Study On Mechnism Of Physiological Ecology Of Two Different Genera Of Perennial Grasses Resistance To Mowing

Mowing was a kind of mechanical stress,which could caused the imbalance of water metabolism and the decrease of photosynthetic leaf area,but most of the grass showed a strong ability of resistance to mowing.Mowing resistance was one of the characteristics of grass self-protection after artificial mowing stress,so it played an important role in garden,lawn management and animal husbandry development.Moreover,the mowing resistance of grass was closely related to compensatory growth induced by mowing.At present,however,there are few studies on compensatory growth physiological mechanism.In this thesis for the degree,two widely cultivated grass(Lolium perenne L and Medago sativa)were used as experimental materials to study the relationship between changes of osmoregulation and antioxidant enzymes after mowing and relationship between mowing resistance and compensatory growth.1.In order to investigate the relationship between the changes of the antioxidant protection system and osmotic regulator in the leaves and the compensatory growth after different intensity mowing,and the physiological regulation mechanism of grass resistance to mowing.In this study,the cutting level of perennial ryegrass could be divided into four levels,that was the Light,moderate,severe and whole cutting levels treated by cutting at 22 cm,15cm,7cm,0cm of plant height.The growth rate,superoxide dismutase(SOD),peroxide(POD),and catalase(CAT)activities;and soluble sugar,proline,and malondialdehyde(MDA)contents were investigated in the leaves of Lolium perenne L.The results showed that the growth rate was higher in the leaves after cutting at the light,moderate,and whole cutting levels,but was lower in the leaves at the severe cutting level than that of control.Compared to that of the control,L.perenne showed significant compensatory growth under light,moderate,and whole cutting levels,and no compensatory growth occurred under severe cutting levels.Compared to the control,at 6 days after different cutting levels,the regrowth of L.perenne leaves had lower MDA,soluble sugar,and proline contents,and lower SOD,and CAT activities.Whereas,at 12 days after different cutting levels,the regrowth of L.perenne leaves still had lower MDA contents,but higher SOD,CAT activities,and proline content.This indicated that cutting decreased the leaf area,reduced the photosynthetic energy availability,and enhanced the compensatory growth function of residual leaves.Therefore,cutting damage was an internal factor resulting in compensatory growth.The compensatory growth rate was correlated positively with the residual leaf size.In addition,although there were differences in the compensatory growth rate in the residual leaves among different cutting levels,the different cutting levels all activated antioxidant enzymes and enhanced proline accumulation.During the compensatory growth of residual leaves,SOD and CAT could scavenge active oxygen free radicals produced during photosynthetic metabolism,inhibit membrane lipid peroxidation,maintain the balance of oxygen free radicals metabolism;and accumulated proline could maintain water balance.Therefore,antioxidant enzymes and osmoregulation play an important role in physiological protection,including photosynthesis and compensatory growth,during rapid self-healing after cutting of residual leaves in L.perenne.2.In order to investigate the relationship between the changes of antioxidant protection system and osmotic regulator content and the compensatory growth of Medago sativa after different intensity mowing,and the physiological regulation mechanism of mowing resistance.In this study,the cutting level of alfalfa could be divided into four levels,that was the light,moderately severe and whole cutting levels treated by cutting at 25cm,17cm,6cm of plant height.After cutting at 6 days and 12days,plant height,SOD,POD and CAT activity,the contents of MDA,soluble sugar and proline were determined.The results indicated that the strength of different mowing compensatory growth was not obvious,after all the processing plant height average net growth rate lower than control,and with the increase of mowing intensity,the extent of the decline.Compared with the control,the MDA content of Medicago sativa regenerated leaves had increased with different intensities,decreased with SOD,POD,CAT activity and soluble protein content,and proline content was higher than that of control.Compared with the Light and moderately sever mowing,proline and soluble protein content were increased in the whole mowing leaves.Therefore,after mowing Medicago sativa had lower activity of antioxidant enzyme,which could not removed oxygen free radicals in time,and the membrane lipid peroxide degree was higher that damaged the cell membrane.At the same time,mowing could promoted the accumulation of osmotic regulation,and the accumulation of soluble protein content played an important protective role in maintaining the cell osmotic pressure and maintaining the water balance.However,compared with Light and moderately severe mowing,whole mowing level was the most important reason for the increased.3.In order to investigate the effects of environmental stress and fertilization treatment on mowing resistance and compensatory growth,and the effect of moderate fertilization on accelerating compensatory growth.In this study,the cutting level of L.perenne could be divided into two levels,that was the environmental stress and fertilization treatment,environmental stress treatment treated by drought(water quantity for the local 10%of annual precipitation)and salt(NaCl concentration of1.0%),fertilization treatment treated by nitrogen fertilizer(urea concentration of 450kg/hm~2)and potassium fertilizer(potassium sulphate,75 kg/hm~2).The plant height,SOD,POD and CAT activity,the contents of MDA,soluble sugar and proline were determined.The results showed that the effect of the drought treatment was not obvious,and the net increase of blade length was lower than control.Leaves and residual strength of different mowing regeneration and leaf MDA content were higher control,regeneration of SOD,POD activity and soluble sugar and proline content were decreased,the mowing regenerated activity of CAT was rised.Therefore,drought and water shortage inhibited the mowing resistance of L.perenne.The main physiological reasons for the inhibition of compensatory growth were the increase of lipid peroxidation,the activity of antioxidant enzymes and the low content of osmoregulation.There was obvious compensatory growth in the treatment of moderately severe and whole mowing level in salt treatment,and the net increase of leaves was higher than control.The MDA content in mow 12 days had decreased,the content of soluble protein,SOD,CAT activity and soluble protein content had increased.It could be seen that moderately salt treatment improved the mowing resistance of L.perenne.CAT and SOD could removed the oxygen free radicals accumulated in the residual leaves in time,and maintained the lower level of membrane lipid peroxidation,that played an important role in physiological protection in its compensatory growth.In the treatment of nitrogenous fertilizer,there was a compensatory growth of mowing,and the net growth of leaves was higher than control.The MDA content at 12days was decreased,and POD activity and soluble protein contents were increased.This indicated that the increase of antioxidant enzyme activity and the accumulation of osmotic regulator content were the important reason for the rapid compensatory growth in the treatment.The net growth of the leaves in mowing treatment was higher than control after potash treatment,showed obvious compensatory growth.The MDA content of regenerated leaves was higher than treatment of mowing at 12 days.The SOD,CAT activity and proline content were higher.Results showed that the potash fertilizer treatment after mowing,antioxidant enzyme(SOD,CAT)and osmoregulation substance(proline)for perennial rapid self-healing,so compensatory growth played an important physiological protection.In short,the response of two different genera of perennial herbage to mowing were different,and the ability of resistance to mowing of forage grass was higher than that of legumes,which was related to its biological characteristics.Forage grasses belonged to a geophyte plant,which means its regenerated bud was underground,Regenerated bud was not damaged by mowing.While,leguminosae were a chamaephytes.Its regenerated bud situated above-ground,and could be easy damaged by mowing so that compensatory growth caused by mowing was not significant.But they both had same physiological responses to mowing.