BackgroundMechanical wounding can cause morphological and developmental changes in plants, which may affect the responses to abiotic stresses. However, the mechano-stimulation triggered regulation network remains elusive. Here, the mechano-stimulation was applied at two different times during the growth period of wheat before exposing the plants to cold stress (5.6 °C lower temperature than the ambient temperature, viz., 5.0 °C) at the jointing stage.ResultsResults showed that mechano-stimulation at the Zadoks growth stage 26 activated the antioxidant system, and substantially, maintained the homeostasis of reactive oxygen species. In turn, the stimulation improved the electron transport and photosynthetic rate of wheat plants exposed to cold stress at the jointing stage. Proteomic and transcriptional analyses revealed that the oxidative stress defense, ATP synthesis, and photosynthesis-related proteins and genes were similarly modulated by mechano-stimulation and the cold stress.ConclusionsIt was concluded that mechano-stimulated modifications of the chloroplast antioxidant system and proteome changes are related to cold tolerance in wheat. The findings might provide deeper insights into roles of reactive oxygen species in mechano-stimulated cold tolerance of photosynthetic apparatus, and be helpful to explore novel approaches to mitigate the impacts of low temperature occurring at critical developmental stages.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0610-6) contains supplementary material, which is available to authorized users.

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Unstratified seed of Engelmann spruce (Picea engelmannii Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) in nylon mesh bags was placed on various natural and disturbed forest floor seed beds in the Engelmann Spruce - Subalpine Fir Zone in the southern interior of British Columbia in September 1995 and recovered just before snow melt in June 1996. Fifty-two and 86% of the viable spruce and fir seed, respectively, had germinated before snowmelt. Germination under snow may be an adaptation of these high-elevation species to short cool growing seasons. Seed viability at recovery was significantly lower on undisturbed forest floor seed beds (spruce, 13%; fir, 12%) than on exposed mineral soil (spruce, 57%; fir, 42%). Viability of seed placed on nurse logs was 38 and 23% for spruce and fir, respectively. Isolation from ungerminated seed yielded a Rhizoctonia sp., an as yet unidentified black mold at high frequencies, and several other seed pathogens at low frequency. Multiple linear regression of the frequency of isolation of Rhizoctonia and black mold on seed viability was highly significant for both tree species. Seed pathogens appear to cause a major loss of seed and seedlings in these forests, and this may explain both the common occurrence of regeneration on nurse logs and the requirement of mineral soil seed beds for adequate regeneration.

The amylose content, size distribution, and processing properties of isolated starch granules were compared between eight near‐isogenic lines (NILs) of a wheat cultivar with different null‐waxy (wx) alleles. The increases in the amylose content (0.6–34.6%), volume percentage of A‐type starch granules (54.8–67.6%), low (118–179 cP) and final viscosities (160–329 cP), and setback value (43–146 cP) were positively related to the number of waxy alleles. All the viscosity values, except those of the peak time and the pasting temperature, of the purified A‐type starch granules were much higher than those of the B‐type granules, and so was the swelling power. The amylose content and pasting properties of the purified A‐ and B‐type starch granules showed similar patterns to those of flour in response to different null‐waxy alleles. In addition, wx‐B1 had greater effects on the amylose content, starch granule diameter, and pasting traits than the other alleles did. The diameter of biscuits baked with the flour of NILs varied between 46.29 mm (the wild‐type) and 44.09 mm (the waxy‐type), but their hardness decreased from 2895 to 1707 g as the number of the null‐wx alleles increased. The varied pasting traits of NILs were indirectly related to the modified size distributions of starch granules, but were directly ascribed to the regulated content of amylose due to deletion of the wx genes.