Effect Of Experimental Warming On Ornamental Value Of The Wild Flower Plant Impatiens Oxyanthera(Balsaminaceae)

Global warming could affect the ornamental value by changing the growth and reproduction of wild flower plants.Therefore,it is of great significance to find out the mechanisms of wild flowers in responses to warming and to evaluate the effects of warming on the comprehensive ornamental value,which could provide theoretical basis for plant protection,application and cultivation management.In this study,we conducted an artificial warming experiment with infrared radiant heaters in the local habitat to examine the effects of warming on the ornamental value of Impatiens oxyanthera Hook.f.from 2017 till 2018.The differences in plant morphology,flowering phenology,floral organ and fruit characteristics under artificial warming,non-warming and natural conditions were compared to determine the warming effect on I.oxyanthera at the stages of vegetative growth,flowering and fruit setting.The ornamental value of I.oxyanthera was comprehensively evaluated using the Analytic Hierarchy Process,principal component analysis and membership function method.The results were as following:1.There were significant warming effects by infrared radiant heaters.In 2017,infrared radiant heaters significantly increased the daily mean air temperature and 10 cm depth soil temperature by 1.863? and 1.416?,respectively.While,it decreased the mean air relative humidity by 10.620%.In 2018,infrared radiant heaters significantly increased the daily mean air temperature and 10 cm depth soil temperature by 2.376?and 1.425?,respectively.But it decreased the air relative humidity by 7.246%.2.Warming significantly altered plant type and leaf morphology during vegetative growth of I.oxyanthera.Both in 2017 and 2018,plant height,crown width and secondary branch number were decreased by warming,while single leaf area,leaf length and leaf width were increased.The base diameter,primary branch number and crown width from warming and non-warming plots were significantly larger than those of plants from the natural field.On the contrary,plant height,single leaf area,leaf length and leaf width were significantly decreased than those from natural plots.3.Warming significantly delayed the time of flowering and shortened the duration of flowering,but had no significant effect on flower numbers per plant at full blooming stage.In 2017,initial flowering,full blooming and last flowering of the plants in warming plots were significantly delayed by 7.111 d,13.148 d and 10.728 d,respectively.In 2018,warming delayed the initial flowering and full blooming by 22.686 days and23.213 days,respectively,compared to the non-warming plots.And warming delayedby 23.075 days and 19.889 days,respectively,in contrast with natural field conditions.In addition,warming shortened flowering duration of individual plant by 9.703% in2017 and by 19.048% in 2018.4.Floral longevity was significantly shortened by warming due to shortened androecium stage.Both in 2017 and 2018,warming shortened androecium stage of plants by 9.599% and 10.870%,respectively,and the floral longevity was shortened by7.699% and 10.281%,respectively.In 2018,androecium stage of plants under natural field conditions was significantly shortened by 0.259 d compared with the non-warming conditions,but the difference of floral longevity was not significant.Flower longevity under warming conditions was significantly shortened by 0.223 d relative to that under the natural field conditions.5.Elevated temperature reduced flower sizes but had no significant effects on the floral color.In 2017 and 2018,warming decreased corolla tube length,vexilla length,wing length,stripe number on the labellum.The vexilla length,wing length and corolla diameter of warmed plants were significantly increased by 4.281%,8.826%,7.821%and 23.036%,respectively,compared to those of plants from natural field,while nectar spur length and peduncle length were shortened by 6.988%and 20.893%,and the stripe number on labellum were significantly decreased by 11.668%.6.No significant differences were observed with the number of fruits,whereas either the length or width of fruit were decreased by warming.In 2017,warming significantly shortened the fruit length of I.oxyanthera by 3.126%,but had no significant effect on fruit width.In 2018,the difference in fruit length between warming and non-warming plots was not significant,while the warming significantly reduced the fruit width by 4.447%.Compared with natural field conditions,the fruit length and fruit width under warming conditions decreased significantly by 3.192% and 5.570%,respectively.There were no significant differences between non-warming and natural field conditions in terms of the length and width of the fruit of I.oxyanthera.7.The comprehensive evaluation of ornamental value by the Analytic Hierarchy Process,principal component analysis and membership function method showed that warming significantly reduced the ornamental value of I.oxyanthera both in 2017 and2018(P < 0.01).The Analytic Hierarchy Process showed that the ornamental value of I.oxyanthera under warming was not significantly different from that in the natural field conditions in 2018(P > 0.05).However,the principal component analysis and membership function evaluation showed that the ornamental value under warming increased significantly by 23.773% than that of the natural field conditions in 2018(P< 0.01).In summary,warming decreased the comprehensive ornamental value of I.oxyanthera due to a reduction in branch numbers,crown width,flower and fruit size,floral longevity and flowering duration per plant.These results suggested that more attention should be paid on the protection of wild ornamental plants in the context of climate warming.