Research On The Drought Tolerance Characteristics And Mechanism Of Seven Species Of Ornamental Grasses

Ornamental grasses have the advantages of salt and alkali resistance,barren resistance,drought resistance,water and humidity resistance,strong cold resistance,and less pests and diseases.Drought tolerance is a prominent feature of ornamental grasses,however,the water consumption,physiological characteristics and metabolomics of ornamental grasses under drought are still unclear.This experiment took seven commonly used ornamental grasses（Miscanthus sinensis‘Changxu’,M.sinensis‘Variegatus’,M.sinensis‘Gold Bar’,Pennisetum alopecuroides‘Dwarf’,Muhlenbergia capillaris‘Regal Mist’,Phalaris arundinacea var.picta,Carex breviculmis）as research objects.Through field experiments and potted experiments,from the aspects of biological characteristics and ornamental properties,water consumption law under drought tolerance,physiological response under drought tolerance,and metabolomic analysis of Carex breviculmis under drought tolerance.The results revealed that:（1）The green period of P.arundinacea var.picta was longest in seven ornamental grasses,the green period of P.alopecuroides‘Dwarf’was shortest in seven ornamental grasses.The florescence of M.sinensis‘Changxu’was longest in seven ornamental grasses,the florescence of M.sinensis‘Variegatus’was shortest in seven ornamental grasses.The highest ornamental grasses was M.sinensis‘Changxu’,the lowest ornamental grasses was C.breviculmis;the longest leaf length of seven ornamental grasses was P.alopecuroides‘Dwarf’,the shortest was P.arundinacea var.picta;the widest leaf width of seven ornamental grasses was P.arundinacea var.picta,and the narrowest leaf width was M.capillaris‘Regal Mist’.The ornamental value sequence of seven ornamental grasses are M.capillaris‘Regal Mist’>M.sinensis‘Changxu’=P.alopecuroides‘Dwarf’>M.sinensis‘Variegatus’>P.arundinacea var.picta>M.sinensis‘Gold Bar’>C.breviculmis.（2）The range of annual water consumption of seven ornamental grasses were 784.1mm～838.7 mm,the annual water consumption was in the order of M.sinensis‘Changxu’,M.capillaris‘Regal Mist’,P.alopecuroides‘Dwarf’,P.arundinacea var.picta,M.sinensis‘Variegatus’,M.sinensis‘Gold Bar’,C.breviculmis.The productivity range of seven ornamental grasses were 55.3 g/m~2～1534.9g/m~2,the productivity was in the order of P.alopecuroides‘Dwarf’,M.capillaris‘Regal Mist’,M.sinensis‘Changxu’,P.arundinacea var.picta,M.sinensis‘Variegatus’,M.sinensis‘Gold Bar’,C.breviculmis.The water used efficiency range of seven ornamental grasses were 0.07 g/（m~2·mm）～1.85 g/（m~2·mm）,the water use efficiency was in the order of P.alopecuroides‘Dwarf’,M.capillaris‘Regal Mist’,M.sinensis‘Changxu’,P.arundinacea var.picta,M.sinensis‘Variegatus’,M.sinensis‘Gold Bar’,C.breviculmis.The sequence of daily evapotranspiration of ornamental grasses of drought tolerance were Carex breviculmis>M.capillaris‘Regal Mist’>P.arundinacea var.picta>M.sinensis‘Gold Bar’>M.sinensis‘Variegatus’>P.alopecuroides‘Dwarf’>M.sinensis‘Changxu’.（3）On the 21st day of drought tolerance,the plant height,crown width and leaf length of the seven ornamental grasses in the control group and the drought group were significantly different,there were significant differences in the leaf widths of M.sinensis‘Changxu’,M.sinensis‘Variegatus’,P.arundinacea var.picta,C.breviculmis.With the increase of drought tolerance time,the malondialdehyde content,proline content and soluble protein content of the seven Ornamental grasses increased,while the superoxide dismutase activity of the plants increased initially and then decreased as drought tolerance was prolonged.（4）Water-deficit increased the content of most primary and secondary metabolites,almost all sugars,amino acids,organic acids,phytohormones,nucleotides,phenylpropanoids and polyketides were negatively associated with plant height and leaf fresh weight and was positively correlated with soluble protein content and malondialdehyde content.Metabolic pathway analysis showed that drought stress significantly affected aminoacyl-t RNA biosynthesis,TCA cycle,starch and sucrose metabolism.It was concluded that the coordination between various metabolic processes and pathways in C.breviculmis enable the plant to adapt under extreme drought environment.This study will provide data support for the water managements of ornamental grasses and the plant selections in water-saving garden construction,in order to contribute to the construction of water-saving landscaping.