Smaller but sweeter: The response of grapevine cultivars to drought determines organ interplay in non-structural carbohydrates allocation

Plant health relies on non-structural carbohydrates (NSC) in plant organs and is jeopardized by different stresses, including drought. Plants may use different hydraulic strategies to cope with drought, often involving modifications in growth and NSC reserves. Our work highlighted the impact of cultivar and drought on the physiological responses at the specific organ levels, utilizing young Vitis vinifera cv. Grenache (GR) (near-isohydric) and Cabernet sauvignon (CS) (near-anisohydric) plants grown in pots and subjected to prolonged water deficit. Plants were harvested at cane maturity, and NSC were measured. The cultivar influenced NSC accumulation in cane, favoured in GR rather than CS, which also showed a reduced root biomass. Drought led to a boost of NSC concentration at the expense of biomass, confirming roots as a key organ in plant drought responses. Moreover, our prolonged water deficit enhanced starch accumulation and its degradation products (water-soluble NSC), leaving the other investigated NSC pool unchanged. In conclusion, our work offers direction on managing the accumulation of NSC in specific grapevine organs, minimizing water inputs and considering cultivar-specific traits. Under this light, the resultant plants will have elevated NSC concentrations which might enhance their resilience to future stresses. • Cultivar hydraulic strategies drive plant growth and non-structural carbohydrates accumulation independently from drought. • A reduction in plant growth induced by drought stimulates carbon accumulation in the reserve organs. • Root carbon reserves are crucial in the stress-related response of grapevine. • The variation in soluble non-structural carbohydrates does not depend on drought duration