Drought tolerance depends on the age of the spring wheat seedlings and differentiates patterns of proteinases

Resumo

The majority of plant species lose their ability to tolerate severe water deficit after germination at the beginning of seedling growth, in the time of emergence of the radical from the seed. The experiment was designed to compare the differences in proteolytic response between 4-and 6-days old spring wheat (Triticum aestivum L.) seedlings of Eta cultivar, respectively tolerant and sensitive to severe drought inducing up to 90% water saturation deficit (WSD). In coleoptiles the changes of proteolytic activity had the same trend regardless on the seedlings age and increased about fourfold upon 85% WSD as compared to the control, from about 4 to 19 (U/mg protein h). The dehydration of roots of 4 day old seedlings resulted in sharp, fivefold activity increase at 85% WSD (from 11 to >50 U/mg protein h). In roots of 6 days old seedlings dehydrated to 55% WSD the proteolytic activity raised twofold and was about 2.5 times higher than in roots of 4 days old seedlings dehydrated to the same WSD. In coleoptiles of both the 4- and 6-days old seedlings subjected to drought appearance of new bands of serine proteinases was observed. Presented results indicate that roots are more sensitive to drought than coleoptiles, which brings an argument for breeders showing that programs involving roots phenotyping have a full biochemical rationale.