WordNet

(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
(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"

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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）』「2015/02/17 15:18:33」(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, sparser 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.

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.^[2] Auxins are not 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.^[3]

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.^[4]

Some of the changes that occur include:

Inhibition of hypocotyl lengthening.
Stimulation of cotyledon expansion.
Opening of the apical hook.
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.^[5]

References

^ Burgess, Jeremy (1985). An Introduction to Plant Cell Development. CUP Archive. p. 55. ISBN 0-521-31611-1. Retrieved 2011-01-17.
^ 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

Phytochrome a function in red light sensing.

Franklin KA1, Whitelam GC.
Plant signaling & behavior.Plant Signal Behav.2007 Sep;2(5):383-5.
Light signals perceived by the phytochrome family of red (R) and far-red (FR) light-absorbing photoreceptors direct plant growth and development throughout their lifecycle. In contrast to other family members, phyA displays rapid light-induced proteolytic degradation upon conversion to the biologica
PMID 19704607

Promotion of photomorphogenesis by COP1.

Boccalandro HE1, Rossi MC, Saijo Y, Deng XW, Casal JJ.
Plant molecular biology.Plant Mol Biol.2004 Dec;56(6):905-15. Epub 2005 Apr 7.
CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) represses photomorphogenesis in darkness by targeting nuclear-localized transcription factors to proteasome-mediated degradation. Upon light exposure, COP1 migrates to the cytosol allowing photomorphogenesis to proceed but the residual nuclear pool down-regulat
PMID 15821989

Elongated mesocotyl1, a phytochrome-deficient mutant of maize.

Sawers RJ1, Linley PJ, Farmer PR, Hanley NP, Costich DE, Terry MJ, Brutnell TP.
Plant physiology.Plant Physiol.2002 Sep;130(1):155-63.
To begin the functional dissection of light signal transduction pathways of maize (Zea mays), we have identified and characterized the light-sensing mutant elm1 (elongated mesocotyl1). Seedlings homozygous for elm1 are pale green, show pronounced elongation of the mesocotyl, and fail to de-etiolate
PMID 12226496

[The input of the chemical potential gradient of the water in the medium to the energy balance of terrestrial vascular plants].

Zialalov AA1, Avduevskiĭ ML.
Zhurnal obshcheĭ biologii.Zh Obshch Biol.2000 Mar-Apr;61(2):173-80.
One of the characteristic feature of activity of plant organism vital functions is a speed of its inner water flow. The main source of energy providing the transport of water is gradient of water chemical potential between soil and atmosphere. In case of equal potentials of these surroundings, the p
PMID 10778391

Japanese Journal

ロックウール・ポット水耕装置によるトウモロコシ栽培について

窪田文武 [他],田中典幸,有馬進,牧山繁生
日本作物學會紀事 60(1), 42-46, 1991-03-05
根系処理に対する植物体の生育反応を観察,測定するための実験手法としてロックウール・ポット水耕装置を創出した.本装置は, ロックウール・ブロックを挿入した鉄製ポットと水耕液槽から成る. ポットの水耕液槽への着脱は容易であり, また,植物体もポットごと容易に移動できる. ここでは,水耕液に木村氏A液を使用し, トウモロコシの栽培実験を試みた. 発芽後10日を過ぎると葉の黄化現象がみられたが,水耕液のM …
NAID 110001732735