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- Author or Editor: Daniel J. Cantliffe x
Abstract
Leaves of nonglaucous cotton and tomato absorbed Mn whether or not a surfactant was added to a MnSO4 spray solution, whereas the leaves of glaucous cabbage and onion absorbed Mn only when a surfactant was added. Manganese was absorbed by cabbage leaves only when a surfactant was added or when leaf surface wax formation was inhibited by ethyl N,N-dipropylthiolcarbamate (EPTC). Non-glaucous and glaucous pea mutants did not significantly absorb Mn unless surfactant was added to a MnSO4 spray, after which both mutants equally absorbed Mn.
Surfactants increased the concn of 59fe penetrating into a wax paraffin model to a 0.5 mm depth by 8- to 30-fold over a no-surfactant treatment. Both the rate and depth of penetration were increased by surfactant. No Fe was absorbed by cabbage leaves unless surfactant was present in the spray solution or the leaf wax was disturbed by brushing.
Thus, surfactant efficiently overcame an external leaf wax layer as a barrier to the absorption of foliar applied ions and thereby increased ion movement into the leaf.
Abstract
In field experiments with cucumber (Cucumis sativus L.) on both sandy and clay loam soils (2-chloroethyl)phosphonic acid (ethephon) at 125 or 250 ppm applied twice to the foliage was more effective in promoting pistillate flowers and yield on ‘Wisconsin SMR 58’, a monoecious cultivar, than granular ethephon applied at various rates as a sidedress at planting, placed directly on the seed at planting, or applied as a sidedress in the first true-leaf stage. Foliar sprays on ‘Pioneer’ were effective in reducing the number of staminate and increasing the number of pistillate flowers. However, ethephon applied by any method did not increase yields in ‘Pioneer’, a predominantly pistillate cultivar.
Abstract
Three herbicides, cycloate, alachlor and lenacil, gave acceptable weed control in spinach (Spinacia oleracea L.), while 7 other herbicide combinations did not Cycloate, alachlor, lenacil, prometryne and chlorpropham + PPG 124 significantly increased the NO3-N concentration of both spinach blades and petioles by as much as 3-4 times over weeded and non-weeded checks. DCPA significantly increased NO3 in the petioles. Cycloate, alachlor and lenacil significantly increased total Ν concentration in the petioles, while none of the herbicide treatments affected total Ν in the blades. Lenacil significantly increased fresh weight of blades and petioles compared to a weeded check, while plant fresh and dry weights from cycloate and alachlor treatments were not less than the checks.
Embryogenic callus growth of sweetpotato [Ipomoea batatas (L.) Lam.] was selectively enhanced by subculture on basal callus proliferation medium modified to contain 15 mm NH4NO3. Embryogenic callus production was doubled on basal callus proliferation medium modified to contain 60 mm K+, while nonembryogenic callus production was reduced 40%. Additions of up to 40 mm NaCl to basal callus proliferation medium did not affect callus proliferation. The development of embryos from calli subculture to embryo production basal medium was unaffected by the KCl or NaCl treatments of the callus proliferation phase. However, embryo production was increased by subculturing callus from callus proliferation medium containing 20 mm NH4 + to embryo production medium containing 10 mm NH4 + Our results demonstrate that changes in mineral nutrition, in addition to growth regulator differences between callus proliferation and embryo production media, are important factors in sweetpotato somatic embryogenesis.
`Galia' (Cucumis melo var. reticulatus L. Naud. `Galia') melons exhibit relatively short postharvest longevity, limited in large part by the rapid softening of this high quality melon. The present study was performed to characterize the physiological responses of `Galia' fruit harvested at green (preripe) and yellow (advanced ripening) stages and treated with 1-methylcyclopropene (1-MCP) before storage at 20 °C. Treatment with 1.5 μL·L-1 1-MCP before storage delayed the climacteric peaks of respiration and ethylene production of green fruit by 11 and 6 d, respectively, and also significantly suppressed respiration and ethylene production maxima. Softening of both green and yellow fruit was significantly delayed by 1-MCP. During the first 5 d at 20 °C, the firmness of green control fruit declined 66% while 1-MCP-treated fruit declined 46%. By day 11, firmness of control and 1-MCP-treated green fruit had declined about 90% and 75%, respectively. The firmness of control yellow fruit stored at 20 °C declined 70% within 5 d while 1-MCP-treated fruit declined 30%. The 1-MCP-induced firmness retention was accompanied by significant suppression of electrolyte leakage of mesocarp tissue, providing evidence that membrane dysfunction might contribute to softening of `Galia' melons. The mesocarp of fruit harvested green and treated with 1-MCP eventually ripened to acceptable quality; however, under the treatment conditions (1.5 μL·L-1 1-MCP, 24 h) used in this study, irreversible suppression of surface color development was noted. The disparity in ripening recovery between mesocarp versus epidermal tissue was considerably less evident for fruit harvested and treated with 1-MCP at an advanced stage of development. The commercial use of 1-MCP with `Galia'-type melons should prove of immense benefit in long-term storage and/or export situations, and allow for retention of quality and handling tolerance for fruit harvested at more advanced stages of ripening.
