Effects Of Nitrogen On Physiology And Biochemistry In Hickory Seedlings And Nutrition Diagnosis

Hickory(Carya cathayensis Sarg.) is a very famous dry-fruit tree in east of China. It is a major income source for many hickory farmers. Because of its'lower input and higher income, the farmers used to fertilize more to get higher yields. Over-fertilized with nitrogen fertilizer not only reduce the utilization efficiency of fertilization,but also cause the waste of nitrogen which will be a risk for pollution. So it is necessary for scientific fertilization and high-efficiency management to develop a simple and quick method which can nondestructively detect the growth of hickory using water culture method, two-year-old hickory seedlings were treated with four different nitrogen concentrations in greenhouse. After the photosynthetic fluorescence and leaf Reflectance spectra had detected at the third leaf, morphological indexs (seedling height,ground diameter) were measured, physiological indexes(such as photosynthetic pigment,related enzymes,soluble proteinand soluble sugar) and the nutrient elements had analyzed. The results showed as follows:(1) With nitrogen concentration increasing,the contents of chlorophyll a, chlorophyll b and carotenoid increased gradually, the seedling height had not changed, but the ground diameter had increased significantly from 5.9% to 30.9%; the nutrient elements of K, Zn, Mn in root,stem, leaf increased , however, the nutrient elements of N, P, Fe, Ca, Mg increased to the peak then decreased.(2) With the nitrogen concentrations increased the net photosynthetic rate of hickory leaves,ФPSⅡ, qP and Fv′/Fm′also increased, when the concentration is up to 1.5 mmol/L,the net photosynthetic rate reached its maximum value.(3) In visible region the reflectance spectra of hickory leaf is decrease with nitrogen concentrations increase,the red edge position moved to long waves,and the wavelength from 525nm to 605nm could be used as the sensitive bands of hickory nitrogen levels(4) The correlation between fluorescence parametersФPSⅡ, qP, Fv′/Fm′and chlorophyll a, chlorophyll b, carotenoid, nitrogen content of leaf have reached significant positive,but the correlation between NPQ and photosynthetic pigment, nitrogen content of leaf have reached significant negative.(5) Reflectance spectra parameters GNDVI, Rch, mSR705, mND705, R800/R700,λred could be used as detecet the nitrogen nutrient of hickory exactly;PRI first increase then decrease with the nitrogen concentrations increase,and its maximum appeared in 1.5 mmol/L,so it also could be used as a qualitative evaluation parameter on nitrogen nutrient of hickory.Meanwhile, the correlation of PRI and Car/ Chl ratio reached an extremely significant level.(6) The correlation between reflectance spectra parameters GNDVI, PSNDb, PRI, mSR705, mND705, R800/R700, R800/R640,λred, R800(1/R520-1/R700) and fluorescence parameters Fv′/Fm′,ФPSⅡ, qP is reached significant positive; but Rch is in contrary; The correlation between NPQ and GNDVI, NPCI, SIPI, PRI, mSR705, mND705, R800/R700, (R678-R486)/R800,λred is reached significant negative, but the correlation between NPQ and PSSRa, Rch is reached significant positive.