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Cold hardiness and water content during deacclimation of grapevine bud and cane tissue




Hamman, Richard A., Jr., author

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Computer assisted thermal analysis was used to measure deep supercooling in dormant bud and cane tissue of Vitis vinifera L. cv. 'Merlot' during a five week deacclimation time period. The temperature of the Low Temperature Exotherm (LTE), an indicator of hardiness, of both cane (internode) and primary bud tissue responded to weekly increases in air temperatures with bud tissue responding faster than cane tissue. Bud tissue from pruned and unpruned canes retained the capacity to supercool until early bud swell 18 April 1987, when the mean LTE temperature of -9.8°C became obscured by High Temperature Exotherms (HTEs) occurring between -5 and -8°C. Cane tissue had lower LTEs than bud tissue on each date and at each position. Cane positions nearest the trunk, whether canes were pruned or unpruned, were found to be slightly hardier than those more distally oriented, which was not observed with buds. Pruning treatments did not influence the loss of hardiness in either bud or cane tissue. Water content of canes was more affected by all three factors (date, position, and pruning) than was hardiness. Bud water content was only affected by date, and was lower than cane water content for every date and each position throughout the study. Canes increased in water content with each more distal position. Pruning slowed the rate of cane hydration during the week it was most rapid, especially at the most distal position. Observations during the most pertinent three weeks of this study indicate that cane tissue hydrates rapidly but dehardens only slowly, while buds deharden more quickly yet have only a small increase in bulk water content. The main effect of pruning was on cane water content.


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Plants -- Hardiness
Plants -- Effect of stress on


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