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- Author or Editor: A. Abdul-Baki x
- Journal of the American Society for Horticultural Science x
Nine heat-tolerant tomato [Lycopersicon esculentum (Mill.)] breeding lines, four heat-tolerant cultivars, and four heat-sensitive cultivars were evaluated in the greenhouse under high temperature (39C day/28C night) and in the field. Criteria for heat tolerance included flowering, fruit set, yield, fruit quality, and seed production. Under high-temperature conditions, the group of heat-tolerant lines, the heat-tolerant cultivars, and the heat-sensitive cultivars produced, respectively, the following per plant: flowers, 186, 94, and 55; fruit set 70%, 52%, and 30%; yield, 410, 173, and 11 g; and normal mature fruit, 72%, 37%, and 7%. Yields of heat-tolerant lines under high temperature in the greenhouse ranged from 118% to 31% of their respective yields in the field. Yields of heat-tolerant cultivars were 62% of those in the field. In contrast, yields of heat-sensitive cultivars under high temperature were < 1% of their respective yields in the field. High temperature induced flower abscission, reduced fruit set and yield, and increased the incidence of abnormalities. Major fruit abnormalities with high temperatures included cracks, blossomed rot, watery tissue, and small, immature fruits. Production of viable seeds under the high-temperature regime was severely reduced or totally inhibited regardless of the heat-tolerance level exhibited by the line or cultivar. The failure of heat-sensitive and most heat-tolerant cultivars or lines to produce viable seeds under such a high temperature suggests that a lower level of heat stress than that applied in these experiments could allow the production of enough seeds to test the relationship between heat tolerance in a genotype and its ability to produce viable seeds under high temperature. The results indicate that certain lines have high tolerance to heat and, therefore, could provide valuable sources of plant material for physiological studies to establish the physiological and molecular bases of heat tolerance. Some of the heat-tolerant lines might also serve as excellent germplasm sources in breeding heat-tolerant tomato cultivars.
A procedure is described for determining pollen viability in tomatoes (Lycopersicon esculentum Mill.) by growing pollen in a growth medium containing 0.29 M sucrose, 1.27 mm Ca(NO3)2, 0.16 mm H3 BO3, and 1 mm KNO3 (pH 5.2) to which 0.001% fluorescein diacetate (FDA) was added. Pollen viability can be evaluated within 30 min by determining percent fluorescing pollen in a sample. The procedure further allows the determination of percent germination in vitro and pollen tube growth within 1.5 hours. Neither the germination medium nor FDA has any adverse effects on germination and pollen tube growth. Percent fluorescent pollen and percent total pollen germination were highly correlated, suggesting that fluorescence is a good measure of pollen viability. The combined fluorescence-germination procedure is simple and adapted to routine screening of many samples.
The diffusion coefficient of CO2 in `Russet Burbank' potato (Solanum tuberosum L.) tubers was determined under steady-state conditions at 10 and 27C. The data showed that the skin is the main barrier to gas diffusion, with an average diffusion coefficient of 6.57 × 10-7 and 7.61 × 10-7 cm·s-1 at 10 and 27C, respectively. The flesh also presents an appreciable barrier to gas diffusion. The average diffusion coefficient of CO2 in the flesh was 2.00 × 10-4 and 2.24 × 10-4 cm·s-1 at 10 and 27C, respectively. Under regular storage conditions, the tuber is well aerated and the concentration of O2 at the center of the tuber is sufficient to maintain aerobic respiration.
Abstract
Green and sun-bleached seeds of cultivars ‘G 2’ and ‘Green Fordhook 861’ lima beans (Phaseolus lunatus L.) were analyzed for total chlorophyll in whole seeds, and for soluble protein and rates of synthesis of carbohydrates, proteins, and lipids in excised embryonic axes. Bleached seeds were lower in total chlorophyll than green seeds. Embryonic axes from bleached seeds synthesized less carbohydrates and proteins, but more lipids than embryonic axes from green seeds. When held in water for 3 hours, embryonic axes from ‘G 2’ lima beans had about 65% more soluble protein, and respired 20% faster than embryonic axes from ‘Green Fordhook 861’. Whole ‘G 2’ lima bean seeds also emerged faster than ‘Green Fordhook 861’ seeds. In each cultivar, green seeds had a higher percent emergence than bleached seeds.
