FROM CELL-GROWTH TO LEAF GROWTH .3. KINETICS OF LEAF EXPANSION

Plant growth models have, in general, not considered the detailed aspects of cell expansion and cell division, A key benefit gained by considering growth from a cellular perspective is a more thorough understanding of the role of water relations and plant growth. The objective of this research was to simulate leaf expansion in monocots using a model that incorporates cell division and cell expansion. The core of the model is a module that couples cell division and cell expansion. Assumptions are made concerning the arrangement within the leaf of the cells produced by the cell growth module. Inputs to the model include the total water potential external to the cells and the temperature of the cells. The effects of varying these input parameters on the model outputs (leaf length, leaf area, cell number, elongation rate, and meristem dimensions) are studied. The output is fairly sensitive to the water potential inputs and somewhat less sensitive to the temperature input, These sensitivities are discussed in relation to leaf expansion in field-grown maize (Zea mays L.) plants under well-watered and water-limiting conditions. An extension to the model is described wherein a simple mass balance is calculated on the amount of C produced by the mature portion of the leaf and the amount of C used in the expanding portion.