Effects Of Light Intensity And Water Depth On The Growth And Physiology Of Hydrilla Verticillata

The restoration of submerged plants in degraded ecosystem is influenced by many factors.The underwater light intensity and water depth are crucial to the survival rate and growth of submerged plants,they are the key factors affecting the recovery of submerged plants.Study on the growth and physiological response of submerged plants to light intensity and water depth change s,determining the ecosystem suitability intensity and water depth of submerged plants are important for the restoration and reconstruction of submerged plants in degraded aquatic ecosystems.In this paper,Hydrilla verticillata was used as the research object to studied and explored the effect of different light intensity conditions and water depth environment on the growth and physiological indexes of H.verticillata.By measuring the morphological indicators,understand the response strategies of plant morphology to different light intensity and water depth environment.By measuring the photosynthetic pigment content of H.verticillata leaves,understand the photosynthetic characteristics of H.verticillata to different light intensity and water depth environment;By measuring the physiological indicators such as SOD,CAT,POD,chlorophyll content,malondialdehyde(MDA)and root activity,studied the response mechanism of H.verticillata to different light intensity and water depth environment from the aspect of action mechanism.The results are as follows:1.Through the indoor light intensity simulation test,studied the effect of different light intensity on the growth,morphology and physiological indexes of H.verticillata.The results showed that the stronger the light intensity,the faster the plant height increased,the stronger the plant ramets ability;with the light intensity decreased,the plant height,the length of the pitch and the increase of the number of stems were inhibited;the plants increased the distribution of material to roots under the full light condition,the root-shoot ratio reached the maximum,and aboveground part of H.verticillata was the most invested at 80% light intensity.Physiologically,under the full light condition,the content of chlorophyll a and chlorophyll b decreased,the content of carotene reached the maximum;under 5%,10% natural light and full light condition,the activity of SOD and CAT increased,the activity of POD reached the maximum under 60% natural light intensity;low light(5%,10% natural light)stresses the normal growth of H.verticillata,lead to the decrease of soluble protein content and root activity.Under 20%~60% natural light condition,H.verticillata grows well,persistent low light(5%,10% natural light)and natural light conditions will inhibit the growth and physiology of H.verticillata.2.The effects of different water gradient on the growth,morphology and physiology of H.verticillata were studied by setting different water gradient environments.The results showed that with the increased of water gradient,the underwater light intensity decreased significantly,the height and internode spacing of H.verticillata increased,the number of stems and branches decreased,and root-shoot ratio of H.verticillata gradually decreased with the increased of water gradient.With the increased of water depth,the content of carotenoid,chlorophyll a and chlorophyll b increased continuously.The effect of water depth on the activity of antioxidant enzymes was significant(P<0.05).The activity of SOD,POD and CAT increased firstly then decreased.The membrane lipid peroxide level increased at 0.5~0.8 m depth,which increased the content of MDA,and the activity of SOD and POD increased;The water depth increased from 0.5 m to 1.4 m,the content of soluble protein did not change significantly,root activity increased from 0.12 to 0.51 mg·g-1 · h-1,and the difference between the water depth groups was significant(P<0.05).The water depth of 0.5~0.8 m has a strong photoinhibition effect on the growth and physiology of H.verticillata.In the ecological restoration of waters,the H.verticillata population should be restored in the depth range of 0.9~1.4 m to facilitate its population growth and restoration of aquatic ecosystems.