Growth, water relations and ion accumulation in Phlomis purpurea plants under water deficit and salinity
2012
The effect of different levels of water deficit and salinity on physiological and morphological alterations in Phlomis purpurea plants was studied to evaluate their adaptability to such conditions. P. purpurea plants growing under greenhouse conditions were subjected to four irrigation treatments between November and May 2008: control (C, 1 dS m-1), moderate water deficit (MWD, 1dS m-1, 60% of the control), severe water deficit (SWD, 1 dS m-1, 40% of the control) and saline (S, 4 dS m-1). Aerial dry weight decreased with salinity, response that was more marked in the water deficit treatments, especially SWD. Stem diameter and leaf number were similarly reduced in both water deficit treatments, while leaf area also decreased in saline treated plants. Throughout the experiment, plant height was similar in both control and saline treated plants and was inhibited 10 weeks after application of the deficit irrigation onwards. Only at the end of the experiment were there significant differences in plant height between all treatments. Plants irrigated with saline water had higher Na+ concentrations in their leaves than in their roots and shoots, while Cl- concentrations were similar in leaves and roots, suggesting some resistance to the movement of the latter ions from root to shoots. The accumulation of salt in the leaves was associated with osmotic adjustment, which maintained midday leaf turgor in saline treated plants. However, no osmotic adjustment was observed in plants submitted to water stress. The results indicate that the effect of osmotic stress due to water deficit was more severe than the toxic effect of salt.
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