; and herbs—Lavandula spp., Pelargonium spp., and Rosmar- inus officinalis. The species were separated into three general groups based on their formaldehyde removal efficiency: excellent (greater than 1.2 mgm -3 formaldehyde per cm 2 of leaf area over 5h), intermediate (1.2 or less to 0.6), and poor(less than 0.6). Species classified as excellent are considered viable phytoremediation candidates for homes and offices where volatile formaldehyde is a concern.

Impact of Kaolin particle film and water deficit on wine grape water use efficiency and plant water relations.

Abstract: Water use efficiency (WUE) and response of grape vines (Vitis vinifera L. cvs. 'Cabernet Sauvignon','Merlot', and 'Viognier') to aparticlefilm treatment (PFT) under varying levels of applied water were evaluated in Victoria, Australia, and southwestern Idaho. Vines that received the least amount of water had the warmest canopy or leaf surface temperature and the lowest (more negative) leaf water potential, stomatal conductance (gS), transpiration (E), and photosynthesis (A). Vines with plus-PFT had cooler leaf and canopy temperature than non-PFT vines; however, temperature difference resulting from irrigation was greater than that resulting from PFT. In well- watered vines, particle film application increased leaf water potential and lowered gS. Point-in-time measurements of WUE (A/E) and gS did not consistently correspond with seasonal estimates of WUE based on carbon isotope discrimination of leaf or shoot tissue. The response of vines with particle film to undergo stomatal closure and increase leaf water potential conserved water and enhanced WUE under non- limiting soil moisture conditions and the magnitude of response differed according to cultivar.

Abscisic Acid Application Enhances Drought Stress Tolerance in Bedding Plants

Abstract: Droughtstress isamajorcauseofpostproduction declineinbeddingplants.The plant hormone abscisic acid (ABA) regulates drought stress responses by mediating stomatal closure, thereby reducing transpirational water loss. Exogenous ABA applica- tions delay wilting and allow plants to survive short periods of severe drought. The effectiveness of the ABA biochemical, s-ABA (ConTego; Valent BioSciences Corp., Libertyville, IL), at delaying wilting and extending shelf life during drought stress was evaluated in six bedding plant species. Spray and drench applications of 0 or 500 mgL -1 s-ABA were applied to Impatiens walleriana (impatiens), Pelargonium ·hortorum (seed geranium), Petunia ·hybrida (petunia), Tagetes patula (marigold), Salvia splendens (salvia), and Viola ·wittrockiana (pansy). Water was subsequently withheld and wilting symptoms were compared between treated and control plants. s-ABA applications delayed wilting in all crops by 1.7 to 4.3 days. Leaf chlorosis was observed after s-ABA application in drought-stressed seed geraniums, marigolds, and pansies. In seed gera- niumsandmarigolds,thedroughtstressitselfresultedinleafchlorosisthatwasequivalent to or more severe than the s-ABA application alone. In pansies, s-ABA applications induced leaf chlorosis that was more severe than the drought treatment. Overall, s-ABA was consistently effective at reducing water loss and extending shelf life for all species treated. Applications of s-ABA to bedding plants before shipping and retailing would allow plants to maintain marketability even under severe drought stress conditions.

Induction of Tetraploidy to Feverfew (Tanacetum parthenium Schulz-Bip.): Morphological, Physiological, Cytological, and Phytochemical Changes

Abstract: An efficient colchicine-mediated chromosome doubling of diploid feverfew followed by the morphophenological, physiological, phytochemical, and cytological changes of the obtained tetraploid plants was conducted. One-week-old seedlings of feverfew were treated with 0.05% (w/v) colchicine for 2, 4, 6, 8, and 24 h. Tetraploid plants were regenerated after 4 months, showing significant changes in stomatal size and density; sizes of seed; flower, pollen, leaf, trichome, cell, nucleus, and parthenolide content; chromosome number; ploidy level; chlorophyll content index; and quantum efficiency of photosystem II. Such characteristics of induced tetraploid feverfews can be useful in medicinal and ornamental applications, e.g., the study of flower morphogenesis, trichome differentiation, and parthenolide biosynthesis. The increase in parthenolide in tetraploidsofthenextgeneration(selfedT0plants)showedthatploidyinductionisagood breeding method for feverfew.

