Effects of elevated pressure on rate of photosynthesis during plant growth

• The aim of this study is to investigate the effects of an artificially controlled environment, particularly elevated pressure, on net photosynthesis and respiration during plant growth.
• The results clearly showed that rate of respiration linearly decreased with an increase in total pressure at a high humidity.
• The amount of respiration linearly decreased with an increase in total pressure up to 0.2 MPa, and increased with an increase in total pressure from 0.3 to 0.5 MPa at a low humidity.
• The rate of net photosynthesis linearly decreased with an increase in ambient pressure.
• The amount of net photosynthesis was clearly increased up to 1.6 fold with an increase in pressure under elevated pressure and a high partial pressure of CO2.

The aim of this study is to investigate the effects of an artificially controlled environment, particularly elevated total pressure, on net photosynthesis and respiration during plant growth. Pressure directly affects not only cells and organelles in leaves but also the diffusion coefficients and degrees of solubility of CO2 and O2. In this study, the effects of elevated total pressure on the rates of net photosynthesis and respiration of a model plant, Arabidopsis thaliana, were investigated in a chamber that newly developed in this study to control the total pressure. The results clearly showed that the rate of respiration decreased linearly with increasing total pressure at a high humidity. The rate of respiration decreased linearly with increasing total pressure up to 0.2 MPa, and increased with increasing total pressure from 0.3 to 0.5 MPa at a low humidity. The rate of net photosynthesis decreased linearly with increasing total pressure under a constant partial pressure of CO2 at 40 Pa. On the other hand, the rate of net photosynthesis was clearly increased by up to 1.6-fold with increasing total pressure and partial pressure of CO2.