An abnormal seedling is categorized as such because it is missing one or more of its essential seedling structures; this may be the root, the shoot or the terminal bud. A normal seedling will have all of the essential structures present for normal growth, often some structures may be slow to develop or they may be missing as well, but an experienced analyst will know how much of a detriment is allowed before the seedling can be classified as abnormal.
There are many types of abnormalities that are caused by various situations and are easily identified by an experienced seed analyst. It is very important to know what caused the abnormalities as they have a significant impact on the longevity or use of your seed.
Frost Damage. This year frost has caused many abnormalities; the symptoms are grainy watery seedlings that are twisted or shortened. There may be an empty coleoptile (no leaf) or very short twisted structures. Frost damage is easy to identify because there are no other defects that are similar to this abnormality. Seedlings mostly affected are oats, barley and wheat.
LEFT IMAGE: Healthy Seedling on Left. RIGHT IMAGE: Healthy Seedling on Top.
Mechanical damage on peas, beans or canola is also very prevalent. Mechanically damaged seed will result in seedlings that have no roots or shoots. Often both structures are missing, but in most cases only one or the other is absent. This is caused by threshing the seed when it is too dry, or processing the seed when it is too dry and without taking the necessary precautions to prevent splitting. Peas and beans are particularly susceptible, and these seedlings will not develop normally.
Pre-harvest desiccation on any crops that are not evenly mature will also create abnormal seedlings. These seedlings will have all of the essential structures, but they will be deformed with short wiry roots that want to grow in the opposite direction (negative geotropism).
Wheat seedling on LEFT affected by pre-harvest desiccation with glyphosate. HEALTHY SEEDLING ON RIGHT.
Chemical damage is caused by storing seed too close to chemicals in the warehouse, or sometimes by overtreating seed with more than the recommended treatment rate. These seedlings will have no root development.
For more information please refer to our Technical Bulletin on Germination.