What symptom is associated with Thifensulfuron injury in soybeans?

The symptom associated with Thifensulfuron injury in soybeans is chlorosis followed by necrosis. This herbicide, which is a sulfonylurea, affects specific biochemical pathways in plants related to amino acid synthesis. Upon exposure, the first noticeable symptoms often present as chlorosis, where the leaf tissue turns yellow due to a lack of chlorophyll. This chlorosis typically progresses to necrosis, where the tissue dies, leading to darkened or dead areas on the leaves.

The other symptoms mentioned do not directly correlate with Thifensulfuron injury. While red veins on the leaves can indicate other forms of stress or damage, they are not a recognized symptom of injury caused by Thifensulfuron. Root damage typically occurs later and presents differently than indicated in the choices. Thus, recognizing the distinct symptom progression from chlorosis to necrosis is crucial for correctly identifying injury from this herbicide in soybeans.