ASSIMILATION, DISSIMILATION AND ACCUMULATION OF C-14 IN 2 MAIZE (ZEA-MAYS L) HYBRIDS OF DIFFERENT DROUGHT TOLERANCE

The effects of exposure in the vegetative phase of growth to 5- or 10-day spells of soil drought (30% field water capacity) on assimilation, dissimilation and accumulation of C-14 and on dry matter growth were studied in two maize hybrids, nos. 8344 and 8388 (Garst Seed Co.) of high and low drought tolerance. Under control water regime in soil there was no difference in (CO2)-C-14 uptake and dry matter growth between hybrids. After five days of drought (CO2)-C-14 assimilation dropped by about 75% referred to unit weight of dry matter in hybrid 8344 and by 56% in hybrid 8388. After 10 days of drought (CO2)-C-14 assimilation rate was reduced by 75% in both hybrids. Soil drought increased the C-14 dissimilation. There were no significant differences between hybrids in all treatments, with the exception of 5 days drought; after this treatment the dissimilation rate of hybrid 8344 was higher than that of 8388. Changes of translocation of C-14 and its accumulation in particular organs occurred in drought treated plants; the amount of C-14 accumulated in roots of plants of hybrid 8344 increased, while that of hybrid 8388 decreased. Changes of C-14 accumulation in roots were positively correlated to changes of dry matter of those organs. One day after 10 days of drought assimilation and dissimilation rates in both hybrids were about 60% of controls.