Frequently asked questions?

This page contains the questions -- and answers -- that most people ask about rice, rice and people, rice research, and IRRI. 
Frequently asked questions about rice and IRRI

• Basic facts about rice

• Rice and people

• Rice research

• IRRI
  
  

Basic facts about Rice

Q. What is rice?

A. Rice is the common name for the genus Oryza. A kind of grass, rice grows best when submerged in water. It is the staple food for over half the world's population.


Q. What does the rice plant look like?
A. It resembles a weed, 2 to 5 feet tall, depending on the variety and depth of submersion. It has round, hollow, jointed stems, rather flat, sessile leaf blades, and a terminal panicle. The grain is produced on nodding panicles of spikelets.

Q. What does the rice grain look like?
A. It looks like a smooth glistening ovoid particle, emerald green in color (during ripening stage, however, it turns golden yellow). After it is milled, the kernel will appear shiny white in color.

Q. How many different kinds of rice are there?
A. There are about 120,000 varieties known to exist.

Q. Where and when did rice originate?
A. The origins of rice have been debated for some time, but the plant is of such antiquity that the precise time and place of its first development will perhaps never be known. It is certain, however, that the domestication of rice ranks as one of the most important developments in history, for rice is the longest, continuously grown cereal crop in the world. Botanical and linguistic evidence point to the early origin of domesticated rice along a broad arc from eastern India through Myanmar, Thailand, Laos, northern Vietnam, and into southern China.

The earliest and most convincing evidence for domestication of rice in Southeast Asia was discovered in 1966 at Non Nok Tha in the Korat area of Thailand. These remains have been confirmed as dating from at least 4000 B.C.

Q. What is rice bran?
A. The tan nutrient-rich outer layer covering a rice kernel. Rice bran has a sweet nutty flavor and is an excellent source of nutrients, minerals, and fiber. 

Q. What are the two types of starch found in rice?
A. Amylose and amylopectin. Amylose makes the rice separate and fluffy. Amylopectin, the waxy starch, gives rice a sticky consistency when cooked. 

Q. Where does rice grow?
A. Rice grows in the upland area, irrigated area, rainfed lowland area, and the flood-prone area. Rice is highly adaptable and can be grown even in diverse environments. 

Q. Describe irrigated rice.
A. Irrigated rice is grown in bunded, puddled fields with an assured water supply for one or more crops a year. Worldwide, 80 million hectares of irrigated rice (55% of the total area) produce about three quarters of all rice harvested. Average yields vary from 3 to 9 tons per hectare.

Q. Describe the upland area and its rice.
A. Many of the world's poorest farmers live in the uplands. Their farming systems are highly diverse, with tree products and livestock often making important contributions to family income. Most farmers still grow traditional varieties without using chemical inputs. More than 17 million hectares of upland rice are grown worldwide -- around 60% of them are in Asia.

Q. What about the rainfed lowland rice and its environment?
A. The rainfed lowland ecosystem covers 37 million hectares or about one-fourth of the world's total rice area. Rainfed-lowlands are heterogeneous in any single location, diverse across locations, and unpredictable everywhere. Hundreds of the world's poorest people depend on them for their livelihood. 

Q. Describe flood-prone rice and its environment.
A. Farmers in South and Southeast Asia grow approximately 10 million hectares of flood-prone rice, which account for nearly 88% of all such rice grown in the world. There are three major kinds of flood-prone rice: deepwater, which tolerates water depths of 50-l00 centimeters; floating, which can be found in water up to 400 centimeters deep; and tidal wetland, which can survive submergence, sometimes in salty water, for short periods. 

Q. What is a paddy?
A. A paddy is a field that is flooded with water. Rough rice is also called paddy rice. 

Q. What is rough rice?
A. Rough rice, or paddy rice, is a rice that has been harvested and threshed but still has its hull and bran.

Q. I have heard about japonica rice. What is it?
A. The japonica varieties have narrow dark green leaves, medium-height tillers, and short to intermediate plant height. It is usually grown in cooler subtropics and temperate climates, such as Japan, Portugal, Spain, USSR, Italy, and France. 

Q. What is indica rice?
A. The traditional indica rice varieties, widely grown throughout the tropics and subtropics, are tall and heavy tillering with long, narrow, light green leaves. 

Q. What is javanica rice?
A. Javanica rice belong to the japonica race of O. sativa, and thus are morphologically similar to japonicas. However, javanicas have wider and more pubescent (hairy) leaves. In addition, the grain frequently has hairlike awns. Varieties belonging to javanicas are grown only in Indonesia, in the rice terraces of the Philippines, and in the mountainous areas of Madagascar. 

Q. What is an accession?
A. An accession is a variety, a strain, or a bulk population registered at the national center and worth conserving.

Q. What do you refer to as the grain?
A. The grain is the ripened ovary and its associated structures such as the lemma, palea, rachilla, sterile lemmas, and the awn, if present. 

Q. What are the main components of the rice grain?
A. The rice grain, commonly called a seed, consists of the true fruit or brown rice (caryopsis) and the hull, which encloses the brown rice. Brown rice consists mainly of the embryo and endosperm. The surface of the seed contains several thin layers of differentiated tissues that enclose the embryo and endosperm.

