Search Results
You are looking at 1 - 10 of 14 items for :
- Author or Editor: Donald N. Maynard x
- Journal of the American Society for Horticultural Science x
Abstract
Fall and spring spinach experiments were conducted in the greenhouse in sand culture. Nutrient stress was produced late in the growth period by removal of N, P, K, Ca, or Mg from the nutritional regime. Nitrogen stress caused a general restriction in growth and chlorophyll concentration while dry weight was reduced by P and K stress only in the spring experiment. Element stress generally resulted in lower concentrations of that element in mature leaves in the fall and in both mature and immature leaves in the spring investigation. Redistribution generally occurred at a sufficient rate to prevent lower element concentrations in the fall but not in the spring study. K, Ca, and Mg accumulated in mature spinach leaves while N and P were found in higher concentrations in immature leaves.
Abstract
Bean, sweet corn, cucumber and pea plants were susceptible to ammonium toxicity when cultured on an ammonium source of N. Growth of plants was normal, however, when the pH of the nutrient solution was maintained near neutrality by the addition of CaCO3. The control of acidity was effective in altering the distribution of ammonium; ammonium accumulation in the shoot was lessened and accumulation of amides in roots was enhanced. A natural resistance to ammonium was exhibited by the onion plant since it did not accumulate ammonium in the leaves; however, the nonchlorophyllous bulb acted as an ammonium sink.
Abstract
The effects of replanting stand-deficient plots on marketable tomato (Lycopersicon esculentum Mill.) fruit size and yields were investigated at Bradenton, Fla. during the 1986 spring and fall seasons. Treatments consisted of a control (10-plant plot) and plots with 9, 8, and 7 (10%, 20%, and 30%) missing plants. Other plots with the same stand deficiency were replanted to attain a complete stand 2 or 3 weeks and 1, 2, or 3 weeks after initial transplanting in the spring and fall experiments, respectively. Plots with 30% stand reduction produced a lower weight and number of marketable fruit per hectare than control plots in both seasons. In spring, replanting stand-deficient plots did not increase marketable fruit yields relative to plots not replanted, regardless of the time of replanting or percentage of stand reduction. In fall, under an unfavorable environment due to a late infestation of bacterial spot, replanting plots with 30% stand reduction increased marketable fruit yields over similar plots that were not replanted, when the replanting occurred 1 or 2 weeks after initial transplanting, but not when replanting was delayed 3 weeks. Small, medium, or extra-large marketable fruit weight per hectare were similar in both seasons for plots with 30% stand reduction, whether replanted or not. Mean fruit size (g/fruit) did not differ significantly among treatments in either experiment. These results suggest that replanting improved marketable tomato yields only when the level of stand deficiency reached 30% and only in a stressed environment.
Abstract
Transplants of asparagus (Asparagus officinalis L.) were grown in sand culture under varying ratios of NO3 and NH4. Maximum growth occurred in a nutrient solution with a N ratio of 75% NO3 – N and 25% NH4 – N. Growth was significantly reduced when the N composition was either 100 or 75% NH4 – N. CaCO3 reduced ammonium toxicity but also reduced seedling growth.
Abstract
Spinach, Spinacia oleracea, L., cv. America, Heavy Pack, and Hybrid 424 were grown in sand culture with variable NO3 concentrations from 0.187 to 48 meq/l. The cultivars were representative of savoyed, semisavoyed, and smooth-leaf types, respectively. The plants were harvested when those cultured at 12 and 18 meq NO3/l had obtained approximate market maturity. At this time an array of deficiency, sufficiency, and toxicity symptoms were evident. Great differences in NO3 accumulation and critical NO3 concentrations occurred among cultivars. Critical NO3-N concentrations for the whole leaves of spinach plants were: ‘America’, 0.17%, ‘Heavy Pack’, 0.15%, and ‘Hybrid 424’, 0.045% of their dry weights. Calculations relating spinach consumption and impaired human health suggest that adult health should not be affected even with massive ingestion of spinach.
Abstract
Brussels sprouts (Brassica oleracea var. gemmifera, Zenker) were grown in sand culture at variable Ca levels in the greenhouse. More Ca accumulated in leaves than in sprouts. With plant growth restricted by late seeding and low greenhouse temp, typical Ca deficiency symptoms occurred on the growing points of plants cultured at low Ca levels, but internal browning did not occur. When growth was enhanced by cultural modifications, sprout internal browning occurred at low Ca levels and decreased as Ca levels were increased. The incidence of internal browning was related to low Ca concn in sprouts.
Abstract
The accumulation of cations and NO3-N was higher in cucumber shoots than in pea shoots grown on nitrate nutrition. Total N concn in shoots did not differ between the species. Ammonium nutrition suppressed cation accumulation in cucumbers but not in peas. Differences in cation accumulation in the shoots are attributed to the form in which N is translocated from root to shoot.
Abstract
Seedlings of 44 tomato strains were screened in low (16.5 mg/plant) Ca nutrient solutions. Tolerance to low Ca was rated according to plant appearance and efficiency ratios, i.e., tissue produced (g) per unit of Ca (mg) in the tissue. Correlations among various symptom ratings and Ca-efficiency ratios for roots, stems and petioles, and laminar tissue showed that only 1 deficiency symptom and dry weight or 1 symptom and 1 efficiency ratio were necessary to rank plants. These methods showed that Plant Introductions (PI) 340909, 341984, and 341988 (all L. esculentum) were Ca-inefficient, whereas PI 205040 (L. esculentum cv. Yellow Peach) and PI 129021 (L. esculentum × L. pimpinellifolium) were Ca-effi-cient. Differences in efficiency were maintained when these selections were grown with higher Ca concentrations.
Abstract
Tomato, tobacco, pepper, petunia, and eggplant were screened for their tolerance to continuous (NH4)2SO4 applications. Stem lesions, analogous to those which appear on tomato during ammonium toxicity, were formed on eggplant but not on the other species. Of the plants tested, tobacco was the most tolerant to applications of (NH4)2SO4. Potassium applications increased the ammonium concentration of tobacco tissues but lowered the ammonium concentration of tomato tissues. Diamine concentrations were increased by the application of (NH4)2SO4. The application of KCl decreased the putrescine concentration of tobacco and increased the concentration of cadaverine in tomato and tobacco. The application of putrescine-2HC1 in aqueous solution to cut stem ends of axillary shoots of tomato and tobacco induced the formation of stem lesions analogous to those formed by the (NH4)2SO4 fertilization of tomato. It is postulated that the tolerance of tobacco to stem lesion formation is related to putrescine utilization in nicotine synthesis.
Abstract
Eighteen spinach cultivars were found to vary considerably in NO3 concentrations in their leaves. Smooth-leafed cultivars were lower in NO3 concentration than heavily savoyed cultivars. Some medium or semisavoyed cultivars were low NO3 accumulators, and others were high accumulators. A low degree of savoyedness appears to be a useful factor in the selection of spinach cultivars with tendencies for low NO3 accumulation.