A Physioecological Study On The Endangered Plant Changium Smyrnioides And The Comparative Species

Based on the research of photosynthetic carbon assimilation in natural habitat, the physiecological features of net photosynthesis (PN) and growth of Changium smyrnioides Wolff and Anthriscus sylvestri (L.) Hoffm were measured under controlled soil water status (saturation status (SS), moderate status (AW50) and dry status (AW20)), the difference of photosynthesis and transpiration to environmental factors and the adaptation to environmental fluctuation compared, to analyze the mechanism of C. smyrnioides to be endangered. Results showed that:1. The photosynthetic carbon assimilation ability of C. smyrnioides was lower than that of A. sylvestris under natural environment. C. smyrnioides germinates in December and A. sylvestri in September, begin dormancy in June and bear fleshy storage roots. The growing season of C. smyrnioides is therefore 160 days shorter than that of. A. sylvestri. They all grew rapidly in February and March, the PN of C. smyrnioides were 9.49 u mol(CO2)m-2 s-1 and 9.36 u mol(CO2) m-2 s-1 respectively, which were 23% and 37% higher than those of A. sylvestri. In the following May, the growth and photosynthesis of them slowered, the PN of C. smyrnioides declined to 1.55 u mol(CO2) m-2 s-1, 75% lower than that of A. sylvestri. The seasonal fluctuation of PN of C. smyrnioides was larger than that of A. sylvestri: the PN of C. smyrnioides was 84% lower in May that of in February, while A. sylvestri was only 19%. The leaf number and aboveground biomass ratio of C. smyrnioides were far less than those of A. sylvestri.2. Under controlled soil water status, the theoretical water niche of C. smyrnioides was saturate and moderate soil water status; Chuanminshen violaceion was moderate, while A. sylvestri was the most broad, and adapted well from saturation to 20% water sattus. The photosynthesis of one-year-old and two-year-old C. smyrnioides was higher in saturate and moderate than that of in dry, the recovery of photosynthesis in dry condition was weak when they watered to saturation. The photosynthesis of one-year-old C. violaceum was higher in moderate than in two others; two-year-old was higher in saturate and moderate than in dry, the former two had little difference. The recovery of C. violaceum was better than that of C. smyrnioides. The photosynthesis of one-year-old A. sylvestri was higher in saturate and moderate than in dry; two-year-old was higher in moderate than in saturate and dry. The declining extent of photosynthesis in dry water status was small, and the recovery was better than two other species.3. C. smyrnioides displayed larger plasticity of photosynthesis and growth than A. sylvestri to soil water status changes: the decline extant of C. smyrnioides in dry water status is higher than those of A. sylvestri. The photosynthesis of one-year-old C. smyrnioides decreased 25-35% in dry water status, A. sylvestri decreased 15-25%; the two-year-old decreased 70-80% and about 30% respectively.4. C. smyrnioides and A. sylvestri took different growth and reproduction strategy. A. sylvestri allocated more resource to leaf and stem, the average ratio of leaf biomass in February, March and April was 49%, which could fix more matter via photosynthesis. C. smyrnioides allocatedmore resource to root, so the resource to aboveground was relatively small, the ratio was only 26%, and the carbon assimilation via photosynthesis was weak. A. sylvestri is monocarpic, and begin to procreate in the second or third year. The reproductive allocation of A. sylvestri was large and produced 1351 seed every individual, it also had asexual reproduction by producing remets from root. C. smyrnioides is polycarpic and takes four to five or more years to procreate. The reproductive allocation of C. smyrnioides small and bore less seeds only one eighth of A. sylvestri, it didn't has asexual reproduction. Accordingly, A. sylvestri took the r-strategy to occupy niche, which growing fast and having shorter heterogamous interval, breeding and spreading quickly. While C. smyrnioides took K-strat...