Poster: Hormones

Abs # 575: Indole-3-acetic acid biosynthesis in various organs of squash plant

Presenter:	Tsurusaki, Ken-ichi , k-tsuru@fuhc.fukuyama-u.ac.jp
Authors	Tsurusaki, Ken-ichi  (A)
Affiliations:	(A): Dept. Environment & Information Science, Fac. Human Cultures and Sciences, Fukuyama Univ.

Recently, it has been reports that the biosynthesis of idole-3-acetic acid (IAA) is converted form indole-3-acetaldoxime (IAox) via indole-3-acetnitrile (IAN), although it is not clear that the first precursor of IAA is tryptophan (Trp) or not. We previously reported that IAA was converted from IAox via rather indole-3-acetaldehyde (IAAld) than IAN in etiolated seedling roots of squash (Rajagopal et al 1993). In this report, I investigated IAA biosynthesis in the various organs of squash plants. Squash plants were grown in 1/5-strength HoaglandÕs nutrient solution at 25.5¡C under white light for 12 h per day in about 2 weeks to get the green leaves and the tendril, or under continuous dark condition in 3 days to get the etiolated hypocotyls. Exogenous IAA promoted the elongation of the petiole segments of young green leaves of squash and the etiolated segments of hypocotyls. IAAld similarly promoted that of those segments. However, IAN, stimulating the elongation of barley coleoptile segments as same as IAA, did not promoted that of those segments. Also high concentration of exogenous Trp, stimulating elongation of barley coleoptile segments, did not promoted that of those segments. Moreover, IAA and IAAld were strongly stimulated the tendril coiling of squash, although Trp and IAN only slightly stimulated. Further, IAA concentrations of any organs of these experiments were similar levels. These results implied that IAN was not main intermedeate of IAA biosynthesis, and that Trp independent pathway existed in the various organs of squash plants. Rajagopal R, Tsurusaki K, Kuraishi S and Sakurai N (1993) Plant Physiol (Life Sci. Adv.) 12:17-26