Using appropriate clinostat rotation methods, it has been shown that increases in root growth and geotropic curvature of oat coleoptiles are related to and explained (within the limits of auxin economy) by increased rates of plant respiration imparted by nullification of the gravitational stimulus. Increased respiration with decreased gravitational stimulus, in turn, is explained by increased u...

Research on the mode of action of auxin in the promotion of growth has shown that auxin treatment leads to hydrogen ion secretion and wall acidification. It has recently been reported that auxin stimulates cell wall beta-galactosidase activity in Avena coleoptiles, presumably by causing cell wall acidification, since the pH optimum for the enzyme is about 5.0. It has been suggested that enhance...

It has been repeatedly observed since early times that if stems from some of our common woody plants are girdled, adventitious roots may be formed above the girdle. Although this regeneration phenomenon may result in part from an interruption of food transport, recent evidence indicates that the regeneration is controlled by hormones w^hich are transported in the phloem. The greater part of the...

Phytochrome A (phyA) mRNA abundance decreased rapidly in total RNA samples isolated from 4-day-old etiolated oat seedlings following a red light pulse. Putative in vivo phyA mRNA degradation products were detectable both before and after red light treatment. Cordycepin-treated coleoptiles were unable to accumulate the chlorophyll a/b-binding protein mRNA in response to red light, indicating tha...

The primary walls of epidermal cells in Avena coleoptiles ranging in length from 2 to 40 mm. have been studied in the electron and polarizing microscopes and by the low-angle scattering of x-rays. The outer walls of these cells are composed of multiple layers of cellulose microfibrils oriented longitudinally; initially the number of layers is between 10 and 15 but this increases to about 25 in ...

Introduction In an earlier publication (2) a comparison was made of the growth regulating activites of various compounds as indicated by the elongation of sections of Avena coleoptiles. From this comparison it was seen that the substitution of various halogen atoms in the phenoxyacetic acid (POA) structure increased its effect on elongation except when both ortho positions were occupied. Also, ...