Humic Substances Generally Ineffective in Improving Vegetable Crop Nutrient Uptake or Productivity

Abstract: Soil application of humic acid (HA), generally derived from leonardite shale, is a common practice in California vegetable production. Five commercial HA formulations were evaluated for their effects on soil microbial activity, seedling emergence, crop productivity, and nutrient uptake when applied to representative agricultural soils. Two soils differing in organic matter content (8 and 25 g·kg -1 ) were wetted to field capacity moisture content with solutions of water, nitrogen and phosphorus (P) fertilizer, HA, or fertilizer + HA and incubated aerobically at 25 °C. In the lower organic matter soil, a synergistic effect of fertilizer and HA was observed after 7 days of incubation on both microbial respiration and the amount of phospholipid fatty acids detected; these stimulatory effects were not observed in the higher organic matter soil. In a greenhouse pot study, the effects of HA on seedling emergence, dry mass accumulation, and P uptake of romaine lettuce (Lactuca sativae L.) were evaluated in four soils of low P availability; HA was applied to the soil at a rate simulating a field application of 2.2 kg·ha -1 a.i. HA had no significant effect on emergence rate or percentage, or P uptake, in any soil; plant dry mass was increased in one soil. Field trials were conducted in 2008 and 2009 evaluating the effects of pre-transplant soil application of HA at 1.1 or 3.4 kg·ha -1 a.i. on growth, nutrient uptake, and fruit yield of processing tomato (Lycopersicon esculentum Mill.). In neither year was macro- or micronutrient uptake increased with HA. Similarly, there was no significant HA effect on plant dry mass accumulation or fruit yield. We conclude that, at typical commercial application rates in representative field soils, HA is unlikely to significantly improve vegetable crop nutrient uptake or productivity.

The Appeal of Biodegradable Packaging to Floral Consumers

Abstract: Currently, one of the most widely discussed topics in the green industry, which is promulgated by consumers exhibiting greater degrees of environmental awareness, is the issue of environmental sustainability. This has led to a desire for products that not only solve the needs of consumers, but are also produced and marketed using sustainable production and business practices. Consumers increasingly place a greater emphasis on product packaging and this has carried over to the grower sector in the form of biodegradable pots. Although various forms of these eco-friendly pots have been available for several years, their marketing appeal was limited as a result of their less- than-satisfying appearance. With the recent availability of more attractive biodegrad- able plant containers, a renewed interest in their suitability in the green industry and their consumer acceptance has emerged. The objective of this study was to determine the characteristics of biodegradable pots that consumers deem most desirable and to identify distinct consumer segments, thus allowing producers/businesses to more efficiently use their resources to offer specific product attributes to those who value them the most. We conducted a conjoint analysis through Internet surveys with 535 valid observations from Texas, Michigan, Minnesota, and Indiana. Our results show that on average, consumers like rice hull pots the most followed by straw pots. Our analysis identified seven market segments and corresponding consumer profiles: ''Rice Hull Likers,'' ''Straw Likers,'' ''Price Conscious,'' ''Environmentally Conscious,'' ''Carbon Sensitive,'' ''Non-discrim- inating.'' Idiosyncratic marketing strategies should be implemented by industry firms to market biodegradable containers to the identified consumer segments.

Yield and Postharvest Quality of Lettuce in Response to Nitrogen, Phosphorus, and Potassium Fertilizers

Abstract: Commercial lettuce production requires adequate levels of nitrogen (N), phosphorus (P), and potassium (K) to provide high-quality postharvest attributes needed for longer shelf life. Factorial experiments wereconducted inSalinas,CA, toevaluate yield and postharvest quality of both romaine and iceberg lettuce using fertilizers containing various levels of N, P, and K. Lettuce was evaluated for yield and postharvest quality parameters, including color, wilt, turgidity, glossiness, decay, brittleness, fringe burn, and saltburn.UptakeofN,P,K,calcium,andsiliconbyplantswasalsodetermined.Regardless of fertilizer treatment, shelf life and visual quality were better in the iceberg lettuce than romaine lettuce when cold-stored at 1 8C for 14 d. Yield increased with increased N application rate, but post-harvest quality fell at high levels of N (337 kgha -1 ) and P (225 kgha -1 ). The most economical treatment providing the highest yield and best post-harvest quality was the combination of 225 kgha -1 Na nd 112 kgha -1 P.

