Impact of Low Concentration of Cadmium on Photosynthesis and Growth of Pea and Barley

Abstract

Photosynthetic gas exchange and growth characteristics were examined in pea and barley plants using 1 mM Cd treatment. Plants were sown into neutral peat substrate and at a leaf development stage were treated with 1 mM cadmium concentration solution. Gas exchange parameters (photosynthetic rate; intercellular CO₂ concentration; transpiration rate; water use efficiency) were measured with portable photosynthesis system LI-6400 on the fifth day after Cd treatment. Under Cd stress the photosynthetic rate of pea and barley plants decreased by 16.7 % (p < 0.05) and 12.8 % (p < 0.05), respectively, compared to the reference treatments. Photosynthetic response of pea leaves to cadmium stress was slightly different from that of barley. Intercellular CO₂ concentration decreased by 27.4 % (p < 0.05) in pea leaves but it increased by 33.5 % (p < 0.05) in barley leaves. Cadmium treatment had no statistical significant effect on the transpiration rate of pea plants, while the transpiration rate of Cd treated barley decreased by 23.1 % (p < 0.05), compared to the reference treatment. CO₂ reduction processes of Cd treated pea leaves increased (because intercellular CO₂ concentration decreased), but that had no positive effect on a photosynthetic rate, and the photosynthetic rate of pea decreased by 4 % more than that of barley. The changes of dry biomass of cadmium treated plants were weak and statistically insignificant.