Abstract
For quantitative growth analysis of pasture plant population, growth analysis formulae containing variables which have physiological, environmental and ecological meanings should be used. In this paper, formulae including such variables are proposed as follows : Net assimilation rate (NAR) can be expressed as the product of the efficiency of dry matter accumulation per unit photosynthetically-active radiation (E_<PAR>) and photosynthetically-active radiation intercepted per unit leaf area index (PARL). NAR=E_<PAR>・PARL. The relationships among leaf area index (LAI), leaf area ratio (LAR), dry matter weight of a tiller (DMT), tiller number of a plant (TNP), plant density (PD). and tiller number per unit area (TNA) are described as LAI=LAR・DMT・TNP・PD=LAR・DMT・TNA. Thereofre, crop growth rate (CGR) is given as follows : CGR=E_<PAR>・PARL・LAR・DMT・TNP・PD=E_<PAR>・PARL・LAR・DMT・TNA. On the other hand, if we assume that chlorophyll amount per unit ground area (Chlorohyll index ; CHI) can be used in place of assimilatory material, CGR is expressed as the product of three components, i.e. photosynthetically-active radiation intercepted per unit chlorophyll index (PARG), E_<PAR> and CHI. CGR=E_<PAR>・PARC・CHI. Furthermore, if chlorophyll content on dry matter basis (CCD) is defined as "the ratio of assimilatory material per unio plant material present", the following relationships can be obtained ; CHI=CCD・DMT・TNP・PD=CCD・DMT・TNA. At any point in time the growth formulae can be written down as follows : CGR=E_<PAR>・PARC・CCD・DMT・TNP・PD=E_<PAR>・PARC・CCD・DMT・TNA. The variables in these formulae are multiplicative factors such as efficiency of dry matter accumulation, radiation absorption and plant population characteristics. These formulae can be linearized by logarythmic transformation and the partial regression coefficients, estimated by multiple regression analysis with standardized data set, are available as indicators, showing effects of physiological, environmental and ecological factors on CGR, if these factors are independent of each other.
