| dc.description.abstract | Endodormancy (ED) and cold hardiness (CH)
are two strategies utilized by grapevine (Vitis vinifera L.)
buds to survive unfavorable winter conditions. Each phenomenon
is triggered by different environmental cues—ED
by short-day (SD) photoperiod and cold hardiness (CH) by
low temperatures. In grapevine buds, CH occurs mainly via
the supercooling of intracellular water, a phenomenon
associated with the low temperature exotherm (LTE). The
seasonal dynamics of ED and CH were studied on
grapevines buds by determining the BR50 (time required to
reach 50 % of bud break under forced conditions) and the
LTE, which measure the depth of ED and the level of CH,
respectively. Overlapping BR50 and LTE curves revealed
that CH began to develop in late April, when buds were
fully endodormant and daily mean temperatures had started
to drop below 14 C, suggesting that ED is a prerequisite
for the acquisition of full CH. Increase in starch content
and thickening of the cell wall (CW) of meristematic cells
which occurs in dormant buds could be involved in structural
and metabolic changes that favor CH subsequent
acquisition. Interestingly, the thickening of the CW and the
synthesis of starch which are associated with ED were
induced by a SD-photoperiod, while the hydrolysis of starch, the accumulation of soluble sugars, and the upregulation
of dehydrin genes, which are associated with
CH, were induced by low temperatures. Overall, the results
indicate that structural, metabolic, and transcriptional
changes that occur during ED in grapevine buds are necessary
for the further development of CH. | |
