Study of water exchange of weed and tomato plants in the process of joint vegetation

Goal. Study of indicators of water metabolism of weed and tomato plants in the process of ontogenesis. Methods. We used generally accepted methods of field and laboratory research (setting up experiments, monitoring plant development, recording the number of weeds, sampling, determining water exchange indicators) and mathematical and statistical (processing of research results). Indicators of water exchange (water deficit, water supply, water-holding capacity, transpiration coefficient) were calculated according to special formulas according to methodological instructions on plant physiology. Results. Dominant weeds in tomato crops during the growing season were (Setaria glauca L.), Echinochloacrus-galli L., Ambrosia artemisiifolia, Portulaca oleracea L., the number of which in the flowering-beginning of tomato fruiting phase was 85, 41, 27, 29 pieces/ m², respectively. In their competitive activity, weeds actively use water. During the cultivation of tomatoes and weeds in the greenhouse, the indicators of water exchange did not have significant differences. The moisture content of the leaves of the studied plants (Lycopersicon esculentum, Ambrosia artemisiifolia, Chenopodium album and Setaria glauca) was at the level of 71.5—78.1%. Tomatoes were characterized by the highest water availability — 65.3%, and ragweed — 21.1% — the lowest. The intensity of transpiration in tomato leaves averaged 143.2 g/m2 per hour. The transpiration coefficient (TC) of plants was at the level of 400 (Ambrosia artemisiifolia) — 497 (Chenopodium album). In field conditions, transpiration processes were recorded in 8 types of weeds during the growing season of tomatoes from flowering to the end of fruiting. During this period, weed plants lost moisture from 2.5% to 23.1%, tomatoes — 23%. TC during the flowering period of tomatoes was 168—301, at the end of the growing season — 146—287, tomatoes were 200 and 158, respectively. Ambrosia artemisiifolia, Chenopodium album, Barbaréa vulgáris, Portulaca oleracea were characterized by the highest level of TC. A high TС of weeds indicates high competitiveness and significant pressure on tomato plants during the growing season. Conclusions. The water exchange of weed and tomato plants depended on the growing conditions. In greenhouse conditions, transpiration processes in weed and tomato plants had no significant differences. The water content in the leaves and the transpiration coefficient of the weed and tomato plants were almost at the same level. In field conditions, the indicators of water exchange of weed and tomato plants during the growing season underwent significant changes. The water content in plant leaves and TC decreased during the growing season. The transpiration coefficient of most weed plants prevailed over the TC of tomatoes, which indicates a higher competitive ability of segetal vegetation for water resources during the joint vegetation with the agricultural culture.