Effect of light intensity on the growth and photosynthesis of rice under different sulfur concentrations

Abstract

Rice (Oryza sativa L. cv IR 72) plants were grown hydroponically in 1.0 mm SO₄ ²⁻ for 1 week and transferred to 0, 0.01, 0.03, 0.1, 0.3, or 3 mm SO₄ ²⁻ under two light treatments, 1,200 (high light) and 550 (low light) µmol quanta m⁻² s⁻¹. When the plants were grown under S-deficient conditions, the biomass production of the shoot was more strongly suppressed in the high-light-grown plants than in the plants grown under low light conditions. The low-light-grown plants showed a lower relative growth rate (RGR), higher leaf area ratio (LAR), and a low net assimilation rate (NAR) that was not affected by S nutrition. Although total S contents of the leaf blades under both light treatments were similar, S allocation to the leaf blades under low light conditions was greater. A large decrease in the Rubisco content was observed in the high-light-grown, S-deficient plants. In contrast, the low-light-grown plants showed relatively high contents of Rubisco even under S-deficient conditions. Chlorophyll content was significantly higher in the plants grown under low light conditions. Irrespective of S and light treatments, leaf photosynthesis could be accounted for by the Rubisco content. The results indicated that S-deficient effects were relatively small in the low-light-grown plants and that high light conditions stimulated S-deficiency.

Key Words:

• growth
• light intensity
• Oryza sativa L.
• photosynthesis
• sulfur nutrition