6th Grade - Science

LESSON PROBLEM: Biology: How does a grass seedling grow to a rice plant? And how does it develop grains that are ready for processing?


STUDY GUIDE

Rice, a grass in the genus Oryza, is a perennial plant. This means that the plant will continue to grow for more than two years. However, rice farmers in the U. S. replant their rice fields each year. Replanting the rice produces much greater yields of the rice grain. In some parts of the world, such as Southeast Asia, where there is a long growing season, farmers may get three harvests from the same rice plant. In rice growing areas of the most southern part of the United States, Texas and Louisiana, the rice farmer is able to harvest two crops of rice from the same plant. These "extra" crops are called ratoon crops. Ratoon means to sprout again.

In the United States, when the time for planting comes in early spring, the seeds will be sown into the soil. The first thing that will come up will be the sheath of the stem. The root system also begins to extend. Leaf blades will begin to grow off of the young stem, called the plumule. Each leaf is made up of a blade with an outer sheath. The leaf will have both a ligule and an auricle. These two structures distinguish rice leaves from those of other grasses.

Nodes and internodes grow along the stem of the rice plant. A leaf and a bud sprout up from each node. The bud may produce a tiller. The tillers are attached to the main stem, but later form their own roots. The last leaf formed from the rice plant is the flag leaf, which is characterized by standing the tallest.

The first stage of the reproductive period of the rice plant is the 'booting stage'. The panicle begins to form and a bulge is visible at the base of the leaf sheath. As the panicle gets bigger, it travels up the stem. The time when the panicle comes out is referred to as the 'heading stage'. This leads into the 'flowering stage'. Each flower is called a spikelet, a bunch of which make up the panicle. Soon after the flowers appear, they self pollinate or fertilize. Now the grain is ready to develop inside the ovary. As the grain matures, beginning from the bottom of the plant, the leaves begin to yellow and die off.

The mature grain is harvested in late summer or fall for processing and for seed for next season's planting. The hull is the inedible outer covering of the seed. Beneath the hull is the germ and the bran. The germ is the plant embryo from which a plant emerges. The bran layers and the germ include fiber, protein, vitamins, minerals and oil. Beneath the bran layers is the the endosperm which is mostly starch, protein, vitamins and minerals. It is the storehouse of food for the embryo. Almost 80 percent of the endosperm is starch, a complex carbohydrate. The food needed for seed germination is in the endosperm. The embryo develops into the shoot and the roots of the rice plant.




ACTIVITIES

Divide a sheet of paper into four squares and draw the following stages of the rice plant:

seedling

tiller

booting

flowering




EXTENDED LEARNING

Learn about more grasses and water plants at botany.com and compare their growth patterns to that of rice.

http://www.botany.com/index.6.htm




VOCABULARY
  • sheath
  • panicle
  • aerate
  • ligule
  • auricle
  • spikelet


Click here to play Rice Rampage!
How is Rice Grown:
Farming rice is hard work. Click here to learn more about the Stages of Farming Rice.
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