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- Author or Editor: Daniel J. Cantliffe x
The National Aeronautics and Space Administration (NASA) is developing a Controlled Ecological Life Support System (CELSS) for long-term space exploration in which plants would be one major component. Volatile emissions from these plants may disrupt the proper functioning of CELSS. This research investigated how environmental factors alter the volatile emissions from hydroponically-grown `Waldmann's Green' leaf lettuce. A growth chamber was modified to allow the injection of purified air into a glass enclosure positioned over individual lettuce plants. Air samples from the enclosure were analyzed by gas chromatography-mass spectrometry (GC-MS). The lipoxygenase pathway products (Z)-3-hexenal, (Z)-3-hexenol, and (Z)3-hexenyl acetate were emitted following the end of the light period. Mechanical damage also stimulated the release of these same compounds. The design of toxin management systems in CELSS may need to incorporate these findings. Additionally, lipoxygenase pathway products have been previously demonstrated to influence insect behavior and pathogen growth, and may indicate future directions for plant breeding.
The effects of the dry-back temperature on sh2 sweet corn seeds primed via solid matrix priming combined with sodium hypochlorite (SMPsh) were studied. Seeds of two sh2 sweet corn cultivars: Crisp N'Sweet 711 (CNS-711) and How Sweet It Is (HSII) were primed via SMPsh. After the treatment, the seeds were dried-back from 50-54% to 6-7% moisture content at 20, 30 or 40C and 25% RH. The rate of dehydration was significantly lower in CNS-711 compared to HSII at all dry-back temperatures. In both cultivars, seed respiration after 4, 16, and 32h of imbibition was greater in those dried at 30 and 40C compared to 20C or non-primed seed. Enzyme activity (glutamic acid decarboxylase activity) was decreased in HSII seeds dried at 20C. There were no differences among treatments in CNS-711. Leakage conductivity was significantly less when the seeds were dried-back at 30C or 40C compared to 20C or nonprimed seeds. Laboratory germination and seedling fresh weight were greater in seeds dried-back at 30C compared the others temperatures or non-primed seeds. The low rate of desiccation at 20C (30h and 8h in CNS-711 and HSII, respectively) may not suppress germination events after priming, thus damaging the embryo during dry-back. This work demonstrated the importance of dry-back temperature to the efficacy of SMPsh seed treatment in sh2 corn.
`Sunny' tomato (Lycopersicon esculentum Mill.) containerized transplants were grown with the standard or conventional systems (SS) and with recently developed flotation systems (FS). Standard system and FS transplants, and direct-seeding using coated seeds were evaluated in the field for root and shoot growth and yield at Parrish, Bradenton, and Naples during fall, winter, and spring plantings. Plant growth characteristics were measured weekly before, during, and after transplanting or sowing. In the Parrish and Bradenton Fall 1987 and Bradenton Spring 1988 experiments, SS transplants had greater leaf area, root volume, shoot dry weights, and shoot: root ratios than FS transplants. During early development, the FS transplants had more lateral root growth than SS transplants, but had similar total root growth and horizontal and vertical root distribution after transplanting in the field. Transplants and direct-seeded plants allocated 72% of the total root mass in the upper 0 to 10 cm of the soil. In Fall 1987, SS transplants had between 29% and 41% more fruit yield than FS transplants at Bradenton and Parrish, respectively. In the Naples Winter 1988 and Parrish and Bradenton Fall 1989 experiments, both transplant types had similar fruit yields, but more than direct-seeded plants. Transplants grown with the flotation system are recommended for use provided that seedlings are grown and maintained with minimum hardening before establishment in the field.
