Abstract:

In order to evaluate the relationship between reflectance spectra parameters and physiological indexes, the reflectance spectra and red edge were characterized in the leaves of two-year-old hickory (Carya cathayensis) seedlings grown under different nitrogen concentration. The results showed that the spectral reflectance gradually became smaller in the visible region with increasing nitrogen concentration, and specifically the reflectance in the range from 525 to 605 nm was changed significantly, which was regarded as sensitive band range used in detecting the nitrogen level in this stualy. The red edge position had a trend shifting to long wavelength direction with an increaseinnitrogen concentration. The concentrations of chlorophyll and total nitrogen of leaves were significantly correlated to the reflectance spectra parameter GNDVI, Rch, mSR705, mND705, R800/R700 and λ_red, which indicated that these parameters were albe to be used to detected the nitrogen level in hickory leaves. PRI was increased with nitrogen concentration below 1.5 mmol ·L^-1, and then was deceased with higher nitrogen concentrations which indicated that PRI was able to be used to qualitatively estimate the nitrogen nutrition status in hickory. Additionally, PRI was significantly correlated to the Car/Chl. These results indicated that non-radiative dissipation of excitation energy associated with the activation of the xanthophyll cycle was initiated under different nitrogen concentration.

Key words: hickory, nitrogen concentration, reflectance spectral, regression analysis