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Thermotolerance is developmentally dependent in germinating wheat seed.
R H Abernethy1, D S Thiel, N S Petersen
1Department of Plant, Soil and Insect Sciences, University of Wyoming, Laramie, Wyoming 82071.
Plant Physiology
|February 1, 1989
Summary
Wheat seeds show high temperature tolerance early in imbibition, which declines over time. This "thermotolerance transition" involves losing initial tolerance while gaining the ability to acquire heat tolerance after pretreatment. Heat shock proteins are synthesized immediately upon imbibition.
Area of Science:
- Plant Physiology
- Molecular Biology
- Stress Biology
Background:
- Wheat seeds (Triticum aestivum L.) exhibit varying tolerance to high temperatures during imbibition.
- Early imbibition (9-12 hours) shows substantial heat tolerance, which diminishes over time.
- This phenomenon is termed the 'thermotolerance transition'.
Purpose of the Study:
- To investigate the dynamics of heat tolerance in wheat seeds during early imbibition.
- To understand the mechanisms underlying the 'thermotolerance transition' in wheat.
- To examine heat shock protein (HSP) synthesis in response to heat shock at different imbibition stages.
Main Methods:
- Assessing seed viability and seedling growth after high-temperature treatments.
- Applying heat pretreatments (38-42°C) followed by heat shock (51-53°C) at various imbibition times.
- Utilizing the 2,3,5-triphenyltetrazolium chloride assay for viability of isolated embryos.
- Detecting heat shock protein synthesis using molecular techniques.
Main Results:
- Wheat seeds possess high temperature tolerance during the first 9-12 hours of imbibition, which decreases thereafter.
- Heat pretreatment before heat shock was ineffective in early imbibition but enhanced survival and growth after 9-12 hours.
- Isolated embryos showed similar viability responses to heat treatments.
- Heat shock induced synthesis of specific HSPs (58-60, 46, 40, 14 kDa) immediately upon imbibition, but these decreased by 12 hours.
- Constitutive HSPs (70, 90 kDa) synthesis was higher at 1.5 hours than at 12 hours of imbibition.
Conclusions:
- The thermotolerance transition in wheat involves the loss of inherent tolerance and the acquisition of inducible thermotolerance.
- Early imbibition heat tolerance is a transient state, distinct from acquired thermotolerance.
- Heat shock protein synthesis is an immediate response to heat stress in imbibing wheat, with developmental regulation observed.