Synthesis and activity of another seleniated auxin: 2,4-dichlorophenylselenoacetic acid

in Plant Growth Regulation (2003), 40(3), 197-200

The synthesis of 2,4-dichlorophenylselenoacetic acid (2,4-D-Se) may be completed in three steps starting from 2,4-dichloroaniline. The selenium is inserted in the molecule by reaction of a diazonium salt ... [more ▼]

The synthesis of 2,4-dichlorophenylselenoacetic acid (2,4-D-Se) may be completed in three steps starting from 2,4-dichloroaniline. The selenium is inserted in the molecule by reaction of a diazonium salt with potassium selenocyanate. 2,4-D-Se has been tested as an auxin in several bioassays including the regeneration of somatic embryos, adventitious root formation and the associated temporary increase of endogenous auxins at the induction phase, and callus formation, and compared with the natural auxin indoleacetic acid (IAA), the classical synthetic auxin(s) naphthaleneacetic acid (NAA) and/or 2,4-dichlorophenoxyacetic acid (2,4-D), and with the synthetic seleniated IAA, 3-(benzo[b] selenienyl) acetic acid, BSAA. These biological assays classified 2,4-D-Se together with BSAA among the most powerful synthetic auxins. The role of selenium is briefly discussed. [less ▲]

Concepts in plant stress physiology. Application to plant tissue cultures

in Plant Growth Regulation (2002), 37(3), 263-285

Because the term stress is used, most often subjectively, with various meanings, this paper first attempts to clarify the physiological definition, and the appropriate terms as responses in different ... [more ▼]

Because the term stress is used, most often subjectively, with various meanings, this paper first attempts to clarify the physiological definition, and the appropriate terms as responses in different situations. The flexibility of normal metabolism allows the development of responses to environmental changes which fluctuate regularly and predictably over daily and seasonal cycles. Thus every deviation of a factor from its optimum does not necessarily result in stress. Stress begins with a constraint or with highly unpredictable fluctuations imposed on regular metabolic patterns that cause bodily injury, disease, or aberrant physiology. Stress is the altered physiological condition caused by factors that tend to alter an equilibrium. Strain is any physical and/or chemical change produced by a stress, i.e. every established condition, which forces a system away from its thermodynamic optimal state. The paper secondly summarises the Strasser's state-change concept which is precisely that suboptimality is the driving force for acclimation (genotype level) or adaptation (population level) to stress. The paper continues with the actual knowledge on the mechanisms of stress recognition and cell signalling. Briefly: plasma membranes are the sensors of environmental changes; phytohormones and second messengers are the transducers of information from membranes to metabolism; carbon balance is the master integrator of plant response; betwixt and between, some genes are expressed more strongly, whereas others are repressed. Reactive oxygen species play key roles in up- and down-regulation of metabolism and structure. The paper shows finally that the above concepts can be applied to plant tissue cultures where the accumulating physiological and genetical deviations (from a normal plant behaviour) are related to the stressing conditions of the in vitro culture media and of the confined environment. The hyperhydrated state of shoots and the cancerous state of cells, both induced under conditions of stress in in vitro cultures, are identified and detailed, because they perfectly illustrate the stress-induced state-change concept. It is concluded that stress responses include either pathologies or adaptive advantages. Stress may thus contain both destructive and constructive elements: it is a selection factor as well as a driving force for improved resistance and adaptive evolution. [less ▲]

Changes in peroxidase activity, and level of phenolic compounds during light-induced plantlet regeneration from Eucalyptus camaldulensis Dehn. nodes in vitro

in Plant Growth Regulation (2001), 33(3), 215-219

Node cultures of Eucalyptus camaldulensis Dehn in Petri dishes in vitro under darkness in the presence of an auxin developed meristematic agglomerates (4 to 6 diameter), i.e. dense shoot clusters in which ... [more ▼]

Node cultures of Eucalyptus camaldulensis Dehn in Petri dishes in vitro under darkness in the presence of an auxin developed meristematic agglomerates (4 to 6 diameter), i.e. dense shoot clusters in which outgrowth of numerous successive buds is limited. Similar cultures under a 16 photoperiod produced small green plantlets with reduced leaves often presenting white hypertrophied lenticels and very short roots crowning the stem bases. The use of half-litre glass vials under light allowed direct development of well-developed rooted plantlets, either in the presence of the same auxin or in the presence of a cytokinin. Light favoured an increase in phenolic compounds and a reverse variation of peroxidase activity during the culture cycles. These aspects are discussed in terms of a possible regulation of the endogenous auxin level through a light control of peroxidase activity and the level of phenolic compounds. [less ▲]

Control of Dioscorea alata microtubers dormancy and germination by jasmonic acid

in Plant Growth Regulation (1999), 27(2), 113-117

Effects of appling exogenous jasmonic acid (JA) on the germination of Dioscorea alata L. microtubers were examined on Murashige and Skoog (MS) medium. Microtuber germination was promoted by JA (0.1 and 1 ... [more ▼]

Effects of appling exogenous jasmonic acid (JA) on the germination of Dioscorea alata L. microtubers were examined on Murashige and Skoog (MS) medium. Microtuber germination was promoted by JA (0.1 and 1 µM) supplemented to the culture medium but higher concentrations (30 and 100 µM) completely inhibited germination. When these inhibited microtubers were transferred to hormone-free medium, germination resumed. After transfer to greenhouse conditions, almost all plants (95%) from tubers previously cultivated on MS medium with 100 µM JA survived and all acclimatized plants had produced tubers after 8 months. It is concluded that depending on JA concentration, both the germination and dormancy processes in D. alata microtubers were affected. The release from dormancy is easily obtained by transferring dormant microtubers to hormone-free medium. [less ▲]

Atypical metabolisms and biochemical cycles imposing the cancerous state on plant cells

in Plant Growth Regulation (1998), 24(2), 135-144

The biological, morphological and biochemical characteristics which define plant cancer cells at the end of a neoplasic progression in the absence of pathogens and which distinguish them from tumorous ... [more ▼]

The biological, morphological and biochemical characteristics which define plant cancer cells at the end of a neoplasic progression in the absence of pathogens and which distinguish them from tumorous cells are summarized. Such plant cancer cells have in common with animal cancer cells many metabolic disturbances. The present paper reviews the biochemical changes in nitrogen, carbon, sugar and heme metabolisms which contribute to polyamine (PAs) accumulation. It indicates how these changes are interconnected and even form between each other biochemical cycles which likely maintain these cells in their irreversible state. The role of these cycles in the maintenance of such cells under a probable permanent oxidative stress is debated. [less ▲]