Auxin Distribution in Seedlings and Its Bearing on the Problem of Bud Inhibition

Publisher Website
Google Scholar
Abstract
A simple method has been worked out by which it is possible to extract auxin from corn without destruction of the auxin-b. The same method was applied to pea and oat seedlings. In the first part of the paper the distribution of auxin in the seedlings is considered. Pea seedlings have the highest average auxin content; oat the average auxin content of oat seedlings is about 1/10, and that of corn seedlings about 1/100, that of pea seedlings. All auxin contents are expressed in indoleacetic acid equivalents, this unit being independent of the sensitivity of the test plants. In the seedlings of oat and corn the highest auxin conc. is in the base of the primary leaf; in pea seedlings it is in the apex. The dormant lateral buds contain a higher auxin conc. than the adjacent stem tissue.[long dash]In the 2d part of the paper the relation between the auxin conc. and bud inhibition was studied in pea seedlings. After decapitation the auxin content of the lateral buds steadily increases, that in the stem always decreases. Application of auxin on decapitated plants increases the auxin conc. of both the stem and lateral bud, yet this bud does not develop; a direct action of auxin on the lateral bud must therefore be excluded as a possible explanation of its dormancy. Exps. with phenylbutyric acid indicated that high auxin concs. in the stem prevent formation of auxin in the lateral bud. Auxin is most effective in inhibiting lateral buds when introduced in the vascular system of the stele. Auxin applied to the stump of decapitated plants some time after decapitation is less effective in bringing about bud inhibition the longer the time between decapitation and auxin application. It is probably the high auxin conc. in the vascular tissue which prevents translocation of growth factors into the lateral buds, thus causing their dormancy. This blocking of the translocation apparently takes place in the narrow leaf trace connecting the stelar bundles with the dormant lateral bud.

This publication has 10 references indexed in Scilit: