Abstract:

Physiological and biochemical indexes of detached leaves of Pseudosasa japonica which treated with different doses of Hg~ 2+ and certain doses of La³⁺ were determined in order to study regulating effects of La³⁺ on physiological response of bamboo leaves and the relationship between La³⁺ and polyamine metabolism under Hg²⁺ stress. The results showed that the accession of cell membrane permeability and the descent of chlorophyll and protein content were inhibited obviously in the presence of 0.25 mg·L^-1 La(NO₃)₃ under 10 mg·L^-1 mercury bichloride stress,and the damage of leaves was relieved noticeably. Under 50 mg·L^-1 mercury bichloride stress,La³⁺ had no significant influence on relieving the damage of leaves. While Under 200 mg·L^-1 mercury bichloride stress,synergistic effect of La³⁺ and Hg²⁺ appeared,La³⁺ even aggravated the damage of leaves. La³⁺ could also increase SOD activity and inhibit the elevation of POD activity,keep stabilizing of protective enzymes under 10 mg·L^-1 mercury bichloride stress. Alleviative effect of La³⁺ on mercury toxicity of P. japonica leaves was likely related with polyamine metabolism. La³⁺ treatment could promote noticeably endogenous putrescine (Put)、spermidine (Spd) and spermine (Spm) content of leaves under 10 mg·L^-1 mercury bichloride stress,which coincided with alleviative effect of La³⁺ ,and presented obviously positive correlation with the change of SOD activity. The study suggested that increasing of endogenous polyamine content was likely a pattern of alleviative effect of La³⁺ on mercury toxicity,and polyamines exerted positive effects on reducing injury of leaves under Hg~ 2+ stress.

Key words: Lanthanum, Hg²⁺ stress, Pseudosasa japonica, physiological response, polyamines