Abstract
The irrigation of sorghum [Sorghum bicolor (L.) Moench] by diluted seawater is in high demand because the plant is a moderately salt-tolerant species. This study was conducted to describe the responses of sorghum seedlings to saline irrigation using successive dilutions of seawater regarding the performance of certain physiological parameters. The germination percentage shoot and root development, chlorophyll content, proline content, hydrogen peroxide content, and scanning electron microscope (SEM) results of both the stem and the root were significantly affected by watering the seeds with 14.29% of natural seawater. Using 14.29% seawater caused reductions in the germination percentage (84.82%), the shoot length (42.62%), the root length (60.0%), the total chlorophyll (17.36%), chlorophyll a (18.20%), chlorophyll b (16.43%), the shoot's fresh weight (44.58%), the shoot's dry weight (48.23%), the root's fresh weight (68.03%), and the root's dry weight (56.37%) compared to the control. There was a steep increase in proline content (by 20.65%), in the leaf and the amount of hydrogen peroxidase in the leaf (by 32.74%), and in the roots (by 30.30%) of the stressed sorghum seedlings compared to the control. SEM showed that diluted seawater stimulated the hairs, causing them to swell and lie on the surface of the epidermis. In 100 um', no differences were observed in the number of stomata and hairs, whereas the number of cells, the cell wall and the intercellular spaces in the leaf, and the number of furrows in the roots varied between the control and the treated sample. The results of this experiment can be important for the development of adapted sorghum to various concentrations of natural seawater to obtain cultivars with improved germination under salt stress.