Morphophysiological and Biochemical Responses of Amaranthus caudatus to Elevated Cultivation Temperatures

In the context of global climate warming, major crop yields such as wheat, rice, corn, and soybeans are expected to decline significantly. Therefore, the search for unconventional crops capable of producing high yields in conditions of elevated temperatures is of great importance. We studied the morphophysiological and biochemical responses of Amaranthus caudatus L. to the effect of temperatures of 22 °C, 30 °C, and 38 °C for 3 weeks. With an increase in temperature from 22 to 30 °C the rate of net photosynthesis significantly increased, as well as the content of chlorophylls a and b, sugars, starch, and protein in leaves. At temperature 30 °C, amaranth plants formed the maximum biomass. A further increase in the cultivation temperature to 38 °C led to a sharp decrease in the rate of net photosynthesis and a decrease in the content of chlorophylls a and b, sugars, starch, protein. Amaranth plants reacted to an increase in the cultivation temperature by raising the content of saturated 16:0 and 18:0 fatty acids and lowering the content of unsaturated 18:3 fatty acid. We concluded that growing A. caudatus at 38 °C would be economically unprofitable due to large yield losses and a decrease in the nutritional value. If the ambient temperature during the growing season does not exceed 30 °C, then A. caudatus is able to become an economically efficient agricultural crop in the face of global climate change.