Thickness Fluctuations in Veins of Corn and Sunflower detected by a Linear Transducer

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Abstract
A short-stroke linear displacement transducer has been used to detect changes in thickness of veins of corn and sunflower. After illumination, continual fluctuations in thickness occurred, some 2–5 min and others 15–20 min apart and from 0.05% to 2% of the total vein thickness in amplitude. These changes, often erratic and usually not simultaneous at points 4.0 cm apart, seem to be related to changes in water potential in the tissue. The short-term fluctuations were not due to major stomatal oscillations but could be due to local variations in transpiration, or to fluctuations in photosynthate moving through the veins, for they often resembled the patterns of radioactivity detected after feeding 11CO2or 11C-sucrose. The magnitude of fluctuation increased as the diameter of vein increased, and thus could be useful in monitoring changes of water potential in leaves.