Mediation of high-temperature injury by roots and shoots during reproductive growth of wheat
Abstract Previous studies suggest that high temperature stress on wheat (Triticum aestivum L.) involves root processes and acceleration of monocarpic senescence. Physiological changes in wheat roots and shoots were investigated to elucidate their relationship to injury from elevated temperatures after anthesis. Plants were grown under uniform conditions until 10 d after anthesis, when shoot/root regimes of 25°C/25°C, 25°C/35°C, 35°C/25°C and 35°C/35°C were imposed. Growth and senescence of shoots and grain were influenced more by root temperatures than by shoot temperatures. High root temperatures increased activities of protease and RNasc enzymes, and loss of chlorophyll, protein and RNA from shoots, whereas low root temperatures had opposite effects. High root temperatures appeared to induce shoot senescence directly. High shoot temperatures probably disrupted root processes, including export of cytokinins, and induced high leaf protease activity, senescence and cessation of grain development. The authors concluded that responses of wheat to high temperatures, whether of roots or shoots, are manifested as acceleration of senescence and may be mediated by roots during grain development.