Abstract
The objective was to evaluate the production components of soybean and the physiological quality of seeds according to the application of subdoses of herbicides at the reproductive stage of healthy plants. The treatments consisted of the application of glyphosate (122.5 g acid equivalent [ae] ha-1), chlorimuron (1.75 g active ingredient [ai] ha-1), 2,4-D (134 g ae ha-1), fomesafen (60 g ai ha-1), glufosinate (55 g ai ha-1), paraquat (35 g ai ha-1), and control (no application). The chlorophyll index, agronomic performance, and physiological quality of seeds were evaluated. Glyphosate, chlorimuron, fomesafen, or glufosinate resulted in an increase in soybean plant height. Chlorimuron increased yield compared to the control. Paraquat or glufosinate, despite the injury, did not reduce yield, but the application of these herbicides is not recommended to stimulate plant development, given the potential for injury. The 2,4-D was the only one that caused a reduction in the physiological quality of soybean seeds.
Highlights
The beneficial effect of subdoses of toxic substances has been known for a long time and this phenomenon is called hormesis (Calabrese & Blain, 2009)
For the variables related to the seed physiological quality, the analysis of variance evidenced a significant effect of the treatments on the variables germination speed index (GSI), germination speed and shoot fresh mass; for other variables (germination test, accelerated aging, shoot length, root length, root fresh mass, shoot dry matter and root dry matter (g) of seedlings) there was no significant effect (Table 2)
There was a difference between glyphosate (21.78 cm) and 2,4-D (17.09 cm); none of them differed from the control (21.22 cm)
Summary
The beneficial effect of subdoses of toxic substances has been known for a long time and this phenomenon is called hormesis (Calabrese & Blain, 2009). Studies have been carried out to assess possible hormesis effects on plants with the use of subdoses of herbicides, which in turn can be advantageous if a desirable phenotypic change is achieved (Jalal et al, 2021). Herbicides are compounds that inhibit plant metabolic pathways or physiological processes through interaction with proteins, or specific pathways and photosynthesis inhibitors, resulting in plant death or growth arrest (Krähmer et al, 2021). As all herbicides act on pathways or processes crucial to plants, such as inhibitors or stimulants, possibly low doses of an herbicide can modify growth, development, or composition in a way that could be beneficial to plants in some circumstances. The hormesis effect can provoke different stimulatory responses, which depend on the chemical, the target plant, and how it acts on plant physiology and morphology and of that plant. The use of subdoses herbicides provides crop protection by eliciting defenses against plant pathogens (Nelson, 2008)
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