Effect of the amputation of the cotyledon and of the application of growth regulators on the transport of32P in decapitated pea seedlings

Abstract

When the epicotyl and one cotyledon is cut off from pea seedlings, only the axillary of the amputated cotyledon is known to grow. When32P is applied to the roots of such plants, then a higher radioactivity appears in the axillary of the amputated cotyledon already 24 hrs. after amputation of one cotyledon, although this axillary is of the same size at this time as that of the remaining cotyledon. This fact indicates a more extensive material transport to the axillary bud of the amputated cotyledon already during the first day after amputation The effect of individual regulators on the32P transport was investigated in an experiment where pea seedlings cultivated in the dark were decapitated and a 0.5% paste, containing the regulatory compounds was placed either on the cutting surface in the apical part of the epicotyl stump or in its central part. After a week the plant roots were supplied with32P and its transport to the upper part of the epicotyl stump was followed. This transport increased about 10-fold in the case of a paste, containing indolyl acetic acid, when the paste was spread on the apical cutting surface of the stump. However, the transport was inhibited when the paste was applied in the central part of the stump. These results indicate that only the transport of32P towards the paste with indolyl acetic acid is accelerated, whereas it is decelerated above this paste. A paste, containing triodobenzoic acid inhibited32P transport only when applied to the apical cutting surface of the epicotyl stump and not when spread over the middle part. In this case32P transport was more rapid above the paste than towards the paste. The situation was similar in the case of gibberellin and kinetin.