Reclaimed Water as an Alternative Water Source for Crop Irrigation

Abstract: Reclaimed water has been safely and successfully used for more than 40 years in Florida and California. Reclaimed water in these states is regulated with restrictions more stringent than World Health Organization guidelines. In the United States, Florida is currently the largest producer and California is the second largest producer of reclaimed water. Reclaimed water is more highly tested than other sources of irrigation water, and the safety of this water has been demonstrated in these and other states. Very high application rates of reclaimedwater to citrus on well-drained Floridasands increased tree growth and fruit production. Although reclaimed water contains some nutrient elements, there is usually insufficient macronutrient content to meet plant nutritional requirements. Most reclaimed waters do not have high salinity levels although they are slightly more salty than the potable waters from which they originated. With an adequate leaching fraction,saltsinreclaimedwatercanbehandledwithappropriateirrigationmanagement.Useofreclaimedwaterhassteadily increased in Florida since 1992, but other entities besides agricultural irrigation are now competing for its use. Public acceptance of reclaimed water has also increased, and crops grown with reclaimed water in Florida and California have been marketed without a negative public reaction. Recent issues of food safety have caused some to question reclaimed water, but there is no evidence of food safety problems with its use. Although reclaimed water in Florida was initially promoted as a way to improve surface water quality, it has now become an important alternate source of water to help meet water shortages and urban demand. In California, reclaimed water has become a necessary part of statewide water management.

Bell Pepper (Capsicum annum L.) Grown on Plastic Film Mulches: Effects on Crop Microenvironment, Physiological Attributes, and Fruit Yield

Abstract: Plastic mulches are widely used for the production of vegetables. There are numerous studies on the use of plastic mulches for peppers, although relatively few have focused on the microenvironmental and physiological impacts of plastic mulches on bell pepper. The objectives were to determine the effects of plastic film mulches on root zone temperature (RZT), soil water status, incidence ofthrips and Tomato spotted wilt (TSW), plant growth, gas exchange, accumulation of mineral nutrients, and fruit yield in bell pepper. The study was conducted in Tifton, GA, in the Fall of 2002 and the Spring of 2003 using eight colored plastic mulches. Plastic mulch color influenced the microenvironmental, physiological, and yield responses of bell pepper plants. Plastic film mulches differed in their soil-warming ability with RZTs in both spring and fall being highest in black mulches and lowest in silver mulches. The percentage of photosynthetically active radiation (PAR) reflected from the mulches was highest in silver mulches and lowest in black mulches. The mean RZT under the plastic mulch decreased with increasing percentages of reflected PAR. The number ofthrips per flower and the incidence of TSW in mature plants were not significantly different among plastic mulch treatments. The number of thrips per flower had no relationship with the percentage of reflected PAR or with RZT. Plastic mulch treatments had no significant effect on soil water status. Neither soil water content nor soil water potential had a relationship with RZT. In the fall season, during the first 28 days after transplanting, plant growth attributes were among the highest in silver mulches and the lowest in black mulches. Gas exchange and accumulation of mineral nutrients in the leaves and the fruit were not significantly affected by plastic mulches. Both marketable and total yields were higher on silver mulches and lowest on black mulch in the fall, whereas they were in general higher on silver with a black strip mulch and lowest on white and silver1 mulches in the spring. The reduced plant growth and fruit yields in black mulches during the fall were probably the result of the increased RZTs, and thus higher heat accumulation, that resulted in higher plant heat stress conditions compared with silver and white mulches. Fruit yield decreased with mean seasonal RZTs above 27.5 °C. The optimal range of RZT for bell pepper fruit yield was computed to be 25 to 27.5 °C or less.

