Allelopathic Impact of Callistemon Citrinus on Sorghum Bicolor Growth under Salinity Stress

The current study assessed the impact of 0.09% aqueous leaf extract from Callistemon citrinus on the growth of two cultivars of Sorghum bicolor L. (Giza 15 - G15 and Dorado - Dor) under two salinity levels (100 mM and 200 mM NaCl). Results revealed that salinity reduced various growth criteria, including insoluble and total carbohydrates, photosynthetic pigments, protein, total phenols, and reduced glutathione, while soluble carbohydrates (sucrose and trehalose) were influenced. Salinity also affected free amino acids (proline and glycine betaine), malondialdehyde, and ascorbic acid. The activity of amylase decreased, while antioxidant enzymes (catalase, peroxidase, superoxide dismutase, ascorbic acid oxidase, and glutathione peroxidase) increased. Additionally, concentrations of K+, Ca++, and Mg++ were reduced, while Na+ accumulated. Application of Callistemon extract improved plant growth under stressed or normal growth conditions. The aqueous leaf extract (0.09%) of Callissstemon sp., with its enriched phenolic allelochemicals, mitigated the impact of salinity by enhancing photosynthesis, osmoregulation, and the antioxidant defense system of sorghum plants. Furthermore, results indicated that Sorghum cultivar G15 exhibited more resistance than Dor, with this resistance correlating with the activity of the antioxidant system.