Abstract
We get average parameters of logistic equations for increase in whole tops dry matter, leaf blades dry matter and leaf areas with growth of Italian ryegrass population in experiment of five years for each season respectively. On these equations, the seasonal changes were discussed of the relations between increase in whole top dry matters (W), and that of leaf blade dry matters (L_w) and leaf areas (L_a). Obtained results are as follows. 1. The relationship between whole top dry matters (W) and leaf blade dry matters (L_w) with growth of the population could well be expressed by the following quadratic equation. L_w=μW-νW^2 μ, ν ; relative growth coefficients 2. The relation of relative growth of whole top dry matters (W) to leaf blade dry matters (L_w) in each seasons could be shown by the following approximate equations respectively. in autumn L_w=0.9W-0.000519W^2 50<W<450g・m^<-2> in winter L_w=0.53W-0.000055W^2 100<W<600g・m^<-2> in spring L_w=0.6W-0.000385W^2 120<W<600g・m^<-2> 3. Changes of the leaf area ratio (L_a/W) with growth in each seasons could be shown by the following approximate equations respectively. in autumn L_a/W=430-0.367W 50<W<450g・m^<-2> in winter L_a/W=23572/W+W/3.48 100<W<600g・m^<-2> in spring L_a/W=9728W^<-0.578> 120<W<600g・m^<-2> 4. Changes of the specific leaf area (L_a/L_w) with growth in each seasons could be shown by the following approximate equation respectively. in autumn L_a/L_w=500-0.238W 50<W<450g・m^<-2> in winter L_a/L_w=48142/W+W/1.75 100<W<600g・m^<-2> in spring L_a/L_w=126.34/W^<0.04>-1.092 120<W<600g・m^<-2> 5. In spring, although less distribution is observed in leaves, the leaf area can develop rapidly, as the specific leaf area is quite large. There arises a rapid reduction in the specific leaf area with growth of population, which seems to lead to the persistance of high NAR. Such transition in the specific leaf area in spring indicates a part of the high production mechanism of spring flush. 6. The fact that the specific leaf area is particularly large in spring seems to have more to do with the stage of growth development than the direct influence of the environmental factors.
