Deep Roots are Pivotal for Regulating Post-Anthesis Leaf Senescence in Wheat (Triticum aestivum L.)

Root activity plays a dominant role in grain filling in cereal crops. However, the importance of deep roots for regulating post-anthesis leaf senescence is not clearly understood in wheat (Triticum aestivum L.). In this study, we used 32P tracing to estimate the difference in wheat root activity at soil depths of 30 and 70cm and the root restriction method to investigate the effects of vertical distribution of deep roots on leaf senescence, with non-restricted plants as controls. Recovery of radioactive 32P indicated that deep roots had significantly higher activity than upper roots in wheat. Root restriction at a soil depth of 50cm caused significant decreases in the activities of superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6) and ascorbate peroxidase (EC 1.11.1.11) at 16days after anthesis and thereafter resulting in an increase in malondialdehyde. As a result, chlorophyll levels and net photosynthesis decreased. Ultimately, the root-restricted wheat produced a significantly lower grain yield than the non-restricted controls. These data suggest that deep roots are pivotal for regulating plant senescence, duration of grain filling, and yield formation.