Structural and functional aspects of photosynthetic response in Eichhornia crassipes (Mart.) Solms under cadmium stress

摘要

E ichhornia crassipes (Mart.) Solms is a floating hydrophyte that dominates metal-polluted wetlands such as industrial effluents. Keeping in view its capability to hyper-accumulate metal ions, the effect of cadmium stress on structural and functional features of photosynthesis was investigated to assess growth response under metal toxicity. Plants were randomly collected from polluted areas of Sheikhupura-Lahore road and multiplied for about one year at research sites of old Botanic Garden, University of Agriculture, Faisalabad. Plants were thereafter treated with cadmium stress and levels of cadmium were 0 (control), 50, 100 and 150 mg L -1 in aqueous solution. E. crassipes reduced their biomass, and photosynthetic features like chlorophyll pigments, net CO 2 assimilation rate, sub-stomatal CO 2 concentration and stomatal conductance under cadmium toxicity. Water use efficiency also decreases significantly in response to metal stress, but this species is a floating hydrophyte. Water is frequently available to this species and any decrease in water use efficiency may not affect growth and development. Leaf features i.e. leaf thickness, chlorenchymatous and sclerchymatous area, aerenchymatous area, vascular bundle region (xylem and phloem area) and stomatal area were reduced in response to Cd treatment. Increase in stomatal density on adaxial and abaxial leaf surfaces and bundle sheath cell area under cadmium stress indicate metal tolerance in plants. It is concluded from the present investigations that E. crassipes accumulates cadmium and can be utilized for phytoremediation in polluted water.