Effects of Partial Root Zone Irrigation on Leaf Photosynthetic Curves and Chlorophyll Fluorescence Parameters in Naked Oat

Abstract

The objective of this study was to provide experimental evidence for photosynthetic mechanism under drought stress and practical technique of water-saving irrigation in naked oat(Avena nuda L.).In a pot experiment with instrument to control root zone irrigation and water amount,the effects on relative chlorophyll content(SPAD),photosynthetic curves,and chlorophyll fluorescence parameters were compared among irrigation models of alternative partial root zone irrigation(APRI),fixed partial root zone irrigation(FPRI),and conventional total root zone irrigation(CTRI).Compared to CTRI,partial root zone irrigation,including APRI and FPRI treatments,decreased leaf SPAD,net photosynthetic rate(Pn),and carboxylation efficiency(CE);however,APRI had no obvious effects on reducing initial quantum efficiency(α),maximum photochemical efficiency(Fv/Fm),actual photochemical efficiency of PSII(ФPSII),apparent electron transport rate(ETR),and photochemical quenching coefficient(qP).The leaf SPAD of APRI was significantly enhanced compared to that of FPRI(P0.05),and the maximum net photosynthetic rate(Pmax),α,light saturation point(LSP),light use efficiency(LUE),Ci/Ca,CE,CO2 saturation point(Ci,sat),Fo,Fm,ФPSII,ETR,qP,and NPQ were all higher in APRI than in FPRI.The reduction of Pn in partial root zone irrigation treatments resulted from stomatal factors,and structural damage of photosynthetic system II(PSII) was found in FPRI treatment.Clearly,partial root zone irrigation can improve the tolerance ability of naked oat against drought stress;particularly,APRI has the effect to maintain higher Pn than FPRI.