THE RESEARCH OF PHOTOSYNTHETIC CHARACTERS ON PHRAGM ITES COMMUN IS (REED) IN HYDRO2FLUCTUATION BELT OF THREE GORGES RESERVO IR AREA

When the Three-Gorges Reservoir was put into use,riparian zones have been formed on both sides of the reser-oirwhere the water level changes periodically. This ecotone of overlapp ingwater aquatic ecosystem and terrestrial ecosys-em,owing to its characteristic ecological vulnerability,biodiversity,water periodical fluctuation and high frequency ofuman activities,has a profound influence on the water aquatic and terrestrial ecosystems. At the same time,the zonesill confront rigorous ecological and environmental problems. Therefore,this paper researches upon the reed (Phragm itesommunis) which lives on the both sides of J ialingjiang River. For researching on soil moisture contents of the hydro-luctuation belt in Three Gorges ReservoirArea and provide the theoretic evidences of restoration and rehabilitation of vege-ation and eco-environment protection,three different types ofwater treatmentswere app lied to the reed (Phragm ites com-unis ) to determine its photosynthetic eco-physiological characteristics. The treatments T1 (with soil being complete sub-erged -cm),T- (with soilwater content being 70 % to 100 % of field capacity) and T3 (with soilwater content 40%o 60 % of field capacity) simulated the conditions in the hydro-fluctuation belt. During the experimental process,theeed was irrigated with the water from the J ialingjiang River. The results showed that the water content of leaves,apparentuantum yields (AQY),dark resp iration rate (Rd) and light compensation point (LCP) were affected significantly underifferent soilmoisture content conditions,however,there were no significant differences about light saturation point (LSP)nd the maximum net photosynthetic rates (Amax). The maximum net photosynthetic rates (Amax) of the reed (Phrag- ites communis) were clearly different for the three treatments. The T1-plants (i. e. the flooded plants) was 17. 63μmolO-/m- ·s,while the T3-plants (i. e. the‘dry-treatment’plants) was -0. 97μmol CO-/m- ·s; In addition,the appar-nt quantum yields (AQY) of the T3-plants was 0. 055 μmol CO-/μmol Photons,which was higher than that of the T1-nd T--p lant significantly,it indicated that T3 had high transitive efficiency of light energy and photosynthetic ability; mo-eover,the T3– p lant had the highest water use efficiency (WUE) and light quantum use efficiency (QUE),but themallest ratio of free water to bound water,it suggested that the reed (Phragm ites communis) had high tolerance to drought.he light compensation point of the T--p lant was 35. 43μmol/m- ·s,which was higher than that of the T1- and T3-p lantignificantly,and light saturation point (LSP) of the T1-p lant,T- and T3 were 91-. 5,803. 89 and 897. --μmol/m- ·sespectively,which showed that there was a wider use range of light in group T1. Moreover,Ci of T1 was the highest thanhat of T- and T3,but the dark resp iration rate was the lowest in group T1,which showed its resource was very p lentifulnd be consumed rarely. Compared to other p lant species,the flooded reed (Phragm ites communis) had still the maximumet photosynthetic rate (17. 63μmol/m- ·s),which indicated that reed also has a high tolerance to inundation. Itwas al-o demonstrated that the reed (Phragm ites communis) could not only tolerate water submersion and wet condition but alsondure drought. Therefore,the reed (Phragm ites communis) could be a precedent species for restoration and rehabilita-ion of vegetation and eco-environment protection in the hydro-fluctuation belt of Three Gorges reservoir region.