The Study Of Phenotypic Plasticity?Physiological Characteristics And Endangered Mechanism Of Ranalisma Rostratum

As a national endangered wild plant,Ranalisma rostratum has a very narrow natural distribution and is found only in Chaling,Hunan Province,Dongxiang,Jiangxi Province and Lishui Zhejiang Province in China.The research was mainly in the 1990s,and the study was terminated because of the gradual decline of its wild population.In addition,as a model species of the Ranalisma,R.rostratum has an important taxonomic status,and its research is conducive to understanding the classification and evolution of the Alismataceae.In recent years,researchers have found their population again in Lishui,Zhejiang.This paper studied the changes of phenotype plasticity and physiological characteristics of R.rostratum in different water depths and light intensities by potted water control methods,and analyzed the characteristics of leaf characteristics of the plants(include leaf length,Leaf width,petiole length and leaf area),leaf anatomical features(include leaf vein structure,vein thickness,mesophyll thickness,and leaf epidermal thickness),biomass(include leaf biomass,stem biomass,root biomass,and total biomass),photosynthetic Curves,stomatal exchange parameters(include net photosynthetic rate(Pn),stomatal concentration(Gs),transpiration rate(Tr),and intercellular CO2 concentration(Ci)),light response parameters(maximum net photosynthetic rate(Pnmax),light saturation point(LSP),light compensation point(LCP),dark respiration rate(Rd),and apparent quantum efficiency(AQE)),to explore the growth of R.rostratum in different habitats and the crisis.The main findings are as follows:1.Leaf type characteristics and biomass analysis showed that under the same light intensity,leaf width,leaf area,leaf biomass,stem biomass,root biomass and total biomass increased first and then decreased while the length of the petiole increases with increasing water depth.Under the same water depth,the decrease of light intensity made the leaf width,leaf area,leaf biomass,stem biomass and total biomass of the plants reduced significantly,however,the changes of light intensity and water depth had no significant effect on leaf length of the plants.2.The observation of leaf anatomical structure showed that there are no epidermal hairs and stratum corneum in the leaves of R.rostratum.As for the mesophyll tissue,there are no palisade tissue and sponge tissue differentiation in it,and the tissue lack mechanical tissue while the transfusion tissue is underdeveloped.Large intercellular space and atmospheric cavity exist in it,too.With the increase of water depth,the thickness of main vein,leaf thickness and thickness of mesophyll tissue increased first and then decreased.Light and water depth had no significant effect on leaf epidermal thickness.3.Photosynthetic physiological characteristics indicate that Pnmax,LSP,AQE,Pn,Gs and Tr decreased with the decrease of light intensity under the same water depth.Rd and Ci increased as the light intensity decreases.Under the same light intensity,with the increase of water depth,Pnmax,LSP,LCP,AQE and Pn increased first and then decreased.Rd decreased first and then increased.The water depth had no significant effect on Gs and Ci.4.Physiological analysis showed that under the same light intensity,the activity of peroxidase(POD),the content of soluble protein and soluble sugar increased first and then decreased with the increase of water depth;the content of malondialdehyde(MDA)decreased first and then increased with the increase of water depth;the content of proline was negatively correlated with water depth.Different light intensities had no significant effect on superoxide dismutase(SOD)and MDA.Light intensity reduces the levels of POD activity and the content of soluble protein,soluble sugar and proline.It can be seen from the above results that unfavorable water depth and light intensity can cause the slow growth of R.rostratum,and the plasticity response of the plant to the heterogeneous habitat is low.Changes in water depth and lack of illumination and their weak adaptability to heterogeneous environments may be important causes of their endangerment.