Wheat coleoptile test

Rothwell and Wain (126) have isolated in crystalline form a growth inhibitor from Lupinus luteus (yellow lupine) pods which they have partially characterized. Analytical data suggested that the inhibitor possessed the characteristics of an unsaturated hydroxyketo acid. Inhibition in the wheat coleoptile cylinder test was obtained with concentrations of 0.25 to 1.0 p.p.m. 

In 1989 Cutler et al.1 reported the isolation of 3,7-dimethyl-8-hydroxy-6-methoxyisochro-man (1) from Penicillium corylophilum and demonstrated that it inhibited etiolated wheat coleoptiles at 10-3 and 1(T4M, as did the acetoxy (2) and methoxy (3) derivatives (Figure 5.1).2 The Parent compound had originally been isolated from moldy millet hay implicated in the death of cattle,3 but the metabolite had not been tested in plants. Because of the encouraging results obtained in the wheat coleoptile bioassay, isochromans 1,2, and 3 were assayed on greenhouse-grown bean, com, and tobacco plants. The methyl ether exhibited the greatest herbicidal activity in all the plants treated, while the parent and its acetoxy derivative were active only on corn. 

A novel fungal metabolite, hydroxyterphenyllin (242) from Aspergillus candidus found in unbleached flour was shown to be an active inhibiting ingredient when tested in wheat coleoptile bioassays at 10 3 - 10-5M. Terphenyllin (244, 245) was also identified from the same source but was less active (at 10 % ). ... 

The strucure-activity response is even more subtly expressed in the etiolated wheat coleoptile (Triticum aestivum L. Wakeland) that has been described in detail elsewhere (13) Subtle modifications in structure cause marked changes in the inhibitory responses induced (Table I). With the exception of 15-acetoxy-T- 2-tetraol, neosolaniol and isoneosolaniol which are inactive at lO M (Fig. 2l, all of the trichothecenes so far tested are active at 10" M. A further one-third are active at 10"°M and the most potent, which are active at 10" M, are verrucarins A and J, and trichoverrin B, Neosolaniol, which inhibits 100% at 10" and 61% at 10" M has an acetate at C15 while isonesolaniol, which has an hydroxyl group at C15 inhibits coleoptiles 80 and 51% at 10" and 10"3, respectively. 

Wheat coleoptile tissue test values assigned based on the minimum concentrations of F. qraminearum metabolites that resulted in significant decreases (P=0.05 or 6.01) in growth of the tissue after 20h exposure. 

Planet, and, microbial responses with the sucroae esters. In addition to the above we have conducted experiments on the effects of the sucrose esters on plants and microorganisms and we report these data for the first time. However it should be reiterated that the sucrose esters were composed of acetic (C2) 2- and 3-methylbutyric (C5) and 3-methylvaleric (C6) acids and only the glucose molecule was ester if ied the fructose portion remained in the free hydroxyl state. Also the sucrose esters were extremely difficult to separate so that mixtures were initially obtained and tested. We shall see in the wheat coleoptiles bioassay that as the number of 3-methylvalerate residues decreases in the glucose moiety so the level of biological activity decreases at the 10 4 M level though in all cases there is 100Z inhibition at 10 3 m (Figure 7). 

The simple test system with wheat coleoptiles made it possible to extensively study how chemical structure influences activity. It was found that an auxin (or antiauxin) had to have ... 

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