Photosynthetic pigments content and parameters of oxidative stress in the amaranth species with increasing water deficiency

The dynamics of the photosynthetic pigments content and parameters of oxidative stress with an increasing water deficit in the leaves of 40-days-old plants of two amaranth species - Amaranthus paniculatus L. (cv. Rubin) and Amaranthus caudatus L. (cv. Chyrvony aksamit), grown in a pot culture, was studied. Specific features of the development of water deficiency in amaranth leaves were revealed: amaranth plants Amaranthus paniculatus L. showed a stronger development of water deficit in leaves than Amaranthus caudatus L. after 4-days soil drought, which after 8 days increased in two species to 73.7 and 55.7 %, respectively. Under moderate drought, the amount of photosynthetic pigments (chlorophyll (Chl) and carotenoids) based on dry leaf weight increased in two amaranth species, but after 8 days of soil drought, the content of Chl (a + b) was reduced by 2.0-2.1 times, and carotenoids - 1.8-1.9 times relative to the physiological level. As a result of a 4-days soil drought in the leaves of Amaranthus paniculatus L., there was a significant decrease in the content of reactive oxygen species (ROS) and the activity of lipid peroxidation (LPO), while in Amaranthus caudatus L. an increase in the levels of ROS and LPO was observed. With an increase in the pressure of the stress factor in the leaves of amaranth of the two studied species, a decrease in the ROS content and LPO activity relative to physiological values was revealed. A conclusion was made about the different mechanisms of ROS generation and the flow of LPO processes at different stages of soil drought in the leaves of different amaranth species.