Plant growth, canopy photosynthesis and light availability in three sugarcane varieties

Phytomass production is a result of physiological processes occurring at plant canopy level, with canopy architecture affecting the availability of solar radiation to photosynthesizing tissues. The aim of this study was to identify a possible association between light availability, canopy photosynthesis and plant growth in three sugarcane varieties under field conditions. As a hypothesis, higher canopy photosynthesis and plant growth are probably found in sugarcane varieties with higher light availability at bottom canopy positions. Measurements of diurnal course of leaf gas exchange were taken in two canopy positions of the sugarcane varieties IACSP93-2060, IACSP95-3028 and IACSP95-5000, maintaining the natural leaf inclination. All sugarcane varieties exhibited similar values of diurnal CO2 uptake at the upper canopy position. On the other hand, the bottom canopy position had an important role on photosynthesis of IACSP95-3028 sugarcane, with slight changes in leaf inclination causing significant variation of photosynthetic active radiation at the bottom canopy positions. High light availability at the bottom canopy position of IACSP95-3028 caused increased photosynthesis and improved plant vegetative growth, given by increases in tillering, leaf area and leaf and stalk phytomass accumulation.