Analytical Procedure for Estimation of the Assimilation Cell Phase CO₂ Mass Transfer Coefficient of Crop Leaf from Experimental Measurements of the Net Photosynthetic Rate

Abstract

Analytical solutions for the CO₂ concentration profile C_A (z, t) and CO₂ mass transfer coefficient k_L within the assimilation cell phase of the crop leaf in the net photosynthesis process were obtained by the concept of “rate of process” in the engineering science.
To solve the CO₂ mass transfer problem of the crop leaf in net photosynthesis, CO₂-H₂O equilibrium at the assimilation-aerenchyma tissue interface within the crop leaf, Henry's Law, was introduced and the net photosynthetic reaction was approximated by a pseudo-1st order irreversible form.
Simultaneously, in order to estimate quantitatively k_L and the over-all gas phase CO₂ mass transfer coefficient k_G from the practical observed results of the net photosynthetic rate R_A, the graphical method and its procedure were proposed, using the results of R_A for “rice” presented by Yabuki (1992). The summary is as follows:
1) CO₂ mass transfer of a crop leaf in the photosynthesis process is a gas absorption-reaction. It is also a diffusion phenomenon in a gas-liquid binary system and the mechanism of CO₂ absorption may be represented schematically by a “two-film penetration diffusion model”.
2) Analytical solutions and the graphical method are available for evaluation of k_L and k_G from R_A observed in the field. These basic analytical procedures for gas absorption engineering are useful to obtain the correlation of the net photosynthesis reaction rate constant k₁ with R_A and CO₂ mass transfer coefficients.
3) k₁ is a primary characteristic parameter to evaluate the net photosynthetic ability of the crop. The over-all assimilation cell phase CO₂ mass transfer coefficients, K_L, k_L, and k_G depend on k₁. Therefore, to estimate a valid R_A or an appropriate net photosynthetic ability of the crop leaf, CO₂ mass transfer coefficients correlated with k₁ must be used.