[Effects of Pb Stress on Photosynthetic Pigment Biosynthesis and Growth of Rabdosia rubescens].

OBJECTIVE: To study the impacts of lead (Pb) stress on the leaf photosynthetic pigment and the growth of Rabdosia rubescens,in order to provide a basis for planting area selection and growth regulation. METHODS: Taking chlorophyll a, chlorophyll b, carotenoids, growth rate, biomass and Pb content as the indexes, the Ramets hydroponic experiments at Pb concentration levels (135,270 and 540 mg/L) in the time(20, 35 and 50 d) were carried out. Photosynthetic pigment content was determined by spectrophotometer, and Pb mass fraction was detected with plasma emission spectrometer. RESULTS: There was uncertain effect on chlorophyll and carotenoid synthesis in different Pb concentrations in-early period (20 and 35 d). At the time of 50 d, the chlorophyll content was higher in the low-mid Pb concentrations, significantly lower in the high Pb concentration compared with the control group, and there were no significant differences on carotenoid contents in different Pb concentrations. CONCLUSION: Low-mid Pb concentrations can promote chlorophyll synthesis, and the bioaccumulation of high Pb concentration can inhibit the chlorophyll synthesis, and then restrict the growth of Rabdosia rubescens.

[Effects of Pb2+ stress on seed germination & seedling growth of Rabdosia rubescens].

The seeds of Rabdosia rubescens were as the materials to research the impacts of different lead (Pb2+) concentrations(0, 135, 270, 540, 1 080 mg x L(-1)) on seed germination and seedling growth. The results show that: Low concentration of lead had no obvious effect on early germination of the seed, the germination vigor and germination speed were lightly higher but not significantly differed at the level of Pb concentration 135 mg x L(-1) with control group; Mid-high concentration of Pb solution (270-1 080 mg x L(-1)) significantly inhibited the seed germination and seedling growth, which reduced the seed germination rate, germination vigor, germination index, embryo root length and shoot length, growth index with increasing of Pb concentrations. There was a inhibitory effect on embryo shoot length and root length at mid-high lead concentrations stress, and stronger inhibitory effect on root , which was more sensitive than shoot to Pb stress(P < 0.05). Pb bioaccumulation coefficient (BC) was 0.76-2.59, increased with concentration of Pb; Pb enrichment in seedling mainly caused the growth inhibition. The fitting model predictive analyses show, the critical concentration of Pb, which causes the germination rate and biomass fresh weight reducing 10%, is 195.18, 101.65 mg x L(-1).