AFTER-EFFECTS OF SHOOT OR ROOT HEATING ON THE THERMOTOLERANCE OF LEAFAND ROOT-CELLS IN WINTER-WHEAT SEEDLINGS

The patterns of thermotolerance development in root and leaf cells in winter wheat (Triticum aestivum L.) seedlings were studied for 5 h fol lowing the heating of either the shoot or root at 40 degrees C for 15, 30, and 180 min. After shoot heating terminated, leaf thermotolerance continued to increase for some time. After root heating, leaf thermot olerance remained at the level achieved during heating. High-temperatu re treatment of shoots and especially roots decreased root thermotoler ance. When roots and shoots were separated immediately after root heat ing, the leaf tolerance pattern remained unchanged, as compared to the leaves of intact seedling, but the decrease in root tolerance was slo wed. After shoot heating, the thermotolerance of the detached leaves d eveloped more slowly than in the leaves of intact seedlings. The concl usion was drawn that plants responded to local heating and to its term ination as an integral system, where shoots and roots mutually affect thermotolerance.