Abstract
Flowering soybeans were sprayed at the tips with 50 ppm TIBA. Microscopic and macroscopic observations were made of the nodes, internodes, and shoot meristems every week for 4 wks after TIBA treatment. TIBA‐treated plants produced open flowers at the upper nodes 1 week earlier than did control plants. Accompanying this early flower development, the following changes occurred in the upper internodes, as compared to controls: (a) increased activity of the procambium; (b) rapid development of thick‐walled protophloem cells; (c) production of small vessels. Three weeks after treatment middle internodes of treated plants showed less cambial activity than did corresponding internodes of controls. The changes in the middle internodes of treated plants suggest a close correlation with increased flowering. Two weeks after treatment some lateral shoot apices at nodes nearest the main shoot apex exhibited the following changes, in contrast with controls: (a) development of conical apices with stack‐of‐brick‐like peripheral cells; (b) shrinkage of protoplasmic contents in some rib meristem cells and young pith cells; (c) frequent thickening of primary walls in young pith cells. Three weeks after treatment cells of lateral shoot meristems with conical axillary buds showed a denser stain for protein than did cells of corresponding meristems of controls. Floral apices in these meristems also stained more densely for protein than did similar apices in control plants. Together with early flower production in the upper nodes of treated plants, less starch occurred 2–3 weeks after treatment than in corresponding nodes of controls. Two to three weeks after treatment lateral shoot apices of both treated and control plants had numerous, large starch grains in the rib meristem, young pith, leaf and bud primordia, and developing flowers but few starch grains appeared in the tunica, corpus, and procambium.
Published Version
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