Studyon The Influence Of Environmental On The Growth Of Submerged Rotala Rotundifolia

Submerged plants are the main members of the river ecosystems.The whole plant is immersed in water,and its roots,stems,leaves and epidermis have absorption,and cortical cells containing chlorophyll,which has a good absorption effect on nitrogen and phosphorus in water.Rotala rotundifolia is a multi-ecological aquatic plant with obvious advantages for nitrogen and phosphorus absorption in water,and has great potential for resource development and utilization and ecological restoration.In order to better play the effect of remediation of polluted water in the submerged Rotala rotundifolia,it is necessary to systematically study the planting conditions.In this paper,the effects of different light intensity,water temperature,water turbidity,dissolved oxygen in water and planting methods on the growth and physiological activities of Rotala rotundifolia were studied.In addition,the Eco-tank system based on Rotala rotundifolia,Vallisneria natans,Hydrilla verticillata and Ceratophyllum demersum were established by simulating the natural river,the purification effects of ammonia,total nitrogen and total phosphorus of the Eco-tank system were discussed.The main conclusions were as follows:?1?Light had a significant effect on the cutting and ramets planting of Rotala rotundifolia:within the experimental light intensity?14300-15784 lux?,the relative growth rate of submerged Rotala rotundifolia decreased with increasing light intensity in the ramets planting group,while in cutting planting group,it increased first and then decreased with the increase of light intensity.At the end of the experiment,the submerged Rotala rotundifolia had maximum relative growth rates of 3.7 mg/?g·d?and2.52 mg/?g·d?under 100%and 60%light conditions,respectively.?2?In the test water temperature range?5-30??,the submerged Rotala rotundifolia could growth normally,and the relative growth rate increased first and then decreased with the increasing of water temperature,and has a maximum at 54°C and5°C?54.05 mg/?g·d??and the minimum value?5.61 mg/?g·d??.?3?In the range of test turbidity?0-70NTU?,the growth rate of submerged Rotala rotundifolia decreased with increasing of turbidity,and except for the 0NTU treatment group,the biomass of the other groups showed negative growth.The relative growth rates of the 20NTU,50NTU,and 70NTU treatment groups were 9.08,-7.81,-24.68,and-27.59 mg/?g·d?,respectively.?4?In the oxygen-rich or anoxic environment,the growth rate of Rotala rotundifolia was slowed down,which had the greatest effect within 7 days,and then decreased with the increasing of the test time,and the relative growth rate in the Control group,Aeration 8.5L/min and Anoxic treatment treatment groups were 19.64,15.91 and13.79 mg/?g·d?,respectively.?5?When the eco-tank ammonia concentration was 4.810±0.004-5.865±0.082mg/L,the total phosphorus concentration was 0.604±0.029-0.894±0.010 mg/L,hydraulic retention time was 2.5 d and the water temperature was 21.23-32.07?,the average concentrations of COD_Cr,NH₄⁺-N,TN and TP in the Rotala rotundifolia were14.195±0.014 mg/L,0.356±0.038 mg/L,1.051±0.006 mg/L and 0.159±0.021 mg/L,respectively,has the best removal ability.