Final answer:
The seed-bearing part of grain plants like barley and wheat is the head or spike, which contains the grains or kernels. It consists of the embryo, endosperm, and bran. These grains are a result of sexual reproduction, with pollen grains carrying male gametes and ensuring plant dispersal.
Step-by-step explanation:
The seed-bearing part of the stem of grain plants such as barley and wheat is referred to as the head or spike, which contains the grains or kernels. These grains are actually fruits, termed caryopses, where the seed coat is fused with the fruit wall. The three parts of the wheat seed are the embryo (also known as the germ), the endosperm, and the seed coat fused with the fruit wall or bran. The endosperm is the stored food that nourishes the embryo. During milling, white flour is produced by removing the embryo, which is sold as wheat germ, and the bran, leaving predominantly the starchy endosperm. Whole wheat flour contains these parts, making it more nutritious but also more susceptible to spoilage.
Pollen grains are male gametophytes that carry the sperm cells and are protected by a coat that prevents desiccation. They allow plants to spread their genes over distances without reliance on water. The evolutionary advances of pollen and seeds have enabled seed plants to dominate land ecosystems.