Abstract
Four main potato cultivars were grown under field conditions for five years to assess the relationship between dry matter production and climatic conditions. Photosynthetically active radiation intercepted by crops during the experimental period (ΔPAR) was the largest in 1984, and smaller in 1983, 1985 and 1986. Mean efficiencies of dry matter production per ΔPAR (EPAR) were smaller in 1982. Accumulated dry weight were proportional to accumulated ΔPAR, although some deviations from the regression line of accumulated ΔPAR and dry weight existed in 1983. Crop growth rates (CGR) were correlated positively with ΔPAR and EPAR during the period from emergence to June 30, and with EPAR during the periods after July. Throughout the growing season, tuber growth rate (TGR) was correlated positively with CGR and EPAR. In the first half of the growing season, the air temperature was related to the leaf growth rate (LGR) and TGR. Radiation influenced specific leaf area (SLA) resulting in rapid expansion of leaf area in cloudy seasons. Tuberization seemed to be very sensitive to water stress, which would make percentages of tuber dry weight larger. In the latter half of the season, there was no marked relationship between the climatic conditions and the growth parameters. At the end of the season, however, sink-source ratio (tuber dry weight/shoot dry weight) tended to increase with increasing accumulated incoming radiation, and to decrease with increasing accumulated air temperature.
