Studies on the mechanism of cell elongation of Lupin hypocotyl segments

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Abstract
The growth rates of hypocotyl segments from Lupinus angustifolius were measured at 1 minute intervals. Lowering the temperature reduced both the initial and steady state growth rates as well as slowing the response to addition of the auxin, indol-3yl-acetic acid. Anaerobic conditions quickly but reversibly inhibit growth. Cycloheximide, an inhibitor of protein synthesis which stops auxin induced growth also prevents the auxin induced increase in the extensibility of the cell walls. Reducing the turgor pressure by placing the segments in mannitol solutions also reduces the growth rate. The extensibility of the epidermal and outer cortex cell walls was found to be lower than that of the cell walls from the inner cortex and pith. The results are discussed from the point of view of the mechanism of cell expansion.