Photosynthetic acclimation of plants to growth irradiance: the relative importance of specific leaf area and nitrogen partitioning in maximizing carbon gain

TLDR

Plants acclimate to growth irradiance by altering specific leaf area and nitrogen partitioning among leaf proteins. The study quantifies how changes in specific leaf area and nitrogen partitioning each contribute to maximizing carbon gain. The authors measured photosynthesis, specific leaf area, and nitrogen partitioning in ten C3 dicot species grown at 200 and 1000 µmol m⁻² s⁻¹ irradiance. High‑light plants exhibited three‑fold higher photosynthetic rates per leaf area, yet rates per leaf dry mass were equal because low‑light plants had twice the SLA; nitrogen per mass was constant, but low‑light plants allocated more nitrogen to light‑harvesting proteins, and daily photosynthesis per dry mass was more strongly affected by SLA than by nitrogen partitioning, with SLA remaining the key determinant even under high light.

Abstract

Abstract Changes in specific leaf area (SLA, projected leaf area per unit leaf dry mass) and nitrogen partitioning between proteins within leaves occur during the acclimation of plants to their growth irradiance. In this paper, the relative importance of both of these changes in maximizing carbon gain is quantified. Photosynthesis, SLA and nitrogen partitioning within leaves was determined from 10 dicotyledonous C 3 species grown in photon irradiances of 200 and 1000 µ mol m −2 s −1 . Photosynthetic rate per unit leaf area measured under the growth irradiance was, on average, three times higher for high‐light‐grown plants than for those grown under low light, and two times higher when measured near light saturation. However, light‐saturated photosynthetic rate per unit leaf dry mass was unaltered by growth irradiance because low‐light plants had double the SLA. Nitrogen concentrations per unit leaf mass were constant between the two light treatments, but plants grown in low light partitioned a larger fraction of leaf nitrogen into light harvesting. Leaf absorptance was curvilinearly related to chlorophyll content and independent of SLA. Daily photosynthesis per unit leaf dry mass under low‐light conditions was much more responsive to changes in SLA than to nitrogen partitioning. Under high light, sensitivity to nitrogen partitioning increased, but changes in SLA were still more important.