Weighing Lysimeters for Developing Crop Coefficients and Efficient Irrigation Practices for Vegetable Crops

Abstract: Additional index words. crop water requirements, drainage, evapotranspiration, irrigation scheduling, microirrigation, water use efficiency Abstract. Large, precision weighing lysimeters are expensive but invaluable tools for measuring crop evapotranspiration and developing crop coefficients. Crop coefficients are used by both growers and researchers to estimate crop water use and accurately schedule irrigations. Two lysimeters of this type were installed in 2002 in central California to determine daily rates of crop and potential (grass) evapotranspiration and develop crop coefficients for better irrigation management of vegetable crops. From 2002 to 2006, the crop lysimeter was planted with broccoli, iceberg lettuce, bell pepper, and garlic. Basal crop coefficients, Kcb, defined as the ratio of crop to potential evapotranspiration when the soil surface is dry but transpiration in unlimited by soil water conditions, increased as a linear or quadratic function of the percentage of ground covered by vegetation. At midseason, when groundcover was greater than 70% to 90%, Kcb was '1.0 in broccoli, 0.95 in lettuce, and 1.1 in pepper, and Kcb of each remained the same until harvest. Garlic Kcb, in comparison, increased to 1.0 by the timethe crop reached 80%ground cover, butwithonly 7% of additionalcoverage,Kcbcontinued to increase to 1.3,until irrigation was stopped to dry the crop for harvest. Three weeks after irrigation was cutoff, garlic Kcb declined rapidly to avalueof 0.16 byharvest.Yields of eachcrop equaled or exceeded commercial averages forCalifornia withmuchless water in some cases than typically applied. The new crop coefficients will facilitate irrigation scheduling in the crops and help to achieve full yield potential without overirrigation.

Color Changes and Antioxidant Content of Vine and Postharvest- ripened Tomato Fruits

Abstract: Tomato fruit ripening is a complex, genetically programmed process that culminates in dramatic changes in texture, color, flavor, and aroma of the fruit flesh The characteristic pigmentation of red ripe tomato fruit is the result of the de novo synthesis of carotenoids, mainly lycopene and b-carotene, which are associated with the change in fruit color from green to red as chloroplasts are transformed to chromoplasts The aim of this study was to examine the effect of ripening conditions on color development and antioxidant content Detached tomato fruit stored at 15 and 30 8C and vine-ripened fruits were studied to characterize the ripening process by Hue (8) index (CIELab color system), which is strongly influenced by the circumstances of ripening Total polyphenols, ascorbic acid, and lycopene content of tomato fruits were analyzed at the end of the experiment Changes in the color of fruit stored at 15 8C and vine-ripened fruit showed significantly higher a* compared with fruit stored at 30 8C Storage temperature influenced positively ascorbic acid and negatively lycopene content, whereas total polyphenols did not show differences among the different ripening conditions

End-of-day far-red light quality and dose requirements for tomato rootstock hypocotyl elongation

Abstract: Plant morphology control is a critical technique in commercial greenhouse transplant production. Light treatment at the end of the day affects a phytochrome- regulated response affecting plant height among other characteristics and has been studied by biologists for many years. Recognizing the need to produce long hypocotyls in vegetable grafting, effects of end-of-day far-red (EOD-FR) light on tomato rootstock hypocotyl elongation were investigated. Two commercial rootstock cultivars, Aloha (Solanum lycopersicum) and Maxifort (S. lycopersicum · S. habrochaites), were used for the experiments examining responses to EOD-FR light quality (red to far-red ratio (R/ FR)) and EOD-FR light dose in a greenhouse environment. In the EOD-FR light quality experiment using 'Aloha' seedlings, incandescent light (R/FR = 0.47) induced significant hypocotyl elongation (20%) compared with the untreated control. Incandescent light with a spectral cut filter (reducing R/FR to 0.05) induced a greater hypocotyl elongation (44%) than unfiltered light, confirming the importance of use of light with a lower R/FR (or purer FR) light source in EOD-FR treatments. In the experiment on EOD-FR light dose-response, hypocotyl elongation of both 'Aloha' and 'Maxifort' was increased by increasing FR intensity as well as FR treatment duration at a lower dose range. The dose saturation curve of hypocotyl length was well described using a Michaelis-Menten-type model with FR dose (in mmolm -2 d -1 ) as an independent variable. The model-based estimation of 90% saturating FR light dose for 'Aloha' and 'Maxifort' was 5 to 14 mmolm -2 d -1 and 8 to 15 mmolm -2 d -1 , respectively, although practical near saturation dose seems to be 2 to 4 mmolm -2 d -1 for both cultivars. None of the EOD-FR treatments affected plant dry weight, stem diameter, or plastochron index. Hence, elongation was achieved without compromising growth and development. EOD-FR was shown to be an effective non-chemical means allowing transplant propagation industry to produce long hypocotyls for grafting use. Phytochromes are photoreceptor proteins making possible the perception of the exter- nal light environment by plants. The light reception region within phytochrome is the chromophore that has two interconvertible isoforms with different peak light absorption spectra in the red (wavelengths of 600 to 700 nm (R)) and far-red (700 to 800 nm (FR)) regions (Hendricks et al., 1962; Siegelman et al., 1966). Irradiation with R or FR light changes the phytochrome isoform ratio and alters biochemical and physiological re- sponses such as germination (Mancinelli et al., 1966), stem elongation, and pigment synthesis (Hendricks and Borthwick, 1967). Red or FR light at the end of the day (photoperiod) is known to affect stem elonga- tion (Blom et al., 1995; Decoteau et al., 1988; Kasperbauer and Peaslee, 1973). Tomato seed- lings with end-of-day (EOD) FR light treat- ment had a greater height and leaf length than those with EOD-R light treatment (Decoteau and Friend, 1991). EOD-FR lighting was also used in fundamental plant biology research, investigating the phytochrome signal trans- duction pathway in Arabidopsis thaliana ,c u- cumber (Cucumis sativus), and other species such as aspen (Populus tremula ·tremloides) in which stem elongation under EOD-FR was used as a positive test in identifying phyto- chrome genes and intermediate molecules such as gibberellic acid (Moe et al., 2003; Naganati et al., 1991; Olsen and Junttila, 2002).

