Phytochrome-mediated phototropism in maize seedling shoots
M Iino1, W R Briggs, E Schäfer
1Department of Plant Biology, Carnegie Institution of Washington, 290 Panama Street, 94305, Stanford, CA, USA.
Planta
|November 22, 2013
Summary
Red and blue light induce mesocotyl curvature in maize seedlings, with red light activating specific photosystems. Far-red light influences curvature by altering phytochrome levels, suggesting complex light responses in plant phototropism.
Area of Science:
- Plant photobiology
- Plant physiology
- Phototropism research
Background:
- Maize (Zea mays L.) seedlings exhibit phototropic curvature in response to unilateral light.
- Red light (R) and blue light (BL) are known to influence plant growth and development.
- Phytochrome and its role in mediating light responses are critical in plant photomorphogenesis.
Purpose of the Study:
- To investigate the fluence-response curves for red and blue light-induced mesocotyl curvature in maize.
- To elucidate the role of photosystems and phytochrome in mediating phototropic responses.
- To understand the interaction between phototropism and gravitropism in coleoptile and mesocotyl development.
Main Methods:
- Unilateral irradiation of maize seedlings with red light (R) and blue light (BL) at varying fluences.
- Measurement of mesocotyl and coleoptile curvature 100 minutes after phototropic induction.
- Application of far-red light (FR) before and after phototropic induction, and use of a clinostat to negate gravitropic responses.
Main Results:
- Red light (R) and blue light (BL) induced positive mesocotyl curvature, with distinct fluence-response curves.
- R-induced curvature is mediated by R-sensitive photosystems, while BL responses are similar but require higher fluences.
- Far-red light (FR) modulated curvature by affecting phytochrome gradients, and clinostat experiments revealed distinct kinetic phases of curvature development.
Conclusions:
- Phototropic curvature of the maize mesocotyl is primarily induced by R-sensitive photosystems.
- Mesocotyl curvature in the second positive range is linked to gradients in the far-red-absorbing form of phytochrome (Pfr).
- Negative coleoptile curvature represents a gravitropic compensation mechanism for positive mesocotyl curvature.
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