How Milk Thistle Responds to Herbicides in the Soil

Jenn Hoskins
20th June, 2024

How Milk Thistle Responds to Herbicides in the Soil

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at the University of Birjand, Iran, studied the effects of four herbicides on milk thistle growth
  • Herbicide treatments generally reduced root and shoot growth, with ethalfluralin at high doses having the most negative impact
  • Metribuzin and pendimethalin had fewer negative effects, suggesting they could be better options for weed control in milk thistle fields
Milk thistle (Silybum marianum) is widely recognized for its medicinal properties and is cultivated globally. However, the presence of weeds poses significant challenges to its production, making effective weed management essential. Chemical weed management is a cost-effective and promising approach. To investigate the tolerance of milk thistle to soil-applied herbicides, researchers at the University of Birjand, Iran, conducted a pot experiment in the spring of 2022[1]. This study aimed to identify herbicides that could manage weeds without severely affecting milk thistle growth. The experiment involved four herbicides: metribuzin, pendimethalin, trifluralin, and ethalfluralin, applied at six different doses (0, 50, 75, 100, 125, and 150% of the recommended dose). The results showed that herbicide treatments negatively impacted the root and shoot growth of milk thistle. Ethalfluralin at 150% of the recommended dose had the most substantial negative effect on root dry weight (-60.1%), while metribuzin at 50% had the least (-13.3%). Similarly, for shoot dry weight, ethalfluralin at 150% had the highest negative impact (-64.4%), and metribuzin at 50% had the lowest (-9.3%). Herbicide applications also reduced the membrane stability index (MSI) and relative water content (RWC) in the plants. Increased levels of malondialdehyde (MDA), total phenol, DPPH scavenging, soluble carbohydrates, and proline were observed in roots and leaves after all herbicide treatments compared to the control. Among the herbicides tested, metribuzin and pendimethalin had fewer negative effects on milk thistle growth, suggesting they could be potential options for weed control in milk thistle fields. This study's findings align with previous research on the effects of abiotic stresses on plants. For instance, various abiotic stresses, including herbicide application, can lead to the overproduction of reactive oxygen species (ROS), which are highly reactive and toxic, causing oxidative stress[2]. The increase in MDA, a marker of oxidative stress, observed in this study, supports the notion that herbicides induce oxidative damage in plants. Moreover, the study's findings are in line with research on the antioxidant defense mechanisms in plants. Plants possess efficient enzymatic and non-enzymatic antioxidant defense systems that protect against oxidative damage by scavenging ROS[2]. The observed increase in total phenol and DPPH scavenging activity in milk thistle suggests an upregulation of antioxidant defenses in response to herbicide-induced stress. Interestingly, the results also mirror findings from studies on the impact of heavy metals on plants. For example, wheat seedlings exposed to cadmium (Cd) exhibited a decline in growth and physiological parameters, which were mitigated by pretreatment with indole-3-acetic acid (IAA) or salicylic acid (SA)[3]. Similarly, in the milk thistle study, certain herbicides had less detrimental effects, suggesting a potential for selective herbicide use to manage weeds without severely impacting crop health. Furthermore, the study contributes to the broader understanding of herbicide interactions in plants. Previous research on the herbicides glyphosate and imazamox showed that mixtures of these herbicides could have varying physiological effects, sometimes being less toxic than individual treatments[4]. While the current study did not investigate herbicide mixtures, it highlights the importance of selecting appropriate herbicides and doses to minimize negative impacts on crops. In conclusion, the research conducted by the University of Birjand provides valuable insights into the tolerance of milk thistle to different herbicides. The findings suggest that metribuzin and pendimethalin could be viable options for weed control in milk thistle fields due to their relatively lower negative effects on plant growth. This study enhances our understanding of herbicide impacts on crops and underscores the importance of careful herbicide selection to balance effective weed management with crop health.

AgricultureBiochemPlant Science


Main Study

1) Physiological and growth responses of milk thistle (Silybum marianum (L.) Gaertn.) to soil-applied herbicides.

Published 18th June, 2024

Related Studies

2) Reactive oxygen species and antioxidant machinery in abiotic stress tolerance in crop plants.

3) Exogenous treatment with indole-3-acetic acid and salicylic acid alleviates cadmium toxicity in wheat seedlings.

4) Physiological performance of glyphosate and imazamox mixtures on Amaranthus palmeri sensitive and resistant to glyphosate.

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