The role of chlorophyll in determining the resistance of soybean plants to prolonged soil flooding

Prolonged inundation of soybean plants leads to their death because of root hypoxia. Therefore, the search for markers of resistance to this factor will provide the opportunity to develop the varieties able to resist this stress. The research was aimed at the study of response of 3 varieties bred by Federal Research Center All-Russian Scientific Research Institute of Soybean to prolonged flooding according to the indicator of chlorophyll a and b content in soybean leaves. The study was carried out in 2019-2021 in laboratory experiments when growing plants on hydroponic installations with 24-day soil flooding (control - soil with optimal moisture content). In soybean varieties Evgeniya and Kukhanna, registered as resistant to overwatering soil, the response by content of chlorophyll forms in leaves under 24-day flooding of the soil surface with 1-2 cm layer of water differed. It was found that increase of chlorophyll a in leaves of Evgeniya variety under flooding was connected with providing the ability of this variety plants to resist the stressful flooding factor. The presence of chlorophyll b in the leaves of this variety before the ripeness phase indicates that it can serve as an indicator of plant resistance to root hypoxia to a greater extent, since the plants continued to grow and develop. In the Kukhanna variety, the content of both forms of chlorophyll at optimum soil moisture of the control variety was higher or at the same level as in the variant with flooding, that cannot serve as the criterion of resistance of this variety to root hypoxia. In the Kitrossa variety, the resistance of which to overwatering has not been noted by the breeders yet there were revealed wavy fluctuations in chlorophyll a/b ratio during the first 10 days of flooding. The fluctuations were caused by changes in the content of chlorophyll b, the concentration of which increased first and then decreased. This fluctuation is most clearly seen in the graph of the change in the ratio between chlorophyll a and b, that may serve as a marker for determination of resistance of soybean varieties to prolonged soil flooding.