Tomato, cv. `Sunny' containerized transplants produced either with overhead (SP1) or sub (flotation) (SP2) irrigation were established in the field in fall, winter, and spring. Leaf area (LA), root volume (RV), and dry weights of shoots (SDW) and roots (RDW) were measured weekly before and after transplanting. In fall 1987, SP1 with 44 cm2 LA, 275 mg SDW, 68 mg RDW, and 0.9 ml RV at transplanting (T0) had 33% more fruit yield than SP2 transplants with 20 cm2 LA, 236 mg SDW, 62 mg RDW, and 0.6 ml RV at T0. In spring and winter 1988, SDW, RDW, and RV increased uniformly in both SP1 and SP2 plants, and yields did not differ significantly. In spring 1989, at T0, SP1 had 182 mg SDW and 7.8 shoot/root ratio (S:R) and SP2 had 92 mg SDW and 4.6 S:R, thereafter SDW and S:R ratios were not different and yields were unaffected. In fall 1989, SP1 total fruit yeild (52.3 t.ha-1) did not differ significantly from that of SP2 (47.4 t.ha-l) plants. Sub irrigated transplants may have similar fruit yields than overhead irrigated transplants provided plants are kept with minimum stress before establishment.
Studies were conducted to evaluate growth of tomato (Lycopersicon esculentum Mill.) transplants in the field in response to age of transplants in Spring and Fall 1989. Transplants were 2 (2W), 3 (3W), 4 (4W), 5 (SW), or 6 (6W) weeks old. Drip and subseepage irrigation were used. In spring, older transplants produced more shoot and root growth up to 2 (T2) weeks after transplanting. At 3 (T3) and 4 (T4) weeks after transplanting, there were no differences between 4W, 5W, and 6W transplants. These trends were independent of irrigation systems. Total yield and early yield were similar for all transplant ages. In fall, shoot growth increased linearly with increasing transplant age at TO, but not thereafter. Chlorophyll a + b increased over time, but no treatment differences were found at T4. At planting, 2W transplants had a higher Chl a: b ratio than older transplants. This difference was reduced at T1 and T2 and became insignificant at T4. These results indicate that no improvement in yields was obtained using the traditional older transplants. Younger transplants might be used to achieve rapid seedling establishment with-minimal transplant production costs.
Abstract
MnSO4 and Rayplex-Mn were found to be effective sources of Mn for tomato seedlings grown on a Mn deficient high organic sandy soil. Tomato seedlings absorbed Mn from MnSO4 or Rayplex-Mn applied in the starter band on or under the seed with equal effectiveness. The amount absorbed was directly related to the Mn concentration in the band. MnSO4 at 100 mg Mn/ft of row increased the Mn content of the tissue from 17 ppm to more than 100 ppm.
MnEDTA at a rate to supply 10 to 25 mg Mn/ft of row in bands on or under the seed did not affect seedling growth and Mn uptake was less than from the same rate of MnSO4. Rates of 50 and 100 mg Mn/ft of row from MnEDTA in the starter band on or under the seed caused death or severe stunting of tomato seedlings because of toxicity. Band applications of Mn sources increased Mn composition of the tomato tissue relatively much more than did the broadcast application.
Abstract
Fat-sugar derived surfactants were examined as to their effectiveness in the promotion of absorption of nutrient ions through leaf surfaces and subsequent translocation of these ions through the plant. The fat-sugar derived surfactants and several other commercial surfactants were added to solutions of P to test the effectiveness of the surfactants in promoting ion absorption and translocation.
The surfactants in the nutrient sprays at a 0.5% concentration were generally more effective than at 0.1% or 1.0% concentration with the exception of Polyoxyethylenated Tallow Sucroglyceride (PTS) which had its greatest effect at a 1.0% concentration. Sucro sperses and Sucro sols with 3 fatty acid molecules per sucrose molecule were more effective in increasing P uptake and transport than formulations with 1.5 or 4.5 fatty acid molecules per sucrose molecule. A 40:1 ratio of ethylene oxide to sucrose was most effective for increase of P absorption. Combining PTS and Sucroglyceride T-110 (T-110) increased P absorption more than if either surfactants were used alone. Ratios of 1:3 or 3:1 respectively, were most effective. T-110 and Sucrose Monotallowate (SMT) did not significantly increase absorption of P at any concentration tested. PTS was effective in increasing nutrient ion uptake at a 1% concentration, but it was found to be somewhat phytotoxic at this level. The fat-sugar complexes used as surfactants increased ion uptake in some instances more than 20 times compared to using no surfactant. When these same surfactants were compared to commercially used surfactants, they generally proved to be superior for use with the foliar applied nutrients.
