Effect of Drought and Salinity Stress on Morpho-physiologycal Variation of the Iranian Endemic Stachys multicaulis Benth. in Different Soil Textures

Adaptation of plants under drought and salinity stress depends directly on the type of soil texture. Therefore, in this research, the morpho-physiological variations of Stachys multicaulis, an Iranian wild endemic plant species, were investigated in different soil textures under drought and salinity stress. For this purpose, plants were cultivated in three different light, medium and heavy soil textures under pot condition (outside the greenhouse near the plant original habitat) in 2016. Then, a set of drought stress (3 day intervals of irrigation; 3 to 15 days) and salinity stress (0, 5, 10, 15, 20 and 25 ds/m- NaCl) was used in two separate factorial experiments based on a completely randomized design with four replications. The results showed that both drought and salinity had significant effects on morpho-physiological properties of S. multicaulis (p<0.01) based on type of soil texture. All of traits had higher performance in heavy soil texture except trichome length. For 15 day interval of irrigation, higher values of plant biomass, plant greenness, leaf length/width ratio, leaf angle, and node distance as 8.25g, 28.1%, 4.17, 55°, 1.5cm respectively were obtained in heavy soil texture. Similarly, for salinity of 25 ds/m, higher values of same traits as 7.7g, 25%, 3.9, 50°, and 1.4cm, respectively were obtained in heavy soil texture. Both drought and salinity stress had no significant effect (p<0.01) on leaves trichome number, trichome length, floret number per plant and branch number per plant in all three soil textures. The morphological variations of the plant occurred with greater intensity in salinity stress and it was concluded that plant tolerance to salinity was lower than drought.