John R. Murray

Differential dihydroflavonol reductase transcription and anthocyanin pigmentation in the juvenile and mature phases of ivy (Hedera helix L.)

Juvenile-phase English ivy (Hedera helix L.) accumulates anthocyanin pigment in the hypodermis of stems and petioles, whereas mature-phase ivy does not. Lamina tissue of both phases of ivy accumulate flavonols, another class of the flavonoids, in response to sucrose and light treatment in vitro. However, juvenile- but not mature-phase lamina tissue accumulates anthocyanin in response to sucrose and light. The lack of anthocyanin accumulation in mature phase tissue is due to a lack of dihydroflavonol reductase (DFR) activity, which catalyzes a reaction late in the anthocyanin biosynthetic pathway. The objective of this work was to determine the level of regulation of gene expression that limits DFR activity in mature phase tissue. There was an induction of DFR transcription and accumulation of DFR mRNA in juvenile-phase lamina tissue treated with sucrose and light. In contrast, transcription and mRNA accumulation of DFR was not detectable in treated mature-phase lamina tissue. The induction of DFR transcription in juvenile tissue required the combination of sucrose and light. There was an induction of transcription of chalcone synthase, which catalyzes the first committed reaction of flavonoid biosynthesis, in both juvenile- and maturephase lamina tissue, indicating that mature-phase tissue is responsive to sucrose and light treatment.

Maturation and rejuvenation in woody species

In the development of all woody plants from seed there is a so-called juvenile phase lasting up to 30–40 years in centain forest trees, during which flowering does not occur and cannot be induced by the normal flower-initiating treatment or conditions. In time, however, the ability to flower is achieved and maintained under natural conditions; at this stage, the tree is usually considered to have attained the adult or mature condition. The length of the juvenile period can be influenced by environmental and genetic factors [20]. Maturation is distinct from aging as used by Wareing [47] to describe changes such as reduced growth rate and type of branching due to increased size and complexity of the tree, which disappear when a scion is grafted onto a young rootstock or when a stem cutting is rooted.

Effect of Ethanol on Absorption of Iron in Rats.

Conclusions Long or short term alcohol administration appeared to have no effect in normal healthy rats on either total body uptake or the isolated intestinal segment uptake of Fe59 in its ferrous or ferric form with the possible exception of the effect of long term alcohol on the segmental absorption of ferric Fe59.

Differential Competence for Adventitious Root Formation in Histologically Similar Cell Types

Shoot tissue formed during the protracted juvenile phase of woody perennials lacks the ability to flower. With the transition to the mature phase, shoot apices or axillary meristems of newly formed tissue gain the ability to flower and this ability is maintained in subsequently formed shoot tissue (Zimmerman, 1973, 1976). In addition to this phase-dependent difference in ability to form flowers, other persistent phenotypic differences exist between shoot tissue of the basal (i.e., juvenile) and apical (i.e., mature) portions of a plant (Hackett, 1985; Poethig, 1990). Due to the protracted nature of both the juvenile and mature phases of woody plants, phase-dependent phenotypic characters are stably expressed through a large number of cell divisions over years of growth within a phase. It is presumed that phase-dependent characters do not result from a genetic change, but result from an epigenetic difference in the capacity to express genes that permit or prevent expression of a phenotype.

Research on Adventitious Rooting: Where Do We Go from Here?

Agronomists, horticulturists and silviculturists have been eminently successful in manipulating rooting of cuttings of many species of plants using auxin treatments and various environmental variables in conjunction with a knowledge of the optimum stage of development of the mother plant for root initiation. Much of this success has come as a result of empirical research. However, even with this successful research effort, there are still many species, particularly in their mature phase of development, which cannot be successfully propagated from cuttings on a commercial scale. In these cases, a better understanding of the mechanisms that control the root initiation process might be useful in efforts to improve rooting.

The Effect of Achylia Gastrica in Rats on the Absorption of Dietary Iron

Summary Achylia gastrica induced in growing rats by X-irradiation of the exposed stomach led to iron depletion despite a normal diet. This implied that gastric secretion or acid was essential for the optimal assimilation of dietary iron by rats.

Effect of Intestinal Contents on Uptake of Radio-iron by Everted Rat Gut Sacs.

Summary Our observations suggest that there is a factor in the intestinal contents of feeding rats not present in fasting rats, which potentiates the uptake of Ferrous59 by everted gut sacs. This factor can be destroyed by heat. There is also a factor in fasting gastric juice other than acid which has a similar effect.

The Effect of Antigastric Mucosal Antibodies on Iron Absorption in Experimental Achylia Gastrica

Summary Absorption of 59Fe given with antibody to gastric mucosa, was studied in rats with and without induced gastric atrophy. Whereas mild but significant depression of absorption occurred in rats without gastric atrophy, profound depression occurred in rats with gastric atrophy. This reduction in absorption could be largely corrected by concurrent administration of normal gastric juice.