PHYSIOLOGICAL AND BIOMETRICAL RESPONSES TO DROUGHT STRESS IN MYCORRHIZED AND NON-MYCORRHIZED PLANTS OF THREE OLIVE CULTIVARS

In order to study the effect of water stress on olive, young mycorrhized (9 kg/m3) and non-mycorrhized plants of three cultivars, Maurino (drought-resistant), Leccino (drought-sensitive) and Degli (cold-resistant ecotype selected in Emilia Romagna region, IT), were irrigated (drip irrigation), for 30 days, with two water supply conditions (water treatments): optimal irrigation (medium moisture kept close to the easily available water) and reduced irrigation (medium moisture kept close to the water buffering capacity). Plants were grown under greenhouse conditions in a medium composed of peat:pumice:coir (40:40:20 V/V). The following parameters were analysed to evaluate the influence of the different water supply conditions, on mycorrhized and non-mycorrhized plants, of the three cultivars: anatomical structure of leaf, plant biometric parameters (diameter of trunk, branch length, sprout number, leaf weight, average specific leaf area), photosynthetic performance, in terms of gas exchange and chlorophyll fluorescence (Fv/Fm), stem water potential (midday leaf ), leaf relative water content (RWC), leaf mass per area (LMA), osmotic potential and leaf content of nitrogen, nitric and reduced, and phosphorus. After the water stress treatments, a decrease in growth capacity was observed for all the combinations tested, demonstrating that the stress was intense. The analysis of data evidenced that cv. Maurino showed a drought tolerance higher than cvs. Leccino and Degli; one of the main differences observed was that the palisade tissue in cv. Maurino leaf occupies about 50% of the leaf mesophyll, while in the other cvs. about the 30%. Minor differences were found between mycorrhized and non-mycorrhized plants.