Suppression of the source activity affects carbon distribution and frost hardiness of vegetating winter wheat plants

Abstract

Effect of suppression of the source activity on some physiological characteristics of winter wheat (Triticum aestivum L., cv. Mironovskaya 808) was studied on plants grown in water culture. The plants were examined at the mixotrophic stage of growth period, during their transition from vegetative state to relative dormancy in autumn. The average temperature over 10 days of the experiment was 6°C at 9-h photoperiod and illuminance of 8–20 klx. The source strength was suppressed successively with a series of treatments: intact control plants (V1); plants with the seed endosperm removed (V2); plants with photosynthesis inhibited (V3); plants with the seed endosperm removed and photosynthesis inhibited (V4); plants with the seed endosperm removed, photosynthesis inhibited, and the root nutrient medium replaced with distilled water (V5). On the 6th–10th day of the experiment, the relative growth rate (RGR) was determined from dry weight increments. At the same time, the distribution of biomass among organs, the CO2 exchange rates (photosynthesis and dark respiration), the content and proportions of sugars (sucrose, glucose, and fructose), the total content of phenolic compounds and flavonoids, the index of membrane stability (IMS) in leaves, and frost hardiness of plants were measured. Frost hardiness of vegetating plants was shown to be inversely related to RGR (R = −0.906), dark respiration rate (R = −0.789), the percentage of sucrose in total sugar content (R = −0.737), leaf IMS (R = −0.390), and the rate of apparent photosynthesis (R = −0.288); it was directly proportional to the content of flavonoids (R =0.973), total phenols (R = 0.743), and sugars (R = 0.385). The role of modified source-sink relations in frost hardiness of vegetating plants at the stage of their transition to cold hardening is discussed. The differences between plants undergoing this transition and cold-hardened plants are considered, as well as the importance of phenolic compounds for the development of frost hardiness.