MULTI-OBJECTIVE ANALYSIS OF PHYSIOLOGICAL AND MORPHOLOGICAL RESPONSES OF WINTER WHEAT (Triticum aestivum L.) TO STRESS INDUCED BY LOW TEMPERATURE DURING AUTUMN ACCLIMATION

Abstract. Based on the literature data, types of morphological and physiological changes occurring in plants during the process of autumn hardening were discussed, as an expression of adaptations to overwintering. They indicate that the level of plant preparation for surviving winter depends on the photosynthesis intensity, leaf area index (LAI) and the development of aboveground part and root system. It was assumed that the use of liquid humic fertilizers (LHF) for seed dressing and in the form of foliar application performed after emergences will have a favourable effect on intensification of processes which favour plant frost hardening. In two field experiments with winter wheat cv. Širvinta conducted in Lithuania in systems of conventional and organic farming in 2010 and 2011, a number of analyses were performed on young plants. In the aboveground part, dry matter of leaves, LAI, the content of chlorophyll and carotenoids were determined, and gross productivity of photosynthesis was calculated, whereas in the underground part – the root area, their diameter and total length. It was shown that the application of LHF affects an increase in values of evaluated biometric indices, and thus, indirectly, contributes to enhancing the potential resistance of plants to stress induce