Physiological, biochemical and growth responses of Italian ryegrass to butachlor exposure

• Butachlor is a herbicide widely used around the world for rice and dryland crop production.
• Systematic research to obtain understanding of the butachlor phytotoxicity is scarce.
• Dose–response investigation was carried out using the relevant Italian ryegrass as a test organism.
• A dataset showing butachlor phytotoxicity to close the knowledge gap was established.
• The findings also have implications for remediation of heavily butachlor-contaminated sites.

A dose–response experiment was conducted to examine the effects of butachlor on the growth, physiology and biochemistry of Italian ryegrass. The plant suffered a >50% reduction in fresh biomass when exposed to a butachlor dose of 5 mg L−1. However, a significant further biomass reduction only occurred when the dosage level of butachlor was increased to 40 mg L−1. The root was more sensitive than the shoot to butachlor toxicity. It appears that the inhibition of fine root development under butachlor stress was the upstream cause for the retarded plant growth. A butachlor dose of 5 mg L−1 was sufficiently high to cause significant H2O2-induced oxidative damage in the plant cells, as indicated by the increased MDA and the lower production rate relative to consumption rate of CAT. The plants tended to maintain sufficiently high levels of root activity and photosynthesis, and possibly relied on these mechanisms for survival in such a stressed environment. Butachlor had a stimulatory effect on the release of dissolved organic carbon but not amino acids from the plant roots. There were 5 types of organic acids in the root exudates, which all exhibited a trend to decrease with increasing level of butachlor.

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