Carbon assimilation dynamics in Pontederia crassipes in response to light intensity and CO2 levels.

Abstract

Pontederia crassipes Mart. is an aquatic macrophyte native to South America, tolerant to high intensity of sunlight and has spread to various countries worldwide. This study aimed to investigate the photosynthetic characteristics of P. crassipes leaves under different light intensities and CO₂ concentrations by analyzing net photosynthetic response, Rubisco activity, and related photosynthetic parameters. The plants were acclimated in a greenhouse under natural light conditions at a temperature of 25 ± 5 °C. The light response curve was measured using a portable infrared gas exchange system, coupled with the 6400-40 Leaf Chamber Fluorometer. The response of net photosynthesis to intercellular CO₂ concentration was determined at 1500 µmol m^-2 s^-1 of photosynthetic active radiation (PAR). P. crassipes demonstrated a remarkable capacity for adaptation to varying light intensities and CO₂ concentrations, exhibiting strong photosynthetic efficiency, as indicated by its net CO₂ assimilation rate in response to PAR, sustained electron transport rate up to 1000 µmol photons m^-2 s^-1, a positive correlation between φPSII and φCO₂, and a high net CO₂ assimilation rate in response to C _i .