Th. Gaspar

Thigmomorphogenesis inBryonia dioica: Changes in soluble and wall peroxidases, phenylalanine ammonia-lyase activity, cellulose, lignin content and monomeric constituents

Rubbing young internodes ofBryonia dioica results in a reduced elongation and an increased diameter of the internodes. In the present study activities of some enzymes involved in the lignification process and levels of lignification were compared in rubbed and non-rubbed internodes. Rubbing caused an increase in the activities of phenylalanine ammonia-lyase and soluble and ionically- and covalently-bound cell wall peroxidases. Sensitivity of the covalently-bound wall peroxidase assay was markedly increased if syringaldazine was used as a substrate. Mechanical perturbation induced an increase in lignin, lignin monomer (sinapylic, coniferylic and p-coumarylic alcohols) content and the number of lignifying vessels. Conversely, rubbing resulted in a decrease in cellulose content. The hypothetical interpretation of the thigmomorphogenetic response through cell wall lignification and hence rigidification is consistent with all the presented results. A comparison is possible between this accelerated lignification and induced lignification as a mechanism of disease resistance. the thigmomorphogenetic response inBryonia dioica can be considered as a mechanism of resistance in order to withstand further environmental mechanical perturbation.

Peroxidase activity and endogenous free auxin during adventitious root formation

That endogenous free auxin has a central role in the process of adventitious root formation is generally accepted [27, 28, 35,46,49, 61]. The concept however has been developed more from the observation that exogenously applied auxins invariably induce the formation of a greater number of roots per cutting than other chemicals, than from established correlation between the auxin content or the auxin variation of cuttings and their rootability. In the mind of many plant physiologists, the exogenously supplied auxins, whatever synthetic, simply grow the bulk of endogenous auxins and act in a similar manner. This concept is out of date, as clearly shown on the one hand by the relationships between exogenous and endogenous auxins in cell cultures [52, 64], and on the other hand by recent analyses of the fate of exogenously supplied auxins in cuttings [7, 68]. The cell signaling eventual role of exogenous auxins supplied to cuttings thus has seldom been distinguished from the role of the endogenous ones. Literature concerning the estimation of endogenous auxin levels at the time of cutting excision in relation with their rooting capacities or concerning the variation of the levels in the course of adventitious rooting was until recently very discrepant [15,36]. First, there were relatively few studies using unequivocal physico-chemical techniques of auxin analyses. Second, it was not clearly stated what developmental stage of rooting was sampled (induction preceding cell reactivation and division, organization of the primordia, growth of the newly formed roots), nor was the physiological condition of the stock plant taken into consideration.

Protective enzymatic systems against activated oxygen species compared in normal and vitrified shoots of Prunus avium L. L. raised in vitro

Vitrification of shoots of Prunus avium L. L. was induced and expressed in a four week in vitro multiplication cycle simply by replacing agar by gelrite. The first vitrification symptoms were visible from the 7th day on. Enzymatic antioxidants were compared weekly in crude extract of normal (on agar) and vitrifying (on gelrite) shoots. The activity of superoxide dismutase was higher in vitrifying shoots. The other enzymes (gaîacol-peroxidase, catalase, ascorbate peroxidase, mono- and dehydro-ascorbate reductases, glutathione reductase) had lower activities. Increased superoxide dismutase activity might mean hydrogen peroxide accumulation and decreased activities of the other enzymes, deficiency in its detoxification. The question therefore is raised whether the hyperhydric morphological abnormalities result from the accumulation of toxic oxygen forms. Vitrification is often considered as a morphological response to several stresses. Contrary to most plants which adapt themselves to stresses by increasing all the above defence enzymes, in vitro shoots under vitrifying conditions appear unable to react in a similar manner.

A comparative biochemical and cytological characterization of normal and habituated sugarbeet calli

Habituated sugarbeet callus examined by means of a light-microscope is characterized by absence of differentiated tracheary elements and of the reaction with syringaldazine. Habituated tissues also were found to exhibit low guaiacol- and syringaldazine-peroxidase activities, a deficiency of lignin as well as lower cellulose, dry mass and chlorophyll contents as compared to the normal auxin-requiring callus. These histological and cytological features led to consider this habituated callus as a vitrified tissue under stress. The question of a relationship between vitrification and habituation is posed.

