Ecophysiological and morpho-anatomical adjustments of grapevines to drought conditions

Abstract

Drought poses the most important environmental constraint to plant survival and crop productivity. Therefore, the goal of this study is to advance a more holistic understanding of drought resistance by examining the ecophysiological and morpho-anatomical adjustments of different cultivars subjected to drought conditions.  Potted grapevine cultivars of Cabernet-Sauvignon, Grenache, and Zinfandel were subjected to four water regimes: Control (well-watered with full irrigation), 2/3^rd and 1/3^rd of full irrigation, and last treatment consisted of drying-down and re-watering cycles. Both physiological and anatomical adjustments differed among the three cultivars. With respect to physiological responses, Grenache displayed higher leaf water potential and relative water content (RWC) than Cabernet-Sauvignon and Zinfandel under all water regimes. The same was true for stomatal conductance. Anatomically, leaf vein density and leaf thickness increased in Grenache, whereas they decreased in Cabernet-Sauvignon and Zinfandel under all water regimes. The increase in leaf thickness of Grenache was due to its longer palisade cells and more intercellular air spaces. Also, differences were observed in stomatal pore areas and stomatal density among all three cultivars. Compositionally, the various fruit attributes that serves as the universal set of criteria for judging fruit for commercial harvesting were, except for anthocyanins, higher under well-watered conditions. The study showed that induction of several physiological and morphological adjustments occurred mostly in Grenache, not in Cabernet-Sauvignon nor Zinfandel; hence Grenache would be a better choice for establishing vineyards in drought prone areas (if the wine quality is also improved).