Temperatures above 30 °C may delay or inhibit germination of most of commercial lettuce cultivars. Ethylene enhances lettuce seed germination at high temperatures. Enzyme-mediated degradation of endosperm cell walls appears to be a crucial factor for lettuce germination at high temperature. The galactomannan polysaccharides in lettuce endosperm cell wall are mobilized by endomannanase. The role of endo-mannanase during germination of lettuce seeds at high temperature (35 °C) and the possible role of etlene in enzyme regulation were investigated. Seeds of thermotolerant (`Everglades'-EVE) and thermosensitive (`Dark Green Boston'-DGB) lettuce genotypes were incubated at 20 and 35 °C in water, 10 mM of 1-aminocyclopropane-1-carboxylic acid (ACC), or 20 mM of silver thiosulphate (STS). Also, seeds were primed in an aerated solution of polyethylene glycol (PEG), or PEG+ACC, or PEG+STS. Untreated seeds germinated 100% at 20 °C. At 35 °C, EVE germinated 100%, whereas DGB germinated only 33%. Seed priming or adding ACC during imbibition increased germination of DGB to 100% at 35 °C. Adding STS during imbibition led to a decrease in germination at 35%C in EVE and completely inhibited germination of DGB. Priming with STS led to reduced germination at 35%C of both genotypes. EVE produced more ethylene than DGB during germination at high temperature. Providing ACC either during priming or during germination led to an increase in endo-mannanase activity, whereas STS inhibited mannanase activity. Higher endo-mannana activity was observed in EVE than DGB seeds. The results suggest that ethylene might overcome the inhibitory effect of high temperature in thermosensitive lettuce seeds via weakening of endosperm due to increased endo-mannanase activity.
In greenhouse crops, fruit yield and quality can be increased by managing shoot pruning and plant density. The effect of plant population density (2, 3, and 4 plants/m2 as function of in-row plant spacings of 66.5, 44.3, and 33.3 cm, respectively), and shoot pruning (one, two, and four main stems) was studied for effects on fruit yield, quality and plant growth of greenhouse-grown sweet pepper (Capsicum annuum L. cv. Robusta) during Summer 1998 in Gainesville, Fla. Red fruit were harvested 84 and 118 days after transplanting (14 Apr.). Additional fruit set was inhibited due to the high temperatures. Marketable yield (number and weight) per square meter increased linearly with plant density and was greater on plants with four stems than in those with two or one stem. Extra-large fruit yield per square meter was not affected by plant density, but was higher in four-stem plants. Total marketable yield and extra-large fruit yields per plant were greatest in the four-stem plants at two plants per square meter. The stem length and the number of nodes per stem increased linearly with the decrease in plant spacing. Stem length and number of nodes per stem were greater in single-stem than in four-stem plants. Number and dry weight of leaves, stem diameter, and total plant dry weight were higher in four- and two-stem plants than in single-stem plants. Results indicated that four plants per square meter pruned to four stems increased marketable and extra-large fruit yield in a short harvest period of a summer greenhouse sweet pepper crop in north central Florida.
Primed, primed + BA, or nontreated lettuce (Lactuca sativa L.) seeds were sown with several soil amendment covers or a sandy soil cover (control) to assess stand establishment in three field experiments. Seeds covered with amendments Growsorb LVM 24/48, Growsorb 6/30, and plug-mix had a higher percent emergence than soil-covered seeds in warm soil. Primed seeds (with or without BA) had a higher percent emergence than nontreated seeds. Emergence was more rapid with plug-mix, LVM 24/48, and LVM 6/30 covers than with the sandy soil control. Primed seeds with or without BA also emerged more rapidly and produced heavier seedling shoots than nontreated seeds. Using primed lettuce seeds combined with specific soil amendments can improve lettuce stand establishment under various field conditions. Chemical name used: 6-benzyladenine (BA).
Production and quality of bell pepper (Capsicum annuum) fruit were evaluated in a passively ventilated greenhouse, in soilless media trellised to a “V” system (two-stempruned plants) or the “Spanish” system (nonpruned plants) in flat bags or nursery pot containers; and densities of 1.5, 1.9, 3.0, and 3.8 plants/m2 (0.14, 0.18, 0.28, and 0.35 plants/ft2), in a winter-to-summer-crop in Gainesville, Fla. The trellis systems did not affect total marketable fruit yields but production of extra-large fruit was higher (38%) in non-pruned than in pruned plants. Marketable fruit yields were similar in plants grown in bags and pots, and had positive linear responses to increased plant density. Not pruning reduced by half the percentage of fruit with blossom-end rot. Pruned plants produced 50% fewer flower bud supporting nodes than non-pruned plants but had a greater percentage of fruit set. Regardless of trellis systems, fruit set per plant decreased linearly as plant density increased. Overall, the “Spanish” trellis system at a density of 3.8 plants/m2 resulted in greater yields of extra-large fruit and required 75% less labor than the “V” system to prune and support the plant canopy.
Weakening of the endosperm tissue around the radicle tip before radicle protrusion and a potential role of endo-β-mannanase during germination of lettuce seeds (Lactuca sativa L.) at high temperature (35 °C) were investigated. Seeds from the thermotolerant genotypes `Everglades' and PI 251245 had greater endo-β-mannanase activity before radicle protrusion at 35 °C than the thermosensitive genotypes `Dark Green Boston', `Valmaine' and `Floricos 83'. Thermotolerant genotypes also generated more ethylene at high temperature. At 35 °C, germination of `Dark Green Boston' and `Everglades' seeds produced at days/nights of 20/10 °C was 10% and 32%, respectively, whereas germination of seeds produced at days/nights of 30/20 °C was 67% and 83%, respectively. Higher endo-β-mannanase activity was observed before radicle protrusion in `Dark Green Boston' seeds produced at 30/20 °C compared with those produced at 20/10 °C. A relationship between seed germination at high temperature, ethylene production, and an increase in endo-β-mannanase activity before radicle protrusion was confirmed.