Auxin biological effects

The biological effects of the auxins are diverse and range from rapid effects, usually growth promotion and occurring within... 

The known biological effects of auxin are numerous. In addition to cellular elongation, apical dominance and root initiation, the more important effects include callus formation, parthenocarpy, phototropism and geotropism. 

Biogenic amines are a group of aliphatic, aromatic or heterocychc bases derived from amino acids, which exhibit a variety of biological effects, as they perform different functions in animal and plant tissues. Some biogenic amines are building materials for the biosynthesis of phytohormones of the auxin group, plant protoalkaloids (such as hordenine and gramine), true alkaloids and other secondary plant metabolites. In animal tissues they have the function of tissue hormones (e.g. histamine) and are precursors of adrenal hormones (catecholamines). 

Indole-3-acetic acid is rather readily oxidized by peroxidases and is, in fact, probably not present in the plant in the free form to any appreciable extent. The nature of the complexing groups is not clear. The inherent instability of the compound in living tissue has made experimental observations difficult, and (the more stable) 1-naphthaleneacetic acid has often been used instead, although it is by no means certain that the biological activities are comparable. One view held is that auxin herbicides are effective either because they do not readily form conjugate systems, or because the conjugate retains the phytotoxic properties. 

Three years after the publication of Buffel s paper, Matsui el al. announced the synthesis of F as a mixture of all of its possible stereoisomers, and found it to be biologically inactive. Thus, neither Matsui s 1966 synthesis of E nor his 1988 synthesis of F, both as stereoisomeric mixtures, yielded evidence to support the existence of auxin-b as a plant-growth promoter. We should, however, be careful enough to think about the possible effect of the wrong stereoisomers in the synthetic E and F. In pheromone perception, as we discussed in Chapter 4, there are some cases in which the opposite enantiomer of the natural pheromone strongly inhibits the bioactivity of the correct enantiomer. Especially in the case of... 

Some biological roles of auxins. The involvement of other hormones is indicated as (+) if the hormone has the same effect as auxin and (-) if it inhibits the auxin effect. Speed of response rapid (R), occurs in less than 1 hr intermediate (I), 1-24 hours slow (S), > 1 day. 

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... 

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