Evaluation On Waterlogging Tolerance And Its Mechanisms In Hemerocallis

With a cultivation history of more than 3,000 years in China,Hemerocallis is called‘mother flower' in ancient times.Considering that the water accumulation generated by the factors such as heavy precipitation and planting terrain has a huge impact on the cultivation and ornamental quality of Hemerocallis,the cultivation of waterlogging-enduring cultivars is one of the important goals of Hemerocallis breeding.The waterlogging-enduring cultivars may carry some resistance genes,so it will provide material for the molecular breeding of Hemerocallis by observing its phenotypic changes under waterlogging stress,researching the variation of antioxidant enzyme activities,and studying the reaction changes of ethanol,lactic acid and pyruvic acid in anaerobic respiration.Meanwhile,this will also lay foundation for the screening and expansion of Hemerocallis germplasm.The major research findings are as follows:1.The waterlogging-enduring evaluation system of Hemerocallis shall be established.Based on potting water-flooding method,the four appearance indicators of the overground part of Hemerocallis are observed and recorded,so that the evaluation system can be constructed by grading and formulating the scoring standards.The method helps quickly screen out the waterlogging-enduring cultivars from appearance.7 waterlogging-enduring cultivars are preliminarily selected by means of identifying 23 Hemerocallis cultivars.2.According to the measurement of photosynthetic parameters of the typically different Hemerocallis cultivars and comparison of their waterlogging-endurance,the Stomatal conductance,Net photosynthetic rate and Transpiration rate of the 6 Hemerocallis cultivars decreases under the stress of waterlogging,while the concentration of Intercellular carbon dioxide presents an increasing trend.After 8 days of waterlogging stress,the Stomatal conductance and Net photosynthetic rate of Marry Reed and Stella de Oro are significantly higher than that of other cultivars;the concentration of Intercellular carbon dioxide of all the 6Hemerocallis cultivars show an increase in comparison,among which Marry Reed,Stella de Oro and Chicago Fire increase significantly;Marry Reed and Stella de Oro have a higher transpiration rate than the other cultivars.The analysis indicates that Marry Reed and Stella de Oro can maintain higher Photosynthetic performance under waterlogging.3.Two cultivars with strong waterlogging-endurance and poor waterlogging-endurance are selected as experimental materials to separately study their phenotypic changes in the aboveground and underground parts,leaf Antioxidant enzyme activities,leaf Malondialdehyde content,root Anaerobic respiratory enzyme activity,Soluble protein and Chlorophyll content under the stress of waterlogging.The results show that after 8 days of flooding,the whole plants of Marry Reed and Here Lies Butch maintain a good growth,aerialroots are found and a small part of the root tip is swollen and softened;2/3 leaves of whole plants of Bonibrae Sharky and Pardon Me go yellow-brown and dry,and the roots are rotten and hollow after 8 days of flooding.Higher Antioxidant enzyme activity can eliminate reactive oxygen species,while weakly tolerant cultivars present aging and death due to severe anaerobic stress and weaker ability of eliminating reactive oxygen.In comparison,the Peroxidase activity,Catalase activity and Ascorbate peroxidase activity of the leaves of Hemerocallis have decreased.As can be learned from the overall trend,the decline of Marry Reed is small,while Pardon Me presents the largest decline,Superoxide dismutase activity shows an upward trend under the stress of waterlogging,Marry Reed and Here Lies Butch have a larger increase,while Bonibrae Sharky and Pardon Me increase smaller;Bonibrae Sharky and Pardon Me have higher Malondialdehyde content than Marry Reed and Here Lies.The main pathway of anaerobic respiration of strong waterlogging-enduring cultivars is Ethanol fermentation,which can maintain high levels of Antioxidant enzyme activity and Photosynthetic performance.However,the main pathway of anaerobic respiration of weak waterlogging-enduring cultivars under hypoxia stress is Lactic acid fermentation.This is one of the important causee for the difference in their waterlogging-enduring capacities.In the experiment,the activity of Lactate dehydrogenase and Pyruvate decarboxylase present a downward trend,among which the activity of Marry Reed shows an upward trend and the activity of Alcohol dehydrogenase increases significantly;the content of Soluble protein is in a downward trend,and the total Chlorophyll content falls down after rising firstly.