Cold temps, snow impact corn emergence in Manitoba
By Pam de Rocquigny Provincial Cereal Crops Specialist MAFRD
May 19, 2015 - Cold temperatures, combined with excessive rainfall in some areas and even snowfall, has created conditions not ideal for the germination and emergence of corn planted recently in Manitoba. Research has shown that temperatures at or below 10 C are most damaging to the germination and emergence process, especially if the cold temperatures persist long after planting.
What is Imbibitional Chilling Injury? Firstly, imbibition is the process by which seeds absorb water for the initiation of germination. In corn, kernels must absorb (imbibe) about 30 per cent of their weight in water before germination begins (by comparison, soybeans must imbibe about 50 per cent of their weight in water).
Imbibitional chilling injury may result when water colder than 10 C is imbibed, and effects can be particularly severe in situations where seeds were planted into cool soils (10 C or colder), combined with cold rain or melting snow after planting (the most critical time for imbibition is within 24 hours of planting). The absorption of cold water can disrupt the reorganization of cells during rehydration and can result in the loss of seed vigor or seed death. Note: A cold, heavy rain after planting seems to increase the chances of imbibitional injury, probably because it overwhelms the ability of the soil to warm the water before it reaches the seed (Source: Joel Ransom, NDSU).
Symptoms of imbibitional chilling injury include swollen kernels that swell but fail to exhibit further signs of germination or arrested growth of the radicle root and/or coleoptile following the initiation of the germination process.
Instances of non-imbibitional chilling injury following germination during the emergence process can also occur, often causing stunting or death of the seminal root system, deformed elongation of the mesocotyl (the so-called "corkscrew" symptom) and either delayed emergence or complete failure of emergence (i.e., leafing out underground). This type of chilling injury is more closely related to physical damage to the outer cell tissues that literally cause death of the plant part or inhibit further elongation of the affected area. Thus, chilling injury to only part of the circumference of the mesocotyl results in the "corkscrew" symptom as the undamaged sections of the mesocotyl continue to elongate.
The Result of Cold Injury? If germination is impacted, poor stands could result impacting yield potential. Plants that also develop from injured seedlings may be stunted and develop more slowly than normal plants. This can result in unevenness in the growth stages of plants within the field.