Tipburn incidence in hydroponically-cultured Chinese cabbage is associated with temporal and spatial coorrdination of ROS regulatory systems

Abstract

Hydroponic cultivation of crops offers a vital strategy for mitigating yield losses resulting from environmental fluctuations; however, it can lead to necrosis at the leaf apex, known as tipburn. To explore the mechanisms contributing to tipburn incidence, we compared two varieties of Chinese cabbage (Brassica rapa L. ssp. Pekinensis), Haru-torai (HT) and Haru-warai (HW), which have varying sensitivity to tipburn. HT showed higher sensitivity to tipburn compared to HW. Before tipburn incidence, HT exhibited a higher level of O₂^•– and lower activity of SUPEROXIDE DISMUTASE (SOD) compared to HW. A high accumulation of O₂^•– in HT was also observed especially in the tips of leaves during the tipburn incidence. Although H₂O₂ accumulation was higher in HW compared to HT prior to the tipburn incidence, a higher level of H₂O₂ was detected in the tips of leaves in HT compared to HW during the tipburn incidence. These results suggest that tipburn incidence is associated with the temporal and spatial coordination of ROS regulatory systems. This conclusion is further supported by the finding that the sequential application of pyridoxine and ascorbic acid prior to tipburn incidence effectively mitigates this physiological disorder, offering potential to enhance crop yield in controlled facilities.