Biomass Allocation And Environmental Regulation Mechanism Within Paris Polyphylla Var. Yunnanensis

The growing demand of Pairs polyphylla var. yunnanensis due to its high pharmaceutical values and the rapidly declining of this wild resource lead to the contradiction between supply and demand, while the growth rate of the medicinal organ(rhizome) of P. polyphylla var. yunnanensis lags behind other organs. In order to explore the resource allocation of P. polyphylla var. yunnanensis and its response mechanism to environment, and provide scientific evidence and theoretical foundation for the implementation of high yield cultivation techniques of P. polyphylla var. yunnanensis and promoting virtuous cycle of agro-forestry ecosystem, the biomass allocation patterns in different growth periods were studied at the individual level, and the responses of biomass allocation to environmental factors(light, water and altitude) was elaborated by analyzing morphology and photosynthetic physiology and the analytical method of SMA. The major conclusions were as follows:(1) The greatest average daily net photosynthetic rate and leaf area ratio, leaf area, specific leaf area and root surface area of P. polyphylla var. yunnanensis were appeared in August, and these values in reproductive stagewere greater than vegetative stage. The root, stem and leaf growth were mainly occurred in May to June, when the biomass flowed to the stem, leaf and root at the expense of rhizome biomass. The rhizome biomass accumulation was mainly occurred in August to September. The allometric relationship between vegetative organs(in addition to the stem) and plant size of P. polyphylla var. yunnanensis has changed from vegetative stage to reproductive stage. Compared with the P. polyphylla var. yunnanensis in reproductive stage, P. polyphylla var. yunnanensisin vegetative stage had a greater growth rate of the root, annual rhizome or leaf versus plant size.(2) There was no strong photoinhabition in P. polyphylla var. yunnanensis in the low shading degree(50% shading degree), and the light compensation point in the high shading degree(90% shading degree) was close to that of shade plants while the light saturation point in the low shading degree(50% shading degree) was similar to that of heliophile herbaceous plant. The highest photosynthetic efficiency of P. polyphylla var. yunnanensis appeared in 50% shading degree where the larger photosynthetic product could be fixed by lower photosynthetic organ biomass, and the current year rhizome biomass in 50% shading degree was 35.6% and 37.2% higher than that in 70% and 90% shading degree, respectively, where the biomass of P. polyphylla var. yunnanensis were largely allocated to stem and leaf. The allometry analysis showed that there was larger rhizome biomass in the low shading degree(50% shading degree)at the given leaf biomass in different shading degree, which displayed that the higher shading degree was to the disadvantage of the rhizome biomass accumulation of P. polyphylla var. yunnanensis,and only about 50% shading degree can be provided in artificial cultivated P. polyphylla var. yunnanensis at the altitude of about 2000 m in Yunnan province.(3) The lower net photosynthetic rate and leaf area in 40%±5% of soil water capacity brought about the significant decline of each organ biomass of P. polyphylla var. yunnanensis. There were largest rhizome biomass and its allocation proportion in 80%±5% and 100%±5% of soil water capacity. The biomass of root, stem, leaf and the total biomass of P. polyphylla var. yunnanensis in 100%±5% of soil water capacity were 43.5%, 33.1%, 22.0% and 32.8% higher than those in 40%±5% of soil water capacity, respectively, and the current year rhizome and total rhizome biomass in 100%±5% of soil water capacity increased 37.1% and 24.6% compared to those in 40%±5% of soil water capacity, respectively. The root biomass of P. polyphylla var. yunnanensis was not increasing in low soil water capacity where P. polyphylla var. yunnanensis may ensure its normal growth at the expense of rhizome biomass. The allometry analysis showed that there were larger rhizome biomass in 80%±5% and 100%±5% of soil water capacity at the given plant size in different soil water capacity. The declining rhizome biomass due to the low soil water content should be avoided in artificial cultivated P. polyphylla var. yunnanensis.(4) There was greater plant biomass at the higher altitude under the condition of the same photosynthetic organ biomass of P. polyphylla var. yunnanensis. The rhizome biomass(24.337±2.481 g) at the altitude of about 2531 m was larger significantly than that(17.647±2.374 g) at the altitude of about 985 m, and the rhizome allocation proportion(68.86%) at the altitude of about 2531 m was larger than that at the other attitudes, while there was largest fruit biomass and its allocation proportion at the altitude of about 2000 m. The allometry analysis showed that there was larger rhizome biomass at the higher altitude at the given leaf biomass at different altitudes. It is an important way for enhancing the economic yield o P. polyphylla var. yunnanensis to select appropriate altitude in artificial introduction and domestication.The responding mechanism of biomass allocation to environment of P. polyphylla var. yunnanensiswas revealed in this study: The variation of photosynthetic physiology and morphology due to the difference of environmental resources brought about the changes of biomass accumulation and allocation of P. polyphylla var. yunnanensis. The net photosynthetic rate declined but the stem and leaf biomass and leaf area increased at the lower light resource, which led to rhizome biomass allocation declining. P. polyphylla var. yunnanensis may compensate for the serious deficiency of assimilative capacity due to the lower net photosynthetic rate and leaf area by consuming rhizome biomass at the lower soil water. The above-ground biomass allocation declined but the root biomass and the photosynthetic efficiency increased of P. polyphylla var. yunnanensis at the higher altitude for adapting to the low temperature environment, and the rhizome biomass allocation increased with the sexual reproduction organ biomass declining and asexual reproductive organs(rhizome) increasing.The results can be conducive to promote the economic organ yield of P. polyphylla var. yunnanensis by takingtargetedmanagement measures in artificial cultivated P. polyphylla var. yunnanensis.