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- Author or Editor: Russell L. Weiser x
Stayman apples are predisposed to cracking. Trees whose trunks were scored and foliage sprayed with GA4+7, NAA 800, and Vapor Guard had significantly fewer apples crack than controls. The skin strength and stretch distance were the same for control and treated apples. However, slices of treated apple expanded significantly more than control apples when immersed in distilled water for 45 minutes. During this treatment the amount of water taken up was not significantly different, which may indicate the difference lies in the cell structure. Hypodermal cells of control apples appear to be more elongated and have thicker cell walls than treated apples. Cell wall sugar and amino acid components will be measured to see if this discrepancy can be attributed to cell wall structural properties. These results suggest that stayman cracking occurs when the expansion of the hypodermic cannot keep pace with expansion of the fruit. It is further hypothesized that this difference is due to a difference in cell wall composition and consequent effect on wall extensibility.
Stayman apples are predisposed to cracking. Trees whose trunks were scored and foliage sprayed with GA4+7, NAA 800, and Vapor Guard had significantly fewer apples crack than controls. The skin strength and stretch distance were the same for control and treated apples. However, slices of treated apple expanded significantly more than control apples when immersed in distilled water for 45 minutes. During this treatment the amount of water taken up was not significantly different, which may indicate the difference lies in the cell structure. Hypodermal cells of control apples appear to be more elongated and have thicker cell walls than treated apples. Cell wall sugar and amino acid components will be measured to see if this discrepancy can be attributed to cell wall structural properties. These results suggest that stayman cracking occurs when the expansion of the hypodermic cannot keep pace with expansion of the fruit. It is further hypothesized that this difference is due to a difference in cell wall composition and consequent effect on wall extensibility.
Abstract
Freezing woody stem segments of supercooling and non-supercooling species resulted in acoustic emissions in characteristic reproducible patterns. In the supercooling species examined (Fraxinus americana, Malus × ‘Dolgo’, Pyrus communis, and Fraxinus pennsylvanica), many acoustic emissions began after extracellular freezing, but before freezing of the supercooled fraction, and ended near −40°C. Acoustic emissions also occurred in species that did not supercool (Pinus edulis, Pinus ponderosa, and Cornus sericea), but to a much lesser extent. Cavitation of water within the cells during freezing is discussed as a source of acoustic emissions and possible cause of freezing injury.
Alaska peas (Pisum sativum `Alaska') were germinated in the dark at 25C. After three days, when the shoots were approx. 1.5 cm, treatments were initiated. ABA, at 10-4M, was exogenously applied through the root solution. The control peas remained in distilled water. All treatments involving the application of ABA were applied under green safe light. Light treatments were applied using overhead fluorescent lights for designated timed intervals (0 to 20 min) over 3 days. A methanol bath was then used to induce freezing stresses from 0 to -9C. The combination treatment of light and ABA had the lowest LT50 (more cold tolerant) followed by light, dark, and dark with ABA (least cold tolerant). Extensin levels, plant growth, and stem bendability were also recorded.
`Tifblue' Blueberries (Vaccinium ashei) have poor or delayed budbreak in warm growing regions due to a lack of chilling temperatures. Hydrogen cyanamide(H2CN2) is known to break dormancy in buds. We tested the response of `Tifblue' blueberry buds to concentrations of hydrogen cyanamide at different dormancy stages with respect to budbreak and phytotoxicity. Blueberry bud sticks were harvested during the growth season at three week intervals. H2CN2 (0.05, 0.125, 0.25, 0.5 M), hot water (47C) and a control (distilled water at 0C) were used. Treated bud sticks were forced to break under light at 18-26C. Flower and leaf buds broke after 10-14 days. H2CN2 above 0.25 M was highly phytotoxic to flower buds, but not leaf buds. H2CN2 at 0.125 M was most effective in breaking flower and leaf buds at all dormancy stages. ABA and polyamine levels in buds shall be analyzed.
Alaska peas (Pisum sativum `Alaska') germinated in a dark growth chamber were treated ABA dissolved in a small amount of acetone before diluting in distilled water with 0.1% spreader. A blank solution was identically prepared without ABA. Both solutions were applied via paintbrush to the epicotyls of the peas every twelve hours for seven days following emergence. The blank solution was applied to two controls, chronological and physiological. A methanol bath was used to induce freezing and chilling stresses. ABA significantly improved cold tolerance (electrolyte leakage) in the pea seedlings for both freezing and chilling stress as compared to the physiological and chronological controls. Visual observation of the pea stems suggested a difference in stem flexibility among ABA treated peas and the controls. Pea stem elasticity and plasticity were measured along with plant dry weight, cell wall weight/gram fresh weight, and the quantity of cell wall sugars and amino acids.