The Variation Of Biomass Allocation And The Mechanisms In Pseudometallophyte Rumes Dentatus L.

The biomass of tolerant plant is generally lower than that of non-tolerant plant. Although the total biomass is different, whether the biomass allocation among organs is also different between the two populations is still unknown. According to the retrieval of literatures, we suggested hypothesis that tolerant plant would differ from non-tolerant plant in the allocation of biomass. Under stress situation, tolerant plant would allocate more biomass to organs which are crucial to survival and reproduction, such as root and seed. In order to test this hypothesis, we did the following researches:(1) the comparative study of root/shoot biomass allocation between tolerant plant and non-tolerant plant;(2) the comparative study of growth/reproduction biomass allocation between tolerant plant and non-tolerant plant;(3) the relationship between biomass allocation and sucrose metabolism;(4) the relationship between acid invertase enzyme-activity and the alteration of amino acid sequence;(5) the relationship between acid invertase enzyme-activity and the expression of acid invertase gene. The plant material of this study was a metallophyte of Rumex dentatus L., one from a copper mine at Tonglushan hill (Cu-tolerant population), and the other from campus of Wuhan university (non-tolerant population). Hydroponic and soil cultures were respectively conducted to investigate the differences of biomass allocation at vegetative growth period and reproductive growth period. Following conclusions could be obtained from this study:(1) There were differences in root/shoot biomass allocation between tolerant plant and non-tolerant plant. The root/shoot ratio of non-tolerant plant was reduced by Cu treatment, while the root/shoot ratio of tolerant plant was increased by Cu treatment. The root length, number of tips, root surface area and average root diameter of non-tolerant plant were significantly inhibited by Cu treatment. The root length, number of tips and root surface area of tolerant plant were a little lower than control, while average root diameter of tolerant plant was a little higher than control. (2) There were differences in growth/reproduction biomass allocation between tolerant plant and non-tolerant plant. Under Cu stress, the aerial vegetative biomass decreased, while the reproductive biomass remained constant, and harvest index thus increased in tolerant plant. The aerial vegetative biomass, reproductive biomass and harvest index of non-tolerant plant were all decreased by Cu treatment. The time to first flowering was decreased in tolerant plant, while it was delayed in non-tolerant plant. The1000-seed weight, number of flowers, number of seeds, number of branches and ratio of seed set in tolerant plant were higher than those in non-tolerant plant.(3) The different biomass allocation between the two populations was related to differential acid invertase enzyme-activity. The cell wall invertase activity and vacuole invertase activity in tolerant plant were higher than those in non-tolerant plant. There were no significantly differences in neutral/alkaline invertase activity and sucrose synthase activity between the two populations.(4) The different acid invertase enzyme-activity between the two populations might be related to the alteration of amino acid sequence. The homology of cell wall invertase amino acid sequence between the two populations was95%. The homology of vacuole invertase amino acid sequence between the two populations was99%.(5) The different acid invertase-enzyme activity between the two populations was related to differential expression of acid invertase gene. Under Cu stress, the expression of acid invertase gene in tolerant plant was higher than that in non-tolerant plant.