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Mature green tomatoes (Lycopersicon esculentum Mill. cv. 674) were gassed with 160 to 275 μl/liter ethylene, depending upon the experiment, from either a Catalytic Generator or gas cylinder. Tomatoes were evaluated during subsequent ripening for fruit color development and taste. The combined results of two triangle difference taste tests indicated that the panel could tell a slight difference in taste of tomatoes based on gassing method. However, panelists did not reveal a strong preference for tomatoes from either method or consistently mention a certain characteristic that made the two groups of tomatoes different. Gas chromatographic analyses of the effluent from the Catalytic Generator indicated that several compounds other than ethylene were present.
A field study was initiated in 1981 in western North Carolina to determine the influence of eight groundcover management systems on quality of `Redchief Red Delicious' apple (Malus domestica) grafted onto rootstock of M VIIA. Management systems included: bare soil, Secale cereale mulch, minimal cultivation, Festuca arundinacea, Dactylis glomerata, Poa pratensis, Muhlenbergia schreberi and Rubus sp. Thus far, fruit quality data indicate that fruits produced in plots of cool-season grasses are smaller and less mature than those produced in vegetation-free plots or plots of warm-season grasses. A negative correlation was noted between high fruit quality and water deficit stress as measured by water potential and stomatal conductance.
A field study was initiated in 1981 in western North Carolina to determine the influence of eight groundcover management systems on quality of `Redchief Red Delicious' apple (Malus domestica) grafted onto rootstock of M VIIA. Management systems included: bare soil, Secale cereale mulch, minimal cultivation, Festuca arundinacea, Dactylis glomerata, Poa pratensis, Muhlenbergia schreberi and Rubus sp. Thus far, fruit quality data indicate that fruits produced in plots of cool-season grasses are smaller and less mature than those produced in vegetation-free plots or plots of warm-season grasses. A negative correlation was noted between high fruit quality and water deficit stress as measured by water potential and stomatal conductance.
The influence of ambient UV radiation on growth and flavonoid concentration of Lactuca sativa L. (`New Red Fire' lettuce) was examined. Plants were grown outdoors for 31 days from seed in window boxes covered with one of three different UV filters—UV transparent tefzel (10%T, 245 nm), UV-B-absorbing polyester (10%T, 319 nm), or UV-Aand UV-B-absorbing Llumar (10%T, 399 nm). Plants were grown in plastic pots filled with vermiculite and subirrigated with nutrient solution. Lettuce plants grown in the absence of solar UV-A and UV-B radiation showed a significant increase in leaf number and biomass of tops and roots as compared to those grown under ambient UV-A and UV-B. They also had a lower concentration of flavonoids and other UV-absorbing substances at 270, 300, and 330 nm (on both an area and on a dry-weight basis). These findings should be of interest to researchers involved in protected cultivation because the transmission of UV-B radiation is greatly attenuated by standard greenhouse glass. Our results also have implications for human nutrition, since bioflavonoids are important as antioxidants.
Carfentrazone is a broadleaf weed control herbicide that is also used for control of silvery-thread moss (Bryum argenteum) in creeping bentgrass (Agrostis stolonifera) putting greens. Field studies were initiated in June 2006 and May 2007 to evaluate silvery-thread moss control with carfentrazone alone, carfentrazone applied with nitrogen (N) and/or topdressing (TD), N alone, TD alone, and mancozeb plus copper hydroxide. All treatments except for mancozeb plus copper hydroxide and the non-treated control reduced silvery-thread moss populations 16 weeks after initial treatment. Carfentrazone applied alone and carfentrazone followed by N decreased silvery-thread moss populations by 39%. Carfentrazone followed by TD and carfentrazone followed by N + TD decreased silvery-thread moss populations by 73% and 66%, respectively. These data indicate the importance of using cultural practices to control silvery-thread moss on creeping bentgrass putting greens.
Over-fertilization (i.e., the application of fertilizer nitrogen (N) in excess of the tree or vine capacity to use it for optimum productivity) is associated with high levels of residual nitrate in the soil, which potentially contribute to groundwater and atmospheric pollution as a result of leaching, denitrification, etc. Overfert-ilization also may adversely affect productivity and fruit quality because of both direct (i.e., N) and indirect (i.e., shading) effects on flowering, fruit set, and fruit growth resulting from vegetative vigor. Pathological and physiological disorders as well as susceptibility to disease and insect pests also are influenced by the rate of applied N. Over-fertilization appears to be more serious in orchard crops than in many other crop species. The perennial growth habit of deciduous trees and vines is associated with an increased likelihood of fertilizer N application (and losses) during the dormant period. The large woody biomass increases the difficulty in assessing the kinetics and magnitude of annual N requirement. In mature trees, the N content of the harvested fruit appears to represent a large percentage of annual N uptake. Overfertilization is supported by a) the lack of integration of fertilizer and irrigation management, b) failure to consider nonfertilizer sources of plant-available N in the accounting of fertilizer needs, c) failure to conduct annual diagnosis of the N status, and d) the insensitivity of leaf analysis to over-fertilization. The diversity of orchard sites (with climatic, soil type, and management variables) precludes the general applicability of specific fertilization recommendations. The lack of regulatory and economic penalties encourage excessive application of fertilizer N, and it appears unlikely that the majority of growers will embrace recommended fertilizer management strategies voluntarily.
