Components of relative growth rate and nitrogen productivity of Brussels sprouts and leeks grown at two widely differing light intensities

摘要

Early in the season, Brussels sprouts have a higher rate of biomass production than leeks at recommended fertilizer (nitrogen) application rates. Furthermore, they have a considerably higher annual biomass production and a higher annual biomass production per unit of nitrogen taken up. In this paper we explore and discuss the possible explanations for these field observations, using information obtained from growth chamber studies and the literature. Young vegetative plants of Brussels sprouts and leeks were grown in a growth chamber at a light intensity of 550 mu mol m(-2) s(-1) and at a light intensity which was 20 of that of the high-light treatment. At both light treatments, Brussels sprouts had an approximately 90 higher relative growth rate than leeks. At both light treatments the higher relative growth rate of Brussels sprouts was mainly explained by its higher leaf area ratio. Only minor differences in the physiological component, the net assimilation rate, between the two species within a light treatment were observed. The higher leaf area ratio of Brussels sprouts was mainly explained by its higher specific leaf area. Brussels sprouts had a higher rate of biomass production pet. unit of internal nitrogen (nitrogen productivity) than leeks. This was mainly explained by a higher allocation of nitrogen to leaves and a higher rate of biomass production per unit leaf nitrogen. We suggest that the higher biomass production per unit of nitrogen taken up of Brussels sprouts compared to that of leeks as observed in the field is explained by its higher nitrogen productivity. The results obtained from the growth chamber studies are discussed in relation with field experiments and data from the literature.