Growth and biomass allocation, with varying nitrogen availability, of near-isogenic pea lines with differing foliage structure

The single-gene mutation afila in pea (Pisum sativum L.) results in the replacement of proximal leaflets with branched tendrils, thereby reducing leaf area. This study investigated whether the afila line could adjust biomass partitioning when exposed to varying nutrient regimes, to compensate for reduced leaf area, compared with wild-type plants. Wild-type and afila near-isogenic lines were grown in solution culture with nitrate-N added to initially N-starved seedlings at relative addition rates (R-N) Of 0.06, 0.12, 0.15 and 0.50 d(-1). The relative growth rate (Rw) of the whole plants closely matched R-N at 0.06 and 0.12 d(-1), but higher R-N resulted in a slightly higher growth rate. At a given R-N, the wild-type line had lower plant nitrogen status than the afila line. R-W of the roots of the afila line was less than R-W of the roots of the wild-type at the three higher rates of N supply despite a greater accumulation of N in the roots of the afila plants. Consequently, plant nitrogen productivity (growth rate per unit nitrogen) was lower for afila. Dry matter allocation was strongly influenced by nitrogen status, but no differences in shoot-root dry matter allocation were found between wild-type and afila with the same plant N status. These results imply that decreased leaf area as a result of the single-gene mutation afila affects dry matter allocation, but only according to its effect on the nitrogen status. (C) 2000 Annals of Botany Company.