The Response of Cowpea (Vigna unguiculata) Plants to Three Abiotic Stresses Applied with Increasing Intensity: Hypoxia, Salinity, and Water Deficit

Abstract

Exposing plants to gradually increasing stress and to abiotic shock represents two different phenomena. The knowledge on plants’ responses following gradually increasing stress is limited, as many of the studies are focused on abiotic shock responses. We aimed to investigate how cowpea (Vigna unguiculata (L.) Walp.) plants respond to three common agricultural abiotic stresses: hypoxia (applied with the increasing time of exposure to nitrogen gas), salinity (gradually increasing NaCl concentration), and water deficit (gradual decrease in water supply). We hypothesized that the cowpea plants would increase in tolerance to these three abiotic stresses when their intensities rose in a stepwise manner. Following two weeks of treatments, leaf and whole-plant fresh weights declined, soluble sugar levels in leaves decreased, and lipid peroxidation of leaves and roots and the levels of leaf electrolyte leakage increased. Polyphenol oxidase activity in both roots and leaves exhibited a marked increase as compared to catalase and peroxidase. Leaf flavonoid content decreased considerably after hypoxia, while it increased under water deficit treatment. NO emission rates after 3 h in the hypoxically treated plants were similar to the controls, while the other two treatments resulted in lower values of NO production, and these levels further decreased with time. The degree of these changes was dependent on the type of treatment, and the observed effects were more substantial in leaves than in roots. In summary, the responses of cowpea plants to abiotic stress depend on the type and the degree of stress applied and the plant organs.

Salicylic acid and proline modulate water stress tolerance in a traditional variety of cowpeas

“…This increase may have been caused by the action of proteinases, which maintain leaf water potential when the concentration of PRO in the cytoplasm rises. This allows plants to control osmotic pressure and prevent dehydration (Carvalho et al, 2019;Jayawardhane et al, 2022). PRO accumulation under water stress mainly results from the activation of biosynthetic enzymes in many plant species (Szabados & Savouré, 2010).…”

“…is an important crop in tropical regions of the world, with high social and economic value. However, cowpea productivity is strongly affected by water shortages in semiarid regions, where water deficit occurs at one or multiple stages of plant development (Jayawardhane et al, 2022).…”

Effect of Salt Stress on the Activity, Expression, and Promoter Methylation of Succinate Dehydrogenase and Succinic Semialdehyde Dehydrogenase in Maize (Zea mays L.) Leaves

“…The important role of alternative oxidase in the maintenance of metabolism and in prevention of ROS formation in the conditions of salt stress has been demonstrated in several studies [ 34 , 35 , 36 , 37 , 38 ]. The involvement of alternative oxidase in “salt respiration” can explain the observed lower rate of nitric oxide (NO) production in salt stressed plants [ 39 ], which differs from the hypoxic stress when NO production increases [ 40 ].…”

Cowpea Constraints and Breeding in Europe

“…In Southern Europe, with reduced water availability looming worldwide [ 14 ], searching for drought-tolerant genetic material along with production stability under limiting water conditions is of primary importance. The development of drought-tolerant cultivars is based on finding efficient methods to evaluate the tolerance levels of the available germplasm [ 194 ], as well as identifying various plant traits [ 119 , 195 ] and physiological and metabolic pathways [ 196 , 197 ] associated with stress resistance.…”