Plant growth screening

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. 

Synthesis and Screening. One of the key problems for industry is the question "How does one screen for new plant growth regulants " (8). In the case of herbicides and insecticides, they either work or they don t. The field effects of plant growth regulators are harder to see, predict or test for. 

The first plant bioassay [Avena sativa L (oat) coleoptile test] was employed by F.W. Went in the 1920 s to demonstrate the existence of and to quantitatively assess the first growth-modifying substance [indole-3-acetic acid (IAA)] isolated from plants.122 Plant bioassays have been extremely useful and intimately linked to the discovery and characterization of the major classes of plant hormones. In fact, many of the bioassays used now were developed for PGRs. Bioassays have been used to screen, evaluate phytotoxicity or plant growth promotion, study mode... 

Chloro-2-thenyl-tri- -butylphosphonium Chloride. Quite active in screening tests and in small-sized plot tests, this plant growth regulant (13) did not show suflBcient activity in larger-scale tests to remain an active product candidate. 

Bulky ketones such as diaryl ketones can be also reduced by biocatalysts. For example, a rice plant growth regulator, (S )-N-isonicotinoyl-2-amino-5-chlorobenzhy-drol, was prepared by microbial reduction of 2-amino-5-chlorobenzophenone with Rhodosporidium toruloides followed by isonicotinoylation as shown in Fig. 15-42(a)1243). A phosphodiesterase 4 inhibitor was also prepared by microbial reduction of a diaryl ketone 9 with Rhodotorula pilimanae, which was found by the screening of 310 microbial strains [Fig. 15-42(b)][244. ... 

In vitro pre-screens do not show up many compounds with plant growth regulator (PGR) potential. Many companies now consider PGRs as uneconomical and this may actually be an advantage. 

Arahidopsis has become the model system of choice in which to study many aspects of plant growth, development, and metabolism, including the biosynthesis of phenylpropanoid natural products. This is, in part, because Arabidopsis accumulates two classes of phenylpropanoid end products that are good targets for mutant screens. For example, many screens have identified mutants defective in fiavonoid biosynthesis. Defects in this pathway in Arahidopsis lead to transparent testa (tt) and transparent testa glabrous (ttg) phenot3Tjes that result from decreases in the condensed tannins found in the seed coat. These mutants have already been exhaustively reviewed, and hence will not be covered here. 

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