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A major factor in gravitropism in radish hypocotyls is the suppression of growth on the upper side of hypocotyls.

Abstract：

:The changes in length on the two opposite sides of etiolated radish (Raphanus sativus) hypocotyls prior to, and following gravitropic stimulation, were measured using an infrared-imaging system. It was observed that the growth suppression on the upper side began first at least 10 min after the onset of gravitropic stimulation, and after 30 min the acceleration in growth on the lower side started. The gravitropic curvature was steadily induced from 10 min. When radish hypocotyls were switched from a vertical to horizontal position for different durations and then replaced to the vertical position, the growth suppression on the gravity-stimulated (upper) side was observed in all cases, but the acceleration in growth on the opposite (lower) side appeared only in continuously gravity-stimulated seedlings, although it occurred later than the growth suppression on the upper side. These results suggest that the suppression in growth on the upper side of the hypocotyls is a direct effect of gravitropic stimulation, but not the acceleration on the lower side. When 4-methylthio-3-butenyl isothiocyanate (4-MTBI), which has an inhibitory activity against radish hypocotyl growth, was applied on the one side of radish hypocotyls and then the 4-MTBI-applied side or opposite side was placed in a horizontal position, the former showed greater bending than the control, suggesting that the growth suppression on the upper side is enhanced and maintained with MTBI application there. In the latter case, the seedlings showed less bending than the control, suggesting a decrease in growth on the lower side with MTBI application. All the results suggest that gravitropism of radish hypocotyls may be caused by an increase in growth-inhibiting substance(s) induced with gravitropic stimulation in the upper side, inducing growth inhibition there.

journal_name

J Plant Physiol

journal_title

Journal of plant physiology

authors

Tokiwa H,Hasegawa T,Yamada K,Shigemori H,Hasegawa K

doi

10.1016/j.jplph.2005.09.006

subject

Has Abstract

pub_date

2006-12-01 00:00:00

pages

1267-72

issue

eissn

0176-1617

issn

1618-1328

pii

S0176-1617(05)00352-4

journal_volume

163

pub_type

杂志文章

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A major factor in gravitropism in radish hypocotyls is the suppression of growth on the upper side of hypocotyls.