Effects of Microalga (Chlorella vulgaris Beijerinck) on Seconder Metabolites and Antioxidative Defense System Improve Plant Growth and Salt Tolerance in Guar [Cyamopsis tetragonoloba (L.) Taub.]

Microalgae, such as Chlorella vulgaris, are beneficial microscopic organisms that may result in a plant having improved nutrient uptake, growth and abiotic stress tolerance. In this study, the application of microalga significantly increased the shoot length and fresh and dry weights; leaf number and area and photosynthetic pigments of guar plants when compared to those under salt stress alone. In addition, following the above-mentioned procedures, there were significant increases in the total phenolic (60.70%), flavonoid (174.80%), K+ (30.6%) and Ca2+ (36.10%) ion contents and ascorbate peroxidase (55.98%), catalase (256.45%), glutathione reductase (63.57%) and superoxide dismutase (113.58%) enzyme activities. However, the malondialdehyde (49.63%), Na+ (41.09%) and Cl– (37.10%) ion contents were significantly decreased. Hence, the results supported the administration of a foliar application of microalga in order to increase the guar plant’s defense system, enabling it to tolerate the negative effects resulting from salinity.