Soluble phenolics, chlorophylls, and malondialdehyde are the best indicators of salt stress in Eichornia crassipes

This work describes the biochemical responses of water hyacinth ( Eichhornia crassipes ) plants to salinity stress under controlled conditions. Low to medium levels of necrosis were observed with plant fresh weight remaining stable across all treatments. Investigation of lipid peroxidation products revealed that levels of malondialdehyde were significantly increased in leaves and stems when plants were exposed to 40 mM NaCl indicative of membrane damage. Measurement of soluble and cell wall-linked phenolics indicated a decrease in levels in response to the stress. Increased concentrations of NaCl also resulted in decreased levels of chlorophyll a and b in leaves and stems, particularly when 40–80 mM NaCl was present. The carotenoid content of leaves and stems was reduced following exposure to NaCl but was more stable in roots. The results indicate that water hyacinth plants are sensitive to salinity stress with toxicity symptoms typified by leaf necrosis. This was apparent in the increased incidence of stress markers (malondialdehyde) and reduced chlorophyll levels. The inability of plants to mobilize an appropriate defense (indicated by reduced phenolic levels) provided further evidence for their biochemical and physiological sensitivity. Key message Sodium chloride modifies levels of aldehydes, phenolics, chlorophylls and carotenoids in water hyacinth.