Temperature is an important environmental factor that affects lettuce (Lactuca sativa L.) germination. The present research was conducted to determine the role of seed coverings on lettuce seed germination at high temperature. Five lettuce genotypes were primed in order to bypass thermoinhibitional effects on germination. During germination of primed and nonprimed seeds, imbibition followed a normal triphasic pattern. Primed seeds had higher final water content, a decreased imbibitional phase II, and germinated at 36 °C compared to nonprimed seeds of thermosensitive genotypes, which did not germinate at 36 °C. Puncture tests were conducted to determine the force required to penetrate the whole seed or endosperm of the five genotypes at 24 and 33 °C. `Dark Green Boston', a thermosensitive genotype, had the highest mean resistance (0.207 N) and PI 251245, a thermotolerant genotype, had the lowest (0.139 N). Resistance to penetration of the endopserm of the five genotypes was different at both temperatures. However, three thermotolerant genotypes had lower endosperm resistance than two thermosensitive types. At 36 °C, the penetration force for primed and nonprimed seeds was compared after the first hour of imbibition and 1 hour before radicle protrusion. The force required to penetrate the seed was affected by genotype, seed priming, and duration of imbibition. Puncture force decreased as imbibition time at 36 °C increased in primed and nonprimed seed of each thermotolerant genotype but not in the thermosensitive genotypes. Priming reduced the initial force necessary to penetrate the seed and endosperm in all genotypes. Thus, for radicle protrusion to occur, there must first be a decrease in the resistance of the endosperm layer as evidenced by priming or thermotolerant genotype. Then, the pericarp and integument are sufficiently weakened so that tissue resistance is lower than the turgor pressure of the expanding embryo, allowing germination to be completed.
Abstract
Ethephon and chlorflurenol were applied to hybrid pickling cucumber Cucumis sativus L. cvs. Pioneer and Pickmore to study the use and effectiveness of the chemicals on promoting fruit yields and quality in a once-over harvest system. Ethephon was applied either at the first or the fourth true-leaf stage of growth. Chlorflurenol was applied at 0, 50 or 100 ppm when 6-8 female flowers reached anthesis. Dollar value per ha was increased by approximately 14% when ethephon or chlorflurenol was used alone. However, when these 2 growth regulators were used in combination, yields were increased by as much as 68% in ‘Pioneer’ and 40% in ‘Pickmore.’ Chlorflurenol significantly increased the number of fruit per plant and reduced the length to diameter ratio. Fruit shape and L:D ratio were significantly improved when ethephon was applied in the fourth true-leaf stage regardless of chlorflurenol usage. Chlorflurenol slightly reduced the fresh quality of ‘Pioneer’ but had no such effect on ‘Pickmore.’ Salt stock quality was improved slightly by chlorflurenol. To obtain best yield, fruit shape, fresh salt stock quality, ethephon should be applied twice, 1 week apart commencing at the fourth true-leaf stage, followed by a 50 to 100 ppm spray application of chlorflurenol when 6-8 female flowers have reached anthesis.
Abstract
Cucumbers (Cucumis sativus L.), ‘Bounty’ and ‘Premier’, were grown at 8 population densities ranging from 50,000 plants per ha (46 × 46 cm spacing) to 850,000 plants per ha (10 × 10 cm spacing). Sections of the field were harvested once-over on 2 sampling dates. Yields as dollars per ha and as tons per ha increased with increasing plant population at densities of 50,000 to 100,000 and 250,000 to 500,000 plants per ha. Over the common commerical populations, 100,000, 150,000, 200,000 and 250,000 plants per ha, yields did not increase as population increased. Delay in harvest for 4 days did not affect dollars per ha yield but doubled the tons per ha produced. Fruit sizing was slower in higher plant populations (250,000 to 850,000 plants per ha) than in the lower plant densities (50,000 to 200,000 plants per ha). The number of fruit per plant decreased with increasing plant population. Length to diameter ratios of ‘Premier’ were lower at the lowest plant population, 50,000 plants per ha. L:D ratios of ‘Bounty’ were unaffected by plant population. Varying plant populations did not affect the percent off-shape fruit, or fruit color (green quality and uniformity) of either cultivar.