Photosynthesis & transpiration from upper & lower surfaces of intact banana leaves

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Abstract
Continuous and simultaneous measurements of photosynthesis and transpiration were made on intact leaves of young potted plants of Musa acuminata var. Gros Michel. The CO2 and water vapor contents of an air stream were measured before and after it passed through transparent, plastic, water-jacketed leaf chambers attached to the upper and lower surfaces of the leaves. The magnitude of photosynthesis and transpiration from the lower surface was much greater than from the upper surface. Much higher light intensities were required to open the stomata on the upper than on the lower surface. Following the onset of illumination, a lag period of at least 15 minutes was found to occur before the commencement of apparent photosynthesis or transpiration. The length of the lag period was not correlated with light intensity. Following the commencement of stomatal transpiration and photosynthesis, the shapes of the curves describing the time courses of the 2 processes were similar, indicating that both processes were limited by the degree of stomatal opening.