The Effect Of Waterlogging On Growth And Physiological-biochemical Characteristics Of Hydrocotyle Vulgaris

The study investigated the effect on growth and physiological-biochemical characteristics of Hydrocotyle vulgaris subjected to different flooding treatment.The study also investigated the responses of H.vulgaris to flooding.Experiments were conducted using H.vulgaris planted in three different levels of flooding.Morphological and physiological indexes were tested in order to analyze how H.vulgaris reacted to flooding.The results can provide theoretical information for wetland horticulture and restoration.The main results are as follows:1.The responses of H.vulgaris to flooding are based on water depth.Submerged H.vulgaris suffer growth inhabitation and invest more energy and biomass to root area.It shows 18.05%decrease in height,28.76%decrease in leaf width and 2.67%increase in root biomass allocation.The plants also grow a small thin aquatic leaves to better conform the environment.On the contrary,half-merged plants shows 65.98%increase in height,555.58%increase in leaf number and 6.68%decrease in root allocation.H.vulgaris subjected to root zone flooding shows 51.55%increase in height,941.3%increase in leaf number and 3.27%decrease in root allocation.They choose to promote stem and leaf growth and increase the parts available to air and light.2.H.vulgaris subjected to root zone flooding remain the highest in plant heights.Half-merged plants continue to grow rapidly when other plants slow down.These results show root zone flooding treatment helps plants grow while half-merged treatment extend plants' growth period.3.The total chlorophyll of H.vulgaris reduces 21.2%when submerged,reduces 13.7%when half-merged and increases 28.3%when root-merged.All terms of photosynthetic pigment contents show significant difference as Root-merged>half-merged>submerged after 60 days' flooding.Chlorophyll account for more than chlorophyll b when copes with flooding.4.Most stomas of H.vulgaris on lower leaf surface were closed when subjected to submergence.H.vulgaris are unable to protect stomas from damage within 100 days of flooding.5.Permeate accumulation happens when H.vulgaris plants are enduring submergence.The accumulation can be 4 times higher than control group in soluble protein,2.84 times in sugar content and 1.7 times in free proline content.For plants in half-merged or root-merged situation,permeate accumulates in 25 days and then returns to control level.H.vulgaris enduring submergence are damaged because of lack of oxygen.While plants in half-merged or root-merged situation positively response to damages and can adjust osmolality in a short time.6.H.vulgaris plants increased SOD activity to respond to flooding.But plants in submergence decreased SOD activity by 17.6%and showed 57.88 times more than control group in POD activity.The damage caused by submergence excesses capacity range of active oxygen removal.7.H.vulgaris plants were damaged after 40-60 days' submergence,with SOD activity decreasing,MDA content and POD activity remaining to a high level,electro-conductibility going up and permeate accumulation.Half-merged H.vulgaris plants response to flooding environment by increase SOD and POD activity.The plants can restore to control level in a short time of half emergence.Root zone flooding does no harm to H.vulgaris.8.H.vulgaris show strong competence in wetlands and other waterlogging environments.The plant may become the dominant species when induce to the wild,and affect the survival and growth of other sensitive plants.Therefore,in the waterlogging environment,H.vulgaris has a high possibility of invasion.