Control and Kinetics of Branch Root Formation in Cultured Root Segments of Haplopappus ravenii

Abstract

(8) with the zinc concentration reduced by a factor of 10, 3% w/v sucrose, 0.1 mg/l of NAA, 100 mg/I of myoinositol, 0.2 mg/l of glycine, 0.5 mg/l of nicotinamide, 0.5 mg/l of pyridoxine, 0.5 mg/l of thiamine, and 0.1 mg/l of p-aminobenzoic acid. Cultures were grown in 250-ml Erlenmeyer flasks with 50 ml of medium, or in 125-ml Erlenmeyer flasks with 20 ml, on a reciprocating shaker (108 strokes/min, stroke amplitude 2 cm) in dim (5 ft-c) light at 25 to 28 C. During the 3-week subculture period, branches formed on inoculated segments, and the branches extended 2 to 4 cm in length. These branches did not form secondary branches within the 3-week subculture period. Segments (1-cm long) cut from the branches in a 3-week-old culture were used as inocula, either for subculturing or, after rinsing with distilled water, in experiments. Three to five segments were used per flask.Assessment of Results. In most of the experiments reported here, the number of branches initiated in a given time interval was the response measured. Segments were generally harvested 1 Abbreviations: NAA: ca-naphthalene acetic acid; BA: benzyladenine.www.plantphysiol.org on May 11, 2018 -Published by Downloaded from

Effects of plant growth regulators on acetylene-reducing associations between Azospirillum brasilense and wheat

“…From this association we conclude that the effect of auxins such as 2,4-0 for wheat seedlings grown hydroponically is to create a niche in which azospirilla can grow. Most auxins have the ability to increase the number of lateral or adventious roots and among these NAA is very effective (Blakely et al, 1972). In our results, although IAA applied at higher concentration gave responses morphologically similar to NAA, the resultant acetylene reduction rates were usually lower and variable.…”

The Effect of Indol-3YL-Acetic Acid Concentration on Cycling and Quiescent Cells in the Apical Meristem of Excised Roots ofPisum SativumL.

“…Thus, treatment of radish (Raphanus sativus) roots with IAA stimulates cell division in a limited number of pericycle cells, which eventually results in the formation of lateral roots (WEBSTER and RADIN 1972). Similar results have been obtained in experiments carried out to investigate the effects of naphthaleneacetic acid (NAA), an IAA-like hormone, on the formation of lateral roots in Haplopappus ravenii (BLAKELY, RoDAWAY, HoLLEN and CROKER 1972). On the other hand, NAA treatments can block the onset of DNA synthesis in the nuclei of lateral bud promeristems of Tradescantia paludosa following removal of the terminal bud (NAYLOR 1958), and treatments with high concentrations of IAA reduce mitotic index and extend the duration of the mitotic cycle in roots of Vicia faba MACLEOD and DAVIDSON 1966).…”

Functions of Hormones at the Cellular Level of Organization

“…Inhibition of root growth by GA has been reported by BURSTROM (1960), BUTCHER andSTREET (1960a, b), and by MANOS (1961). Others have found no effect of physiological concentrations of GA on root elongation (BLAKELY et al 1972, SVENSSON 1972 and, in a few cases (PALEG 1965, MERTZ 1966, FONNESBECH 1972, enhancement of root growth by GA has been reported. That the effect of GA on root elongation is variable is an indication that its action is dependent on other factors such as light, auxin content, inhibitor levels, etc.…”