What is the effect of nematode on crop plant?

Nematodes (roundworms) are microscopic parasitic organisms that attack the root system of crop plants. Species such as root-knot nematodes (Meloidogyne) penetrate root tissues, forming galls and disrupting the root's ability to absorb water and mineral nutrients from the soil.

When roots are severely damaged by nematode infestation, the plant can no longer take up sufficient water to replace what is lost through transpiration. This imbalance causes the plant to wilt, even when soil moisture is adequate. This is sometimes called "wilting disease" in nematode-infested fields.

The other options do not describe effects of nematode attack:

• A mosaic appearance on leaves is a symptom of viral infections (such as tobacco mosaic virus), not nematode damage.
• Nematodes damage and stunt roots rather than causing them to grow faster.
• Flowering induction is controlled by hormones and photoperiod, not by nematode activity.

Exam tip: Nematode symptoms are primarily below-ground (root galls, stunted roots), but the visible above-ground sign is wilting because damaged roots cannot supply adequate water to the shoot.