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

Experiments have been done to confirm the previously reported effect of indoleacetic acid (IAA) on the rate of CO(2) assimilation in bean leaves. It was shown that spraying the leaves of a variety of plants caused an increase in the rate of CO(2) assimilation from 30% to 100% during the half-hour to 1 hour period following spraying. The only plant tested which did not show such an effect was corn.The breaking of dormancy of axial buds in the bean plant was correlated with an increase in the rate of CO(2) assimilation in adjacent leaves for a brief period of time. It has been shown that IAA solution sprayed on 1 leaflet of a leaf can cause an increase in the rate of CO(2) assimilation in the other leaflets, and that IAA applied to the cut stem of a leaflet or a developing bud can be transported to adjacent leaves and cause an increase in the CO(2) assimilation rate. The reaction caused by IAA is very similar to that caused by the breaking of dormancy of a bud. This indicates that the bud break response in CO(2) assimilation in leaves is caused by auxin synthesized in a bud as it begins to grow, and exported into adjacent leaves.