Language：English   Publishing type：Research paper (scientific journal)  

When maize coleoptiles were unilaterally exposed to red light (7.9 micromol m(-2)s(-1) for 5 min), 3 h after treatment IAA levels in coleoptiles decreased in all regions, from top to basal, with levels about 60% of dark controls. Localized irradiation in the 5 mm top zone was sufficient to cause the same extent of IAA reduction in the tips to that in the tips of whole irradiated shoots. When coleoptiles were treated with N-1-naphthylphthalamic acid (NPA), an accumulation of IAA in the tip and a decrease of diffusible IAA from tips were simultaneously detected. IAA accumulation in red-light treated coleoptiles by NPA was much lower than that of dark controls. NPA treatment did not affect the content of conjugated IAA in either dark or light treated coleoptile tips. When (13)C(11) (15)N(2)-tryptophan (Trp) was applied to the top of coleoptiles, substantial amounts of stable isotope were incorporated into free IAA in dark and red-light treated coleoptile tips. The ratio of incorporation was slightly lower in red-light treated coleoptile tips than that in dark controls. The label could not be detected in conjugated IAA. The rate of basipetal transport of IAA was about 10 mm h(-1) and the velocity was not affected by red light. These results strongly suggest that red light does not affect the rates of conversion of free IAA to the conjugate form or of the basipetal transport, but just reduces the IAA level in the tips, probably inhibited by IAA biosynthesis from Trp in this region.

PubMed

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.plantsci.2004.09.010

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Language：Japanese   Publisher：The Japanese Society for Chemical Regulation of Plants  

DOI： 10.18978/jscrp.37.2_183

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Language：Japanese   Publisher：The Japanese Society for Chemical Regulation of Plants  

The plant hormone auxin (indole-3-acetic acid (IAA)) plays important roles for response to external factors such as light and gravity. We reported that IAA was biosynthesized mainly at 0-2mm tip region and that the synthesized IAA was continuously transported to basal part in maize coleoptiles. It has been well investigated that IAA distribution rapidly changes at upper and lower side of the coleoptile within 20 minutes after gravi-stimulation. Here, we examined not only free IAA level in the tissues but also diffusible IAA level from upper or lower tip region after gravi-stimulation. The results revealed that flow direction mainly changed at 0-3mm tip region, not at 4-8mm region, indicating that apical zone was a main site for gravi-response, where IAA was transported to lower parts causing asymmetric IAA distribution throughout the coleoptile.

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Language：Japanese   Publisher：The Japanese Society for Chemical Regulation of Plants  

The plant hormone auxin (indole-3-acetic acid (IAA)) plays an important role in physiological responses such as gravitropism and phototropism. We reported that in maize coleoptiles the main site of IAA biosynthesis is 0-2mm tip region and the produced IAA moves constantly to the lower part. It has been reported that red light irradiation to the coleoptiles caused the reduction of the IAA level in the tip region and therefore the diffusible IAA from the tip to the lower parts was also decreased. In the present work, to investigate the mechanism(s) for the IAA reduction by red light irradiation we examined free and conjugated IAA levels, and rate of IAA transport. IAA was extracted by an improved method using Micro-Smash (TOMY) and determined with GC-SIM-MS. The results revealed that the red light did not cause any changes in the amount of conjugated IAA and the rate of polar transport, indicating that red light suppresses the rate of IAA biosynthesis in the coleoptile tip.

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Language：Japanese   Publisher：The Japanese Society for Chemical Regulation of Plants  

DOI： 10.18978/jscrp.38.2_159

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Language：Japanese   Publisher：The Japanese Society for Chemical Regulation of Plants  

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