EFFECT OF SPLIT-ROOT-SYSTEM WATER STRESS ON PHYSIOLOGICAL AND MORPHOLOGICAL ASPECTS OF EGGPLANT (SOLANUM MELONGENA L.)

In view of increasing water demand by other sectors, and expected reduction of water availability in the future, it is necessary to adopt water management strategies which aim at water saving while maintaining satisfactory levels of production. One of these strategies is to improve water use efficiency through the application of deficit irrigation (DI) which deliberately sustains some degree of water deficit and yield reduction. The expectation of these strategies is that any yield reduction will be not significant as compared with the benefits gained from water saving. Partial root-zone deficit irrigation (PRD) is a DI technique to save irrigation water without much yield reduction. In fact, several authors report that when only part of the root system undergoes water-stress, abscissic acid (ABA) may be produced. This is transported through the xylem towards the leaves and reduces stomatal opening. On the contrary, poor root function reduces the production of cytokinins which are responsible for stomatal opening. These two aspects may combine to reduce stomatal opening and, consequently, gaseous exchange between the leaves and the surrounding environment. This study focused on the effect of DI via PRD on gas exchange, assimilated distribution, yield, and water use efficiency (WUE), to acquire useful information for the possible application of this technique on eggplant crop. Research has been carried out in southern Italy to study the split-root water stress effect on some physiological and morphological parameters of eggplant (Solanum melongena L. cv Tania). Plants were grown in pots and the root system was divided into two equal halves by a plastic wall. The pots were put in open air and the soil surface was covered by a waterproof film to protect the soil from rain water. The following treatments were compared: 1) the entire rhizosphere (both halves) well watered during the whole vegetative cycle (WW); 2) half a rhizosphere well watered and the other half water stressed after the beginning of blooming until the end of the vegetative cycle (WS1); 3) half a rhizosphere well watered and the other half water stressed, 30 days later in respect to treatment WS1, and until the end of the vegetative cycle (WS2). It was adopted a randomized blocks layout with 5 replicates. The results showed that stomatal conductance (gs), transpiration and assimilation rate (A) decreased at beginning of partial root water shortage cycle, but after the first days of plant adaptation to the new situation, was observed a recovery in this parameters, mainly in A. The reduction of gs is likely to depend not only by the low water potential in the xylem but also by ABA and cytokinins produced by the stressed root system. The shoot/root ratio decreased in PRD plants, mainly in WS1. In PRD plants was observed a reduction in yield, by around 13 (WS1) and 9% (WS2) but, because of lower evapotranspiration experienced by these plants, the WUE increased significantly. The application of DI via PRD at cultivation of eggplant can be an effective strategy to save water for this crop in areas where the water resource is limited.