Study of the Growth and Nutritional Changes in Four Prunus sp. Rootstocks under Drought Stress

Rootstocks can affect the reaction of the grafted trees to water stress by controlling vegetative growth and nutrients uptake and studying morpho-physiological and nutritional mechanisms and responses of the rootstocks submitted to drought stress would make it feasible to select the tolerant rootstocks. For this purpose, to investigate the effects of drought stress on some clonal Prunus sp. rootstocks, an experiment, in completely randomized design was conducted in a greenhouse in Saman (Sharekord) and Shahrekord University laboratories in 2017-2018.

Rooted cuttings of Cadaman, Myrobalan29c, GF677 and GN15 were planted and maintained under greenhouse conditions employing regular practices including irrigation and nutrients supplementation and pest management for three months. Plants were submitted to drought stress at three levels including 100, 75 and 50% of field capacity for 40 days. Plant height, dry weight, relative water content, water use efficiency, electrolyte leakage and mineral content (P, K+, Ca2+, Mg2+, Fe2+ and Zn2+) in leaves and roots were assessed.

The results showed that the total dry weight was significantly decreased under the influence of drought stress. Leaf moisture content and specific leaf weight (SLW) decreased but leaf area ratio (LAR) and specific leaf area (SLA) increased under water deficit condition. Also, due to the drought stress, the greatest decrease in growth rate occurred in Cadaman and Myrobalan29c rootstocks, but no significant changes were observed for GN15 rootstock. Under drought stress conditions, relative water content (RWC) of the leaves decreased, while electrolyte leakage (EL) increased, with the highest figures observed for Myrobalan29c. With the increasing intensity of drought stress, water use efficiency (WUE) decreased for the Cadaman rootstock, but it was increased for GF677 and GN15 rootstocks. While no significant changes were observed for Myrobalan29c rootstock. Drought stress reduced the mineral contents (P, K+, Ca2+ and Mg2+) in the roots and leaves of the rootstocks. The highest decrease in concentrations of elements such as K+, Ca2+, P and Fe2+ were found for Myrobalan29c and Cadaman rootstocks.

All the tested rootstocks were significantly affected by drought stress, including growth retardation, but they resisted to drought stress at different levels and by varying mechanisms. So that some rootstocks with better use of available water and more nutrients absorption efficiency, showed a greater ability to maintain their biological activities in the face of dehydration. Other rootstocks showed poorer performance against drought stress and underwent damages compared to other rootstocks.