Analysis of Non-Structural Carbohydrates and Xylem Anatomy of Leaf Petioles Offers New Insights in the Drought Response of Two Grapevine Cultivars

Abstract

In grapevine, the anatomy of xylem conduits and the non-structural carbohydrates (NSCs) content of the associated living parenchyma are expected to influence water transport under water limitation. In fact, both NSC and xylem features play a role in plant recovery from drought stress. We evaluated these traits in petioles of Cabernet Sauvignon (CS) and Syrah (SY) cultivars during water stress (WS) and recovery. In CS, the stress response was associated to NSC consumption, supporting the hypothesis that starch mobilization is related to an increased supply of maltose and sucrose, putatively involved in drought stress responses at the xylem level. In contrast, in SY, the WS-induced increase in the latter soluble NSCs was maintained even 2 days after re-watering, suggesting a different pattern of utilization of NSC resources. Interestingly, the anatomical analysis revealed that conduits are constitutively wider in SY in well-watered (WW) plants, and that water stress led to the production of narrower conduits only in this cultivar.

Abscisic Acid Mediates Drought and Salt Stress Responses in Vitis vinifera—A Review

“…Recent evidences on poplar, highlighted that recovery of embolized conduits is a spatially coordinated and energy-demanding process, which requires the active translocation of sugars and other resources from the symplast to the apoplast of parenchyma cells [ 78 ]. These results confirm previous observations on grapevine [ 79 ] and support the studies speculating that different grapevines cultivars recover differently according to a divergent ability in translocating and utilizing nonstructural carbohydrates (NSCs) [ 20 ].…”

“…This topic is still debated, but a few researches aimed at investigating leaf as the biosynthetic source of ABA in grapevine. Indeed, in grapevine, the investigation of stress response was more focused on cultivar [ 48 , 49 ], scion–rootstock interaction [ 50 ], observational scale [ 51 ], geographical area [ 49 ], acclimation, and experienced drought stress [ 20 ]. However, the localization of the response to stress mediated by ABA represent an important information for the application of specific viticulture techniques such as irrigation.…”

“…Furthermore, these observations may suggest a possible role of ABA in mediating processes related to carbohydrates metabolism where its role has not been considered so far. A recent study [ 20 ] pointed out that under drought, different grapevine cultivars display a contrasting pattern of NSCs utilization. The anisohydric Shiraz delayed NSCs consumption, and it implemented remarkable anatomical adjustments (decreased the size of xylem conduits).…”

“…The anisohydric Shiraz delayed NSCs consumption, and it implemented remarkable anatomical adjustments (decreased the size of xylem conduits). Conversely, in the near-isohydric Cabernet Sauvignon, stress response was based on an earlier starch depletion and NSCs mobilization [ 20 ].…”

“…Yet, it is involved in mediating physiological responses to stressful conditions, especially excessive temperature, salinity, and drought [ 15 , 16 , 17 , 18 ]. ABA has been mainly investigated as it promotes the loss of turgor pressure in guard cells triggering stomatal closure [ 9 ], however, an increasing amount of evidences, also based on V. vinifera , address to ABA a central role in other fundamental processes as the hydraulic response to prolonged drought conditions [ 19 ], the regulation of carbohydrate metabolism during recovery [ 20 ], and the exclusion of excessive salts dissolved in the soil solution [ 21 ].…”