Growth and physiological characteristics of Arnebia guttata at different altitudes in Wushi County of Xinjiang

[Objective] The study aims to investigate the growth and physiological characteristics of Arnebia guttata along the altitudinal gradients, in order to understand its ecological adaptation mechanism under different habitat conditions and provide a theoretical basis for the conservation and utilization of the wild resources of A . guttata. [Methods] A . guttata in Wushi County in northwestern Tarim Basin was chosen as the research subject. The leaf morphology, growth indicators, photosynthetic pigments, proline, soluble osmoregulatory substances, malondialdehyde content, and the activities of antioxidant enzyme were measured at five different altitudinal sites (1 155, 1 227, 1 332, 1 533, 2 137 m). [Results] The plant height, aboveground biomass, total biomass, leaf area, specific leaf area, and the content of chlorophyll a and chlorophyll b of A . guttata were the highest at the lowest altitude (1 155 m) and decreased with increasing altitude, reaching the lowest at 2 137 m. Among them, plant height, aboveground biomass, and leaf area were decreased by 22.89%, 31.77%, and 26.58%, respectively. The minimum value of specific leaf mass, root/shoot ratio, and carotenoid content, carotenoid/chlorophyll ratio, malondialdehyde, proline, soluble sugar, and ascorbate peroxidase and peroxidase enzyme activity of A . guttata were at 1 155 m, and increased with increasing altitude, reaching the maximum at 2 137 m. [Conclusion] The environmental condition of lower altitude is conducive to the growth and biomass accumulation of A . guttata in Wushi County. As altitude rises, the physiological stress on A . guttata becomes intensified, which adapts to the harsh environment to increase the soluble osmotic substances and the activity of antioxidant enzymes.