Natural inducing factors of grape bud dormancy and their regulation on respiratory metabolism during dormancy induction

High chilling requirement grape (Vitis vinifera-V. labrusca cv. Summer Black) was used to evaluate its dormancy under short sunlight day (SD), long sunlight day (LD) and natural condition (CK). The results indicated that grape bud dormancy could be induced by natural low temperature and short sunlight alone or together. Short sunlight was the main contributor to the dormancy of grape bud, followed by natural low temperature. SD had more effect on dormancy induction under the same temperature when compared with LD. The grape dormancy induction stopped when the total respiratory rate reached the highest level. During the dormancy induction period, the proportion of pentose phosphate pathway (PPP) operation activity or capacity to total respiratory rate increased from 16.0% to 20.1% or 22.3% to 26.0%, respectively; similarly, the proportion of operation activity or capacity of alternate pathway to total respiratory rate rapidly increased, i.e., from 19.4% to 27.3% or 38.2% to 46.8%. Both low temperature and shor