Effects Of Water Flow On The Physiological,Biochemical Characteristics Of Vallisneria Natans And Its Periphytic Structure

Water flow can affect the growth and distribution of submerged plants,thus limiting the recovery of them.In this work,the effect of water flow on the aqueous DO content,the physiological and biochemical characteristics of Vallisneria natans(V.natans)and its periphytic structure were explored.Then we demonstrated the conclusion from the reverse side through the conversion of water flow and static.At the same time,from the perspective that water flow can influence the physiological and biochemical characteristics of V.natans by the increase of DO content,we explored the effects of different DO content on the physiological and biochemical characteristics of V.natans and its periphytic structure.The main results of this thesis are as follows:1.Water flow can increase aqueous DO content and transparency.Under the high nutrient salt concentration condition,the DO content of statistic water decreased to 2-3 mg/L,and the turbidity increased,while the water flow kept the DO content in the range of 7-8 mg/L.And the same result was obtained after the water flow and static conversion.2.Water flow can promote the growth of V.natans.After 60 days culturing,the leaves of V.natans increased by 192%in the water flow state,its wet weight and root length also increased.However,in the control group,the tip of V.natans showed rot and its wet weight decreased significantly.The water flow also increased the total chlorophyll content and root activity of V natans,and enhanced the ability of antioxidative stress.Then we converted statistic to water flow.The flow of water reduced the corrupt of V natans,and the leaves of them became green.After 20 days culturing,the leave increased by 166.26%,the chlorophyll content and root activity of V.natans also increased significantly.3.Water flow increased the diversity and abundance of the periphytic bacteria of V.natans.Especially increased the abundance of Pseudomonas and Methylophilus bacteria.The diversity,species and abundance of the periphytic algae of Vallisneria natans decreased.Similar results have occurred after the water flow and static conversion.4.Under dark condition,the DO content of aqueous,leaves and root microenvironment of V.natans decreased sharply to the state of hypoxia or even hypoxia,and the V.natans was in a state of hypoxia stress.But the water flow significantly increased the DO content and maintained it at about 5 mg/L,alleviating the hypoxic stress caused by the insufficient DO concentration in the dark condition.5.Hypoxia(1.32±0.06 mg/L)reduced the total chlorophyll content by 41%and root activity by 66.12%,hindered the synthesis of protein,caused the imbalance of CN metabolism and increased the accumulation of MDA in V natans.At the same time,hypoxia reduced the diversity and abundance of periphytic bacterial,but increased the density and diversity of periphytic algae.The proliferation of periphytic algae under hypoxic conditions may become an important factor in inhibiting the growth of V.natans.In conclusion,the existence of periphytic can reduce the aqueous DO concentration.But water flow can increase the aqueous DO concentration,which can alleviate hypoxic stress on the growth of V.natans.and enhancing its anti-oxidative ability.