Stomatal Opening and Cell Enlargement in Response to Light and Phytohormone Treatments in Primary Leaves of Red-Light-Grown Seedlings of &lt;italic&gt;Phaseolus vulgaris&lt;/italic&gt; L.

Cell enlargement in primary leaves of bean is promoted by bright white light, gibberellic acid, or the cytokinin N6-benzyladenine. I examine the combined effects of light and hormones on growth, cell wall properties, and osmotic parameters during growth over 24 h. Applied alone, benzyladenine (10 μM), gibberellic acid (10 μM), and white light produced similar increases in the length and fresh weight of excised leaf strips over 24 h. The combined effects of hormones and light on growth were much less than additive. Individually, all three treatments significantly increased cell wall plastic extensibility over 24 h. However, benzyladenine combined with white light were additive in effect on plastic extensibility, and gibberellic acid combined with white light were synergistic. The differences in effects of hormones in white light on growth versus plastic extensibility indicate a decrease in growth potential, which is attributable in part to hormonal effects on osmotic concentration. Although white light alone increased osmotic concentration, both benzyladenine and gibberellic acid greatly decreased it, with or without white light. Furthermore, because growth potential is a function of both osmotic potential and wall yield threshold, it appears that yield threshold does not decline in parallel with osmotic potential in hormone-treated bean leaf strips. Finally, both benzyladenine and gibberellic acid inhibit the increase in osmotic solutes normally produced by white light. This effect, coupled with water uptake during cell expansion, would produce the observed decreases in osmotic concentration in hormone-treated strips. Hence, both benzyladenine and gibberellic acid interfere with light-induced growth, primarily through effects on the apparent ability of light to direct solute accumulation. Key words: Phaseolus vulgaris, leaf growth, cytokinin, gibberellic acid, light.

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Stomatal Opening and Cell Enlargement in Response to Light and Phytohormone Treatments in Primary Leaves of Red-Light-Grown Seedlings of <italic>Phaseolus vulgaris</italic> L.

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Light-dependent movement responses

Light-dependent movement responses

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Combined effects of hormones and light during growth promotion in primary leaves of Phaseolus vulgaris

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