Rubus Pharmacology: Antiquity to the Present

Abstract: The genus Rubus L., indigenous to six continents, includes blackberries, raspberries, and their hybrids and is commonly referred to as brambles or briers. Rubus species were a food and medicinal source for native peoples soon after the Ice Age. This short article presents only a sample of the wealth of historical reports of medicinal uses for Rubus. Brambles were documented in the writings of the ancient Greeks: Aeschylus, Hippocrates, Krataeus, Dioscorides, and Galen; Romans: Cato, Ovid, and Pliny the Elder; Asian medicinal traditions; traditional Chinese medicine; and the Ayurvedic tradition of India. Folk traditions of native peoples throughout the world have also applied Rubus for multiple medicinal uses. Although in modern times Rubus is grown for its delicious and vitamin-rich fruit for fresh and processed product consumption, the ancients used the whole plant and its parts. Stems, branches, roots, leaves, and flowers were used in decoctions, infusions, plasters, oil or wine extractions, and condensates. Decoctions of branches were applied to stop diarrhea, dye hair, prevent vaginal discharge, and as an antivenom for snakebites. Leaves were chewed to strengthen gums and plastered to constrain shingles, head scurf, prolapsed eyes, and hemorrhoids. Flowers triturated with oil reduced eye inflammations and cooled skin rashes; infusions with water or wine aided stomach ailments. Greeks and Romans recorded female applications, whereas the Chinese described uses in male disorders. The fruits of R. chingii are combined in a yang tonic called fu pen zi, "overturned fruit bowl," and prescribed for infertility, impotence, low backache, poor eyesight, and bedwetting or frequent urination. The Leechbook of Bald described the use of brambles against dysentery, combining ancient medicinal knowledge with pagan superstition and herb lore. Medicinal properties of Rubus continue in Renaissance and modern herbals, sanctioning leaf infusions as a gargle for sore mouth, throat cankers, and as a wash for wounds; the bark, containing tannin, was a tonic for diarrhea; and root extract, a cathartic and emetic. Recent research has measured high ellagic acid, anthocyanin, total phenolics, and total antioxidant content in Rubus fruits. Fruit extracts have been used as colorants and are now being tested as anticarcinogenic, antiviral, antiallergenic, and cosmetic moisturizing compounds. From ancient traditions through conventional folk medicines to the scientific confirmation of health-promoting compounds, Rubus is associated with health-inducing properties.

Correlations between Some Horticultural Traits in Walnut

Abstract: Correlation and causal relationships among 21 horticultural traits were determined using 71 walnut genotypes selected from seven valleys in Kerman Province, Iran. Pearson's correlation coefficient was calculated. Kernel percentage and blight susceptibility were used as dependent variables in a stepwise regression model to determine predictor variables. Direct and indirect effects of each independent variable were calculated using path analysis. A highly significant correlation was observed between lateral bearing habit and yield. Lateral-bearing trees were also more susceptible to blight and winter cold than terminal bearers. Kernel and nut weights, shell thickness, and difficulty of extracting kernel halves were the most important traits accounting for kernel variation. Kernel weight and difficulty extracting kernel halves had the strongest positive direct effects and nut weight the most negative. Flowering habit, nut shape, and leafing date had positive direct effects on blight susceptibility, but the large residual effects suggest there are other important determinant traits for blight susceptibility, which were not considered in this study.

