Cell growth, wall deposition, and correlated fine structure of colchicine-treated lettuce hypocotyl cells

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Abstract
The effects of colchicine, singly and in combination with gibberellic acid (GA3), on growth of lettuce hypocotyl cells are reported. After 72 h of growth, the cells in GA3 are extremely long and cylindrical, whereas those in GA3 + colchicine are very large and more or less isodiametric. The cell volume in colchicine is not significantly different from that in the water control. Kinetic data on cell growth and on dry weight of cell walls indicate a parallelism between the GA3 and GA3 + colchicine treatments and between the colchicine treatment and water control. In all treatments, certain cytological changes, viz. proliferation of dictyosomes and their vesicles, increase in endoplasmic reticulum (ER) and polyribosomes, and increased connections between the ER and plasmalemma, occur at the same time as in the water conrol and proceed ahead of evident cell growth. Changes in wall fibrils and microtubules are described. It is concluded that colchicine does not inhibit the kinetics of cell growth or the deposition of wall material, but since it causes dissolution of microtubules, the deposition of new wall fibrils is random even though it shows some degree of order, and if at that time the cells are growing rapidly under the influence of GA3, they become spherical. These results are discussed with a view to understanding the mechanisms underlying cell enlargement.