Water transport distance’s effect on tylose development and sap flow in Meili grapevine

Grape pruning may lead not only to some physical damages to the xylem vessels but also to the tylose blockage in these vessels. However, there is little information on vessel lumens blockage by tylose decreasing the original capability of sap flow transportation. In present studies, to elucidate the effect of tyloses on both water transport during xylem development and variations in hydraulic conductance with increasing distance of water transport, shoots of three different-shaped vines were evaluated in this study, based on observation of tylose developments and sap flow measurements. The study showed that, for different-shaped vines, sap flow transport distance was significantly associated with quantity of tyloses. Vessels of cordon training (CT) vines had the largest percentage of partly and completely blocked vessels among three different-shaped vines, up to 65.4% and 33.2%, respectively. For renewal crawled cordon training (rCCT) and perennial crawled cordon training (pCCT) vines, shoots of perennial branches (pCCT) had a larger percentage of partly and completely blocked vessels (39.7% and 16.7%, respectively) than shoot of current-year shoots (rCCT vines, 35.6% and 9.3%, respectively). Sap flow rates and sap flow transport distances had a negative correlation for sap flow rates of same-shaped vines. In addition, sap flow rates and sap flow transport distances (namely, number of nodes) and/or quantity of tyloses varied during different-shaped vines. Overall, vessels with few tyloses showed significantly higher values of hydraulic conductance than vessels were completely or partially occluded by more tyloses.