Molecular Weight and Concentration of Chitosan Affect Plant Development and Phenolic Substance Pattern in Arugula

The present research reports the role of chitosan’s molecular weight (1, 10, and 100 kDa) on the differentiation of its effects on arugula (Eruca vesicaria ssp. sativa) cultivation in a controlled environment. The leaves' phenolic substance pattern from the plants treated with the chitosan variant that gave the best developmental results was analyzed through a reversed-phase HPLC. The leaf production was enhanced after 10 kDa chitosan treatment at 5 mg L-1, while the leaf area expansion was significantly improved after 1 and 100 kDa chitosan at 20 mg L-1 and 10 kDa chitosan at 5 mg L-1. The plant's rhizogenic development was restricted after all chitosan treatments regardless of their molecular weight and concentration. The contents of chlorophyll b and carotenoids increased after the treatments; however, chlorophyll a content was not significantly affected by the treatments and remained unchanged. The chromatographic analysis showed that 10 kDa chitosan treatment at 5 mg L-1 increased gallic acid, rutin, and p-coumaric acid contents and made significant changes in the individual phenolic substance pattern. The current study indicated that direct application of chitosan to soil restricts root production in arugula but enhances foliar growth, which is beneficial to producers. On the other hand, constant- or over-treatment with chitosan could inhibit root growth and further lead to developmental deficiencies sourced by nutrient uptake disorders. The use of chitosan as an organic and natural biostimulant in controlled-environment agriculture could be a better option than synthetic growth stimulants.