An Improvement of Semiempirical Method for Estimating the Total Photosynthesis of the Crop Population : II. On light attenuation and vertical distribution of Pmax in rice plant population

[摘要] The profiles of light intensity and light saturated value of photosynthesis, Pmax, in the rice canopy were observed from tillering stage to ripening stage. Using the parameters obtained from the observation, the theoretical values of dry matter production estimated by the semiempirical model were compared with the values obtained by biomass method. Results were summarized as follows: 1. Light attenuation in the canopy was approximated well using either exponential law (I=I0e-KF) or reciprocal law (I=I0/(1+kF)). Light attenuation cofficient k became larger with growth stage. 2. Pmax decreased with accumulated LAI, F increasing and linear relation was found between Pmax and F. Pmax at the top of the canopy (Pmax, H) and vertical gradient of Pmax in the canopy became smaller after the heading stage. 3. Using the Uchijima's model for estimating the total photosynthesis and dry matter production of rice stand, we found that the theoretical values almost coincided with the values obtained by biomass method. But, assumed that the foliage was constructed with upper active leaves, the theoretical dry matter production was considerably overestimated.

[学科分类] 农业科学（综合）