Q. What are the parts of a hull?
A. The hull is composed of two modified leaves, the palea and lemma. They are held together by hooklike structures. The cells of the mature hull are highly lignified and brittle, with high concentration of silica. 

Q. What do you refer to as the embryo of the rice grain?
A. The embryo or germ is extremely small and is located on the ventral side of the caryopsis. It contains the embryonic leaves (plumule) and embryonic root (radicle), which are joined by a very short stem (mesocotyl). The plumule is enclosed by a cylinderlike protective covering, the coleoptile, and the radicle is ensheathed by a mass of soft tissue, the coleorhiza. The outer side of the embryo is enclosed by the aleurone layer.

Q. What is the endosperm?
A. Consisting of the aleurone layer and the starchy endosperm, it serves as food for the germinating embryo.

Q. What consists the vegetative organ of the rice plants?
A. The vegetative organs consist of roots, culms (stems), and leaves.

Q. What is a panicle?
A. The panicle is the terminal shoot of a rice plant that produces grain.

Q. What is a spikelet? 
A. A spikelet is a unit of the panicle, and consists of two sterile lemmas, the rachilla, and the floret (flower). Since rice has only one fully developed floret per spikelet, these terms are often used interchangeably.

Q. What is a tiller?
A. A tiller is any of the extra stems or culms in a rice plant that arise from its base. Varieties that have genetic capacity to put out many stems are referred to as "heavy-tillering" varieties.

Q. What is a ligule?
A. It is a small, papery, triangular structure at the base of the leaf blade of the rice plant.

Q. How can you distinguish a male from a female rice plant?
A. Rice is naturally a self-pollinating plant. It is self-fertilizing, that is, it has both male and female organs. To cross two varieties, you must normally remove the male parts from one variety and then fertilize it with pollen from the other.

Q. How do we get the grains from the rice plant?
A. In some countries, rice plants are harvested by a machine called a combine harvester. Most harvesting, however, is done by hand, using a knife or a sickle. Then the grain has to be separated from the straw in a process called threshing. 

Q. The rice we eat is always white but on the rice plant, and when drying on the road, it is golden in color. How do the grains change color from golden to white?
A. After the moisture content of the rice has been reduced due to sun drying, the milling process begins. A sheller removes the inedible hull from the rice. The bran is then removed from the brown rice by abrasion as the grains are forced to rub against one another.

Q. What are the methods of growing rice?
A. Transplanting and direct seeding.

Q. What is direct seeding rice?
A. It is a method of planting rice wherein the seeds are sown directly in an upland or lowland field.

Q. What is transplanting rice?
A. In transplanting rice, seedlings are first grown in seedbeds before they are transplanted in the fields.

Q. What are the three growth phases of the rice plant?
A. Vegetative, reproductive, and ripening.

Q. How do you characterize the vegetative stage?
A. It is characterized by active tillering (when shoots arise from the main culm or stem), gradual increase in plant height, and leaf emergence at regular intervals. 

Q. How do you characterize the reproductive growth stage?
A. It is characterized by culm elongation (which increases plant height), decline in tiller number, emergence of the flag leaf (the last leaf), booting, heading, and flowerings.

Q. How do you characterize the ripening stage?
A. It is characterized by leaf senescence and grain growth.

Q. In the reproductive growth stage, what do you refer to as the booting?
A. During the latter part of the panicle development stage (about 16 days after visual panicle initiation), the sheath of the flag leaf swells. This swelling of the flag leaf sheath is called booting.

Q. What about the heading stage?
A. It is the emergence of the panicle out of the flag leaf sheath.

Q. What about flowering?
A. The flowering stage occurs when the anthers of the terminal spikelets protrude and shed pollen. It occurs 25 days after visual panicle initiation regardless of the variety.

Q. Ripening involves three stages; what are these?
A. These are the milky grain stage, the dough grain stage, the yellow-ripe grain stage, and the mature grain stage.

Q. How do you describe the milky grain stage?
A. The contents of the caryopsis (the starch portion of the grain) are first watery but later turn milky in consistency. When held upright, the top of the panicle during milk stage will bend gently in an arc. The content of the grain is a white liquid that can be squeezed out.

Q. What about the dough grain stage?
A. It is when the milky portion of the grain turns first into a soft and later hard dough.

Q. And what about the mature grain stage?
A. The grain color in the panicles begins to change from green to yellow. The individual grain is mature, fully developed, and is hard and free from green tint. The mature grain stage is complete when 90-100% of the filled spikelets have turned yellow. The panicle arches further with the exception of a few still green spikelets and all grains are yellow and hard.

Q. Does climate affect rice yields?
A. Temperature, solar radiation, and rainfall influence rice yield by directly affecting the physiological processes involved in grain production, and indirectly through diseases and insects.

Q. How long will it take to produce one variety of rice?
A. By conventional breeding method, it will take 5 to 10 years to develop one variety of rice but with biotechnology as a tool, an outstanding variety can be developed within 1 to 2 years.

Q. How long does it take to produce a rice crop, from beginning to end?
A. The duration depends upon the maturity of the rice being produced. It takes about 90 to 200 days for a rice crop to mature.

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