COMPARISON OF SALINITY AND DROUGHT STRESS EFFECTS ON SOME MORPHOLOGICAL AND PHYSIOLOGICAL PARAMETERS IN ONION (ALLIUM CEPA L.) DURING EARLY GROWTH PHASE

Abstract

This study was conducted to investigate the effects of drought and salinity on four onion (Allium cepa L.) cultivars (Texas Early Grano, Kantartopu-3, Besirli-77 and Akgun-12) in the early plant growth phase. Seeds were germinated in peat material. After 21 days of sowing, seedlings were transferred to plastic pots (1.6 L). The plants have been grown in vermiculite by “substrate culture” technique. After ten days of transplanting, irrigation was stopped gradually for drought stress. For this aim, three different levels of irrigation were used. (D0 was 90% of field capacity, D1 was 70% of field capacity, and D2 treatment was 40% of feed capacity). In order to determination of effects of salinity on onion plants, 0. 50 mM and 125 mM NaCl were added to nutrition solution. To determine the effect of salinity and drought stress factors, tolerance indexes based on plant neck diameter (mm), leaf diameter (mm), plant length (cm), amount of leaves, leaf water potential (%) and waxy on leaves were measured as morphological parameters. At the same time, amount of proline, the concentrations of total chlorophyll (µg/ml), chlorophyll-a (µg/ml), chlorophyll-b (µg/ml) carotenoids (µg/ml) and chlorophyll-a/b were investigated as physiological parameters. Cultivars showed different responses to drought and salinity. The significant varietal differences were observed for the proline amount, chlorophyll-a, leaf water potential index and leaf amount under drought stress; and for the proline amount, chlorophyll-a and leaf diameter under salinity stress.