强冷空气过程中3种柑橘光合生理特性的变化及抗寒性综合评价

Changes in photosynthetic physiological characteristics of three citrus species during occurrence of strong cold air and comprehensive evaluation of cold resistance

【目的】探明一次强冷空气过程对柑橘植株生长影响的生理机制,并以此进行品种间抗寒性评价。【方法】以江西地方特色柑橘品种南丰蜜橘(Citrus reticulata‘Nanfengmiju’)、金沙柚(C.grandis‘Jinshayou’)和纽荷尔脐橙(C.sinensis‘Newhall Navel Orange’)为试材,研究强冷空气过程对3个柑橘品种叶片的叶绿素含量、光合荧光特性、活性氧物质含量和抗氧化酶活性的影响,并对上述生理参数进行主成分分析,最终确定3个柑橘品种的抗寒性强弱。【结果】强冷空气过程初期,随着空气温度的降低,3个柑橘品种的叶绿素含量(Chla和Chlb)、最大光合速率(P_(max))、表观量子效率(AQY)、PSII原初光能转化效率(F_(v)/F_(m))和光饱和点(LSP)均呈现下降趋势,在气温回升期间,叶绿素含量、P_(max)、AQY、F_(v)/F_(m)和LSP的值随温度的回升而增加,整个强冷空气过程中南丰蜜橘的值均最大;3个柑橘过氧化氢(H_(2)O_(2))和丙二醛(MDA)含量在整个强冷空气过程中,表现为先上升后降低的趋势,且H_(2)O_(2)和MDA含量的平均值以纽荷尔脐橙最大,金沙柚次之,南丰蜜橘最小;抗氧化化酶(SOD和POD)的活性在整个降温和升温过程中也呈现先上升后降低的趋势,但整体活性仍处在较高水平,且SOD和POD活性的平均值南丰蜜橘最小,纽荷尔脐橙最大。【结论】空气温度的骤然降低是柑橘生理生化参数变化的主要原因,3个柑橘品种的抗寒性强弱依次为南丰蜜橘>金沙柚>纽荷尔脐橙。研究结果可为柑橘的引种、生产布局及栽培管理提供理论依据。

【Objective】The study investigated the physiological effects of strong cold air flow on three major local citrus species in Jiangxi(Citrus reticulata‘Nanfengmiju’,C.grandis‘Jinshayou’,C.sinensis‘Newhall Navel Orange’),and evaluated the cold resistance among the species in order to provide reference for the introduction,production and cultivation management of citrus.【Methods】This experiment was carried out in Jiangxi Academy of Agricultural Sciences from December 23,2021 to December 30,2021,with 5-year-old citrus trees used as the experimental materials.The effects of strong cold air flow on the chlorophyll content,photosynthetic fluorescence characteristics,reactive oxygen species and antioxidant enzyme activities in leaves of the three citrus species were studied,and principal component analysis was performed on the above physiological parameters,and the cold resistance of three citrus species was finally determined.【Results】The daily minimum temperature on December 24 and December 26 was 7.2℃and-1.5℃,respectively.The difference between the daily minimum temperature within 48 hours was greater than 8℃,and the daily minimum temperature dropped below 8℃.Therefore,according to the national standard of Cold Air Grade(GB/T 20484-2017),it was classified as a strong cold air flow.As a result of this strong cold air flow,the daily maximum temperature and daily minimum temperature had the same trend.They declined continuously from December 24 to 26,reaching a minimum value on December 26,after which temperature gradually recovered.The content of chlorophyll in the leaves of the three citrus species changed greatly with a similar change pattern.From December 24 to 26,the contents of Chla and Chlb gradually decreased,but slowly increased after December 26.At the end of the experiment on December 30,Chla content in the three citrus species was slightly lower than that at the beginning,but Chlb decreased significantly.The change in carotenoid content varied among citrus species.With the decrease in air temperature,the maximum photosynthetic rate(P_(max)),apparent quantum efficiency(AQY),PSⅡprimary light energy conversion efficiency(F_(v)/F_(m))and light saturation point(LSP)showed a downward trend.During the temperature recovery period,the values of chlorophyll content,P_(max),AQY,F_(v)/F_(m) and LSP increased.The change trends of light compensation point(LCP)and non-photochemical quenching(NPQ)were similar.With the temperature drop,they first increased and then decreased,and reached a highest value on December 26.The change trends of MDA and H_(2)O_(2) contents in the three citrus species were basically the same,showing a trend of first rising and then falling.Their values were the highest on December 26,and then showed a downward trend.However,at the end of the experiment,MDA and H_(2)O_(2) contents maintained higher than those at the initial day.During the whole process of strong cold air flow,the contents of MDA and H_(2)O_(2) in C.sinensis‘Newhall Navel Orange’were the highest,followed by those in C.grandis‘Jinshayou’,and those in C.reticulata‘Nanfengmiju’were the lowest.The trend of POD content in the three citrus varieties was basically the same,and all showed a trend of first rising and then decreasing.The POD values of the three citrus cultivars were highest on December 26,increasing by 34.29%(Nanfengmiju),30.77%(Jinshayou)and 39.02%(Newhall Navel Orange)compared to the values on December 24,respectively,and then showed a downward trend,but the POD value on the end day of the experiment was still higher than the initial day.The change trend of SOD activity was consistent with that of POD.During the temperature drop,the POD and SOD activities in Newhall navel orange were the highest,followed by those in Jinshayou,and Nanfengmiju had the lowest enzyme activity.【Conclusion】Through the principal component analysis of chlorophyll content,photosynthetic fluorescence characteristics,reactive oxygen species and antioxidant enzyme activities in leaves of the three citrus species,the order of cold resistance among the three citrus species from strong to weak was Nanfengmiju>Jinshayou>Newhall Navel Orange.