Influence of hardening by contrast temperatures on the growth of new for Russia heat-loving vegetable crops

Abstract

Under conditions of low temperature, seedlings of heat-loving vegetable crops are more strongly affected by various pathogenic micromycetes, and the content of photosynthetic pigments in the leaves of plants decreases. Using fungicides cannot constantly interrupt the spread of pathogens and the death of plants. The authors determined the effect of the hardening regime, including the four-day keeping of germinating seeds of Momordica (Momordica charantia L.), asparagus cowpea (Vigna unguiculata (L.) Walp.), kiwano (Cucumis metuliferus E. Mey. ex Naudin), Benincasa (Benincasa hispida (Thunb.) Cogn.) and anguria (Cucumis anguria L.) at a variable temperature during the day - hardening (10℃) at night and optimal (30℃) during the day for keeping pigments in leaves and damage to seedlings by pathogenic micromycetes at low temperatures (6–15 ℃). This effect allowed authors to assess the therm adaptive potential in experiments conducted in 2018–2022. Microbiological analysis of the soil on PDA medium (potato dextrose agar) showed the presence of Fusarium spp. in the amount of 290 CFU/g of earth. The trap method revealed the presence of Pythium Pringsh in the soil. The most significant reduction in the death of seedlings was achieved in seedlings of anguria - 29 times, Kivano, Benincasa and cowpea - 2.5, 2.0 and 1.3 times, respectively. Periodic hypothermia in 3 cultures out of 5 - Kiwano, Cowpea, and Benincasa - reduced the ascorbic acid content in the leaves by 17%, 36% and 3%. The range of photosynthetic pigments - chlorophylls (a + b) in the variant with hardening increased, respectively, in 4 (except cowpea) crops out of 5 by 8–40%, and carotenoids in 3 crops - Momordica, Anguria and Benincasa - by 46, 3 and 8% respectively. The ratio of chlorophylls a/b in most cultures, both in control (at the optimum temperature) and after low-temperature exposure, was close to 2.0. Only in Anguria did this ratio decrease from 2.8 to 2.1. Asparagus cowpea showed a decrease in the content of both ascorbic acid (by 36%) and photosynthetic pigments (chlorophylls and carotenoids) - by 6–8% in the hardening option.