Abstract
Moderate heat stress may provide protection against a subsequent severe high temperature stress in plants. However, the exact mechanisms of heat acclimation of wheat are still poorly understood. In the present work, two wheat varieties Ellvis and Soissons were exposed to a moderate elevated temperature at 30 °C, and the changes of certain protective mechanisms were investigated. Although the differences in the proline level between the genotypes were not substantial, it was approx. 2–3 times higher in the heat-treated plants than in the controls. After exposure to moderate elevated temperature, the activities of ascorbate peroxidase and catalase were also induced. Similarly, the amount of the free salicylic acid also increased after moderate heat stress, independently on the genotypes. The amount of the main polyamines, namely, putrescine, spermidine, and spermine either did not change or decreased after the same period. However, heat acclimation increased the level of 1,3-diaminopropane, in parallel with a polyamine oxidase gene, TaPAO. While the expression level of the peroxisomal polyamine oxidase gene TaperPAO hardly changed, TaPAO showed a substantial increase after 1 day, especially in Soissons, and at the end of the heat treatment was still significantly higher than in the controls. These suggest that signalling processes related to polyamine metabolisms or salicylic acid-related processes might also contribute to the higher heat tolerance induced by moderate heat stress. The variations in recorded measurements were mainly temperature dependent, and the effect of genotype was less pronounced than the effect of moderate heat treatment itself.
Highlights
Heat stress is one of the most important abiotic stress factors limiting growth of crop plants in many regions of the world leading to dramatic reduction in the economic yield (Battisti and Naylor 2009)
Ellvis and Soissons were grown in pots filled with 3:1 (v:v) mixture of loamy soil and sand in a Conviron PGV-15 growth chamber (Controlled Environments Ltd., Winnipeg Canada) at 20/18 °C day/night temperature with 16/8 h photoperiod at 250 μmol m−2 s−1 photosynthetic photon flux density (PPFD) at the canopy level, and 75% relative humidity. 10 days after sowing part of the plants were heat-treated at 30/27 °C day/night temperature, while others were grown at 22/20 °C for 14 days
The amount of SPD significantly decreased during the moderate heat stress, but it was statistically significant only in case of Soissons
Summary
Heat stress is one of the most important abiotic stress factors limiting growth of crop plants in many regions of the world leading to dramatic reduction in the economic yield (Battisti and Naylor 2009). Global climate change has exacerbated the severity of many abiotic stresses, including temperature extremes, with significant yield reductions in several crop plants (Huang et al 2018). When these changes are rapid and extreme, they are often unable to avoid or significantly mitigate stress. This is especially true for crop plants, which often originate from far regions with different climate and have relatively narrow genetic diversity to cope with the fluctuating environment. Better understanding of stress adaptation mechanisms may provide useful information for breeders for developing new crops with better stress tolerance
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