Biometrical studies of plant growth

Abstract

Abstract Relevant mathematical properties of the Richards function are described, along with references to its employment in previous work, and a brief description is given of some of the difficulties encountered in its use. Two introductory experiments were undertaken: firstly, applying the Richards function to leaf growth of Impatiens parviflora DC; and secondly, applying the function to artificial sets of data of differing variability and differing spreads of observation‐values along the growth curve. The purpose of the latter analysis was an attempt to elucidate some problems of fitting and interpretation arising in the first experiment. It was concluded that the prime aim in experimental work generally is the acquisition of data covering as large a range of sizes as possible; low variability of the replicate observations, while desirable, is not so important. In another series of experiments, plants of Impatiens parviflora were grown at four different temperatures in the range 13–23°C inclusive. In terms of leaf dry weight, increase in temperature decreased the final size attained and increased the mean relative growth rate; the curvature of the growth curve and the mean absolute growth rate were, however, temperature independent. These results are brought together in a simple model which shows clearly how temperature affects the course of leaf dry weight increase in these plants. The results for leaf area are less clear, but both the mean absolute and relative growth rates increased with rise in temperature. The final area of a leaf and the curvature of the growth curve seemed to be little affected by temperatures in the range 16–23°C, but there was some evidence of differences in these features in leaves growing at 13°C. No model summary was attempted for leaf area increase.