Bioassay plant growth regulator

Naphthalene Acetic Acid and Naphthalene Acetamide. Naphthalene acetic acid [26445-01-2] (38) is historicaHy one of the first plant growth regulators. Reports concerning its activity in crops and plants have been a subject in much of the eady Hterature (57). Consequently, it has been used as a starting matedal for other compounds, eg, vide infra Sevin. Naphthaleneacetamide [31093-43-3] (39) has been used as a standard matedal to evaluate abscission pnor to 1953 and its effect on apple drop was reported in 1953 (58). The substance is used as an internal standard in the abscission bioassay (59). 

The results presented here demonstrate that these approaches can be applied to Potamogeton sp. and Hydrilla verticillata. In both assay systems, typical responses to known plant growth regulators were observed in most cases. The unique response of P.nodosus to ABA however, clearly shows the importance of not relying solely on "classical" bioassays. 

Cutler, H. G. 1984. A fresh look at the wheat coleoptile bioassay. Proceedings of the 11th Annual Meeting of the Plant Growth Regulator Society of America, pp. 1-9... 

Since the use of techniques to measure IAA, bioassays have been important to discover PGR activity of many other compounds. Several bioassays for the PGR gibberellic acid (GA3) have been developed. One bioassay was based on reduction of amaranthin levels in Amaranthus caudatus (tassel flower) seedlings.63 This method was sensitive to GA3 from 0.01 to 1 mg L"1. GA3 was also bioassayed, based on anthocyanin reduction in tomato (Lycopersicon esculentum L.).62 Reduction of anthocyanin in tomato seedlings was linear from 10"5 to 10 mg L 1, and thus, this latter plant bioassay method was more sensitive. A multitude of bioassays for nonvolatile and volatile plant growth regulator compounds have been developed and their uses and limitations have been discussed.129 Since many allelochemicals have been shown to have relatively weak phytotoxicity (especially compared to herbicides), some of these bioassays that have been developed for detecting and quantitatively measuring PGR activity may be useful in allelopathy. 

Elakovich, S. D. 1995. Bioassay methods applied to allelopathic herbaceous vascular hydrophytes. Proc. Plant Growth Regul. Soc. Amer. pp 39-43... 

Mangnus, E. M., Stommen, P. L. A., and Zwanenburg, B. 1992. A standardized bioassay for evaluation of potential germination stimulants for seeds of parasitic weeds. J. Plant Growth Regul. 11, 91-98... 

Yopp, J. H., Aung, L. H., and Stefens, G. L. 1986. Bioassays and other special techniques for plant hormones and plant growth regulators. Plant Growth Regulat. Soc. Amer. 208 p. 

Different Activities of Several Brassinosteroids in Two Bean Internode Tests. It is a well-known phenomenon that structurally closely related plant growth regulators exhibit different orders of activity in different bioassays. This makes it difficult to define the criteria of specificity of their hormonal action. The same situation exists in the case of BRst, and it can be documented by the comparison of different BRst in the two bioassays. 

Several diterpenes present in tobacco plants were evaluated by Cutler (240) for growth-regulating activity in wheat coleop-tile bioassays. Except for isodihydroabienol and B-levantenolide, all of the endogenous tobacco diterpenes showed growth inhibition of the wheat coleoptiles at concentrations of 10 3m or less (Table 14). 

In a search for safer biodegradable plant growth substances that may have potential uses in agriculture, particularly for crop production, our laboratory has developed some new bioassay systems to screen various plants for growth-regulating activity. Our screening efforts resulted in the discovery of both growth promoters and inhibitors. 

While ethylene has been known as a major modulator of plant growth and development for nearly a century [1], extensive studies on its mode of action came later than was the case for most other growth regulators. To a significant extent this was for two reasons firstly it was difficult accurately to measure ethylene production by plants and bioassays were tedious and complicated and secondly because there was some resistance to even recognising ethylene as a hormone, partly because of its small size and simplicity, but largely because it is a gas and did not therefore fit easily with classical conceptions of a hormone. 

Some lines of evidence point to other, non-indolic, natural products that may also act as auxins in plant tissues. Some are as yet unidentified chemically, others (like phenylacetic acid) act as auxins in bioassays, occur in plant tissues, but have not been shown to play a role in natural growth regulation. Also some other hormones, such as the gibberellins, have at least weak auxin activity. Interpretation of the importance of substances such as these will have to await the development of specific chemical methods of analysis which are at least as sensitive as the relatively non-specific bioassays now employed out of necessity. 

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