Effects Of Foliar Selenium Application On Growth,Yield And Quality Of Tomato In Greenhouse Under Drought Stress

Selenium is one of the essential trace elements for human body and crops,and it is of great significance for crop growth and nutrition of agricultural products.Based on the potted experiment of greenhouse tomato(Jingfan 404)in a daylight greenhouse in 2022,three irrigation levels were set up(the lower limit of irrigation was 50% of field capacity(W1: severe drought)and 65% of field capacity(W2: mild drought)).,80%(W3:sufficient water supply))and four concentrations of exogenous selenium(selenium source: Na2 Se O3)(S0:water control,S2.5: 2.5mg/L,S5: 5mg/L and S10: 10mg/L),12 treatments were set up in Xinxiang Integrated Experimental Base of Chinese Academy of Sciences.The effects of different soil moisture conditions and foliar application of different concentrations of exogenous selenium on the growth of tomato plant and fruit,selenium content in fruit,yield and water use efficiency(WUE)were studied.The main results of the study are as follows:(1)Plant cells were oxidatively damaged under drought stress,and leaf MDA content increased significantly,SOD and POD activities increased,and osmoregulatory substances content increased to alleviate the oxidative effects of stress brought about by drought;foliar selenium application significantly reduced leaf MDA content and increased leaf GSH-PX The foliar application of selenium significantly reduced the leaf MDA content and increased the leaf GSH-PX activity.Under drought stress,the reactive oxygen species content in plants was high,and selenium application increased the CAT activity to scavenge the high concentration of free radicals while significantly reducing the SOD and POD activities.The plants under adequate water supply were less damaged by oxidation,and selenium application increased POD activity to scavenge low concentrations of free radicals,while selenium application reduced the content of osmoregulatory substances proline and soluble sugars,increased the breakdown of selenoproteins and thus increased soluble protein content.Thus,selenium application increased leaf antioxidant enzyme activities,reduced or even avoided oxidative damage to the plants,and thus alleviated different degrees(2)Foliar application of selenium improved the antioxidant capacity of the plants and alleviated the drought stress,which in turn had a positive effect on plant growth and development.The spraying concentrations of 2.5～5 mg/L showed the greatest promotion effects on photosynthesis,leaf water potential and leaf water content,increased plant height and its average growth rate,increased leaf net photosynthetic rate,stomatal conductance and transpiration rate,and also increased leaf water potential and leaf water content.Under mild drought stress,selenium application increased the relative amount of leaf chlorophyll(SPAD)and fruit N accumulation,promoted plant uptake of N and translocation to fruit,which in turn increased fruit N accumulation and promoted fruit growth,and significantly increased the average fruit growth rate under mild drought stress.(3)Drought stress caused damage to plant cell membrane lipidation,foliar application of selenium increased the antioxidant enzyme activity of the plant,alleviated the adverse effects of drought stress on the plant and promoted plant and fruit growth,and selenium application increased the number of tomato fruit set,significantly increased the fruit weight per plant and thus improved the yield and water use efficiency per plant.Compared with the control S0 treatment,the fruit weight and yield per plant of S2.5 treatment were significantly increased by 6.7% and 12.0%.The selenium content of leaves and fruits increased significantly with increasing concentration of exogenous selenium spraying,and the fruit selenium content of selenium application treatment increased 3.5 to 14.3 times compared with the control S0 treatment.Under severe drought stress,the fruit soluble solids content and sugar-acid ratio of S2.5W1 increased by 7.9% and 6.4%on average compared to S0W1.In conclusion,foliar sprays at concentrations of 2.5 to 5 mg/L provided greater relief to greenhouse tomatoes under mild drought stress and had a more pronounced effect on the growth and yield composition of greenhouse tomatoes.