Investigating the effect of water stress and plant density on some physiological characteristics and water use efficiency in two ecotypes of Thymbra spicata L

The present study aims to investigate the changes in some physiological characteristics and water use efficiency of two ecotypes of Thymbra spicata L. in response to changes in water stress and plant density. For this purpose, an experiment was carried out as a split factorial based on the randomized complete block design with three replications in two growing seasons (2016 and 2017). The highest content of chlorophyll-a and chlorophyll-b was observed in the treatments of non-stress and mild stress and at a density of 6 and 8 plants per m2. The highest content of total chlorophyll was observed in the treatment of non-stress and mild stress and at a density of 8 plants per m2 during the first year of the experiment. Increased plant density and intensity of water stress led to a decrease in the content of photosynthetic pigments. The highest content of carotenoids was observed at the treatment of mild water stress and a density of 8 and 12 plants m2 during the first year of the experiment. The highest content of anthocyanins was observed at the treatment of mild water stress and a density of 8 plants per m2. The highest content of total phenol and flavonoids was observed at the treatment of severe water stress and a density of 12 plants per m2. Finally, the highest amount of proline in the plant was observed in the second year of the experiment at the treatment of severe water stress and a density of 12 plants per m2.