Cultivated barley is a grass that may be either a winter or spring annual. Barley growth can be divided into a number of stages: germination, seedling development, tillering, stem elongation, heading (ear emergence), flowering and ripening.

The duration of each of barley’s developmental stages can vary widely. Growth rate depends on the weather, water supply, soil fertility the degree of competition with other plants, the presence of pests and diseases, and the time of planting. Initially the growth is slow while the plant’s seedlings establish and the tillers form. Total time to maturity will depend on variety, location and planting date.

When a seed is unable to actually germinate, even when conditions are most favourable, that is known as dormancy.

BARLEY PLANTS AT SUCCESSIVE STAGES OF GROWTH

DORMANCY

Dormancy of the barley grain is typically imposed by the seed-covering structures known as lemma, palea, pericarp and seed coat.

Primary dormancy is intrinsic; whereas secondary dormancy arises as a result of external factors such as water sensitivity, where germination is reduced under excessive moisture conditions.

While low dormancy is desirable in malting barley, too little dormancy can lead to pre-germination or pre-harvest sprouting, where germination of the grain begins on the mother plant in rainy conditions before harvest.

Both pre-germination and pre-harvest sprouting trigger the hydrolysis of the endosperm and can have adverse effects on the yield, malting quality and storage life of the grain.

In addition to the influence of barley variety, dormancy varies with grain maturity and with the conditions during ripening, harvest and storage. Freshly harvested grain is the most dormant, and dormancy declines as the grain ripens. Cool, moist conditions during ripening encourage the expression of dormancy, while low dormancy is generally associated with high temperatures, short days, low moisture and high nitrogen levels.

BARLEY CARYOPSIS

In the natural environment, the release of seed dormancy is promoted by factors including after-ripening (exposure of the seed to hot, dry conditions) and stratification (imbibition of water at low temperature).

In cultivation practices, dormancy is commonly relieved by after-ripening, which is achieved by storing the grain after harvest in warm temperatures and low humidity. Seed coat-imposed dormancy in barley may last between a few weeks to 9 months in dry storage. In contrast, storing grain in cold and moist conditions can hold on to dormancy. Barley seeds have been known to stay dormant for 3 years at 2°C under high humidity.

Shed grain may exhibit more prolonged dormancy than grain kept in dry storage. This is possibly because the wet periods following harvest encourage the retention of dormancy, so that self-sown grain often germinates just before the following crop.