Genotypic Variation in the Postharvest Performance and Ethylene Sensitivity of Cut Rose Flowers

Abstract: Natural variation in the postharvest quality and longevity of ornamental plants can often be related to differences in their response to ethylene. In the present study, we determined the postharvest performance and ethylene sensitivity of cut flowers from 38 cultivated Hybrid Tea rose genotypes. The vase life of the cultivars varied considerably from 4.5 to 18.8 days at 21 8C. There was also substantial variation in the degree of flower opening among genotypes. Exposure to 1 mLL -1 ethylene for 24 h at 21 8C reduced the longevity of 27 cultivars by 0.8 to 8.4 days (18% to 47%) by accelerating petal wilting and abscission. Ethylene treatment also significantly reduced rates of flower opening in 17 sensitive cultivars and in six cultivars that showed no ethylene-related reduction in vase life. Five cultivars showed no reduction in vase life or flower opening in response to ethylene exposure. Pre-treating stems with 0.2 mM silver thiosulfate liquid or 0.9 mLL -1 1-methylcyclopropene (1-MCP) gas for 16 h at 2 8C reduced the deleterious effects of ethylene. The release of 1-MCP from two sachets containing EthylBloc into individual shipping boxes also protected flowers against ethylene applied immediately after a 6-d commercial shipment. The duration of protection afforded by the 1-MCP sachet treat- ment was greatest when flowers were maintained at low temperature.

Performance of ‘Valencia’ Sweet Orange Trees on 12 Rootstocks at Two Locations and an Economic Interpretation as a Basis for Rootstock Selection

Abstract: Two field experiments with 'Valencia' sweet orange (Citrus sinensis (L.) Osb.) trees propagated on 12 rootstocks were conducted in commercial orchards. The objectives were to compare rootstock horticultural performance between two locations with soils representative of the Central Florida Ridge (AP) and coastal flatwoods (I), the major citrus-growing regions in Florida, and to see if financial analysis would provide an improved basis for interpreting rootstock performance. The randomized complete-block trials involved six-tree plots replicated eight or 10 times at planting densities of 358 trees (AP) or 252 trees (I)/ha, respectively. Tree growth and survival, yield, and juice quality were measured for 15 years. When losses occurred, trees were replaced annually with another one on the same rootstock. The data of seven rootstocks were subjected to a financial interpretation of three scenarios: tree loss and tree loss with or without tree replacement using the discounted cash flow and internal rate of return methods at a 15% rate. At the flatwoods location, when differences among replications became apparent on several rootstocks, soil data were collected to study its possible association to tree performance; also in this trial, 400-kg fruit samples were differentially harvested in 2 successive years from mature trees on each of five commercial rootstocks when the juice soluble solids/acid ratio was near 15. The juice was extracted, pasteurized, and evaluated for flavor by an experienced taste panel. The horticultural data obtained for trees on specific well-studied rootstocks (Volkamer (C.volkameriana Ten. & Pasq.)) and rough (C. jambhiri Lush.) lemons, Carrizo citrange (C. sinensis · Poncirus trifoliata (L.)), sour orange (C. aurantium (L.)), Cleopatra mandarin (C. reshni Hort. ex Tan.), trifoliate orange (P. trifoliata), a selection of sweet orange (C. sinensis), and Swingle citrumelo (C. paradisi Macf. · P. trifoliata) at both locations were typical of their well-documented performance in Florida and elsewhere. Tree losses were virtually only from citrus blight and ranged from none (sour orange) to greater than 50% (Volkamer and rough lemons) at both locations, although tree loss began later at the Central Florida location. 'Valencia' cuttings (only at the flatwoods site) were long-lived and cropped well for their smaller size compared with the budded trees. Taste panelists were not able to distinguish differences over two seasons among pasteurized 'Valencia' juices produced from trees on different rootstocks and normalized by soluble solids/acid ratio. Yield and planting density were the main factors affecting financial outcome; also, in the highly variable soils of the coastal flatwoods, trees growing in sites with greater depth to an argillic layer had 30% to 200% higher yields. Trees on Volkamer lemon had only '50% survival at both locations but had the highest ($7,338/ha I) or one of the highest cash flows ($13,464/ha AP) as compared with one of the commercial standards, Carrizo citrange ($6,928 I; $16,826 AP), which had only '25% tree loss. Inclusion of financial analysis, with certain limitations, was concluded to considerably improve rootstock selection decisions compared with selection based only on horticultural data.