Abstract
Green seeds from lima bean (Phaseolus lunatus L.) cvs. G 2 and Green Fordhook 861, contain chlorophylls a and b in a ratio of about 2:1. Chlorophyll content per seed increases during development, reaches a max about 5 weeks after pod formation, then declines sharply during maturation. Bleached seeds have less chlorophyll, especially chlorophyll a, and carotene than non-bleached seeds.
In developing and mature lima bean seeds max chlorophyllase activity appears during the stage which corresponds with max chlorophyll content rather than the stage of most rapid loss of chlorophyll. The enzyme is particulate, located in the chloroplast membranes, and has an optimum pH of 8.5 ± 0.2.
The low carotene content of seeds of green-seeded commercial cultivars might contribute to their sensitivity to light. Several cultivars that were obtained from other countries. (Plant Introductions) contain 10 to 20 times as much carotene as the commercial cultivars tested. These “Introductions” provide genetic material for increasing the carotene content of lima bean seeds. High carotenes would improve nutritional value of beans and might reduce or prevent bleaching.
Temperature and root length at selected locations within a raised bed under black polyethylene, hairy vetch (Vicia villosa Roth) residue, or bare soil were measured and correlated with tomato (Lycopersicon esculentum Mill.) growth. Early in the season, before the tomato leaf canopy closed, soil temperature was influenced more by vertical depth in the bed than by horizontal position across the bed. Maximum soil temperatures under black polyethylene averaged 5.7 and 3.4C greater than those under hairy vetch at 5 and 15 cm deep, respectively. More hours at optimum temperatures for root growth (20 to 30C) during the first 4 weeks of the season probably accounted for greater early root and shoot growth and greater early yield of tomatoes grown with black polyethylene than hairy vetch residue or bare soil. After canopy closure, soil temperatures under tomato foliage within the row were reduced by an average of 5.2 and 2.2C at 5 and 15 cm deep, respectively, compared to those on the outer edge of the beds. Most tomato roots were in areas of the bed covered by the tomato canopy where temperatures in all treatments remained in the optimum 20 to 30C range almost continuously. Soil temperature, therefore, did not explain why tomato plants in the hairy vetch treatment had equal or higher total yields than the black polyethylene or unmulched treatments.
Abstract
The leachate from seed of tomato (Lycopersicon esculentum Mill., PI 341984), an accession whose seeds germinate well at low temperatures, promoted the germination of seeds of the same and other tomato cultivars. The leachate from ‘Red Rock’ seed, a cultivar whose seeds germinate poorly at low temperatures, inhibited the germination of seeds of the same and other tomato cultivars. The promotive and inhibitory effects of these leachates on seed germination is apparently highly specific and restricted to tomato seeds. The activity was highest in fresh seeds and the responses were best exhibited at low germination temperatures.
Abstract
The transport of arginine and α-aminoisobutyric acid from the cotyledon to the axis of Phaseolus lunatus L. was followed during a 4-day germination. Transport of both amino acids to the axis was slow during the first 2 days and increased rapidly during the third and fourth days of germination. Both amino acids accumulated in the axis of viable seeds. Alpha-aminoisobutyric acid was not metabolized by the cotyledon or axis, whereas arginine was rapidly fixed by both tissues into protein. Percent incorporation of arginine into protein was lower in the cotyledon than in the axis. Rapid synthesis of proteins in the cotyledon appears to limit transport and availability of amino acids to the axis. No transport or accumulation of α-aminoisobutyric acid was observed in seeds that lost germinability through accelerated aging.
Concern for the environment has focussed attention on the need for environmentally sound, yet economically profitable, farming practices. A hairy vetch (Vicia villosa L. Roth.) organic mulch system for fresh-market tomato (Lycopersicon esculentum Mill.) production provides environmental benefits by enhancing the soil and reducing the need for fertilizer and herbicide inputs and is more profitable than conventional practices. Tomato field trials over 3 years at the Beltsville (Md.) Agricultural Research Center compared the hairy vetch mulch system with black polyethylene mulch and bare ground (no mulch). Using partial budget analysis in a farm context, the hairy vetch mulch treatment was more profitable in all years under all market and yield adjustment scenarios. The vetch mulch system also was the preferred system for a risk-averse grower, according to a safety-first criterion. The combination of environmental benefits and the economic benefits to the grower make the hairy vetch mulch system an attractive alternative for producing fresh-market tomatoes in the Mid-Atlantic and parts of northeastern United States.