The Morphological Adaptation Of Several Cultivated Flooding-tolerant Herbaceous Plants To Submergence Stress Of Water-level-fluctuation Zone

After the construction of the Three Gorges Reservoir, riparian zones have been formed on both sides of the reservoir where the water level changes greatly, as much as30m, according to the special attemperation of water. Compared with the river hydro-fluctuation belt, some riparian areas along the river bank would be submerged as long as8month. Many plants can not survive greatly, and it would bring about some serious problems such as injury of biodiversity, soil erosion and environment polution. It is one of the most serious ecological problems which we must face with.In order to protect ecological environment in the Three Gorges Reservoir region, structuring a vegetation by man in the area is considered to be one of the important measures except some engineering measures. In this process, selecting the opt submergence-tolerant species and knowing their mechanism of living underwater are the key, and is needed for cope with the environment problem in the Three Gorges Reservoir region. On the basis of many simulated experiments, researchers concluded many valuabe results. Because the submergence depth and environment are very different with the Water-level-fluctuation Zone because of objective conditions, it is necessary to make field experiments on cultivated candidate species.The experiments were conducted in the Ecology treatment and recovery experimental base of water-level-fluctuation zone in Three Gorges Reservoir, Zhong city, Chongqing. And cultivated Polygonum2#, Arisaema2#,Graminoid3#, Graminoid5#, and Graminoid1#were selected as our experimental materials. Graminoid3#, Graminoid5#and Graminoid1#were planted in the base in2008, while Polygonum2#, Arisaema2#in2009. The experiment were devided into2parts:(1) Survival and recovery of Polygonum2#, Arisaema2#after the winter water submergence of2010.(2) Recovery of Graminoid3#, Graminoid5#and Graminoid1#after the winter water submergence in2010. Mass density of root and internode of Graminoid3#, Graminoid5#, and Graminoid1#before the winter water submergence in2011, as well as after the submergence in2011.Part(1) found that (1) The survival of both Polygonum2#and Arisaema2#kept at100%in all elevations after the submergence.(2) Areas of their initial leaf increased significantly with the decrease of elevation, while thickness of those leaves changed reversely.(3) No significant differences were found in leaf’s area and leaf’s thickness of Polygonum2#and Arisaema2#among different elevations after2months growth following submergence termination.Part(2) found that (1) Thickness of their initial leaf decreased significantly with the decrease of elevation, and the area of initial leaf also increased significantly with the decrease of elevation except the comparison of166m、170m and control elevation.(2) No significant differences were found in leaf’s area and leaf’s thickness of the three species among different elevations after2months growth following submergence termination.(3) Before the winter water submergence in2011, no significant differences were found in mass density of both roots and mature internodes.(4) Compared with contiguous elevations, mass density of both roots and mature internodes of Graminoid3#and Graminoid5#in173m showed no significant differences. While mass density of both roots and mature internodes decreased significantly with the decrease of elevation after the submergence in2011.(5) After several month growth following submergence termination, all of the cultivated flooding-tolerant species in different elevations storaged nutrition in roots and mature internodes.Therefore, we can make a conclusion that (1) Both Polygonum2#and Arisaema2#had high survival after long-term submergence, they shows good tolerance to submergence.(2) Graminoid3#, Graminoid5#and Graminoid1#storaged nutrition in roots and mature internodes before the submergence. Plants growing in different elevations consumed different nutrition reserves.(3) All of the cultivated flooding-tolerant species changed the ratio of their leaf’s area to thickness for accomulating photosynthesis outcome.(4) In order to endure the upcoming high stress of winter water submergence, all of the cultivated flooding-tolerant species storaged nutrition in roots and mature internodes. On the base of these results above, we can make a conclusion that several cultivated flooding-tolerant herbaceous plants in our experiment have their own adaptation to submergence, and both of them could survive in the revegetation of water-level-fluctuation zone in Three Gorge reservoir region.