A New Strategy to Improve Vineyard Resilience: Grapevine Morphological Adaptation to Short-Term Nitrogen Deficiency

Nitrogen (N) deficiency causes a morphological disequilibrium between shoots and roots, favoring hypogeal growth. Our hypothesis is that short-term nitrogen deficiency could induce an increase in vine resilience, inducing root growth before the appearance of significant dysfunctions in the epigeal part of the plant. Then, nitrogen availability could be promptly restored through a well-thought-out fertilization plan. In this experiment, two table grape cultivars grafted onto three different rootstocks were studied in three hydroponic growing conditions characterized by different nitrogen availability. After 53 days of treatment, plant morphologies were described, and leaf photosynthetic pigments were quantified. The short-term nitrogen deficiency induced root growth, leading to significantly different proportions among the hypogeal and the epigeal parts, despite no significant differences were recorded concerning shoot growth. Some small differences in the leaf pigmentations indicated an incipient symptom of nitrogen deficiency, and significant differences in the phytomer morphology indicated the possibility of developing low-cost indices for prompt identification of incipient symptoms. This will allow the exploitation of the advantages of short-term nitrogen deficiency while avoiding negative effects on shoot growth by promptly restoring the nitrogen availability.