Sequential rooting media and rooting capacity of Sequoiadendron giganteum in vitro. Peroxidase activity as a marker

The rooting capacities of tips of seedling, juvenile and mature shoots of Sequoiadendron giganteum were compared on different rooting media (inductive and expressive media) after passage on an elongating medium. None of the cuttings rooted when continuously kept on medium containing the auxin NAA and vitamin D2. Peroxidase activity of all those cuttings on NAA+D2 first increased during the 7–9 first days and decreased in the days after. Rooting was obtained by transfer of the cuttings after periods longer than 7–9 days from the NAA+D2 inductive medium to a basal medium supplemented or not with rutin (expressive medium). The rooting capacity was emphasized by rutin treatment and was in correlation with the peroxidase peak reached on the NAA+D2 medium. Seedlings, characterised by the highest peroxidase activity, were most performing in rooting.

Modifications des Isoperoxydases et de l'Allongement des Entre-Noeuds de Bryone à la Suite d'Irritations Mécaniques

Summary Rubbing young internodes of Bryonia dioica plants significantly decreases their elongation. Old internodes which do not grow anymore do not react to the mechanical stimulus. The initial response to rubbing is very rapid. It is followed by important modifications at the level of pith cells, as shown by anatomical data. Analysis of soluble and cell wall bound peroxidases of irritated and control internodes indicates rapid changes in soluble and ionicallybound cell wall basic (cathodic) peroxidases, with the appearance of an additional isoenzyme. Changes in acidic (anodic) peroxidases are more progressive and similar to those occurring along internodes increasing in age. This, joined with previous observation, leads us to correlate the growth effect with an auxin catabolism mediated by the basic peroxidases. Further increase of the acidic enzymes is associated with an increase in pith cells diameter, joined to the decrease in length. Thigmomorphogenesis in Bryonia dioica thus appears as an accelerated senescence process.

Vitrification of carnation in vitro: changes in cell wall mechanical properties, cellulose and lignin content

Vitrification of internodes of carnation was brought about by culturing in liquid medium. Cell wall extensibility of these internodes was kinetically followed in comparison to that of normal plants using the constant stress method. Liquid culture induced increased immediate and total deformation capacities of the walls from the second day. Measurements indicated that these deformation capacities involved plastic properties rather than elastic ones. These changes were paralleled by decreased relative levels of cellulose and lignin.

Calcium-controlled peroxidase secretion by sugarbeet cell suspensions in relation to habituation

Sugarbeet cells from normal and habituated callus released peroxidases in liquid cultures, in proportion to their endogenous level. Calcium promoted this release more in the normal than in the habituated line. Treatment of the cells with sodium azide, sodium hydrogenarsenate or phenothiazine inhibited the calcium effect, which indicated a dependence on metabolic energy and on calmodulin regulation. The Ca ionophore Ro (bromolasalocid ethanolate) restricted peroxidase release.

Occurrence, titration and enzymatic degradation of 3- (3-indolyl)-acrylic acid in Lens culinaris med. extracts

Abstract Indolylacrylic acid (AIAcryl) was identified as the main auxin in lentil root extracts. A sensitive and specific method has been developed for the quantitative determination of AIAcryl at a concentration as low as 10 -7 M. The AIAcryl level in lentil roots increases with increasing age of the seedlings. The compound is enzymatically destroyed by a crude lentil root extract and the reaction shows two optimum pH. Purified horseradish peroxidase also destroys AIAcryl. AIAcryl destruction by fractions obtained from Sephadex filtration of the crude lentil extract parallels the occurrence of IAA-oxidase and peroxidase activities in the fractions.

Vegetative multiplication of sugarbeet through in vitro culture of inflorescence pieces

In vitro vegetative multiplication of sugarbeet was obtained by culturing of inflorescence explants. Subapical segments or 5-mm-long tips from nine varieties developed axillary shoots (up to 50 per tip) on a medium containing indolebutyric acid (IBA) and benzylaminopurine (BAP). Zeatin was ineffective as cytokinin. Gibberellic acid (GA3) enhanced the process. Such vegetative shoots were subsequently isolated and were each allowed to develop up to 20 supplementary axillary shoots on a multiplication medium containing IBA, BAP, and naphthaleneacetic acid (NAA). Rooting of shoots was obtained in the absence of growth regulators and plants were established.