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Relationship between Thermal Transitions and Freezing Injury in Pea and Soybean Seeds
1U.S. Department of Agriculture, Agriculture Research Service, Ft. Collins, Colorado 80523.
Plant Physiology
|July 1, 1989
Summary
Freezing injury in pea and soybean seeds depends on water content, not just the presence of freezable water. Seed damage occurs even when freezable water is undetectable at low temperatures.
Area of Science:
- Plant physiology
- Cryobiology
- Agricultural science
Background:
- Freezing injury in seeds is a major concern for agriculture.
- Understanding the relationship between water content and freezing damage is crucial for crop survival.
Purpose of the Study:
- To investigate the correlation between freezable water content and freezing injury in pea and soybean seeds.
- To determine the thermal behavior of seed parts at various moisture levels and their impact on survival.
Main Methods:
- Differential scanning calorimetry (DSC) was used to study thermal transitions between -150 and 10 degrees C.
- Pea (Pisum sativum L.) and soybean (Glycine max L. Merr) seeds were analyzed at different moisture contents.
- Seed germinability and survival were assessed after exposure to sub-zero temperatures.
Main Results:
- Pea seed germinability decreased at a constant moisture content (0.33 g H2O/g dry weight) irrespective of temperature, above the detectable freezable water level (0.26 g H2O/g dry weight).
- Soybean seed damage occurred at progressively lower moisture contents as temperatures decreased from -18 to -50 degrees C.
- Soybean seeds showed damage even when freezable water was not detectable at temperatures of -50, -80, and -180 degrees C.
Conclusions:
- While water quantity influences freezing injury, the presence of freezable water alone does not fully explain the observed damage.
- Different seed types exhibit distinct responses to freezing temperatures concerning water content and injury thresholds.
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