English abstract
Salinity is a significant threat to crop production in Oman and worldwide. Salt stress
severely reduces plant productivity and yields. In Oman, the amount of cultivated land
that is exposed to salinity is about 50%. Therefore, developing effective strategies for
surviving with salinity and increasing plant's tolerance to salt stress is essential. The
cowpea plant is considered an important grain legume because of its great nutritional
value and ability to adapt to environmental stress like salinity. However, the cowpea
loses its ability to grow and develop at a high salinity level. Proline is an amino acid
that helps different crops tolerate salt and minimize the damage caused by salinity.
Therefore, this study focuses on understanding proline's effect on cowpea plants
exposed to salinity. The cowpea seeds were planted on soil and irrigated with different
concentrations of NaCl (0, 40, 80, 100, and 150 mM) and proline solutions (0, 10, 20,
30, 60, and 80 mM) to evaluate the positive effect of proline on different levels of
salinity by measuring changes in various plant's growth parameters. These
measurements include plant height, leaf area, chlorophyll pigments, root system
photosynthetic efficiency, and antioxidant defense integrity.
Salinity negatively affects different morphological and photosynthetic parameters,
such as the root system, chlorophyll pigments, and photosynthetic efficiency. In
addition, it reduces a plant cell's capacity to absorb water and minerals and leads to
ROS accumulation in cowpeas. However, the use of proline positively affected
different morphological and photosynthetic parameters when the plants grew under
control and saline conditions. For example, proline enhanced leaf area, plant height,
chlorophyll pigments, photosynthetic efficiency, and antioxidant defense system.
Additionally, proline showed a positive effect on the TPC, TFC, and glutathione when
grown under saline conditions.
Overall, the results showed that the cowpea plants treated with proline at a
concentration of 30 mM were more tolerant to salt stress than the control. Furthermore,
the results showed that cowpea plants had evolved effective antioxidant defense
enzymes, including SOD, CAT, and APX to control oxidative damage under salt stress
and proline conditions. This study is looking for a radical solution to the soil salinity
issue and the role of proline in solving this problem to develop crops in Oman and the
world.
