Studies on Productivity in Orchardgrass : VI. Varietal differences in efficiency of solar energy utilization and dry matter production

Abstract

This experiment was carried out in order to know the relationship between the efficiency of solar energy utilization and the dry matter production in orchardgrass. The varieties examined were Pennlate, Latar, Hokkai-1, Potomac, Chinook, Kitamidori, Daprime, S143, Apanui and Frode. The main results obtained were summarized as follows :1. The efficiency of solar energy utilization (Eu) can be expressed in the following formula ; Eu=Efficiency of intercepting energy (Ei)×Efficiency of energy conversion (Ec)=Ei×Ec 2. It was found that the relationship between Ei and leaf area (F) can be expressed by the following equation (Fig.1) ; Ei=1-exp (-K'・F) K': The light diminution coefficient (Regression coefficient between increase in leaf area and degrease in relative light intensity at ground level). 3. Eu averaged through the whole examined period was different among varieties. It was in the range of 1.82% (Pennlate) to 1.00% (S143), and the mean value of 10 varieties was 1.47% (Table 1). 4. Eu of the tiller weight type varieties and the medium type varieties were increased up to LAI 10 to 11, but Eu of the tiller number type varieties reached the maximum at approximate LAI 7. This fact suggests that the tiller number type varieties may be more productive under frequent cutting (Fig.2). 5. Highly significant correlation was found between the dry matter production and Eu during the growing season. Eu indicated significant correlation with both Ei and Ec for the earlier stage of the season, but only Ec for the latter half. E_i was related closely with LAI, and Ec was related with specific leaf weight (SLW) and K' (Fig.3, Fig.4, Table 2). 6. To clarify the relative contribution of LAI, SLW and K' to Eu, the multiple regression analysis was applied. Eighty six to 93% of the variation among varieties were accounted for by LAI, SLW and K'. The ratios of standard partial regression coefficients of 3 characters were 60:30:10 at the early stage of growth, but 37:43:20 at the late stage of growth