Mode of mechanism of action for herbicides

Question 1

What is Mechanism of action?

Answer 1

Mechanism of action refers to the process that leads to the failure of biological process needed by plants to grow properly. This is basically the action that is caused when herbicides are applied to weed, the phytotoxic agents bind to a single protein in the weed that eventually will lead to failure of a biological process and lead to the death of the weed

Question 2

The weed control effect of herbicides are at their maximum and minimum stage when?

Answer 2

Weed control effect is at maximum when the plant is at emergence state, it is at minimum when the plant is at maturity state

Question 3

Different herbicides of different mode of action why?

Answer 3

Because of the difference in chemical composition

Question 4

Mention 6 physiological and bio-chemical effects caused by herbicides on weeds

Answer 4

Chlorosis
Defoliation
Stunting
necrosis
Cupping of leaves
delayed emergence
germination failure

Question 5

List the seven major modes of action of herbicides

Answer 5

Growth regulation
Amino acid inhibition
phosynthesis inhibition
Lipid inhibition
Seedling growth inhibition
Cell membrane distruption
Pigment inhibition

Question 6

Growth regulators selectively kill what kind of weeds

Answer 6

Broadleaf weed

Question 7

Describe the growth regulators

Answer 7

Growth regulators include herbicide familes like phenoxy acetic acid and benzoic acide . They attack multiple plant sites that affect the protein synthesis in plant and the hormonal balance. They usually affect broad leaf weeds but can also affect grasses. They move through the xylem and the phloem therefore making them suitable for perennial and annual weeds. Injury is first seen in newly developing weeds. Herbicide uptake is usually through the foliage but it can be seen through the root as well.

Question 8

Describe photosynthetic inhibitors

Answer 8

These are herbicides that bind to specific sites in the chloroplast of the leaf, causing the plant not to be able to carry out its photosynthetic reaction, therefore, leading to starvation , lack of energy, and eventually death. These inhibitors do not have any soil activity, mostly used on foliar.

Question 9

Describe amino - acid inhibitors

Answer 9

These are herbicides that bind to enzymes necessary for synthesis of amino acid which is in turn used to produce proteins. Eventually protein is depleted from the plant and the plant can no longer grow properly. These inhibitors are non-selective and can affect annual, perennial, grass or broadleaf weeds. They are mostly taken up through the phloem

Question 10

Mention herbicide families that are amino acid inhibitors

Answer 10

sulfonylureas
amino acid derivatives
sulfonamide

Question 11

How long does injury symptom take to develop for lipid synthesis inhibitors

Answer 11

7 - 14days

Question 12

Describe lipid synthesis inhibitors

Answer 12

These are herbicides that stop the formation of fatty acids needed to make plant lipids which is very essential to plant growth. Broadleaf plants are tolerant to it, but they really affect annual and perennial grasses and move through the phloem they are usually taken up by the foliage. They attack the enzyme involved in fatty acid biosynthesis

Question 13

Describe seedling growth inhibitors

Question 14

Describe pigment inhibitors