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United States Department of Agriculture

Agricultural Research Service

Title: Antagonistic But Complementary Actions of Phytochromes a and B Allow Optimum Seedling De-Etiolation

Authors
item Smith, H - UNIV LEICESTER, UK
item Xy, Y - USDA/UCB PGEC
item Quail, Peter - USDA/UCB PGEC

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 1997
Publication Date: June 1, 1997
Citation: Smith, H., Xy, Y., Quail, P.H. 1997. Antagonistic but Complementary Actions of Phytochromes A and B Allow Optimum Seedling De-Etiolation. Plant Physiology 114(2):637-641.

Interpretive Summary: Using dichromatic radiation, we show that the actions of phytochromes A and B (phyA and phyB) in Arabidopsis thaliana are antagonistic in mediating red and farred radiation effects on seedling deetiolation and yet act in a complementary manner to regulate deetiolation, irrespective of spectral composition. The antagonistic and complementary actions of phyA and phyB allow the optimum regulation of seedling growth after emergence from the soil.

Technical Abstract: Using dichromatic radiation, we show that the actions of phytochromes A and B (phyA and phyB) in Arabidopsis thaliana are antagonistic in mediating red and far-red radiation effects on seedling de-etiolation and yet act in a complementary manner to regulate de-etiolation, irrespective of spectral composition. At low phytochrome photoequilibria inhibition of hypocotyl extension was strong, because of the action of a far-red high-irradiance response mediated by phyA. At high phytochrome photoequilibria inhibition of hypocotyl extension was also strong, because of the action of phyB. At intermediate photoequilibria hypocotyl inhibition was less strong. In their natural environment, this dual action will strongly retard hypocotyl growth and promote cotyledon opening and expansion both in open daylight and under dense vegetation. Overlapping action by phyA and phyB will substantially promote de-etiolation in sparse vegetation. The antagonistic and complementary actions of phyA and phyB, therefore, allow the optimum regulation of seedling growth after emergence from the soil.

Last Modified: 7/31/2014
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