Abstract
Bud dormancy and cold hardiness are critical adaptations for surviving winter cold stress for temperate perennial plant species. In grapevine, acquisition of cold hardiness requires dormancy induction in the early winter and careful maintenance of dormancy state throughout winter. With sufficient exposure to low, non-freezing temperatures (chilling requirement), grapevine buds transition between early (endodormant) and late winter (ecodormant) states. The objective of this study was to uncover the relationship between fulfilment of the chilling requirement and the effects of various temperatures on loss of cold hardiness (deacclimation). The relationship between chilling requirement and temperature as it affects the rate of deacclimation (kdeacc) was examined for dormant cuttings of Vitis vinifera, V. aestivalis, V. amurensis and V. riparia. The effect of temperature on kdeacc was exponential at low and logarithmic at high temperatures. Deacclimation rates also increased in magnitude as chilling accumulated demonstrating a change in deacclimation potential (Ψdeacc), following a logarithmic response. The combination of Ψdeacc and kdeacc indicates genotype-specific thermal efficiency for deacclimation and growth in Vitis that may be overlooked by simple growing degree-day computations. The Ψdeacc and kdeacc parameters are genotype-specific and will greatly increase the refinement of models predicting effects of climate change on phenology. Deacclimation rates represent a quantitative determinant of dormancy transition and budbreak in grapevine and will assist researchers in selecting germplasm for differences in chilling requirement and thermal efficiency.
Highlights
Due to their general stationary habit, plants have evolved many different coping mechanisms to survive stressful environments such as drought and temperature
Dormancy state, cold hardiness and budbreak are complex traits driven by the interaction of physiological and climactic attributes
This study was conducted to gain a better method for predicting dormancy transition and chilling requirement in grapevine, as well as to understand how deacclimation processes and resulting budbreak are impacted by dormancy state
Summary
Due to their general stationary habit, plants have evolved many different coping mechanisms to survive stressful environments such as drought and temperature. Dormancy is the temporary cessation of visible growth in meristem containing structures, such as buds, and is divided in three types: para-, endo-, and ecodormancy Paradormancy is the suspension due to physiological factors within the plant but outside of the dormant structure, such as the suppression of lateral growth by the apical meristem (i.e. apical dominance). Paradormant buds transition into endodormancy as daylength and temperatures decrease, a state suspension of growth due to unknown endogenous factors within the dormant structure, preventing growth during times when environmental conditions fluctuate between conducive and inhibitory (Horvath, Anderson, Chao, & Foley, 2003). It is generally understood that exposure to low, non-freezing temperatures is necessary (chilling requirement) to transition to the third dormancy state, ecodormancy. Tissues maintain a dormant state during ecodormancy due to unsuitable environmental conditions
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