Release of cotyledonary shoots of pea (Pisum sativum) seedlings from inhibition as related to endogenous zeatin and ethylene and exogenous IAA and benzyladenine

Abstract

This paper deals with apical dominance using a dicotylar model obtained after decapitation of pea seedlings with two shoots -one dominant and the other inhibited. When the dominant shoot was decapitated the inhibited one is released from inhibition and after 24 to 72 h begins to grow. However, the levels of trans-zeatin and production of ethylene increase within 4 and 6 hours respectively after release from inhibition, and within an interval of 72 h the levels of both phytohormones begin gradually to decrease. This indicates that also in this model, the release from apical dominance is associated with an increase in the level of cytokinin zeatin and, thereafter, also with an increased production of ethylene. If indolyl-3-acetic acid (IAA) is applied on the decapitated main stem after decapitation of the dominant shoot, the growth of the initially inhibited one is very strongly retarded; if, however, IAA is applied on the decapitated dominant shoot, this inhibition is significantly weaker. This means that the inhibiting effect of IAA on the inhibited shoot originates to a greater degree from the main stem rather than from the dominant shoot. The effect of benzyladenine (BA) is transferred equally from the decapitated main stem and from the decapitated dominant shoot because the initially inhibited shoot begins to grow as well as also other shoots from serial cotyledonary buds.

Estimation of ethylene production and 1-aminocyclopropane-1-carboxylic acid in plants by means of gas chromatography

“…Radin and Loomis (1969) observed an inhibiting effect of ethylene (2-3 µl/1) on the formation of lateral roots in radish (Raphanus sativus var. radicola), Dimasi-Theriou et al (1993) recorded an increase in number of adventitive roots at the concentration of ethylene 0.01-10 µl/l when regenerating petunia (Petunia hybrida) leaves, and/or Burg (1968) mentioned that a majority of physiological reactions took place within the range of 0.01-1.0 µl/l of volume concentration of ethylene] it is possible, when using a suitable experimental layout, to obtain a response in the order of nanolitres (Fišerová et al 2006(Fišerová et al , 2007.…”