Effects of Heavy Metal Pollution on Photosynthetic Characteristics and Heavy Metal Contents in Forage Leaves under Different Planting Patterns

Abstract:

In order to explore the effects of heavy metal pollution on physiological characters of forage under different planting patterns, three forages, such as Pennisetum sinese, Lolium perenne and Juncus effusus, were single cropping and intercropping, the effects of heavy metal pollution on photosynthetic parameters, photo-synthetic pigments and heavy metal contents in leaves under different planting patterns were studied. The results showed that compared with monoculture, the contents of chlorophyll (Chl) a, Chl a+b and carotenoid (Car) of P. sinese leaves under intercropping increased significantly, while P_n, G_s, C_i and Chl b content decreased signi-ficantly, but there was no significant difference in transpiration rate (T_r). The C_i and Car content in L. perenne and J. effusus increased significantly, while P_n, T_r, G_s, contents of Chl a, Chl b, and Chl a+b decreased significantly except of Chl a content in J. effusus. The leaf and total biomass, heavy metal contents in three forage leaves increased significantly under intercropping, except that copper content of J. effusus decreased significantly. Compared with control, the photosynthetic parameters, photosynthetic pigment content in leaves, leaf and total biomass of P. sinese were significantly improved treated with low concentration heavy metal pollution, while the P_n, T_r, G_s, C_iin leaves, leaf and total biomass of L. perenne and J. effusus decreased significantly, and photo-synthetic pigment contents increased significantly, but there was no significant difference in T_r, C_i, leaf biomass of L. perenne and Chl b content in L. perenne and J. effusus. The contents of heavy metals in three forage leaves increased significantly under heavy metal pollution. The interaction of planting pattern×heavy metal pollution on photosynthetic parameters, photosynthetic pigment content, leaf and total biomass, and heavy metal content of forage leaves were significant. Therefore, on the heavy metal combined pollution soil, it was beneficial for accumulation of dry matter and absorption of heavy metals of three forages under intercropping, while under monoculture, it was more beneficial to improve their photosynthetic capacity. Under different planting patterns, the adaptability of P. sinese to heavy metal pollution was stronger than that of L. perenne and J. effusus.

Key words:Heavy metal;Pollution;Forage;Planting pattern;Photosynthetic characteristics