Effects of AMF on Photosynthetic Characteristics and Gene Expressions of Tea Plants Under Drought Stress
In order to explore the effect of arbuscular mycorrhizal fungi(AMF)on the photosynthetic characteristics of tea plants under drought stress,the seedlings of Camellia sinensis.'Fuding Dabaicha'were subjected to water and AMF inoculation experiments under greenhouse pot conditions.The results showed that drought stress(55％of the maximum field water capacity)significantly inhibited the AMF infection on tea plant roots,reduced the chlorophyll b content,maximum quantum effect(QY_max)value,intercellular CO2 concentration(Ci),stomatal vertical and horizontal diameter and stomatal opening,as well as down-regulated the expressions of carbon assimilation-related enzymes(CsRbcL,CsTK,CsFBPase,CsPRK)genes and chlorophyll synthesis-related enzyme gene CsHEME.Whereas,drought stress significantly increased the chlorophyll a/b and non-photochemical quenching(NPQ_lss)parameters,and up-regulated the expression of chlorophyll synthase enzymes gene CsHEMA1 in tea seedlings.Howbeit,under well-watered(75％of the maximum field water capacity)and drought stress conditions,inoculation with AMF significantly increased the content of chlorophyll a and total chlorophyll,net photosynthetic rate(Pn),stomatal conductance(Gs),Ci,and transpiration rate(Tr)but decreased NPQ_lss and stomatal density,accompany with the up-regulated expressions of carbon assimilation-related enzyme genes CsRbcL,CsTK,CsFBPase,CsPRK and chlorophyll synthesis-related enzyme genes CsHEMA1,CsHEMC,CsHEME,CsHEMG and CsCHLE in different degrees.Meanwhile,AMF inoculation also significantly increased the chlorophyll b content,QY max,stomatal vertical,horizontal diameter and aperture under drought stress and chlorophyll a/b under well-watered.The results indicated that AMF can improve the adaptability of tea plant under drought stress by promoting photosynthesis,and the promotion effect was more significant under drought stress.
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