Deficit irrigation and transparent plastic covers can save water and improve grapevine cultivation in the tropics

We examined the interactive effects of deficit irrigation and transparent plastic covering (TPC) on key physiological traits in tropically grown grapevines. 'Niagara Rosada' grapevine (Vitis labrusca) was subjected to both Regulated Deficit Irrigation (RDI) and Partial Rootzone Drying (PRD) while being grown under a TPC to address the following questions: (i) Does the grapevine present anisohydric or isohydric behavior? (ii) How does deficit irrigation affect leaf water potential (Psi)? (iii) Can RDI and PRD improve plants water use efficiency? (iv) How does deficit irrigation affect leaf photochemical and biochemical capacity? (v) What are the effects of deficit irrigation on leaf respiration and leaf carbon balance? (vi) Is it possible to save water without affecting yield and fruit quality? Three water management techniques were applied: full-irrigated (FI): 100% of the crop evapotranspiration (ETc) was supplied to both sides of the root system; RDI: 50% of the ETc was supplied to both sides of the root system; and PRD: 50% of ETc was alternately supplied to only one side of the root system. These irrigation treatments were replicated such that the two plots were either covered by a polyethylene plastic structure or remained uncovered. We found that: (i) 'Niagara Rosada' grapevine presented anisohydric behavior; (ii) deficit irrigation did not affect Psi; (iii) Neither RDI nor PRD had a significant effect on water use efficiency (iv); no limitations by the carboxylation reactions of photosynthesis or Rubisco oxygenation (V-o (1500)) were observed, and photochemical capacity was not inhibited; (v) Light and dark leaf respiration rates were not affected by either RDI or PRD and therefore deficit irrigation did not damage the leaf carbon balance; (vi) a considerable volume of water was saved when deficit irrigation was used, without affecting production; (vii) TPC use can be an effective strategy for growing grapevine in tropical conditions.