A barley seed is an embryonic plant. The structure of all plant seeds contain three basic parts: a dormant embryo, storage tissue and a coat or covering. Barley seeds are monocotyledons, meaning that the embryo contains a single cotyledon, or “seed leaf.” Barley and other monocotyledon grasses have leaves with parallel veins.
A covering that botanists called the integument covers the female ovule in a barley plant. When an egg cell from a barley ovule unites with a sperm cell, it forms a zygote, containing genes from both parent plants. The zygotes grows into a seed embryo. The integument covering the ovule becomes the covering of the barley seed. Many seeds remain dormant or have other conditions under which the seeds germinate, the process by which a plant emerges from an embryo. Barley seeds do not have a special period of dormancy. When they have water and warm temperature, they germinate.
The protective layer of endosperm tissue surrounds the embryo, which rests in a special sac. The endosperm collects fats, protein and starch for the growing embryo.
The seed absorbs water through a process called imbibition. The water moves a hormone called Gibberellic acid to the aleurone cells, which are protein in the endosperm. The Gibberellic hormone activates the DNA coding for amylase, an enzyme that turns the starch in the endosperm into maltose, sugar that the embryo needs for nutrition. This is the malt sugar that is the necessary ingredient for making beer, giving it its distinctive flavor. The protein-rich aleurone layer of the endosperm is what makes barley, brown rice and other grains “chewy.”
The amylase is shipped into the embryo by endoplastic reticulum, usually abbreviated ER. The amylase goes to the golgi, a sac-like, flattened, layered organ near the nucleus of the barley seed embryo. The golgi loads proteins and carbohydrates into vesicles or bubbles bound by membranes for transport to the growing plant cells.
The radicle is the first part of the barley plant to emerge from the seed. Fueled by sugar carried by the visicles, the new plant grows larger.