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

Plant growth models have, in general, not considered the detailed aspe cts of cell expansion and cell division, A key benefit gained by consi dering growth from a cellular perspective is a more thorough understan ding of the role of water relations and plant growth. The objective of this research was to simulate leaf expansion in monocots using a mode l that incorporates cell division and cell expansion. The core of the model is a module that couples cell division and cell expansion. Assum ptions are made concerning the arrangement within the leaf of the cell s 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 out puts (leaf length, leaf area, cell number, elongation rate, and merist em dimensions) are studied. The output is fairly sensitive to the wate r potential inputs and somewhat less sensitive to the temperature inpu t, These sensitivities are discussed in relation to leaf expansion in field-grown maize (Zea mays L.) plants under well-watered and water-li miting conditions. An extension to the model is described wherein a si mple mass balance is calculated on the amount of C produced by the mat ure portion of the leaf and the amount of C used in the expanding port ion.