Study On Ecophysiological Response Of Sedges (Carex: Cyperaceae) To Heterogeneous Environment

The genus Carex (Cyperaceae), with large number of species and extremely wide distribution in the world, almost occur in every type of habitats, such as lake margins, wet forests, swamps where they are often dominant and make up an important part of the vegetation. Carex species often lack mycorrhizae, but under conditions of low phosphorus availability many species facultatively form dauciform root structures that are implicated in phosphorus uptake. Many of them play very important role in maintaining the most fragile eco-environment where they live in. The cultivating experimental materials, growth characters, ecophysiological traits, dauciform roots development and their distribution pattern in Carex genus, and evolution to different environments of Carex species were mainly conducted in the phytotron of McGill University. The conclusions of this study are as follow:(1) The growth traits, chlorophyll concentration, biomass, root:shoot ratio, the response curve of light and the response curve of CO₂ across different P concentration and light treatment were systematically observed and measured.On average, plants in low-P growth regimes had higher root:shoot ratio, and lower productivity in both sun and shade; total root length did not differ between high-P versus low-P growth regimes, but investment in fine roots increased under low-P. Sun-growth plants had greater productivity, greater foliar chlorophyll content and higher root:shoot ratio under both regimes(2) This study revealed that dauciform roots only occurred in the Subgenus Carex, did not form in the Subgenus Vignea among genus Carex species. The study further proved that dauciform roots mainly occurred in the tribes Rhynchosporeae and Cariceae and the induction of dauciform roots in Carex is allied with phylogeny, rather than the influence of the environment (nutrition and light)(3) This study introduced light factor to induce dauciform roots. The result indicated that low P was main factor to induce dauciform roots; shade affected dauciform roots to development and it decreased the possibility of dauciform roots.(4) This sort of high functional diversity was also apparent in a trio of foliar traits defining the leaf economics spectrum. These traits appeared to be tightly linked in comparisons across a wide range of species globally, but in this set of closely related species within a single genus some of the more subtle variation in foliar design stood out. Low light reduced Amax, low P always does. However, the effects of insolation were greater than the effects of phosphorus availability.(5) Nitrogen is an important component of chlorophyll and protein related to photosynthesis 75% nitrogen in plant is concentrated in chloroplast. Generally, chlorophyll will increase with nitrogen increasing. The result of principal component analysis was that functionally significant shifts in nitrogen investments in Rubisco versus chlorophyll across the light and phosphorus availabilities in this experiment.(6) This study compared the relationship of carex species between the hierachical clustering dendrogram using growth characters, root and leaf traits and phylogenetic tree.This study showed that the hierachical clustering dendrogram reflected the relationship of their kindred.To sum up, every Carex species has fuctional difference both in same and different environments, and is allied with phylogeny; There is clear differentiation at a suit of growth and productivity among all the species in "trait space" as well as differentiation between sister species; This divergent pattern exhibits first in productivity, then in form aspects.