Long Term Effects of High CO2Concentration on Photosynthesis of Water Hyacinth (Eichhornia crassipes(Mart.) Solms)

Abstract

The photosynthetic response to CO2 concentration, light intensity and temperature was investigated in water hyacinth plants (Eichhornia crassipes (Mart.) Solms) grown in summer at ambient CO2 or at 10000 μmol(CO2) mol−1 and in winter at 6000 μmol(CO2) mol−1 Plants grown and measured at ambient CO2 had high photosynthetic rate (35 μmo1(CO2) m−2 s−1), high saturating photon flux density (1500–2000) μmol m−2 s−1 and low sensitivity to temperature in the range 20–40 °C. Maximum photosynthetic rate (63 μmol(CO2) m−2 s−1) was reached at an internal CO2 concentration of 800 μmol mol−1. Plants grown at high CO2 in summer had photosynthetic capacities at ambient CO2 which were 15% less than for plants grown at ambient CO2, but maximum photosynthetic rates were similar. Photosynthesis by plants grown at high CO2 and high light intensity had typical response curves to internal CO2 concentration with saturation at high CO2, but for plants grown under high CO2 and low light and plants grown under low CO2 and high light intensity photosynthetic rates decreased sharply at internal CO2 concentrations above 1000 μmol−1.