grown under furrow or drip-irrigated conditions in California ( Stoddard et al., 2013 ). Soil moisture stress is one of the crucial abiotic stress factors that limits growth and development of sweetpotato, affecting storage root production and yield
Bandara Gajanayake, K. Raja Reddy, Mark W. Shankle, and Ramon A. Arancibia
R.J. Bula, R.C. Morrow, T.W. Tibbitts, D.J. Barta, R.W. Ignatius, and T.S. Martin
Development of a more effective radiation source for use in plant-growing facilities would be of significant benefit for both research and commercial crop production applications. An array of light-emitting diodes (LEDs) that produce red radiation, supplemented with a photosynthetic photon flux (PPF) of 30 μmol·s-1·m-2 in the 400- to 500-nm spectral range from blue fluorescent lamps, was used effectively as a radiation source for growing plants. Growth of lettuce (Lactuca sativa L. `Grand Rapids') plants maintained under the LED irradiation system at a total PPF of 325 μmol·s-1·m-2 for 21 days was equivalent to that reported in the literature for plants grown for the same time under cool-white fluorescent and incandescent radiation sources. Characteristics of the plants, such as leaf shape, color, and texture, were not different from those found with plants grown under cool-white fluorescent lamps. Estimations of the electrical energy conversion efficiency of a LED system for plant irradiation suggest that it may be as much as twice that published for fluorescent systems.
Wlodzimierz Bres and Leslie A. Weston
`Buttercrunch', `Grand Rapids', and `Summer Bibb' lettuce (Lactuca sativa L.) seedlings were grown with the nutrient film technique (NIT). The influence of two K concentrations (150 and 225 mg·liter-1) and four solution pH levels (5.0, 5.5, 6.0, and 6.5) on lettuce tipburn was investigated in four experiments. Additionally, the influence of pH on foliar nutrient concentration was examined. Even though tipburn was observed in `Buttercrunch' and `Summer Bibb' lettuce, neither K nor pH level consistently affected tipburn incidence. No tipburn was observed in `Grand Rapids'. Solution pH generally did not affect concentration of total N and NO3-N in lettuce tissue. Increasing the pH increased K concentration and resulted in increased proportions of K compared to Mg or Ca. Although the influence of solution pH on P, Ca, and Mg concentration was significant, nutrient accumulation differences were not reflected in lettuce fresh-weight differences. The influence of K solution concentration and pH on lettuce yield was not significant. Tipburn incidence in NIT-produced lettuce appears to be primarily affected by environmental conditions maintained during greenhouse growth.
Albert Z. Tenga, Beverley A. Marie, and Douglas P. Ormrod
Field experiments in open-top chambers were conducted to study the recovery of tomato (Lycopersicon esculentum Mill. cv. New Yorker) plants from ozone (O3) injury. Plants were pot-cultured and exposed for 7 hours per day for 4 days at a vegetative or flowering stage to charcoal-filtered air, 0.06, 0.09, 0.12, 0.18, or 0.24 μl O3/liter. Half of the plants were harvested 2 or 3 days after the O3 exposure; the remaining plants were held in open-top field chambers in filtered air and harvested after the appearance `of the first red fruit. Ozone exposure at either growth stage resulted in visible foliar injury and decreased leaf area of plants harvested 2 or 3 days after exposure. In spite of extensive foliar injury after O3 exposure at the vegetative stage, there was no significant decrease in fruit yield or change in fruit quality at the final harvest. In contrast, exposure of plants to O3 at flowering progressively reduced fresh weight of fruit and, to a lesser degree, its concentration of titratable acidity.
Peter M Hirst and David C Ferree
Floral development was studied in buds of `Starkspur Supreme Delicious' apple trees growing on B.9, M.26 EMLA, M.7 EMLA, P.18, and seedling rootstocks. In each of 3 years, buds were sampled from the previous years growth at intervals throughout the growing season and dissected to determine whether the apex was domed, indicating the start of floral development. Number of bud scales and true leaves increased during the early part of the growing season, but remained fairly constant beyond 70 days after full bloom. The type of rootstock did not affect the number of bud scales or transition leaves, and effects on true leaf numbers were small and inconsistent. Final bract number per floral bud was similarly unaffected by rootstock. The proportion of buds in which flowers were formed was influenced by rootstock in only one year of the study, which was characterized by high temperatures and low rainfall over the period of flower formation. Bracts were observed only in floral buds, and became visible after doming of bud apices had occurred. Flowers were formed during the first 20 days in August, regardless of rootstock or year. The appendage number of vegetative buds was constant from 70 days after full bloom until the end of the growing season, but the number of appendages in floral buds increased due to the continued production of bracts. The critical bud appendage number for `Starkspur Supreme Delicious' before flower formation was 20, and was stable among rootstocks and years. Buds with diameters above 3.1 mm were generally floral, but on this basis only 65% of buds could be correctly classified. Spur leaf number, spur leaf area, and spur leaf dry weight were not good predictors of floral formation within the spur bud.
Haofeng Chen, Vanessa E.T.M. Ashworth, Shizhong Xu, and Michael T. Clegg
understanding of the genetic determination of economically important traits. Usually commercially important traits of avocado, such as tree growth rate, fruit precocity, fruit quality, flavor, and so on, are controlled by multiple genes, and those of large
Hans-Peter Kläring and Angela Schmidt
Decreasing the temperature in heated greenhouses significantly reduces heat energy consumption and thus heat costs and CO 2 emissions ( Elings et al., 2005 ). However, growth of the plants may also decrease, with major implications for yield. The
James H. Aldrich and Jeffrey G. Norcini
107 POSTER SESSION (Abstr. 665–676) Growth and Development–Floriculture
Josh B. Henry, Ingram McCall, Brian Jackson, and Brian E. Whipker
fertilization to control plant growth. Although the nitrate (NO 3 − ) form of N has often been used to keep plants compact, it is the low P levels in high NO 3 − –N fertilizers that are responsible for compactness ( Nelson et al., 2012 ). Most NO 3 − based
E.W. PAVEL and T.M. DEJONG
73 ORAL SESSION (Abstr. 457-464) FRUIT CROPS: GROWTH AND DEVELOPMENT II