Cell wall auxin effect

Zimmerman, U., Steudle, E. Lelkes, P.I. (1976). Turgor pressure regulation in Valonia utricularis. Effect of cell wall elasticity and auxin. Plant Physiology, 58, 608-13. 

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). 

Auxin is known to stimulate proton secretion from the cytosol to the cell wall matrix. BR also does the same in cucumber hypocotyl sections as has been reported for other plant materials (16-20). When sections with the epidermis peeled off are incubated in a weakly alkaline buffer, the pH of the buffer drops considerably, indicating that protons are secreted from the tissue to the medium. BR at 10 nM and IAA at 10 iM are almost equally effective (Figure 5). The interaction of BR and IAA is rather inhibitory at the early period of incubation. However, proton secretion continues longer in the presence of both BR and IAA, and finally exceeds those by BR or IAA alone. BR behaves similarly to IAA in this effect. 

Auxins are also involved in so-called long term responses which may be more directly gene-mediated responses. Auxins stimulate and sustain mRNA and protein synthesis to form enzymes that catalyze the production of cell wall materials, sugars, and other cellular components. Applied lAA has induced mRNA and protein synthesis in Avena coleoptiles (16), yeast cells (17), pea stem sections (18), and bean endocarp (19). Artichoke tuber disks responded to exogenously applied lAA with growth and a substantial amount of new RNA and protein synthesis. When the metabolic inhibitors actinomycin D and 8-azaguanine were added simultaneously with lAA, effects of the auxin were negated (20). 

Auxin only induced growth in segments of rice coleoptile when the cell wall was rich in non-cellulosic D-glucose residues.The effect decreased with age and with the total amount of non-cellulosic polysaccharide present. A decrease in the relative amount of non-cellulosic D-glucose and an increase in the content of D-xylose residues were found in the growth cycle of cell walls of rice coleoptiles irrespective of the culture conditions. ... 

Baker, D.B. Ray, P.M. (1965a) Direct and Indirect Effects of Auxin on Cell Wall Synthesis in Oat Coleoptile Tissue , Plant Physiology, 40, 345-52... 

Baker, D.B. Ray, P.M. (1965b) Relation between Effects of Auxin on Cell Wall Synthesis and Cell Elongation , Plant Physiology, 40, 360-8 Barber, G.A. (1982) Observations on the Enzymatic Synthesis of a P 1,4 Glucan by a Soluble Preparation from Mung Bean (Phaseolus aureus). Archives of Biochemistry and Biophysics, 215, 253-9... 

Rosso, G.C., Masushige, S., Warren, C.D., Kiorpes, T. Wolf, G. (1976) The Anomeric Configuration of the D-Mannosyl Retinyl Phosphate Formed in Rat Liver Microsomes , Journal of Biological Chemistry, 251, 6465-7 Rubery, P.H. Northcote, D.H. (1970) The Effect of Auxin (2,4-dichloro-phenoxyacetic Acid) on the Synthesis of Cell Wall Polysaccharides in Cultured Sycamore Cells , Biochimica et Biophysica Acta, 222, 95-108... 

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... 

Sorokin HP, Mathur SN, Thimann KV (1962) The effects of auxins and kinetin on xylem differentiation in the pea epicotyl. Am J Bot 49 444-453 Stant MY (1961) The effect of gibberellic acid on fibre-cell length. Ann Bot 25 453-462 Stant MY (1963) The effect of gibberellic acid on cell width and the cell wall of some phloem fibers. Ann Bot 27 185-196... 

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