Oryza sativa, rice

Back to top

Taxonomic lineage

cellular organisms - Eukaryota - Viridiplantae - Streptophyta - Streptophytina - Embryophyta - Tracheophyta - Euphyllophyta - Spermatophyta - Magnoliophyta - Liliopsida - commelinids - Poales - Poaceae - BEP clade - Ehrhartoideae - Oryzeae - Oryza - Oryza sativa

Back to top

Brief facts

• Rice is a staple food for a large part of the world's human population, especially in East and Southeast Asia, making it the most consumed cereal grain in the world.
• Oryza sativa is a semiaquatic plant whose growth, at both the seedling and adult stages, is well investigated. It is cultivated in five ecosystems where the source of water supply and the degree of flooding are the major environmental determinants. The rice types corresponding to these ecosystems are rain-fed low- and upland rice, rice grown under controlled irrigated conditions, deepwater rice, and rice in tidal wetlands.
• The oldest archeological evidence of rice use by humans that has been found in the middle and lower Yangzi River Valley in China is dated to 11,000 - 12,000 BC.
• There are two distinct types of domesticated rice, Oryza sativa, or Asian rice and Oryza glaberrima, African rice, both of which have unique domestication histories. Oryza sativa is divided into two distinct groups: indica and japonica, which were distinguished as early as in records of the Chinese Han dynasty (approx. 100 AD). The antiquity of the divergence between indica and japonica has been estimated at more than 100,000 years ago. This date far precedes domestication (approx. 8,000 years ago or earlier), supporting independent domestication of the two species.
• Rice is the cereal that has been selected to be sequenced as a priority. It has the smallest genome of all the cereals: 430 million nucleotides (~40-fold smaller than genome of wheat).
• The indica genome contains 466 million base pairs. This is nearly four times larger than the genome of Arabidopsis thaliana.
• Rice has a relatively large number of genes: somewhere between 43,000 and 63,000 genes.
• The indica strain has relatively short genes that are on average about 4,500 base pairs long. The average human gene is about 72,000 base pairs long.

Back to top

Developmental stages (life cycle)

Rice varieties can be categorized into two groups: the short-duration varieties which mature in 105-120 days and the long-duration varieties which mature in 150 days.

• seed stage MeSH
  • dormant seed
  • germinating seed MeSH
• vegetative
  • emergence stage 0
  • seedling MeSHstage 1; this stage continues for up to 30 days: from seedling emergence until beginning of tillering
  • tillering stage 2; growth of shoots (tillers) that sprout from the base of a grass; 30-60 days affter seedling emergence
  • stem elongation stage 3; accelerated internodal growth of the stem before panicle initiation; this stage is more pronounced in long-duration varieties of rice; maximum tillering, stem elongation, and panicle initiation occur almost simultaneously in short-duration varieties
• reproductive
  • booting stage 4; 20-25 days before flowering; at this stage panicle initiation and formation occur as indicated by a bulge at the base of the leaf sheath
  • heading stage 5; panicle emergence
  • flowering stage 6; flowering starts approx. 85-110 days after emergence and takes 6-10 days
• ripening stages 7-9; the rice kernel reaches its maximum length in 12 days, its maximum width in 2 days, its maximum thickness in 28 days, and its dry weight in 35 days after flowering
• mature stage 9; 107-120 days after emergence; harvest-ready

Back to top

Definitions

Plant Components

• panicle inflorescence, head; terminal shoot of a rice plant that produces grain
• spike also called ear; elongated inflorescence with stalkless flowers arranged along an axis
  • spikelet small or secondary spike, with a number of reduced flowers each subtended by one or two scale-like bracts

Back to top

References

• Robert V, Le Goff G, Ariey F, Duchemin JB. A possible alternative method for collecting mosquito larvae in rice fields. Malar J. 2002 Apr 8;1:4.

  Copyright © 2002 Robert et al; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.

  

  General view of rice fields at the end of rainy season in Madagascar.

• Suzaki T, Ohneda M, Toriba T, Yoshida A, Hirano HY. FON2 SPARE1 redundantly regulates floral meristem maintenance with FLORAL ORGAN NUMBER2 in rice. PLoS Genet. 2009 Oct;5(10):e1000693.

  In wild-type rice, a single pistil derived from congenitally fused carpels develops into a floret, and a single ovule is formed in the pistil. After fertilization, a single seed is formed within the husks, which are derived from the palea and lemma in a floret

• Potera C. U.S. rice serves up arsenic. Environ Health Perspect. 2007 Jun;115(6):A296.

  

  Arsenic and new rice. Cotton pesticides still contaminate fields now used for food crops.

• Itoh J. et al. Rice plant development: from zygote to spikelet. Plant Cell Physiol. 2005 Jan;46(1):23-47. Epub 2005 Jan 19.
• Kende H. et al. Deepwater rice: A model plant to study stem elongation. Plant Physiol. 1998 Dec;118(4):1105-10.
• Sweeney M, McCouch S. The complex history of the domestication of rice. Ann Bot. 2007 Nov;100(5):951-7.

Websites

• Rice Developmental stages
• Wikipedia: Rice
• Growth Stages of the Rice Plant

Back to top