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8‐Epixanthatin, a light‐induced growth inhibitor, mediates the phototropic curvature in sunflower ( Helianthus annuus ) hypocotyls
Author(s) -
YokotaniTomita Kaori,
Kato Jun,
Yamada Kosumi,
Kosemura Seiji,
Yamamura Shosuke,
Bruinsma Johan,
Hasegawa Koji
Publication year - 1999
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1999.106310.x
Subject(s) - etiolation , phototropism , hypocotyl , helianthus annuus , sunflower , auxin , botany , chemistry , biology , horticulture , biochemistry , physics , blue light , enzyme , optics , gene
The distribution of the endogenous auxin‐inhibiting substance, 8‐epixanthatin, was determined in the lighted and shaded sides of phototropically‐stimulated, de‐etiolated sunflower ( Helianthus annuus L. cv. Taiyo) hypocotyls. From 40 min after the onset of phototropic stimulation, the growth rate at the lighted side was inhibited, whereas that at the shaded side showed no change. In the lighted side, 8‐epixanthatin increased by 20 min after the onset of unilateral illumination and, after 40 min, reached a 3‐fold larger concentration than that in the shaded side. Unilateral application of 8‐epixanthatin suppressed the growth of etiolated hypocotyls at the applied side only, causing the hypocotyls to bend at the site of application. It is concluded that phototropic curvature in sunflower hypocotyls is caused by a lateral gradient of the auxin‐inhibiting substance 8‐epixanthatin.