THE LONG-TERM EFFECT OF COLD ON THE METABOLISM OF WINTER-WHEAT SEEDLINGS .1. GROWTH AND HYDRATION OF SEEDLINGS AT IN-VITRO CONDITIONS

1. Growth rate, hydration and distribution of dry matter between the p articular organs in seedlings of winter wheat grown under in vitro con ditions at the vernalization temperature (2 degrees C) and at 20 degre es C have been compared.2. At the end of the cold period an inhibition of the increase of the fresh weight in seedlings was observed, wherea s fresh weight of control seedlings continued to increase. 3. At both temperatures the dry weight of upper parts of seedlings (coleoptile an d first true leaves) and roots became stabilized at the end of the exa mined growth period. Mesocotyl attained its maximum dry weight in the initial growth period, which was significantly higher in seedlings gro wn in cold. At 20 degrees C the upper part represented about 73% of th e total dry weight of the seedling, whereas at 2 degrees C, its dry we ight was only equal to approx. 60%. 4. The hydration of the seedlings decreased during the growth at 2 degrees C, and increased at 20 degree s C. At 2 degrees C the hydration of the roots was higher than that of upper part whereas at 20 degrees C a reversed dependence was observed . 5. Transfer of the seedlings from 2 to 20 degrees C enabled further increase in their dry weight, reaching values observed in the controls . However, the hydration of these seedlings was still lower, although the interrelations between the hydration of the roots and that of the upper parts approached the values observed in control plants. 6. It ha s been demonstrated that neither fresh nor dry weight can be used as p arameters allowing for equalization between the development stage of p lants grown at high temperature and that of plants grown in cold, whic h is of fundamental importance in studies of vernalization or frost ha rdening processes.