Effects Of Indoor And Outdoor Potting And Salicylic Acid On The Growth,Physiological And Biochemical Characteristics Of Poinsettia

Poinsettias（Euphorbia pulcherrima Wild）,a variegated foliage-viewing plant native to Tasko,Mexico.Because of climate problems,poinsettia is only suitable for greenhouse cultivation in most areas of China after its introduction.Therefore,exploring the response and mechanism of Poinsettia to indoor and outdoor cultivation environment and water has important practical and theoretical significance for cultivating excellent varieties of poinsettia.In this study,two cultivars of Poinsettia’Red Lotus’and’Shining’were used as experimental materials.The chlorophyll fluorescence and color difference of leaves and bracts were measured to compare their growth status indoors and outdoors（The greenhouse temperature is 20℃and the average outdoor temperature is 16℃）and their adaptability to the environment.The effects of three treatments on the relative conductivity,MDA content,H₂O₂ content,chlorophyll fluorescence parameters,relative water content,water saturation deficit and the expression of drought stress genes LEA3 and VOC of Euphorbia pulcherrima were studied.The main experimental results are as follows:1.Greenhouse is more suitable for the growth of’Red lotus’and’shiny’.After the cultivation of’Red lotus’and’shiny’in greenhouse,the bud Fo（initial fluorescence）decreased.After greenhouse cultivation,Fm（maximum fluorescence yield）of bracts increased.Whether outdoors or greenhouses,’shiny’is bigger than’Red lotus’.The outdoor low temperature will reduce Fv/Fm（maximum photochemical quantum yield）,damage the PS II system of poinsettia.Greenhouse cultivation can improve the electron transfer efficiency of leaves,increase the photosynthetic rate of leaves,and increase the net photosynthetic rate.The red degree of Poinsettia bracts cultivated in greenhouse is better and more ornamental;’Shining’has strong cold tolerance,whether inside or outside greenhouse.The green of the bright leaves is deeper than that of the red lotus leaves,while the red lotus leaves are more suitable for planting bracts in places with strong light,while the bright ones are more suitable for greenhouse planting,and the bracts will be brighter.2.Under drought stress,the cell membrane permeability,water saturation deficit,initial fluorescence F0,H₂O₂ content and MDA content of Euphorbia pulcherrima leaves were significantly increased,while Fv/Fm value and relative water content were lower than those of normal water treatment,which induced the expression of drought stress genes LEA3 and VOC.After rehydration,the leaf recovery ability of SA treatment was significantly stronger than that of non-SA treatment,but did not return to the level of normal control group.The expression of LEA3 and VOC gradually returned to near normal level.SA treatment can effectively control the content of H₂O₂ and MDA,maintain the cell membrane permeability of leaves,play a certain role in water retention and chlorophyll protection.In addition,the expression of LEA3 and VOC was reduced,and the expression of LEA3 and VOC was close to normal level,which effectively alleviated the damage of Poinsettia caused by adversity.Drought stress genes LEA3 and VOC can improve photosynthetic efficiency and reduce the damage of reactive oxygen species to Euphorbia pulcherrima,thus ensuring the normal growth of Euphorbia pulcherrima under drought conditions.