FUNDAMENTAL GROWTH-RESPONSE TO FERTILIZER IN RICE PLANTS .1. VARIETAL DIFFERENCE IN THE GROWTH-RATE AT THE SEEDLING STAGE

Varietal differences in growth rate and its related characteristics at seedling stage were examined with 35 rice varieties of different ecotypes and growth types, which were grown until the 8.5-leaf stage under seven levels of nutrient concentrations of Kimura B culture solution. Distinctive varietal differences were found particularly in dry matter increase (Δ W), relative growth rate (RGR) and net assimilation rate (NAR). Certain varieties had higher ΔW at every nutrient level. And the correlations between ΔW and RGR, RGR and NAR, and NAR and nitrogen content per leaf area (NCLA) were highly positive, while highly significant negative ones were found between NAR and SLA, and NCLA and SLA at every nutrient level. However, NAR did not correlate with nitrogen content per leaf dry weight (NCLW). Based on these results, NCLA was specified as a very important factor relating to varietal differences of growth rate. Consequently, it is concluded that the high ability to increase NCLA is one of the most important characteristics for high growth rate at lower nutrient level, and also at higher level where SLA is apt to increase. However, neither ecotype nor growth type corresponded with this characteristic. © 1990, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.