Preharvest 1-Methylcyclopropene Treatment Reduces Soft Scald in 'Honeycrisp' Apples during Storage

Abstract: The main objective of this study was to investigate the effectiveness of preharvest 1-methylcyclopropene (1-MCP) treatment on the development of soft scald in 'Honeycrisp' apples. In addition, the effects of preharvest 1-MCP on fruit quality at harvest and after storage were examined. For two consecutive years of study, 'Honey- crisp' trees were sprayed preharvest with 1-MCP and fruit were harvested twice during each year. Preharvest 1-MCP treatments had little consistent effect on fruit maturity at the time of harvest. In both years of study, preharvest 1-MCP reduced the incidence of soft scald in 'Honeycrisp' apples after air storage at 0 or 3 8C for 5 or 6 months. Soggy breakdown developed only in the second year of study and high incidences were reduced by preharvest 1-MCP treatments. Preharvest 1-MCP often reduced flesh firmness loss in 'Honeycrisp' during storage, especially during the second year of study, and with 1-MCP application closer to harvest. Malic acid content was often higher in apples with the preharvest 1-MCP spray closer to harvest. Overall, the most important benefit of preharvest 1-MCP treatments on 'Honeycrisp' apples was the reduction in soft scald development. Due to the high potential for substantial fruit losses from this disorder, the use of preharvest 1-MCP sprays on 'Honeycrisp' apples could be very advantageous.

Light Intensity Affects Growth, Photosynthetic Capability, and Total Flavonoid Accumulation of Anoectochilus Plants

Abstract: Anoectochilus formosanus, a medicinal plant used to treat hypertension, lung disease, and liver disease, was grown to maximize biomass and secondary metabolite pro- duction in a controlled environment under four levels of photosynthetic photon flux (PPF), namely, 10, 30, 60, or 90 mmolm -2 s -1 ,thatisL10,L30,L60,andL90treatments, respectively. On Day 45, allgrowth valueswere greatestfor the L30 plants. Dry weight was lowest for the L10 plants. Leaf area, stem length, and fresh weight were lowest for the L90 plants. The chlorophyll concentration was highest in the L10 treatment and decreased with increasing PPF. Electron transport ratios of leaves were highest in the L30 treatment and lowest in the L90 for the second leaf (counted down from the apex) and in the L10 for the third leaf. An increase in light intensity from 10 to 60 mmolm -2 s -1 increased the superoxide dismutase activity and was associated with an increase in the total flavonoid concentration. The total flavonoid concentration (mgg -1 DW)wasgreatestintheL60andlowestintheL90. However, the total flavonoid content (mg/plant) was highest in the L30 plants as ar esult of great biomass. The results indicated that A. formosanus is a typical shade plant suitable to grow under low light intensity at PPF of 30 to 50 mmolm -2 s -1 for both growth and production of total flavonoid. A light intensity of 90 mmolm -2 s -1 induced stress on plant growth and reduced photosynthetic capability and the flavonoid accumulation.

Growth and Water Use of Petunia as Affected by Substrate Water Content and Daily Light Integral

