Shoot morphology, xylem anatomical traits, and hydraulics vary with grapevine vigor

Abstract

Unraveling the mechanistic basis of grapevine vigor would allow for better management decisions prior to planting resulting in uniformity in yield and fruit quality year after year. To address this planting material metrics, the grapevine cultivar, Merlot was pruned to a range of bud numbers to induce differential shoot growth.  Vines with different bud number displayed a negative relationship with shoot length, which was used as an index of vigor and to generate several classes of vigor levels.  Morpho-anatomical and physiological measurements were recorded at specific phenological events in all vigor levels.  Regardless of vigor levels, the shoot architecture was modular wherein the internode length and the corresponding leaf area increased linearly at the proximal end whereas opposite occurred at the distal end.  The tendril-less basal internode tended to be shorter but bore more lateral branches.  A close relationship was found between internode length and leaf size above or below that internode.  With an increase in vigor, shoot fresh weight, internode number, and total leaf area increased.  The morphometric features of xylem tissues and its hydraulic conductivity values were smaller at the distal ends than at the proximal ends of the shoot, whereas the same features increased with shoot length.  We found that xylem anatomy played a key role in determining the hydraulic conductivity of the shoot with which the shoot length, a manifestation of vigor had a strong relationship.