Symbiotic Properties of Sinorhizobium meliloti and Ethylene Production by Alfalfa Plants at the Early Stages of the Symbiosis Formation under Different Water Supply and Seed Treatment by Lectin

Abstract

The symbiotic properties of bacteria significantly influence on the effectiveness of symbiosis and the yield capacity of plants. Therefore, it is important and relevant to study the features of micro- and macrosymbionts interactions, in particular under stressful conditions, and to find ways to improve the productivity of symbiotic systems. Aim. The investigation of the nodulation and nitrogen-fixing activities of Sinorhizobium meliloti as well as the ethylene production by alfalfa plants at the early stages of the formation of symbiotic system under conditions of both optimal and insufficient water supply and the pre-sowing treatment of seeds by lectin. Methods. Microbiological (cultivation of bacteria culture, seed inoculation), physiological (pot experiment), biochemical (nitrogenase activity and ethylene production determination). Results. It was observed a decrease of the nodulation activity of Sinorhizobium meliloti under drought as well as under lectin application, which was accompanied by an increase in the amount of produced by macrosymbiont ethylene at the early stages of the symbiosis formation. At the same time, the nitrogen fixing activity was inhibited at the insufficient water supply only. The use of lectin promoted the symbiotic apparatus functioning under optimal and insufficient water supply. After renewal of irrigation an increase of the nodule weight and nitrogen fixing activity as well as the aboveground mass of alfalfa plants were noted under lectin treatment. Conclusions. It was identified the role of ethylene as a negative regulator of the nodulation processes at pre-sowing treatment of alfalfa seeds with lectin. The formation of the effective nitrogen-fixing system capable of full recovery after drought under lectin application confirms the prospects for further research in the use of lectins to create optimal conditions for the realization of the symbiotic potential of rhizobia and to increase the symbiotic systemˊ resistance to the action of stress factors.