Shifts in Pigment Content along an Arid Altitudinal Gradient as a Mechanism for the Regulation of the Photosynthetic Capacity of Plants in the Gobi

The influence of altitude on the pigment composition of plants has not been studied very much in arid climates. In this work, we study pigment content along the altitudinal gradient in Gobi, Mongolia. The altitude negatively correlates with climate aridity, which affects traits of the leaf. Along the gradient, the thickness and density of photosynthetic organs decrease and the content of chlorophylls (Chl) and carotenoids (Car) increases, while the photosynthesis rate and the ratios of pigments Chl a/b and Chl/Car do not change. A decrease in the nitrogen-to-chlorophyll (N/Chl) ratio with altitude is also revealed, which indicates a change in the ratio between RuBP carboxylase and pigment-protein complexes of thylakoids in the leaf. Despite the simultaneous changes in chlorophyll content and leaf thickness with altitude, the analysis of partial correlations shows that these parameters change independently of each other. Path analysis confirms that pigment content and leaf thickness are two independent ways a plant adapts to environment. We conclude that changes in the pigment complex of plants with altitude are required to maintain the photosynthetic capacity under changing climate aridity.