Pages

Friday, April 24, 2015

Spring Bud Deacclimation and Cold Weather

We have been having a very cold week with temperatures dipping into the low 30's. One of the critical times for vine damage is during the spring deacclimation phase, when the grapevine is rapidly transitioning from a cold-hardy to a cold-tender stage based on the air temperature. By budbreak and shoot growth, only a few degrees below 32 oF may be lethal to grapevine tissue.
The bud however, has developed certain survival strategies:
  • During cold acclimation, the cells in the bud dehydrate and develop freeze resistant compounds such as sugars, amino acids and proteins.
  • The overwintering bud is only weakly connected to the vascular system of the vine, protecting it from rehydration.
  • A hard, almost varnish-like scale covers the bud making it impervious to exterior moisture.
  • Dense, woolly hairs found on the outer surface of all of the interior bud scales keeps the bud tissues dry over the winter.
  • It is a complex bud made up of primary, secondary and tertiary buds. If the primary bud is damaged, the secondary bud or the tertiary bud may grow.
Since we haven't had bud break yet, we may be safe. Crossing fingers since the weather forecasters are calling for a hard freeze tonight.
References:
1. A really informative online article on cold and the grape vine can be found here:
Understanding and Preventing Freeze Damage in Vineyards
~ Workshop Proceedings ~
December 5-6, 2007 University of Missouri-Columbia

No comments:

Post a Comment