Abstract. Wheat (Triticum aestivum L. var. TAM‐W101) leaf segments exhibited an acquired protection against metal toxicity following exposure of the seedlings to heat shock temperatures in the dark. The acquired protection of the leaf segments to cadmium was 400‐fold greater than leaf segments from seedlings kept at 25°C and exhibited the greatest change in protection of the five metals tested. Increased protection against aluminium and iron toxicity was also detected in the leaf segments from heat shocked seedlings. The concentration of aluminium at which a 50% loss of 2,3,5‐triphenyltetrazolium chloride reduction occurred was 5.5 mol m−3 in control leaf segments and 20 mol m−3 in the leaf segments from heat shocked seedlings. The 50% loss of 2,3,5‐triphenyltetrazolium chloride reduction in the leaf segments from heal shocked seedlings was four‐fold higher for iron. A small, yet reproducible change in the 2,3,5‐triphenyltetrazolium chloride reduction was observed for copper and no change in reduction was observed for zinc treatments in the leaf segments from heat shocked seedlings. These data indicate that exposure of wheat seedlings to heat shock temperatures results in the acquisition of protection against metal toxicity to otherwise lethal concentrations of aluminium, cadmium, and iron.
Progressive soil compaction is a disadvantage of intensive tillage. Compaction exerts a negative impact on the physical properties of soil and decreases crop performance. The adverse effects of soil compaction can be mitigated by replacing conventional tillage with simplified tillage techniques. Simplified tillage exerts a protective effect on soil, reduces production costs and preserves agricultural ecosystems. The aim of this study was to determine the influence of compaction and different tillage methods on the bulk density and moisture content of soil. The experimental factors were as follows: Soil compaction before sowing (non-compacted control treatment and experimental treatments where soil was compacted after the harvest of the preceding crop) and four different methods of seedbed preparation in a three-field rotation system (winter oilseed rape, winter wheat, spring barley). The influence of compaction on the bulk density and moisture content of soil varied across the rotated crops and their developmental stages. Soil compaction had no significant effect on the analyzed parameters in the cultivation of winter oilseed rape. In treatments sown with winter wheat, soil compaction resulted in significantly lower soil density and significantly higher soil moisture content. In plots sown with spring barley, soil compaction led to a significant increase in the values of both parameters. The average bulk density of soil after various tillage operations in the examined crop rotation system ranged from 1.49–1.69 g·m−3 (winter oilseed rape), 1.47–1.59 g·m−3 (winter wheat), 1.47–1.61 g·m−3 (spring barley). The bulk density and moisture content of soil were lowest after conventional tillage (control treatment) and higher after simplified tillage. Regardless of soil compaction, the greatest reduction in winter oilseed rape yields was noted in response to skimming, harrowing and the absence of pre-sowing plowing. Spring barley yields were higher in non-compacted treatments, whereas the reverse was observed in winter wheat. Chisel plowing and single plowing induced the greatest decrease in wheat yields relative to conventional tillage. Single plowing significantly decreased the grain yield of spring barley relative to the tillage system that involved skimming and fall plowing to a depth of 25.
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