Effect of Growth Regulators on CO2 Assimilation in Leaves, and its Correlation with the Bud Break Response in Photosynthesis

Abstract

Experiments with a variety of plants (ferns, cereals, vegetables, etc.) confirmed the previously reported stimulation of the rate of CO2 assimilation in bean leaves by indoleacetic acid (IAA). It was shown that spraying the leaves caused an increase in the rate of CO2 assimilation of 40-100% during the 1/2 to 1 hour period following spraying. Corn did not show such an effect. A variety of other growth substances were tested; only indolebutyric acid showed the IAA effect. The breaking of dormancy of axial buds in the bean plant was correlated with an increase in the rate of CO2 assimilation in adjacent leaves. It was shown that IAA solutions can be applied to the cut petiole of an adjacent leaf, or can be sprayed to an adjacent leaf, or can be supplied to the cut stem of a bud, and cause an increase in the rate of CO2 assimilation in a leaf. The nature of the effect caused by IAA is very similar to that caused by the breaking of dormancy in a bud. It is concluded that the bud break response in CO2 assimilation in leaves is caused by auxin synthesized in a bud as it begins to grow, and exported into adjacent leaves.