The main difference between glyphosate and paraquat lies in their modes of action and applications:

Mode of Action:

Glyphosate: It works by inhibiting an enzyme involved in the synthesis of essential amino acids, thereby disrupting protein production in plants. This action leads to systemic effects, causing plants to wither and die from the inside out.

Paraquat: It acts as a non-selective contact herbicide, causing rapid desiccation and death of green plant tissue upon contact. Paraquat disrupts photosynthesis by generating toxic free radicals in chloroplasts, leading to tissue damage and plant death.

Selectivity:

Glyphosate: It is a systemic herbicide that kills a wide range of plants, both grasses and broadleaf weeds. It is often used in agriculture, landscaping, and non-crop areas.
Paraquat: It is a non-selective herbicide that kills most green plant tissues upon contact. It is primarily used in non-crop areas, such as on weeds in industrial sites, along roadsides, and in non-agricultural settings.

Toxicity:

Glyphosate: It is considered to have low toxicity to humans and animals when used according to label instructions. However, there is ongoing debate and research regarding its potential ecological and health impacts.
Paraquat: It is highly toxic to humans and animals and can cause severe poisoning if ingested or absorbed through the skin. Due to its high toxicity, paraquat is subject to strict regulations and handling precautions.

Persistence:

Glyphosate: It typically degrades relatively quickly in the environment, depending on factors such as soil type, temperature, and microbial activity.
Paraquat: It is less persistent in the environment compared to glyphosate but can still persist in soil and water under certain conditions, posing potential risks to non-target organisms.

In summary, while both glyphosate and paraquat are widely used herbicides, they differ in their modes of action, selectivity, toxicity, and persistence, making them suitable for different applications and management strategies.