WordNet

(botany) the act of causing a plant to develop without chlorophyll by growing it without exposure to sunlight; "the etiolation of celery"
a pale and sickly appearance; "his etiolation signaled years in prison"
the act of weakening by stunting the growth or development of something; "the etiolation of the critical tradition"
(especially of plants) developed without chlorophyll by being deprived of light; "etiolated celery" (同)etiolated, blanched
bleach and alter the natural development of (a green plant) by excluding sunlight
make pale or sickly; "alcohol etiolates your skin"
make weak by stunting the growth or development of

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(光をあてずに)〈植物〉‘を'白く生長させる

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/07/06 11:43:57」(JST)

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Spanish Bluebells Hyacinthoides hispanica, showing both leaves and flowers in both etiolated and non-etiolated states. The longest etiolated leaves are about 50 cm long

Etiolation /iːtɪəˈleɪʃən/ is a process in flowering plants grown in partial or complete absence of light.^[1] It is characterized by long, weak stems; smaller leaves due to longer internodes; and a pale yellow color (chlorosis).

Effects

Etiolation increases the likelihood that a plant will reach a light source, often from under the soil, leaf litter, or shade from competing plants. The growing tips are strongly attracted to light and will elongate towards it. The pale color results from a lack of chlorophyll.

Some of the changes that occur include:

elongation of stems and leaves;
weakening of cell walls in stems and leaves;
longer internodes, hence fewer leaves per unit length of stem;
chlorosis, a pale yellowish-white coloration.

De-etoliation is the transition of seedlings from below-ground growth to above-ground growth form.^[2]

Causes

Elongation is controlled by the plant hormones called auxins, which are produced by the growing tip to maintain apical dominance. Auxin diffuses, and is transported, downwards from the tip, with effects including suppressing growth of lateral buds.^[3] Auxins are active in light; when they are active they stimulate proton pumps in the cell wall which increases the acidity of the cell wall and activates expansin (an enzyme that breaks bonds in the cell wall structure) that weaken the cell wall and allow the cell to expand.^[4]

Chloroplasts that have not been exposed to light are called etioplasts (see also plastids).

De-etiolation

De-etiolation, on the other hand, is a series of physiological and biochemical changes a plant shoot undergoes in response to sunlight. This process is also known informally as greening. The changes triggered in the plant shoot all occur in preparation for photosynthesis.^[5]

Some of the changes that occur include:

Inhibition of hypocotyl lengthening.
Stimulation of cotyledon expansion.
Opening of the apical hook, see: Seedling's photomorphogenesis and etiolation for details.
Stimulation of synthesis of anthocyanins.
Stimulation of chloroplasts development from etioplasts.

This process is regulated by the exposure of various photoreceptor pigments to light. Phytochrome A and phytochrome B both respond to an increasing proportion of red light to far-red light which occurs when the shoot comes out into the open. Cryptochrome 1 responds to increasing amounts of blue light when the shoot reaches the surface.^[6]

References

^ Burgess, Jeremy (1985). An Introduction to Plant Cell Development. CUP Archive. p. 55. ISBN 0-521-31611-1. Retrieved 2011-01-17.
^ "PHOTOMORPHOGENESIS". photobiology.info. Retrieved 2016-02-11.
^ Whippo, CW; Hangarter, RP (2006). "Phototropism: Bending towards enlightenment". The Plant cell 18 (5): 1110–9. doi:10.1105/tpc.105.039669. PMC 1456868. PMID 16670442.
^ Purves, William K.; Sadava, David; Orians, Gordon H. (2004). Life: The Science of Biology. Volume III: Plants and Animals. Macmillan. p. 745. Retrieved 2011-01-17.
^ "Biology 7th Edition" Campbell and Reece (2004)
^ "Plant Physiology 4th Edition" Taiz and Zeiger (2006)

External links

Etiolation

English Journal

FHY3 promotes shoot branching and stress tolerance in Arabidopsis in an AXR1-dependent manner.

Stirnberg P, Zhao S, Williamson L, Ward S, Leyser O.SourceDepartment of Biology, University of York, Wentworth Way, York YO10 5DD, UK.
The Plant journal : for cell and molecular biology.Plant J.2012 Sep;71(6):907-20. doi: 10.1111/j.1365-313X.2012.05038.x. Epub 2012 Jun 28.
The transposase-related transcription factor FAR-RED ELONGATED HYPOCOTYL3 (FHY3) promotes seedling de-etiolation in far-red light, which is perceived by phytochrome A (phyA). In this role, FHY3 indirectly mediates the nuclear import of light-activated phyA, which triggers downstream transcriptional
PMID 22540368

The cyclophilin ROC1 links phytochrome and cryptochrome to brassinosteroid sensitivity.

Trupkin SA, Mora-García S, Casal JJ.SourceIFEVA, Facultad de Agronomía, Universidad de Buenos Aires and CONICET, 1417-Buenos Aires, Argentina Fundación Instituto Leloir, Instituto de Investigaciones Bioquímicas de Buenos Aires-CONICET, C1405BWE Buenos Aires, Argentina.
The Plant journal : for cell and molecular biology.Plant J.2012 Sep;71(5):712-23. doi: 10.1111/j.1365-313X.2012.05013.x. Epub 2012 Jul 6.
Although multiple photoreceptors converge to control common aspects of seedling de-etiolation, we are relatively ignorant of the genes acting at or downstream of their signalling convergence. To address this issue we screened for mutants under a mixture of blue plus far-red light and identified roc1
PMID 22463079

FtsHi1/ARC1 is an Essential Gene in Arabidopsis that Links Chloroplast Biogenesis and Division.

Kadirjan-Kalbach DK, Yoder DW, Ruckle ME, Larkin RM, Osteryoung KW.SourceDepartment of Plant Biology, 612 Wilson Road, Room 339, Michigan State University, East Lansing, MI 48824 USA Michigan State University-Department of Energy Plant Research Laboratory, 612 Wilson Road, Room S206, and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824 USA.
The Plant journal : for cell and molecular biology.Plant J.2012 Aug 18. doi: 10.1111/tpj.12001. [Epub ahead of print]
The Arabidopsis arc1 (accumulation and replication of chloroplasts 1) mutant has pale seedlings and smaller, more numerous chloroplasts than wild type. Previous work has suggested that arc1 affects the timing of chloroplast division but does not function directly in the division process. We isolated
PMID 22900897

Japanese Journal

Or mutation leads to photo-oxidative stress responses in cauliflower (Brassica oleracea) seedlings during de-etiolation

Journal of plant research 126(6), 823-832, 2013-11
NAID 40019863766

極晩生エダマメ「安房在来15A2」における莢色と食味関連要素及び食味官能評価との関係

千葉県農林総合研究センター研究報告 (5), 1-9, 2013-03
NAID 120005594564

畦畔と本圃の遮断処理によるリンドウこぶ症の抑制

北日本病害虫研究会報 (62), 89-92, 2011-12
NAID 120005580223

Effect of Ascorbic Acid and Etiolation on Antioxidant Enzyme Activity and Phenylpropanoid Metabolism during Shoot Regeneration from Cut Ends of Tomato Stems