Rice refers to the seeds without rice husk removed, which belongs to the common rice subspecies in the subgenus of Gramineae common cultivated rice in botany. Humans have identified 22 kinds of rice, but the only one used for bulk trade is ordinary rice. China is one of the countries with the longest history of rice cultivation and the richest rice genetic resources. The ancient cultivated rice specimens unearthed from Yuchanyan site in Shouyan Town, Dao County, Hunan Province, confirm that China has been cultivated for more than 6.5438+0.4 million years, and it is the known origin of cultivated rice in the world.

Rice refers to the seeds without rice husk removed, which belongs to the common rice subspecies in the subgenus of Gramineae common cultivated rice in botany. Humans have identified 22 kinds of rice, but the only one used for bulk trade is ordinary rice. China is one of the countries with the longest history of rice cultivation and the richest rice genetic resources. The ancient cultivated rice specimens unearthed from Yuchanyan site in Shouyan Town, Dao County, Hunan Province, confirm that China has been cultivated for more than 6.5438+0.4 million years, and it is the known origin of cultivated rice in the world.

Rice husk:

It consists of four parts: inner glume, outer glume, glume guard and glume tip (glume tip is elongated into awn). The outer glume is slightly longer and larger than the inner glume; The inner glume and the outer glume are rolled up along the edge into hooks, which hook each other to cover the caryopsis and play a protective role. There are needle-like or hook-like hairs on the surface of glume, and the density and length of hairs vary with varieties, and some varieties have smooth glume without hair. Generally speaking, the villi of indica rice are thin and short and scattered on glume noodles. Japonica rice has many hairs and dense edges, which gradually increase from the base to the top, and the hairs at the top are longer than those at the base.

So the surface of japonica rice is generally rougher than that of indica rice. The thickness of glume is 25-30μm, and the glume mass of japonica rice accounts for about 18% of the grain mass. The quality of indica rice glume accounts for about 20% of rice quality. The thickness and quality of glume are related to the type, variety, cultivation and growth conditions, maturity and fullness of rice. Generally mature and full, glume shell is thin and light. The glume of japonica rice is thinner than that of indica rice, with loose structure and easy to stand out. The glume of early rice is thinner and lighter than that of late rice.