Hormonal Regulation of Genome Activity in Higher Plants

1979 ◽  
pp. 245-261 ◽  
Author(s):  
G. RAM CHANDRA ◽  
S. MUTHUKRISHNAN ◽  
E. S. MAXWELL
Keyword(s):  
Hormonal Regulation ◽  
Higher Plants ◽  
Genome Activity

The possible rôle of xanthoxin in plant growth and development

1978 ◽  
Vol 284 (1002) ◽  
pp. 499-507 ◽  
Keyword(s):  
Abscisic Acid ◽  
Hormonal Regulation ◽  
Growth And Development ◽  
Higher Plants ◽  
The Other ◽  
Regulatory Function ◽  
Root Tip ◽  
Root Tips ◽  
Root Primordia ◽  
Lateral Root Primordia

In higher plants, abscisic acid and xanthoxin are two potent growth regulators. Although similar properties in both substances have been demonstrated in several biological tests including biochemical interconversion of the substances, evidence is available that in the plant as a whole, xanthoxin has regulatory functions other than those of abscisic acid. Several environmental factors, such as water supply, photoperiod and low temperature, which affect growth and development also greatly change the level of abscisic acid in the plant; however, only small variations in the xanthoxin level have been observed in response to changes in the environmental conditions. On the other hand, a strong enhancement of the xanthoxin level can be induced when dark-grown seedlings are briefly illuminated; this treatment, however, has no influence on the abscisic acid level. This observation supports the hypothesis that light-induced inhibition of growth may be mediated by an increased formation of the growth inhibitor xanthoxin. Light-induced enhancement of the xanthoxin level may also contribute to the phototropic bending in dictyledonous seedlings. Evidence has been obtained from experiments in this laboratory that xanthoxin may be involved in the regulation of root branching. Decapitation of root tips causes a significant increase in the number of lateral root primordia. Chromatographic studies reveal the presence of two substances in the root, which, in a specific bioassay, are active inhibitors of the development of root primordia. The activity of these root inhibitors in the basal part decreases when the root tip is removed. They are probably produced in the root tip and are transported to the base. One of these inhibitors has been identified as xanthoxin, the other is cytokinin. The hormonal regulation of abscission is another process where xanthoxin may have a regulatory function. Senescent, abscinding petioles contain a factor called ‘senescence factor’ which promotes the abscission of leaves. In an attempt to identify its chemical nature, it was found that at least three different abscission accelerating substances, including xanthoxin, participate in the composition of the senescence factor.

Hormonal Regulation in Higher Plants

Science ◽  
1969 ◽  
Vol 163 (3873) ◽  
pp. 1288-1297 ◽  
Author(s):  
A. W. Galston ◽  
P. J. Davies
Keyword(s):  
Hormonal Regulation ◽  
Higher Plants

In vitro and in vivo polysaccharides assembly: ultrastructural and cytochemical study of growing plant cell wall components.

1978 ◽  
Vol 36 (2) ◽  
pp. 434-435
Author(s):  
D. Reis ◽  
B. Vian ◽  
J. C. Roland
Keyword(s):  
Cell Wall ◽  
Self Assembly ◽  
Plant Cell Wall ◽  
Higher Plants ◽  
Three Dimensional ◽  
Cytochemical Study ◽  
Wall Components

Wall morphogenesis in higher plants is a problem still open to controversy. Until now the possibility of a transmembrane control and the involvement of microtubules were mostly envisaged. Self-assembly processes have been observed in the case of walls of Chlamydomonas and bacteria. Spontaneous gelling interactions between xanthan and galactomannan from Ceratonia have been analyzed very recently. The present work provides indications that some processes of spontaneous aggregation could occur in higher plants during the formation and expansion of cell wall.Observations were performed on hypocotyl of mung bean (Phaseolus aureus) for which growth characteristics and wall composition have been previously defined.In situ, the walls of actively growing cells (primary walls) show an ordered three-dimensional organization (fig. 1). The wall is typically polylamellate with multifibrillar layers alternately transverse and longitudinal. Between these layers intermediate strata exist in which the orientation of microfibrils progressively rotates. Thus a progressive change in the morphogenetic activity occurs.

Localization of Adenosine Triphosphatase Activity in the Phleom of Nicotiana Tabacum

1972 ◽  
Vol 30 ◽  
pp. 230-231
Author(s):  
James Cronshaw ◽  
Jamison E. Gilder
Keyword(s):  
Plasma Membrane ◽  
Atpase Activity ◽  
Adenosine Triphosphatase ◽  
Higher Plants ◽  
High Surface ◽  
Root Tip ◽  
Animal Cells ◽  
Physiological Processes ◽  
Tip Cells ◽  
Atpase Localization

Adenosine triphosphatase (ATPase) activity has been shown to be associated with numerous physiological processes in both plants and animal cells. Biochemical studies have shown that in higher plants ATPase activity is high in cell wall preparations and is associated with the plasma membrane, nuclei, mitochondria, chloroplasts and lysosomes. However, there have been only a few ATPase localization studies of higher plants at the electron microscope level. Poux (1967) demonstrated ATPase activity associated with most cellular organelles in the protoderm cells of Cucumis roots. Hall (1971) has demonstrated ATPase activity in root tip cells of Zea mays. There was high surface activity largely associated with the plasma membrane and plasmodesmata. ATPase activity was also demonstrated in mitochondria, dictyosomes, endoplasmic reticulum and plastids.

A Scanning Electron Microscopic Study of Pro-Vascular Cellular Morphology in Chaetophora Incressata

1985 ◽  
Vol 43 ◽  
pp. 638-639
Author(s):  
A. E. Hotchkiss ◽  
A. T. Hotchkiss ◽  
R. P. Apkarian
Keyword(s):  
Green Algae ◽  
Vascular Plants ◽  
Vascular System ◽  
Higher Plants ◽  
Wall Structure ◽  
Electron Microscopic ◽  
Physiological Processes ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

Multicellular green algae may be an ancestral form of the vascular plants. These algae exhibit cell wall structure, chlorophyll pigmentation, and physiological processes similar to those of higher plants. The presence of a vascular system which provides water, minerals, and nutrients to remote tissues in higher plants was believed unnecessary for the algae. Among the green algae, the Chaetophorales are complex highly branched forms that might require some means of nutrient transport. The Chaetophorales do possess apical meristematic groups of cells that have growth orientations suggestive of stem and root positions. Branches of Chaetophora incressata were examined by the scanning electron microscope (SEM) for ultrastructural evidence of pro-vascular transport.

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