Effects Of Potassium Deficiency On Physiological And Biochemical Characteristics In Hickory

Potessium is one of the essential macronutrients in plant and plays a vital role in various physiological and biochemical process. To investigate the physiological and biochemical mechanism of hickory (Carya carthcryerisis) seedling under potessium deficiency, the photosynthetic characteristics (including gas exchange parameters, fluorescence parameters, Drate, Jf and so on), antioxidant enzymes activities, photosynthetic pigments, soluble protein, essential nutrients, carbohydrate and reflection spectrum were studied. The results are summarized as follows:1. The net photosynthetic rate(Pn), stomatal conductance(Gs), pigments and soluble protein decreased significantly, while intercellular CO2 concentration(Ci) decreased at first, and then increased, from the beginning to the 60th day after potassium deficiency treatment in the hickory seedling. The further study on chlorophyll fluorescence measurement showed that maximal photochemistry of PSⅡ(Fv/Fm),excitation energy capture efficiency of open PSⅡ(F′v/F′m),ФPSⅡ(Effective quantum yield of FSII),qP (Photochemical quenching) and ETR (Electron transport rate through PSII) were declined under potassium deficiency, indicating that the PS II reaction center was damaged. We also detected a significant increase of NPQ ( Non photo-chemical quenching) in the stressed leaves of hickory, which indicated that the mechanism of thermal dissipation had been started to dissipate excess light energy, and protect the plants from photo-inhibition and photo-oxidation. Prate decreased, Drate increased, significantly , indicating that a remarkable photoinhibition of photosynthesis existed in the stressed leaves of hickory. A high Jo/Jf indicated hickory was a high photorespiration plant, but hickory did not promote photorespiration to adapt to potassium deficiency stress. Potassium deficiency caused hickory to increase the reactive oxygen. The activity of SOD (Superoxide dismutase) increased and the activities of POD(Peroxidase) and CAT(Catalase) were declined under potessium deficiency. Potassium deficiency accelerated the membrance liquid peroxidation and increased the content of MDA.2. Potassium deficiency resulted in the increase of the content of P in the root, stem and leaf, Mg in the root and leaf, Ca, Zn and Mn in the leaf and the decrease of K and Fe in the root, stem and leaf,N in the leaf, Mg in the stem, Ca and Mn in the root and stem of hickory. The content of soluble sugar, sucrose and total starch decreased, while the content of sugar and fructose increased under potessium deficiency. The change mechanisms of various essential nutrients and carbohydrates in hickory caused by potassium deficiency needs further investigations.3. Potassium deficiency caused leaf reflection spectrum in the visible region (500~710nm) and near infrared bands increased. Potassium supplement shifted the red edge position to red band, narrowed the red edge range. GNDVI, PSNDa, PSNDb, PRI, mSR705, mND705, R800/R700 and R800/R640 increased while Rch decreased significantly with potassium supplement. However, NVDI, PSSRa, PSSRb, PSSRc, PSNDc, NPCI, SIPI, (R678-R486)/R800, R800(1/R520-1/R700) did not show significant differences. There were no correlation between NVDI, PSSRa, PSSRb, PSSRc, PSNDc, SIPI, R800(1/R520-1/R700), (R678-R486)/R800, pigments and potassium contents. However, there were significent correlation between GNDVI, Rch, PSNDa, PSNDb, NPCI, mSR705, mND705, R800/R700, R800/R640, Sred, pigments and potassium contents.