Growth and Physiological Response of Organs of Phragmites australis to Different Water Compensation in Degraded Wetlands

To study the effect of different water compensation on growth and physiology of reed in degraded wetlands,three water treatments in the field were conducted to test the height and photosynthesis of reed,the ions and soluble sugar contents of different organs.In the controls(without extra water compensation for 10 years),the height of reed was only 50 cm,the net photosynthetic rate,stomatal conductance,the intercellular CO2 concentration and transpiration rate were very low.The contents of Na + and Clin rhizome were higher than those in other organs.Discontinuous water compensation(continuous for 8 years,then stopped for 2 years)increased the height(2.1-fold),the net photosynthetic rate(41.8%),stomatal conductance(1.8-fold),transpiration rate(1.3-fold)of reed(Phragmites australis),and decreased the content of Na + (62.3%)and Cl - (71.1%)of rhizome significantly.Continuous water compensation(continuous for 10 years)increased the height(3.2-fold),the net photosynthetic rate(104%),stomatal conductance(2.4-fold),transpiration rate(1.5-fold)of reed,and decreased Na+ (82.5%)and Cl - (64.7%)contents in rhizome, then accumulated the K+ ,H2PO4-,SO42- and soluble sugar contents significantly in rhizome.Interrupting water compensation led to the decrease of height(25.3%),the net photosynthetic rate(30.7%),stomatal conductance(17.3%) and increase of Na + (1.16-fold)in rhizome when comparing to the continuous water compensation.These results showed that recovering the degraded reed wetlands needed continuous water compensation yearly to promote reed growth.The organs of reed had corresponding physiological response characteristic to the different water compensation condition.Under long-time dry and waterlogging condition,the rhizomes both helped reed to adapt located environment,by enriching the ions such as Na+ ,Cl- ,and K+ ,H2PO4-,SO42- ,respectively.