Rice is one of the important food crops for human beings, with a long history of planting and consumption. Rice cultivation originated in China. After being widely planted in China, it gradually spread westward to India and into southern Europe in the Middle Ages. At present, half of the world's population eats rice, mainly in Asia, southern Europe and parts of tropical America and Africa. The total output of rice ranks third in the world, lower than corn and wheat, but it can feed a large number of people, so the United Nations designated 2004 as the "International Year of Rice". As rice is the main food crop of human beings, it is known that there may be more than 6.5438+0.4 million kinds of rice in the world, and scientists are still developing new rice varieties, so it is difficult to estimate the number of rice varieties. African rice and Asian rice are classified, but the simpler classification is based on the starch content of rice. Rice starch can be divided into straight chain and branched chain. The more amylopectin, the higher the viscosity after cooking.
Indica rice: about 20% is amylose. It belongs to viscosity. Indica rice originated in the subtropical zone, planted in tropical and subtropical areas, with short growth period and can mature many times a year in places with long frost-free period. After hulling, indica rice has a slender appearance and low transparency. Some varieties have red skins, such as Redmi from Jiangxi, China. After cooking, the rice is dry and loose. Usually used for radish cake, rice flour and fried rice. Japonica rice: The amylose content of japonica rice is less than 15%. Planted in temperate and cold regions, it has a long growing period and usually ripens only once a year. After hulling into japonica rice, the appearance is round, short and transparent (some varieties of rice have local white powder). Cooking characteristics are between glutinous rice and indica rice. The purpose is to eat rice in general. Glutinous rice: the content of amylopectin in the middle branch is close to 100%, and the viscosity is the highest. It is also divided into japonica glutinous rice and indica glutinous rice. The appearance of japonica rice is round and short, while that of indica rice is slender and white and opaque. Cooked rice is soft and sticky. Usually, japonica rice and glutinous rice are used for wine making and rice cakes. Eight-treasure porridge and zongzi are made of indica rice and glutinous rice. Rice plant profile
When rice leaves are tender, they look like weeds and grow flat. Farmers rely on the special ears and tongues of rice leaves to distinguish them. Spikes are spikes growing at both ends of rice leaf rings, and tongues are thin films growing on rice leaf rings. The veins of rice leaves are parallel, with obvious midvein in the center, which is green, and sometimes there is purple pigment on the midvein, edge or tip.
The roots of rice are beard-shaped, thin and short, and numerous. With the growth of rice, the number will be more and more, and the twigs will continue to grow next to the rice plants.
When rice becomes an ear of rice, an ear of rice will bloom about 200-300 rice flowers, and one rice flower will form a grain of rice. Rice fragrance has no petals, so it is difficult to see stamens and pistils. They are all protected by the inner and outer glumes of rice flowers. When rice is self-pollinated, the anthers on the stamens will be broken, and the pollen will be quite small, which will fall on the female powder next door with the wind and the sway of rice. It combines with the ovule in the ovary of female pollen and develops into germ, which is the main source of human consumption and intake of nutrition. Near the germ, there is a fleshy endosperm that will continue to increase, making the ovary increasingly hypertrophy. In appearance, you will see fine hairs on green rice, called rice awn.
From outside to inside, there are rice husk (glume), chaff layer (pericarp, seed coat and aleurone layer), embryo and endosperm. draw
Rice grows very fast, the longest one year, the fastest three to four months, from germination, flowering to fruiting. It takes only two or three days for rice seeds to sprout out of buds, and only three days for buds to pull out the first leaf. So in areas with mild climate, rice can be planted three times a year. When farmers choose rice seeds, they often soak them in water, and the lightly floating rice seeds will be eliminated, and the rest will be cultivated into rice seedlings. In the lower reaches of the Mekong River, there is a kind of rice (floating rice) that lives in the water. Its leaves grow with the rise of the water, and the longest can reach 8 meters. Vietnamese people call it devil rice (this kind of rice was first planted by Luoyue people in Baiyue, in the lower reaches of Mekong River, Red River, salween and Irrawaddy River). The northernmost limit of rice growth is Huma, Heilongjiang Province, China. However, the main planting areas are South China and Taiwan Province Province, which can be planted on the Lancang River Plateau above 2500 meters above sea level. Rice is also grown in Japan, the Korean Peninsula, Southeast Asia, South Asia, the Mediterranean coast of southern Europe, the southeastern part of the United States, Central America, Oceania and parts of Africa, as well as along the Yangtze River in northern China. In other words, rice grows almost everywhere except Antarctica.
According to statistics in 2003, the world rice output reached 589 million tons. The output of Asia alone is 534 million tons. The total paddy field area in the world can reach 6.5438+0.5 million square kilometers. At present, the largest rice exporter is Thailand.
According to the agricultural statistics database of FAO, the rice yield of each continent in 2005 is as follows: the regional rice planting area (hectare) and yield (rice, metric ton) are153,511755 614,654,895 Africa, respectively. 960 Asia135,657,614,556,0/kloc-0,8,828 Europe 565,249 3,235,900 North America and Central America 2,0610/0. 300 45 1, 300 south America 6,038,592 23,951,664 source: agricultural statistical database, and the output of major rice-producing countries are as follows: national rice planting area (hectare) output (rice, metric tons) Bangladesh1/kloc-0. 000 China 29,300,000184,254,000 India 43,000,000129,000,000 Indonesia1800,90/kloc-0. 000 1 0,989,000 Thailand10,200,000 27,000,000 USA1,352,88010,012,/.