The plants that tend to be the least sensitive to auxins are the __.
The correct answer and explanation is:
Correct answer: monocots
Explanation (300 words):
Auxins are a class of plant hormones that play key roles in coordinating many growth and behavioral processes in the plant’s life cycle. They are especially important for cell elongation, root initiation, and responses to light and gravity (phototropism and gravitropism). However, different types of plants respond differently to auxins, and one major group — monocots — tends to be less sensitive to them compared to dicots.
Monocots, or monocotyledons, include grasses, lilies, orchids, and cereals like wheat, rice, and corn. These plants have a single cotyledon (seed leaf), parallel leaf venation, fibrous root systems, and scattered vascular bundles. They typically show lower sensitivity to synthetic auxins, such as 2,4-D (2,4-dichlorophenoxyacetic acid), which is commonly used as a herbicide. Synthetic auxins mimic natural auxins but can cause uncontrolled growth and eventually kill the plant. While dicots (broadleaf plants) are usually killed by such herbicides, monocots often survive, which is why synthetic auxins are used to target weeds in cereal crop fields.
This difference in sensitivity is largely due to differences in auxin transport systems and receptor proteins. Monocots metabolize synthetic auxins differently or less efficiently bind them, making them less responsive or even resistant.
In contrast, dicots — which include most garden plants, legumes, and broadleaf trees — are highly sensitive to auxins. Inappropriate levels of auxin in dicots disrupt their normal growth patterns, leading to plant death.
Understanding this difference is crucial in agriculture and horticulture. Farmers use auxin-based herbicides to kill dicot weeds while leaving monocot crops unharmed.
In summary, monocots tend to be the least sensitive to auxins, especially synthetic ones, which is a key factor in selective weed control strategies.