Abstract: More efficient irrigation practices are needed in ornamental plant production to reduce the amount of water used for production as well as runoff of fertilizers and pesticides. The objective of this study was to determine how different substrate volumetric water contents (u) affected petunia (Petunia ·hybrida) growth and to quantify the daily water use of the plants. A soil moisture sensor-controlled irrigation system was used to maintain u within '0.02 m 3 m -3 of the u threshold values for irrigation, which ranged from 0.05 to 0.40 m 3 m -3 . Shoot dry weight increased as the u threshold increased from 0.05 to 0.25 m 3 m -3 and was correlated with the total amount of irrigation water applied over the 3-week course of the experiment. The daily water use of the petunias grown with a u threshold of 0.40 m 3 m -3 was 12 to 44 mL/plant and was positively correlated with both plant age and daily light integral. Lower u thresholds resulted in a decrease in both leaf water (c) and osmotic potential (cS). A decrease in turgor pressure (P) at lower u was seen at 11, but not 20 days after the start of the treatments. There were no significant effects of u on c, cS, or P on fully rehydrated plants at the end of the study. Plants were able to survive and grow at all us, although water at a u less than 0.20 m 3 m -3 is generally considered to be unavailable to the plants. Results show that it is possible to automatically irrigate plants with the use of soil moisture sensors, and this approach to irrigation may have applications in controlling the growth of ornamental plants.

Potassium Silicate Drenches Increase Leaf Silicon Content and Affect Morphological Traits of Several Floriculture Crops Grown in a Peat-based Substrate

Abstract: Silicon (Si) is a beneficial nutrient that improves biotic and abiotic stress tolerance of several crop species. Previous Si research with container-grown floriculture crops has either focused on a limited number of species or has been conducted in hydroponics using purified water, but little research has been conducted with plants grown in soilless substrates. The objective of this experiment was to examine whether weekly potassium silicate drenches would alter leaf Si concentration or affect morphological traits of several floriculture species grown in soilless substrate. Rooted liners of 21 cultivars were transplanted into a peat-based substrate. Control plants received no Si supplementation, whereas treated plants were given weekly drenches of 100 mg·L -1 Si from potassium silicate for 10 weeks. Leaf Si concentration of control plants ranged from 211 mg·L -1 for petunia (Petunia xhybrida Vilm. 'Cascadias Cherry Spark') to 2606 mg·L -1 for argyranthemum [Argyranthemum frutescens (L.) Sch. Bip. 'Sunlight']. Si supplementation increased leaf Si concentration of 11 cultivars; leaf Si concentrations for these supplemented plants were 13% to 145% greater than control plants. Among the taxa studied, Si supplementation response was variable; Si either increased or decreased height, diameter, fresh weight, dry weight, flower diameter, and leaf thickness. For three cultivars, these morphological traits were apparently unaffected by Si supplementation despite accumulating Si. Similarly, significant morphological differences were observed in four cultivars that did not accumulate Si. Eight cultivars both accumulated Si and showed significant morphological differences. Our results demonstrate that many common floriculture species grown in a peat-based substrate do take up Si and that SI may have an effect on plant development. Consequently, more work is needed to determine the appropriate rate of Si supplementation and to examine additional species.

Effects of early defoliation on yield, fruit composition, and harvest season cluster rot complex of grapevines.

Abstract: Viticulture in Michigan is limited by a cool and humid climate and as a result, there is a problem of harvest season cluster rot, especially in cultivars with compact cluster morphology. Economically important wine grape varieties in eastern North America possess varying susceptibility to harvest season cluster rot. Some important cultivars that are susceptible are Pinot gris, Pinot noir, Riesling (Vitis vinifera L.) as well as Seyval and Vignoles (French-American hybrids or interspecific hybrid cultivars). A common characteristic of these cultivars is the compactness of the berries held on the cluster rachis. The aim of this work was to determine whether a quantified amount of leaf removal or a temporary reduction in carbon assimilation at the beginning of bloom would reduce fruit set and cluster compactness. Vines subjected to removal of four or six basal leaves had an average fruit set reduction of ≈45% from a non-treated control. Cluster weight and berries per cluster were similarly reduced with a greater effect on the basal than the apical cluster of the shoot. Reduced fruit set was associated with a reduction in cluster compactness and harvest season rot. This was also reflected in yield and basic fruit chemistry parameters associated with the importance of basal leaves to the developing cluster. Multiple applications of stylet oil at different time intervals resulted in significant reduction in net photosynthesis (P n ). A single application had no significant impact on P n , whereas multiple applications reduced leaf assimilation rates. However, this reduction in P n did not reduce fruit set or improve cluster compactness. There was a strong negative effect of early leaf removal in Year 1 on vine performance in Year 2; this carryover effect increased shootless nodes per vine, reduced the number of clusters per shoot and per vine, and dramatically reduced fruit set and consequently yield per vine.