Grain kernel or simply called kernel and what hull or husk is

All grains start life as whole grains. In their natural state growing in the fields, whole grains are the entire seed of a plant. 

This seed (which industry calls a "kernel") is made up of three key edible parts – the bran, the germ, and the endosperm – protected by an inedible husk or called hull that protects the kernel from assaults by sunlight, pests, water, and disease.

 (Info source: http://wholegrainscouncil.org/whole-grains-101/what-is-a-whole-grain )

The following kernel with hull shown is from http://www.riviana.com/how_rice_is_processed.html

The following picture is from http://www.barleyfoods.org/article-12-2004-2.html

.-----------------

The following is from http://www.english-online.at/biology/rice/rice.htm

Each rice plant carries hundreds or thousands of kernels . A typical rice kernel is 6—10 mm long and has four parts:

The hull is the hard outer part which is not good to eat. The bran layers protect the inner parts of the kernel They have vitaminsand minerals in them. The endosperm makes up most of the kernel. It has a lot ofstarch in it. The embryo is a small part from which a new rice plant can grow.

After harvest, rice is processed in mills . First the hull and the bran layers areremoved carefully so that the inner part of the kernel doesn’t break. The endosperm is the white rice that most people eat because it is easier to cook. It is enriched with vitamins and minerals to make it better. Sometimes brown rice , in which the bran layers remain, is produced . Then it ispackaged and sold.

The following is from http://apps.geckovilla.com/Blog/?e=38987&d=10/22/2009&s=The%2520Rice%2520Cycle%2520in%2520Northeast%2520Thailand

--------------

The following is from

http://nidhiraizada.blogspot.sg/2009/08/bran.html?m=1

What is Bran?

Bran is the hard outer layer of grain (the grass fruit) and consists of combinedaleurone and pericarp. Bran should not be confused with chaff, which is coarser scaly material surrounding the grain, but not forming part of the grain itself.

Significance of Bran for the Seed:

• The aleurone layer surrounds the endosperm tissue (endosperm is the part of the seed which surrounds the embryo and provides nutrition in the form of starch) and functions for both storage and digestion.
• During germination, aleurone secretes the amylase enzyme that breaks down endosperm starch into sugars to nourish the growing seedling.
• In cereals with starchy endosperm, the aleurone contains about 30% of the kernel's proteins.
• In multicolored corn, anthocyaninpigments in the aleurone layer give the kernels a dark, bluish-black color
• Pericarp is the tissue that develops from the ovary wall of the flower and surrounds the seeds. It provides protection to seed.