Chilling and heat requirement of pomegranate (Punica granatum L.) trees grown under sustained deficit irrigation

Abstract

Soil moisture is one of the important factors affecting the chilling requirement of a plant, and many plants do not resume normal growth and set fruit without satisfying their required chilling. The effect of water deficit on chilling requirement, heat requirement, stomatal density, non-structural carbohydrate, and leaf area of two Iranian pomegranate cultivars, ‘Shishecap’ and ‘Malas-Yazdi’ was studied. The experiment was carried out during two successive years of 2015 and 2016. Two sustained deficit irrigation (SDI) regimes, 75% (moderate stress) and 50% (severe stress) of water requirement were applied, while 100% water supply served as the control treatment for each cultivar. The experiment was setup as a randomized complete block design with three replications and two trees were measured in each replicate. Results indicated the chilling requirement and stomatal density increased with greater water restriction in both cultivars and in both years. Non-structural carbohydrates and leaf area were reduced in water deficit treatments compared to the well irrigated trees in both cultivars. Based on our findings, water deficit treatments did not affect the heat requirement of either cultivar. Overall, these results strengthened the idea that leaf stomatal density, level of stem non-structural carbohydrate and leaf area at the end of the growing season are three key variables for pomegranate growth analysis, and correlate with chilling requirement under water stress conditions.