Figures & data
Figure 1 Spectral photon flux density (PFD) distributions for the lighting treatments. Blue-light PFDs were (a) 0, (b) 30, (c) 100 and (d) 150 µmol m−2 s−1. Total photosynthetic photon flux density was 300 µmol m−2 s−1 in any lighting treatment. The PFD was measured every 0.4–0.5 nm.
Figure 2 The relationship between (a) the light-saturated rate of photosynthesis per unit leaf area (LA) and (b) leaf N content per unit LA as functions of blue-light photon flux density in spinach leaves. Gas-exchange measurements were made at a photosynthetic photon flux density of 1,800 µmol m−2 s−1, an ambient CO2 partial pressure of 36 Pa, a leaf temperature of 25°C and a leaf-to-air vapor pressure deficit of 1.1 ± 0.1 kPa. Light for measurements was provided from a white halogen lamp. Error bars represent standard error (n ≥ 4). Means with different letters are significantly different using Tukey's honestly significant difference test (P < 0.05).
Figure 3 The relationship between (a) leaf dry weight (DW) per unit leaf area (LA) and (b) leaf N content per unit DW as functions of blue-light photon flux density in spinach leaves. Error bars represent standard error (n ≥ 6). Means with different letters are significantly different using Tukey's honestly significant difference test (P < 0.05).
Figure 4 The relationships between (a) cytochrome (Cyt) f, (b) light-harvesting chlorophyll-binding protein of photosystem II (LHCII) and (c) chlorophyll (Chl) content per unit leaf area (LA) and (d) Chl a/b ratio as functions of blue-light photon flux density in spinach leaves. Error bars represent standard error (n ≥ 3). Means with different letters are significantly different using Tukey's honestly significant difference test (P < 0.05).
Figure 5 The relationship between the ratio of cytochrome (Cyt) f content to light-harvesting chlorophyll-binding protein of photosystem II (LHCII) content as a function of blue-light photon flux density in spinach leaves. Eror bars represent standard error (n = 3). Means with different letters are significantly different using Tukey's honestly significant difference test (P < 0.05).
