Understanding of water deficit responses of plants can lead to better establishment and management of water-conserving landscapes. Due to the importance of landscape plants and the need for water relations of field-grown herbaceous species, this study investigated morphological and biochemical responses of Malva sylvestris, Althea rosea, Callistephus chinensis and Rudbeckia hirta under water stress. The main plots were the four plant species and the subplots were irrigation levels of 25%, 50%, 75%, and 100% reference evapotranspiration (ET0). The results indicated that 75% ET0 irrigation treatment had no effect on the relative water content of Althaea rosea and Rudbeckia hirta. Althaea rosea and Rudbeckia hirta had the highest deficit irrigation tolerance index for root length and root density in 25% ET0. Only Althaea rosea, exhibited no oxidative stress as reduced chlorophyll content under 75% ET0 to 50% ET0, and also under 50% ET0 to 25% ET0. Only in Rudbeckia hirta, the ratio of chlorophyll a/b was linearly increased. Water stress had no effect on total soluble carbohydrates in Callistephus chinensis, Rudbeckia hirta and Malva sylvestris. Moving from 75% to 25% ET0, Rudbeckia hirta showed the lowest electrolyte leakage which was followed by Althaea rosea. Althaea rosea and Rudbeckia hirta displayed a drought avoidance mechanism.

Keywords