This is a diagram of the seed of barley (Hordeum jubatum)

As any "typical" seed it has three fundamental parts:

The seed coat is really a fruit coat. In all grains, the seed coat (former ovule integument) is fused to the ovary wall (the true fruit wall). So in fact, the grain is technically a fruit (caryopsis) even though we often call it a seed.

Barley is used primarily in beer making. Brewers use barley as a source of sugar to make the alcohol for beer. Brewers knew that sprouting the barley seeds improves the sugar yields tremendously, but they wanted even more sugar yield. The brewers came to plant physiologists to find out if anything could be done.

Study of the seed showed that the seed/fruit coat is water-resistant and thereby reduces the rate of water uptake by the seed, and water uptake is essential for seed germination and the improved sugar yields.

The sugar content of a dry barley seed is actually quite low, but the endosperm holds a huge reserve of starch. Starch is a polymer of sugars. In a sense it is a long chain of sugar molecules linked together. This is probably the source of the sugar.

The barley embryo has three parts:

Seed germination is said to have occurred when growth of the radicle bursts the seed coat and protrudes as a young root. The energy for seed germination probably comes from respiration of the sugar in the endosperm. However, the embryo and the starch are separated from each other. There must be some chemical communications that physiologists could manipulate to enhance sugar yield for the brewers.

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