Auxins plant cell-wall growth

How IAA can elicit profound changes in the size and form of a plant is totally unknown. At the cellular level it is known that the plant cell walls must be "softened" for growth promotion to occur (cf. 18J. Such effects, however, may be concomitants of growth and not the "primary" effects of auxin (19). 

One of the ways in which auxin could affect MTs is through a control of their dynamic instability and turnover rates [53], the latter being characteristically rapid in plant cells [54]. We suggest that such effects could allow a swift alteration of auxin level to act as a potent morphogenetic factor since an auxin-related intervention into the pattern of MT assembly (Fig. 1), if confined only to certain cells, or even certain walls of a cell (or cells), might be sufficient to invoke a new structural framework for subsequent growth and... 

The phenylpropanoid pathway (Fig. 3.1) is responsible for the production of many natural products that are of interest in the context of plant growth and development, human health, and ecology. For example, flavonoids are necessary for pollen viability in maize and petunia, and have been suggested to play a role in directed auxin transport. Flavonoids and sinapate esters have been found to be important UV-protectants in many species, including Arabidopsis. Furthermore, wall-bound phenolics are thought to impart control over cell wall expansion, and hydroxycinnamic acids are an important structural component of the hydrophobic barrier polymer suberin. Finally, lignin is a phenylpropanoid polymer ubiquitous in higher plants, which is necessary for mechanical support and water transport. " ... 

Mondal MH (1975) Effects of gibberellic acid, calcium, kinetin, and ethylene on growth and cell wall composition of pea epicotyls. Plant Physiol 56 622-625 Morgan PW, Gausman HW (1966) Effects of ethylene on auxin transport. Plant Physiol 41 45-52... 

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