What can cause malformation of plant parts?

Malformation of plant parts can often be traced back to specific biological factors, such as insect damage, viral infections, and fungal diseases. These agents can disrupt normal plant growth and development in a variety of ways. For example, insects may feed on specific tissues, leading to distorted growth patterns as the plant responds to the injury. Viruses can alter genetic expression, affecting how cells divide and differentiate, which can result in malformations such as curled leaves or stunted growth. Similarly, fungal infections may produce toxins or create physical blockage in the plant tissues, further contributing to deformities.

In this context, the other choices relate to environmental conditions that generally do not directly cause malformations in the same manner. For instance, excessive watering can lead to root rot and waterlogging issues, which primarily affect overall plant health rather than causing specific malformations in parts. Exposure to sunlight is essential for photosynthesis, and while insufficient light may stunt growth, it does not directly cause malformations in plant structures. Lastly, soil erosion impacts the availability of nutrients and stability for plants, but like the other environmental factors mentioned, it does not specifically lead to malformations as caused by the biological agents noted in the correct answer.