Abstract
Mung bean (Phaseolus aureus Roxb.) cuttings and cucumber (Cucumis sativus L. cv. Marketer) seedlings were cultured in water extracts of bark from silver maple (Acer saccharinum L.) hackberry (Celtis occidentalis L.), sycamore (Platanus occidentalis L.) and cottonwood (Populus deltoides Marsh.). Extracts of fresh silver maple bark inhibited root elongation of cucumbers and the adventitious rooting of mung bean. Composting the silver maple bark for 30 days prior to preparing the water extracts reduced inhibition. Pretreatment of fresh silver maple bark extracts with insoluble polyvinylpyrrolidone (PVP) reduced inhibition and indicated that the inhibitory compound was phenolic in nature. Chromatography and spectral analysis of common phenolic compounds and silver maple bark extracts revealed the toxic substance was similar to tannic acid.
Carbon and nitrogen budgets were determined for `Colonial' (spring) and `Equinox' (fall) tomato (Lycopersicon esculentum Mill.) plants grown on raised beds with black polyethylene mulch and supplied with preplant-N at 0, 67, 134, 202, or 269 kg·ha–1. For both spring and fall experiments, we quantified the partitioning of dry matter, N, and C, and determined marketable and total yield. In the spring study, the concentration of N in leaves, stems, and in total plants increased linearly with level of N fertilization, whereas a quadratic relationship described the amount of N contained in the fruit (maximum with 202 kg·ha–1). Quadratic relationships occurred between rate of fertilization and leaf weight, stem weight, total plant weight, marketable yield, and total yield in the spring study, with maximum values at 134 or 202 kg·ha–1 rates of N fertilization. In the fall crop, fewer significant relationships occurred between dependent variables and rate of N fertilization, and coefficients of determination tended to be much lower than in the spring study. The fraction of N in leaves, stems, and roots (fall study only) was influenced by N fertilization. Effects of N fertilization on the fraction of C partitioned to any plant part was either nonsignificant or significant at P = 0.05. Total yield was related to N fertilization in a quadratic manner, but marketable yield was significantly affected only in the spring study. In both studies, increasing the rate of N fertilization reduced the C: N linearly for all tissues. In all cases, the quantity of N partitioned to vegetative tissue was at least 65% of that partitioned to the fruit, and the quantity of C in the plant was at least 74% of that in the fruit. In conclusion, although N fertilization above 202 kg·ha–1 generally increased the concentration and total amount of N in vegetative tissues, it did not increase yield. Also, the highest rate of N fertilization (269 kg·ha–1) resulted in a much lower efficiency of applied N [defined as: (N plant + N fruit)/N applied], and a much higher level of residual soil nitrate-N.
Rootstock significantly alters the pattern of shoot growth of pistachio (Pistacia vera) cv. Kerman. Trees on P. atlantica typically produce a single flush of spring growth whereas trees on P. integerrima selection PGI and P. atlantica × P. integerrima selection UCB-1 can produce multiple flushes during the season. Terminal buds of shoots on all three rootstocks were dissected during the dormant season to determine the number of preformed nodes. Data indicate that there are 8-9 nodes preformed in the dormant terminal bud of shoots from Kerman trees and that this number is independent of rootstock, canopy location, crop load, and shoot carbohydrate concentration, suggesting genetic control. This number corresponds with the number of nodes typically found on a shoot at the end of the spring growth flush. Unlike the spring flush which is preformed in the dormant bud, later flushes are neoformed, that is, nodes are initiated and extended during the same season. Neoformed growth depends on current season photosynthates and may compete with fruit growth for available resources. Neoformed growth is sensitive to water stress and trees on all three rootstocks grown under two levels of regulated deficit irrigation showed a reduction in both the number and length of neoformed shoots. Preformed shoot growth did not appear to be reduced under water stress conditions, supporting the hypothesis that preformed shoots are more dependent on environmental conditions during the season they are initiated than during the season they are extended. Additionally, preformed shoots on well irrigated trees were similar in length for all rootstocks, further supporting the idea that preformed shoots are under genetic control and are not easily manipulated.
`Colonial' tomato (Lycopersicon esculentum Mill.) plants were grown on raised beds with black polyethylene mulch, drip irrigation, and preplant-N rates of 0, 67, 134, 202, or 269 kg·ha-1. Petiole sap was collected 7 and 13 weeks after transplanting. Concentrations of NO3-N, free amino acids, total amino acids, and total-N (the sum of NO3-N and amino acid-N) were examined as functions of the rate of N fertilization. Also, each of these compounds was used as an independent variable as a predictor of fruit yield. Seven weeks after planting, the concentrations of NO3-N and 15 of 18 of the free amino acids were correlated with the rate of N fertilization, but concentrations of bound or total amino acids were not. The amount of NO3-N accounted for 37% of the total-N in the 0 kg·ha-1 treatment, and up to 83% in the 202 kg·ha-1 treatment. NO3-N was highly correlated with total-N for both nonhydrolyzed and hydrolyzed sap (R 2 = 0.98). Thirteen weeks after transplanting, neither the concentration of NO3-N nor that of amino acids, other than asparagine, glutamine, and proline, were significantly related to the rate of N fertilization. On both dates, concentrations of glutamine plus glutamic acid were correlated with rate of N fertilization whether expressed as absolute values or as percentage values. N fertilization rate and the concentration of NO3-N or total-N were related to total fruit yield (R 2 = 0.69 to 0.74), and marketable fruit yield (R 2 = 0.78 to 0.82). N-fertilization rate and petiole sap concentrations of NO3-N or total-N were also correlated with the N contained in total or marketable yield. Petiole sap variables measured 13 weeks after transplanting were not significantly correlated with fruit yield or the quantity of N contained in the fruit. Free, bound, or total amino acids in petiole sap were not as well correlated with fruit yield parameters as were N-fertilization rate, NO3-N, or total-N in petiole sap.