Response Of Exogenous Silicon Addition To Heavy Metal Tolerance Of Festuca Arundinacea

Soil is the basis of sustainable agricultural development.After nearly 40 years of rapid economic development and highly intensive agricultural and forestry production,the problems of soil pollution and degradation of soil environmental quality have become increasingly apparent in China.Soil heavy metal pollution causes damage to crops and grass plants,has a negative impact on the quality of human life,and then threatens human health and life.Therefore,it is urgent to study soil heavy metal pollution remediation technology.Festuca arundinacea is one of the commonly used grass species in lawn construction.Using extraneous silicon to improve the tolerance of tall fescue to heavy metal stress is of great significance to the restoration of heavy metal contaminated soil,the construction and quality improvement of lawn.In this article,tall fescue cultivar of Fire Phoenix Ⅱ was used as tested material,three experiments were carried out:（1）The germination on paper method,with different concentrations of Cu,Cd,Pb solution infiltration seedling bed,through the observation of the seed germination and seedling growth of tall fescue,to explore the tolerance of seed germination to different heavy metals;（2）using hydroponics 1/2 Hoagland nutrient solution,selection of test（1）the moderate concentration of heavy metals,and set up the exogenous silicon concentration gradient,based on the shape of reed sheep echoing the determination of the index and physiological index system,to explore the added exogenous silicon under reed of festuca changes of different heavy metal stress tolerance,determine the most effective silicon helps relieve the stress of the heavy metal concentration;（3）Indoor pot experiment:High concentration of heavy metal stress in test（1）was selected,and different application methods of exogenous silicon were set.Through observation of morphological and physiological indexes of tall fescue,the optimal application method of silicon to alleviate stress of tall fescue under high concentration of heavy metal was investigated.The main research results were as follows:（1）The tolerance to Cd stress was the strongest,but the tolerance to Cu and Pb stress was weak.Under Cu stress,the tolerance of 200 and 300 mg·L-1 seedlings was poor.With the increase of stress concentration,all germination indexes showed a downward trend and the growth of seedlings was inhibited.Under Cd stress,leaf surface area increased by 50.16%compared with the control at 1 mg·L-1,and seed germination and seedling growth were significantly inhibited with the intensification of stress degree.Under Pb stress,the seed vigor index at 500 mg·L-1 was 25.26%higher than that of the control.Under medium and high concentration of Pb stress,the growth of tall fescue seedlings was significantly inhibited.When Pb2+≥1 500 mg·L-1,the root growth of tall fescue seedlings was completely inhibited,and the growth amount was 0,and "rootless seedlings" appeared.（2）Under different heavy metal stress,exogenous silicon addition in certain concentration level significantly increased the relative water content,relative aelectrical conductivity of leaves,root system activity and root growth of tall fescue.The results showed that the best alleviation effect of tall fescue tolerant to Cu and Cd heavy metals stress was otained when 2 mmol·L/1 Na2SiO3 treatment was used.whilst the relief effect was best while 3 mmol·L-1 Na2SiO3 applied under Pb stress.These results suggested that exogenous silicon addition effectively alleviate the heavy metal stresses of tall fescue.（3）The promoting effect of exogenous silicon on seedling growth and development of tall fescue indicated that exogenous irrigation of exogenous silicon was better than by leaf spraying of exogenous silicon under various heavy metal stresses,thereafter tall fescue’s tolerance to heavy metals under the condition of exogenous silicon adding were improved significantly.Compared with leaf spraying,the contents of chlorophyll and soluble sugar while exogenous silicon applied by irrigation were increased by 25.37%and 81%,respectively under Cu stress,otherwise the content of malondialdehyde content was decreased by 40.66%.Under Cd stress,Contrasted to leaf spraying of silicon,relative water content,chlorophyll content and soluble sugar content in leaves when exogenous silicon addition using irrigation increased by 7.7%,24.18%and 52.16%,respectively,meanwhile the malondialdehyde content decreased by 48.75%.Relative water content,chlorophyll content and soluble sugar content in leaves when exogenous silicon used by irrigation increased by 7.45%,17.96%and 133.41%,respectively under Pb stress.Under combined stresses,relative water content and chlorophyll content of leaves while exogenous silicon applied by irrigation increased by 8%and 14.15%,respectively,otherwise malondialdehyde content in leaf decreased by 59.56%,compared with leaf spraying of exogenous silicon addition.The research findings is of great significance to efficient utilization and cost saving of exogenous silicon.The study in this paper showed that when the accumulation of heavy metal ions to a certain concentration,turf grass seed germination and seedling growth will cause stress;At this time,the application of a certain concentration of exogenous silicon can effectively alleviate the damage of cell plasma membrane under heavy metal stress,and improve the heavy metal tolerance of turfgrass.Compared with foliar spraying,silicon application could effectively reduce cell membrane permeability and MDA content,and increase soluble sugar content,which had a better effect on enhancing heavy metal tolerance of Festuca arunculata.At the same time,the chlorophyll content in the plant was greatly increased,which was of great significance to improve the photosynthetic efficiency of turfgrass.The application of silicon in combination with turfgrass with strong adaptability and resistance can provide more open ideas and approaches for soil heavy metal pollution prevention and control.