Growth in Vitro of Excised Roots of Equisetum arvense as Modified by Indole-3-Acetic, Indole-3-Butyric, and α-Naphthaleneacetic Acids

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Abstract
Roots of E. arvense following excision continued growth through 7 passages of 2 wks. each in White''s medium. In light the roots showed progressive increase in growth rate; in darkness the rate was uniformly lower and root survival less. Roots in light became green, and spectro-photometric analysis of acetone extract showed the pigment to be chlorophyll. Cultures with appropriate modifications of full medium demonstrated necessity of an organic source of fixed C (sucrose); thus indicating an incomplete or inadequate photosynthetic mechanism. An organic source of fixed N (glycine), moreover, was essential for growth comparable to that in full medium. Roots cultivated in White''s medium in darkness with 10-8 g./l. of indole-3-acetic acid (IAA) showed a low growth rate and low root survival. Roots surviving toxic effects of IAA produced 1-7 laterals each; the laterals exhibited high meristematic activity. Lower concns. of IAA (10-9 and 10-10 g./l.) produced high initial acceleration in growth rate followed by progressive reduction after the 2d passage with no induction of laterals. Indole-3-butyric acid in concn. 10-7 g./l. induced laterals in all roots in passages 1 and 2. Roots and laterals that survived toxicity of this concn. showed high meristematic activity. One of 2 surviving roots in passage 7 had produced 169 laterals. Lower concns. showed less toxic effect, higher root survival, increased acceleration of growth rate and no inductions of laterals. With NAA. concn. 10-9 g./l., was lethal to all roots in passage 2. At 10-10 and 10-11 g./l. there was little evidence of toxicity, and acceleration in growth rate increased inversely with concn. At 10-11 g./l. of this particular growth substance acceleration in rate of growth was the highest with little or no evidence of toxicity.