Studies on the effects of auxins and allied compounds on the extension growth of excised roots

Abstract

The present investigation was undertaken with a view to study the extension growth of root sections of Pisum sativum L. var. Duke of Albany obtained from Messers Sutton and Sons Ltd., Calcutta, by applying growth regulators, viz. gibberellic acid (GA), B-indolylacetic acid (IAA), inhibi-tors maleic hydrazide (MH), coumarin (CM) and two vitamins thiamine hydrochloride (TH) and pyridoxine alone and in various combinations in 0.5% sucrose medium. 2 mm long root sections were excised from the ex- tension zone of the radicle about 1.5 mm behind the extreme tips by using a specially devised guilletine. Healthy seeds used for the purpose were surface-sterilised with HgCl2 (1:1000) to eliminate the growth of micro-flora bac-teria and fungi which generally arrest to a certain extent the growth of the growing root cells. Seeds soaked for overnight were then planted in sterile sand pots and seeds were allowed to germinate in a dark room maintained at a temperature of 270C (+-10C) and high humidity. After harvest at the end of two days root sections were cut. 10 such root sections constituting each sample were placed in a petri-dish over a sterile filter paper the ends of which were kept dipped in test solutions. The filter paper was supp-orted on a horseshoe shaped glass rod. This device is specially meant for oxygen supply to the growing root sec-tions, which is an essential prerequisite condition for continued growth. Root sections were allowed to grow in complete darkness inside a humidity cabinet maintained at 270C (+-10C) and saturated humidity. Length measurements of sections were made at regular time intervals under a travelling microscope. Isolated root sections from the elongating zone was preferred for convenience of having a unified picture of the true effectiveness of externally added growth regula-tors strictly on the growth in elongation. Such sections are deprived of their possible share of the growth regula-tors such as IAA and GA from the aerial parts or from the root tip. Since significant growth promoting