Evaluation Of Flooding Tolerance And Mechanism In Different Warm-Season Turfgrasses

Turfgrass is widely used in conservation of water and soil,urban afforestation and environmental improvement due to the wide distribution and outstanding adaptation.Due to the various responses to flooding stresses,the core of riparian recovery is to select flooding-tolerant turfgrass as flooding is one of the most common stresses in riparian ecosystem.Thereby,our study was evaluated on flooding tolerance for 15 turfgrass cultivars or accessions of 6 species.Four representive species were selected to study the mechanism(including anatomical structure,metabolite enzyme activity and photosynthetic characteristics)of flooding to provide alternative materials for the reconstruction of riparian vegetation.The main results were listed as followings:1.Evaluation on flooding tolerance of different warm-season turfgrass cultivarsTo determine the growth after seasonal submergence of 15 turfgrass cultivars or accessions of 6 species which were distributed in riparian zone.The test turfgrass were subjected to 30 d complete submergence(the water levels 7 cm higher than the plants that all plants growing under water),partial submergence(the water level submerged the soil surface)and a control(no submergence).Relative clipping dry weight,relative recovery dry weight,relative shoot dry weight and relative root dry weight of the tested turfgrass are ananlyzed as the indexes of flooding tolerance evaluation.The results of comprehensive evaluation showed that the flooding tolerance of different species were significantly different.Flooding tolerance decreased after 30 d partial submergence in the following order:Pseudoraphis spinescens>Paspalum distichum>Cynodon.transvaalensis×Cynodon.dactylon>Eremochloa ophiuroides>Paspalum vaginatum>Cynodon dactylon.P.spinescens and P.distichum are flooding tolerance species since they could grow out of the water surface quickly after complete submergence.While other species are less flooding tolerance since they have been submerged in water all the times during the treatment,submergence inhibited the growth of these plants,and their growth were almost stagnant.The evaluation also shows that flooding tolerance of these species decreased in the following order after 30 d complete submergence:P.spinescens>P.distichum>C.transvaalensis×C.dactylon>C.dactylon>P.vaginatum>E.ophiuroides.The tested turfgrass growing in partial submergence was significantly less harmed than those growing in complete submergence situation.As growing in different habitats,even the same accessions of same turfgrass had different flooding tolerance.The final result shows PX02(P.spinescens),P018(P.distichum),P019(P.distichum),C751'Tifdwarf',C807'Tifway' and C291(C.dactylon)have strong resistance to flooding in 15 warm season turfgrass,and they are ideal materials for vegetation reconstruction in natural riparian zone.2.Flooding tolerance mechanism of four representive warm season turfgrass(1)Anatomical structureThe anatomical characteristics of four representive warm season turfgrass were studied in a 30d artificial flooding experiment.Comparison and observation of anatomical structure showed the structure of four species were similar,with good ventilation organization visible in root cortex cell gaps and different degree air cavity in stem in which flooding tolerant species had more air cavity than that of less flooding species,wheras umerous cavities were developed in E.ophiuroides between the epidermis and fiber tape under flooding stress to increase the ventilation in its stem.Mesophyll cells tightly arranged in control expressed aerenchyma formation in leaves of E.ophiuroides;wheras the leaf anatomical characteristics of flooding tolerant species didn't show obvious variation under the flooding stress.(2)Metabolite enzyme activityThe turfgrass could adjust its metabolite enzyme activity to adapt the stress in flooded condition.The root vigor,the activity of ADH,LDH,SOD and POD of all tested species showed significant variation under the flooding treatment and control.P.distichum and P.spinescens had high relative shoot dry weight compared with E.ophiuroides and P.vaginatum.The root vigor of E.ophiuroides and P.vaginatum declined significantly under flooding,while P.distichum and P.spinescens showed high root vigor in the early stages of flooding stress,and declined slightly after flooding treatment for 30 d.The activities of alcohol dehydrogenase(ADH)and lactate dehydrogenase(LDH)were increased in root of all species following the flooding stress,the degree of increase in E.ophiuroides and P.vaginatum were significantly greater than that in P.distichum and P.spinescens.The leaf and root activities of superoxide dismutase(SOD)and peroxidase(POD)in P.distichum and P.spinescens were increased significantly under flooding treatment,wheras the leaves and root activities of superoxide dismutase(SOD)and peroxidase(POD)in E.ophiuroides and P.vaginatum showed the increase and decline trend.The contents of water soluble protein of E.ophiuroides and P.vaginatum decreased significantly under the stress,while contents of water soluble protein in P.distichum and P.spinescens were not significant difference compared with the control.(3)Photosynthetic characteristicsThe photosynthetic characteristics of flooding tolerance were studied in an artificial flooding experiment in pots with 4 warm-season turfgrass.The chlorophyll contents of E.ophiuroides was declined significantly under flooding treatment,while P.distichum and P.spinescens kept a stable even higher chlorophyll contents during the treatment.The net photosynthetic rate,stomata conductance,CO2 assimilation and transpiration rate of E.ophiuroides and P.vaginatum were declined significantly after flooding treatment,which resulted in declined photosynthetic capacity.While the intercellular CO2 concentration were increased significantly and the net photosynthetic rate were also increased significantly in P.distichum and P.spinescens due to the good adaptation to the flooding stress.