Study On Photosynthetic Physiological Response Of Lycaste Macrobulbon To Shading And Drought Stress

In this paper,Lycaste macrobulbon as experiment material,through the determination of chlorophyll fluorescence parameters and chlorophyll content determination to made a research on the photosynthetic characteristics of Lycaste macrobulbon?s different photosynthetic organs;Through the determination of gas exchange parameters and chlorophyll fluorescence parameters under different light to explores Lycaste macrobulbon appropriate light conditions;Through the determination of diurnal variation of photosynthetic rate ?diurnal variation of total acid content and diurnal movement of stomata under drought stress to explores Lycaste macrobulbon photosynthetic physiology under drought stress.The main results are as follows:?1?Lycaste macrobulbon?s photosynthetic organ leaf?pseudobulb and calyx lobes all participate in photosynthesis,stomatal in the calyx lobes? under skin,the results of photochemical efficiency of PS?in the light?electron transport rate and optimal quantum yield of PS?,photosynthesis leaf is the highest and calyx lobe is the lowest,Indicating that leaf photosynthesis is the most.Pseudobulb?s total chlorophyll content is 17.9% of the leaf,the carotenoid content is 17.1% of the leaf;Calyx lobes? total chlorophyll content is 3.1% of the leaf,the carotenoid content is 13.2% of the leaf.Pseudobulb?s and calyx lobes? chlorophyll content is lower than leaves?.The Chla/Chlb leaves? is 2.258,pseudobulb?s is 2.231,calyx lobes? is 1.04.?2?Lycaste macrobulbon?s light saturation point is between 400⁵00?mo·m^-2·s^-1,light compensation point is between 0 ²0?mol·m^-2·s^-1,it is lower than others.Gas exchange parameters 20% light is higher than 40% light and 10% light,show Lycaste macrobulbon?s photosynthetic capacity under 20% light conditions is the highest.The results of minimal fluorescence?maximal fluorescence?maximal quantum yield of PS? are not very different,photochemical efficiency of PS?in the light?electron transport rate?photochemical quenching coefficient show that leaf under 40% light is the most,the second is 20% light.That 40% light Lycaste macrobulbon?s PS? reaction center photosynthetic reaction center activity.?3?Lycaste macrobulbon?s photosynthetic rate is positive in the day,it is negative in the night.Photosynthetic rate decreased significantly under drought stress,Pnmax is 0.859?molCO2·m^-2·s^-1,the control group?s Pnmax is 3.789?molCO2·m^-2·s^-1.Drought stress group leaves? stomatal conductance is still low between 0⁰.02mmolH2O·m^-2·s^-1 and had a little change over time;The control group?s stomatal conductance present unimodal type curve,the maximum is 0.088 mmolH2O·m^-2·s^-1.Drought stress group leaves? titratable acid content is higher than the control group,at 10:00o 'clock and 16:00o 'clock ha s no significant change in the daytime,it is declined clearly at 22:00,it rised again at 4:00.The control group leaves? total acid content have no obvious change in the four time of the day and night,it did not appear obviously increased in night,it not seen CAM acid metabolism under dry conditions.The result of stomatal?s open rate,length,width and density showed,drought stress group?s and control group?s stomatal are nonuniform closed,drought stress group stomatal?s volume is small and density is large,open rate changed not obvious at 10:00 and 22:00,the control group?s stomatal open rate changed a lot between day and night,the drought stress group group?s stomatal open rate changed a little between day and night,tow group stomatal?s length changed a little.