| Abstract: | Under controlled environmental conditions, the effect of optimal (20 °C) and supraoptimal (30 °C) root-zone temperature on root activity (respiration, soluble sugar content, ethylene release, nitrogen uptake and translocation) was studied in water culture with two potato clones differing in the heat tolerance of their root systems. Root respiration was little affected by raising temperature from 20 °C to 30 °C. However, in both clones assimilate allocation to the roots was strongly depressed. In the heat sensitive clone LT-1 exposed to 30 °C root-zone temperature, concentrations of soluble sugars in the apical root zone (0–10 mm) increased with time, presumably as a result of the cessation of root growth. The rate of nitrate absorption was not significantly affected by root-zone temperature. However, the export of nitrogen (xylem exudate) was depressed in the heat tolerant clone whereas in the heat sensitive clone the export of total nitrogen and the proportion of nitrate increased. No effect of root-zone temperature on ethylene release was observed in our experiments. |
