Abscisic Acid Pretreatment Research Articles

Transport and metabolism of [214-C]abscisic acid in maize root

The tips of intact maize (cv. LG 11) roots, maintained vertically, were pretreated with a droplet of buffer solution or a bead of anion exchange resin, both containing [2(14)-C]abscisic acid (ABA). A significant basipetal ABA movement was observed and two metabolites of ABA (possibly phaseic acid and dihydrophaseic acid) were found. ABA pretreatment enhanced the gravireaction of 10 mm apical root segments kept both in the dark and in the light. The possibility that ABA could be one of the endogenous growth inhibitors produced or released by the cap cells is discussed.

Ultrastructural and cytochemical aspects of induced apogamy following abscisic acid pre-treatment of secondary moss protonema

Abscisic acid (ABA) treatment of secondary protonema of Physcomitrium pyriforme Brid in the presence of sucrose does not prevent cell division but results in shorter cells with vesicular cytoplasm and an accumulation of lipid. When transferred to sucrose medium without ABA and with low irradiance isodiametric intercalary cells are cut off which give rise to apogamous sporophytes either directly or after the formation of a small amount of callus. The organization of the cells leading up to the apogamous sporophyte is described. The cells initiating the sporophyte develop dense cytoplasm and the walls become labyrinthine and callosed, but they do not form any recognizable placenta. It is proposed that labyrinthine walls are a consequence of a perturbation of cell wall metabolism as growth changes from gametophytic to sporophytic. The use of the term "transfer cell" for this kind of cell is questioned and the need for a causal approach to the investigation of labyrinthine walls is stressed.

EFFECTS OF ABSCISIC ACID ON NUCLEOHISTONE AND HISTONE SYNTHESIS IN MAIZE COLEOPTILES

Effects of abscisic acid (ABA) on the melting point (Tm) of nucleohistones when melted at pH 7.0 in a low ionic buffer and at pH 8.2 in a high ionic buffer were investigated. ABA, when added in vivo, affected the Tm during the first 18 hours of ABA pretreatment neither at pH 7.0 nor at pH 8.2. Added in vitro ABA decreased the Tm of nucleohistones melted at pH 8.2 but had no effect at pH 7.0. Histone synthesis was not affected by ABA during the first 12 hours; after 24 hours a significant increase of synthesis above control was observed. It is concluded that ABA does not affect binding between DNA and proteins in the nucleohistone complex, nor has it a direct effect on histone synthesis.