Adaptation of lentils to high-temperature stress at phytopathogenic infection and application of molybdenum nanoparticles

The study of the impact of high-temperature stress on the plant-phytopathogen system, including using nanoparticles, is relevant in connection with climate changes. Therefore, our work was aimed at studying the impact of high-temperature stress on the physiological, biochemical, and growth processes of lentil plants under the conditions of pre-sowing treatment of seeds with Mo nanocitrates (Mo Ncit) and artificial infection with phytopathogenic microorganisms. Under high-temperature stress at 32-34°C (humidity 45 and 40%) in field conditions, a decrease in the photochemical activity of leaves of intact lentil plants was observed, due to the acclimatization of the photosynthetic apparatus. Infection with phytopathogenic phytoplasmas and bacteria disrupted the balance of free radicals in leaf tissues, because of which the activity of antioxidant enzymes SOD, POD, and phenolic compounds increased. This was likely the main reason for the disruption of the adaptation of the photosynthetic apparatus of plants to high-temperature stress under artificial infection with phytopathogenic phytoplasmas and bacteria, which destroyed pigment-protein complexes of PS II. As a result, the chlorophyll content in the leaves decreased. At the same time, physiological and biochemical changes in metabolism during pre-sowing seed treatment with Mo Ncit compared to the control, caused an increase in the productivity of lentil plants in natural conditions under the combined action of various factors during the growing season: temperature fluctuations, air humidity, infection with phytopathogenic microorganisms. Therefore, infection with phytopathogenic microorganisms worsened the growth processes of plants, including due to a decrease in the adaptation of the photosynthetic apparatus to high-temperature stress. It is worth emphasizing that pre-treatment with molybdenum nanocitrates had a growth-stimulating and, to some extent, adaptive effect on plants and increased tolerance to phytopathogens. • Under high-temperature stress in the field, a decrease in the photochemical activity of leaves (determined by the chlorophyll fluorescence induction method) of intact lentil plants was observed, which is associated with the photosynthetic apparatus adaptation to stress. • In leaves affected by phytopathogenic bacteria or phytoplasmas, the adaptation of the photosynthetic apparatus to high-temperature stress worsened. • Pre-treatment with Mo nanocitrates improved the photochemical activity of leaves of healthy and phytopathogenic microorganisms-infected plants, compared to untreated plants which positively affected their growth and productivity.