Effects of a growth retardant, CCC, on leaf growth in Phaseolus vulgaris

Abstract

1. CCC applied at 10-2 M during early stages of germination of darkgrown plants led to increases in cell number and fresh and dry weight of the primary leaves. These effects could be reversed by application of 10 μg GA3 per plant after emergence above the soil. 2. Irradiation with red light for short periods also increased cell number and fresh weight of leaves. This effect could be reversed by far-red radiation, but not by application of GA3. 3. Responses to both CCC and light were dependent upon the continued presence of the cotyledons, which it is suggested supply a growth factor required by stem and leaves. 4. Treatment of plants grown in 12-hour days with CCC, reduced area and rate of expansion of primary and trifoliate leaves. For the latter, a change in leaflet shape was found. Cell number of primary leaves was not affected under these conditions, but that of trifoliate leaves was reduced. A smaller reduction in cell number was noted for the third trifoliate leaves on treated plants; this was shown to be due to the fact that this leaf was not shaded by the primary leaves as was the case for first and second trifoliate leaves. 5. The effects of GA3 in counteracting the responses to CCC are described. It is suggested that applications of CCC and GA3 may modify the pattern and polarity of cell expansion in leaves.