Antioxidative Responses and Morpho-anatomical Alterations for Coping with Flood-Induced Hypoxic Stress in Grass Pea (Lathyrus sativus L.) in Comparison with Pea (Pisum sativum)

Flooding stress constrains crop growth and yield because most agricultural species are flood-sensitive. However, many of the plant species that live in permanently or temporarily flooded habitats have evolved specific traits to cope with these harsh conditions. Grass pea (Lathyrus sativus L.) is a legume that tolerates stresses such as drought, diseases, and pests; however, it is unclear whether grass pea has a tolerance mechanism for flooding stress. To understand if grass pea tolerates hypoxia and how it deals with hypoxic stress, the effects of hypoxia on root tip death, physiological, and morpho-anatomical alterations in grass pea and pea (Pisum sativum), which is sensitive to hypoxia, were compared. The results showed that activities of antioxidant enzymes, namely superoxide dismutase, catalase, ascorbate peroxidase, and glutathione content in grass pea were greater than in pea during hypoxia, which protected the root tip from oxidative damage and reduced ion leakage, which helped maintain membrane integrity. Furthermore, aerenchyma and lateral root development accompanied by ethylene production, moderate ROS accumulation-mediated cell death, and Ca2+ spatial-temporal heterogeneity developed well in grass pea compared to pea, which may not only facilitate internal gas diffusion but also promote removal of toxic by-products under hypoxic conditions. These results demonstrate that grass pea is more tolerant to hypoxic stress induced by flooding than garden pea seedlings. This discovery not only provides significant information for understanding the hypoxia-tolerant mechanisms in plants, but also promotes the usability of grass pea in flood-prone areas.