The Biochemistry of Bakanae Fungus

Abstract

The abnormal internodal elongation appears when young plants are cultured in a definite concentration of gibberellin (GIB). In the previous paper it was reported that with GIB the auxin assays were negative such as avena standurd test, pea test, epinastic curvature of petioles. However, the authors found that the straight growth of various tissues isolated from young vigorously growing organs was promoted by floating on the solution containing GIB. In this report, the promoting effect of GIB is described on the straight growth of etiolated pea epicotyl sections, when compared with plant growth hormones such as indoleacetic acid (IAA), under various conditions: concentration, time-course of growth, pH, temperature, starvation in water, and addition of other substances. It is suggested that the stimulation due to GIB may be attributed to acceleration of water absorption. At suitable concentrations GIB has the stimulating effect comparable with at IAA a lower concentration (0.02 γ/cc) (Fig 2). The effects of a large number of substances were examined such as sucrose, amino acids, organic acids, and vitamins on the stimulation of GIB. Only tryptophan was found to have promoting effect and the following substances had depressing effect: L-hydroxyproline, DL-methionine, DL-proline, and nicotinamide (Table 7). With the section starved in water for about 19 hours at room temperature, IAA again gives marked stimulation, but GIB does not (Table 3). The stimulation due to GIB is not recovered when sucrose and phosphate are provided .(Table 5). By feeding of exogenous tryptophan, however, the effect of GIB is partly recovered (Fig. 5). Also it is suggested that the effect of GIB, as compared with that of IAA, depends mar-kedly on the endogenous growth of the section.

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