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- Author or Editor: J.W. Hall x
- Journal of the American Society for Horticultural Science x
Abstract
Broccoli (Brassica olerica L. var. italica) and corn (Zea mays L.) N-treated adjacent plots had essentially the same initial Ν content. Extractable inorganic Ν to a depth of 60 cm (N at 28 to 48 kg·ha-1) was considerably less than the Ν taken up into the total above-ground parts of the crop (N at 118 to 157 kg·ha-1); thus, both crops depended on mineralization of soil Ν for their growth. Although broccoli and corn had the same total demand for Ν as shown by total uptake, only broccoli responded to Ν application. Since corn required Ν over a longer period of time (116 days) than broccoli (90 days), the net mineralization rate of soil Ν [0.8 to 1.0 kg·ha-1 (per day)] matched approximately the average Ν uptake rate over the whole season [1.1 to 1.2 kg·ha-1 (per day)] in the corn trial. Net Ν mineralization rate [-0.1 to 1.4 kg·ha-1 (per day)] tended to be less than the average Ν uptake rate by broccoli (1.3 to 3.1 kg·ha-1 (per day)], resulting in the response to Ν applied. Slightly more downward movement of inorganic Ν occurred in the 1982 than in the 1979 broccoli trial. This coincided with slightly higher precipitation in 1982 particularly late in the growing season. By using path coefficient analyses, it was found that several plant variables were consistently correlated with horticultural yield, but the nature of the relationship was not consistent from year to year, suggesting that slightly different mechanisms contributed to the yield effect each year but that the net result was similar.
Abstract
A single harvest method using horticultural maturity rating data was tested in 2 years of Ν application field trials with broccoli. Using analysis of variance with the maturity data as covariates, it was possible to evaluate how broccoli yield response to Ν was influenced through the effect of Ν on maturity. This single harvest method simplified field operations and facilitated interpretation of Ν uptake data. Nitrogen treatments did not significantly alter maturity of broccoli in either year. Broccoli yield increased with up to 250 kg·ha–1 of Ν in both years. Sweet corn, which was grown adjacent to the broccoli in the first year, did not respond to similar applications. Nitrogen did not preferentially increase vegetative growth of broccoli, but in one year increased head yield. Nitrogen accumulated in the head of broccoli. The corn crop accumulated extra Ν in the vegetation and this was assumed to be luxury uptake. The difference in response to Ν of corn and broccoli was assumed to be the result of a difference in Ν use or uptake efficiency rather than overall demand, since the total above-ground uptake by corn and broccoli was quite similar.
Greenhouse-grown `Bison' and `Doria' peppers (Capsicum annuum L.) were harvested when mature green (MG) (>95% surface green) or ripe (>95% of surface red or yellow). Both cultivars responded similarly to temperature and neither exhibited chilling injury (CI), as indicated by surface pitting, after storage at 13C for 1 or 2 weeks. Ripe peppers showed no CI when held at 1C for 1 or 2 weeks, while MG peppers exhibited CI after these treatments. Exposing MG peppers to 1C for 3 days caused CI and stimulated C2H4 (12.3x) and CO2 production (2.5x). In contrast, a similar exposure of ripe peppers did not cause CI but stimulated C2H4 (6.5x) and CO2 production (1.4x). It seems that CO2 and C2H4 production was stimulated by exposure to 1C, not necessarily by CI development. Our data question the physiological significance of elevated CO2 and C2H4 production in CI development. The observed tolerance of ripe peppers to 1C suggests that ripe greenhouse-grown peppers can be stored at temperatures lower than those currently recommended for bell peppers.
Abstract
Results from a 4-year study indicate that flesh browning in CA-stored ‘Delicious’ apples (Malus domestica Borkh.) is a low-temperature disorder. Little or no flesh browning occurred at storage temperatures of 2°C or higher. Prestorage treatments which reduced flesh browning were dips in calcium and diphenylamine solutions, delays at 20° prior to storage, and exposure to 38°. Gibberellic acid dips had no effect on the disorder. Less flesh browning was found in a 1% CO2 than in a 1.7% CO2 atmosphere at −0.5°, but little effect was observed from CO2 concentration at a 2° storage temperature. The disorder was more prevalent with advanced maturity of the fruit. Regression analysis of variables evaluated at or before harvest showed that increased fruit size, and to a lesser extent the presence of watercore, were important factors in development of flesh browning.
Various stem-training systems were applied to greenhouse-grown `Mustang' cucumber (Cucumis sativus L.) plants at two production stages. Training systems determined the number of stems per plant, orientation of laterals, and leaf: fruit ratio. Training systems permitting high canopy light penetration resulted in darker fruit and a longer shelf life. Shelf life was positively related to rapid fruit growth in Expt. 1 but not in Expt. 2. Training systems to achieve a long shelf life of greenhouse-grown long English cucumber are described.
Abstract
Pseudomonas syringae van Hall, an ice nucleation active (INA) bacterium, increased frost susceptibility of tomato (Lycopersicon esculentum Mill.) and soybean (Glycine max L.) when sprayed on leaves prior to low temperature stress. Tomato and soybean plants inoculated with INA bacteria were nucleated and frozen at −4° and −5°C respectively. Control plants that were free of INA bacteria supercooled and survived to −8°. A threshold INA bacterial concentration of about 4 × 105 cells/ml was necessary for ice nucleation. Ice nucleating active bacteria preconditioned at 2° showed a marked increase in efficiency of ice nucleation. Preconditioned INA bacteria had ice nucleation temperatures 5° higher than INA bacteria held at 21°.