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Gong, M., Chen, B., Li, Z. - G., & Guo, L. - H. (2001). Heat-shock-induced cross adaptation to heat, chilling, drought and salt stress in maize seedlings and involvement of H2O2. Journal of Plant Physiology, 158(9), 1125–1130.
Abstract: A heat-shock pretreatment at 42 °C for 4 h followed by a 4-h recovery significantly enhanced survival rates of seedlings from two varieties of maize that differ in stress resistance. The procedure mitigated electrolyte leakage of primary roots and alleviated vitality loss of coleoptiles under severe heat, chilling, drought and salt stress, indicating that heat-shock pretreatment can induce cross adaptation. The heat-shock pretreatment, that induced cross adaptation, also produced an endogenous H2O2 peak in maize seedlings. Exogenous H2O2 treatments simultaneously enhanced multi-resistance to heat, chilling, drought and salt stress, implying that H2O2 may play a signalling role in triggering cross adaptation of maize seedlings to various stresses.
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Hanley, M. E., Fenner, M., & Ne'eman, G. (2001). Pregermination heat shock and seedling growth of fire-following Fabaceae from four Mediterranean-climate regions. Acta Oecologica, 22(5-6), 315–320.
Abstract: The role of heat-shock in stimulating the germination of soil-stored seeds from fire-following plant species is well known. However, the effects of high pre-germination temperatures on subsequent seedling growth are less well understood. In this study, we examined the effect of pre-germination heat shock at five temperatures (60°, 75°, 90°, 105° and 120°C, each applied for 5 min) on the seedling growth of four, fire-following Fabaceae species from four Mediterranean-type ecosystems; Hippocrepis multisiliquosa (Israel), Gastrolobium villosum (Western Australia), Cyclopia pubescens (South Africa) and Lupinus succulentus (California). Following heat treatment and subsequent germination, seedlings were grown in controlled conditions before being harvested at either 10, 20- or 40 d old. A significant increase in mean dry weight biomass was found at 10 days for Hippocrepis seedlings germinated from seeds pre-heated to 90°C. However, subsequent comparison of mean dry weight biomass for seedlings of this species at 20 and 40 d old showed no significant response to heat shock pre-treatment. Similarly, an initial increase in growth of Gastrolobium seedlings germinated from seeds heated to 90° and 105°C disappeared as the plants matured. Seedling growth of Lupinus and Cyclopia was unaffected by the pre-germination heat treatment of their seeds. Since seedling competition is influenced by the size and growth rates of neighbouring plants, any changes in seedling growth rates as a consequence of the temperature environment experienced by their seeds, may therefore influence patterns of post-fire plant community recovery.
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Horowitz, M. (2001). Heat acclimation: phenotypic plasticity and cues to the underlying molecular mechanisms. Journal of Thermal Biology, 26(4-5), 357–363.
Abstract: Acclimation, in contrast to evolutionary adaptation, is a “within life time phenotypic adaptation” resulting in a widening of the dynamic regulatory range of body temperature. Increased efficiency and capacity of the thermoregulatory effectors, and delayed onset of the temperature threshold for thermal injury, contribute to the beneficial effects of acclimation. Reprogrammed gene expression and changes in cellular signaling underlie these responses. Constitutive elevation of the inducible heat shock protein (HSP) 72 kDa provides cytoprotection and delays thermal injury without the need for de novo HSP synthesis upon thermal stress. The time window for evocation of heat acclimation is the early phase of acclimation, the short-term heat acclimation (STHA), with accelerated sympathetic excitability and a drop in plasma thyroxin playing an essential role. An important consequence of thermal acclimation is the development of cross-tolerance between heat acclimation and ischemia/reperfusion insults. The beneficial implications of this feature are discussed.
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Lee, A. H., Eme, J., Mueller, C. A., Manzon, R. G., Somers, C. M., Boreham, D. R., et al. (2016). The effects of increased constant incubation temperature and cumulative acute heat shock exposures on morphology and survival of Lake Whitefish (Coregonus clupeaformis) embryos. J Therm Biol, 57, 11–20.
Abstract: Increasing incubation temperatures, caused by global climate change or thermal effluent from industrial processes, may influence embryonic development of fish. This study investigates the cumulative effects of increased incubation temperature and repeated heat shocks on developing Lake Whitefish (Coregonus clupeaformis) embryos. We studied the effects of three constant incubation temperatures (2 degrees C, 5 degrees C or 8 degrees C water) and weekly, 1-h heat shocks (+3 degrees C) on hatching time, survival and morphology of embryos, as these endpoints may be particularly susceptible to temperature changes. The constant temperatures represent the predicted magnitude of elevated water temperatures from climate change and industrial thermal plumes. Time to the pre-hatch stage decreased as constant incubation temperature increased (148d at 2 degrees C, 92d at 5 degrees C, 50d at 8 degrees C), but weekly heat shocks did not affect time to hatch. Mean survival rates and embryo morphometrics were compared at specific developmental time-points (blastopore, eyed, fin flutter and pre-hatch) across all treatments. Constant incubation temperatures or +3 degrees C heat-shock exposures did not significantly alter cumulative survival percentage (~50% cumulative survival to pre-hatch stage). Constant warm incubation temperatures did result in differences in morphology in pre-hatch stage embryos. 8 degrees C and 5 degrees C embryos were significantly smaller and had larger yolks than 2 degrees C embryos, but heat-shocked embryos did not differ from their respective constant temperature treatment groups. Elevated incubation temperatures may adversely alter Lake Whitefish embryo size at hatch, but weekly 1-h heat shocks did not affect size or survival at hatch. These results suggest that intermittent bouts of warm water effluent (e.g., variable industrial emissions) are less likely to negatively affect Lake Whitefish embryonic development than warmer constant incubation temperatures that may occur due to climate change.
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