Responses of leaf photosynthetic characteristics to low temperature stress in 10 Ophiopogoneae germplasms and evaluation of cold resistance
[Objective]Low temperature is one of the main factors limiting plant growth and development.The effects of different low temperature stress on the photosynthetic parameters and chlorophyll fluorescence characteris-tics of Ophiopogoneae germplasm were studied in order to provide the basis for the rational cultivation and utilization of grass germplasm along the stage in Northwest China.[Method]In this study,the cold resistance of 10 Ophiopogo-neae germplasm was comprehensively compared at 4 low temperature treatment levels(5℃,0℃,-5℃and-10℃)and 20℃as control(CK).[Result]The results showed that low temperature increased photoinhibition of photosynthesis.With the intensification of stress,the net photosynthetic rate(Pn)increased first and then decreased,the transpiration rate(Tr)and stomatal conductance(Gs)decreased,while the intercellular CO2 concentration(Ci)increased,indicating that non-stomatal factors were the main factors leading to the decrease of photosynthesis.The trend of germplasm change was the same among the 10 Ophiopogoneae,but there were differences in their responses to low temperature stress.The Pn of Liriope muscari Phnom Penh decreased the least,indicating that the influence of low temperature was relatively small,while the influence of the Ophiopogon angustifoliatus was the greatest.In terms of chlorophyll fluorescence parameters,when the temperature droped to-10℃,the initial fluorescence(Fo)showed an increasing trend,the maximum photochemical efficiency(Fv/Fm)and the actual photochemical efficiency(PSⅡ)show an increasing trend and then a decreasing trend,the electron transfer rate(ETR)and photochemical quenching(qP)show a decreasing trend.The results showed that the lower the temperature was,the greater the variation range of Ophiopogoneae germplasm along the rank was,the more obvious the photosynthetic inhibition was,and the greater the photosynthetic organ damage was.There was a significant positive correlation between net photo-synthesis and intercellular CO2 concentration(P<0.05).There was a significant negative correlation between net photosynthetic rate and initial fluorescence(P<0.05).There was a significant positive correlation between transpira-tion rate and stomatal conductance(P<0.01).There was a significant negative correlation between maximum photo-chemical efficiency and stomatal conductance and intercellular CO2 concentration(P<0.05).The initial fluorescence was positively correlated with the maximum photochemical efficiency(P<0.05),and negatively correlated with the electron transport rate(P<0.05).According to the comprehensive analysis by membership function method,the cold resistance of 10 Ophiopogoneae germplasm members of the grass family was in the order of O.angustifoliatus>O.bodinieri(Kangxian)>Ophiopogon bodinieri(Wenxian)>O.bodinieri(Wudu)>L.muscari>L.spicata>O.japonicus>O.reversus(Henan)>L.graminifolia>O.japonicus.[Conclusion]The germplasms of O.angustifo-liatus,O.bodinieri(Kangxian)and O.bodinieri(Wenxian)were more suitable for promotion in northern China be-cause of their strong cold resistance.
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