XVI International Botanical Congess
Convective gas throughflow was evaluated for twelve floating-leaved and two free-floating plants. Air flow due to pressurization was observed for leaf thin sections of five Nymphaea species, Victoria amazonica, Hydrocleis nymphoides, Nymphoides peltata, N. indica, Hydrocharis dubia, and Eichhornia crassipes, while was not in leaves of Brasenia schreberi, Trapa japonica, and Potamogeton distinctus. Species whose leaf thin sections were pressurizing also had substantial gas flow when measured at their cut petioles except for two free-floating plants, H. dubia and E. crassipes. The species whose leaf thin sections were not pressurizing had no gas flow at their cut petioles. Ventilating ability primarily depends on whether the leaf can pressurize or not and may secondarily on resistance to mass flow.