Hormonal herbicides like 2,4-D mimic natural plant growth regulators.
When applied in excess, they cause rapid, uncontrolled, distorted growth (epinasty), which is seen as "whip-like" rolled leaves in grasses.
Step 1: Understanding the Concept:
Sorghum (Sorghum bicolor) is highly sensitive to certain selective herbicides if they are applied incorrectly, at high doses, or at the wrong growth stages.
Herbicide phytotoxicity can cause distinct physiological and morphological disorders in the crop. Detailed Explanation:
The hormonal herbicide 2,4-D (2,4-Dichlorophenoxyacetic acid) is commonly used to control broadleaf weeds in cereal crops.
However, if 2,4-D is applied at an excessive rate or during sensitive vegetative stages in sorghum, it can disrupt the plant's natural auxin balance.
This hormonal imbalance causes abnormal cell elongation and tissue distortion:
- The emerging leaves fail to unfurl properly from the whorl.
- The leaves become tightly bound, rolled, and twisted, resembling a whip or a buggy whip.
- This condition, known as "buggy whipping" or "onion leafing," stunts crop growth and can reduce yields.
- In contrast, nitrogen and zinc deficiencies cause chlorosis (yellowing) and leaf bronzing, while atrazine toxicity typically causes leaf burning and chlorosis starting from the margins. Step 2: Final Answer:
The buggy whipping condition in sorghum is caused by the application of a higher dose of 2,4-D.
