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Effect of Sprouting on Seed Quality
The effects of sprouting is detrimental to seed viability and seedling vigor. Before planting sprout damaged seed, a determination of potential impact on productivity should be made. Sprouting, or germination, generally only occurs when a kernel has matured and dried to a harvest ripe stage. Germination then begins when a kernel adsorbs water which activates a number of enzymes that break down starch and proteins producing some basic constituents required for respiration.
Sprouting or the germination process can be initiated multiple times in barley and wheat. The process has the indirect effect of lowering test weight and each time it occurs the viability of the seed will be reduced. The lowered test weight is a result of seed swelling and loss of carbohydrates due to expenditure of energy.
Identifying sprout damage: The extent of sprouting can be evaluated in several ways. The simplest and probably most effective way is to visually inspect the seed. Visible indicators of pre-harvest sprouting include weathered appearance, seed swelling, a split seed coat leaving the embryo exposed, and emergence of the coleoptile and radicle (the seedling shoot and root). In wheat, a falling number test is used to measure the level of enzyme activity. Falling numbers below 300 generally indicate pre-harvest sprouting has occurred.
The effect of the pre-harvest sprouting on germination and seedling vigor is correlated to the extent of damage. Research data is limited but indicates that kernels with sprout damage but no visible damage to the germ perform well in standard germination tests. Seed with low levels of pre-harvest sprouting can have germination that is nearly as good as that of undamaged seed. However, when such seed is subjected to accelerated ageing the percent of germination can drop dramatically. Seed with an exposed germ or ruptured seed coat where either the radicle or coleoptile emerged perform less well in standard tests. Furthermore, seed with exposed germ structures is susceptible to physical damage during handling.
Planting sprout damaged seed can compound environmental conditions that impede the ability of a new seedling to emerge and produce photosynthetically active leaves required for good seedling vigor. These conditions may include water logged soils, dry soils, crusting, and deep seeding.
Before using sprout damaged seed the percent germination should be determined so seeding rate can be adjusted accordingly. Percent germination can be easily determined using a simple paper doll test. Simply place 200, or more if you fill inclined, randomly selected seeds on heavy duty paper towels, roll the towels up and secure the role with paper clips, wet the towel and place it in a bread bag. Then place it in a location that remains about 50 to 60o F. After seven days count the germinated seed and divide by the total tested for percent germination. When counting germinated seed only those with a fully extended coleoptile should be counted. (This test is only as representative of seed lot as the sample used.) When percent germination falls below 90% consider using a different seed lot.
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