How can a biostimulant be defined in the context of seed treatment?

A biostimulant can be defined in the context of seed treatment as a substance that enhances growth through biological processes. This definition highlights the role of biostimulants in promoting plant health and growth by stimulating natural processes within the plant. They often include a range of ingredients such as beneficial microorganisms, plant extracts, or natural compounds that work synergistically to improve nutrient availability, enhance stress tolerance, or promote root development.

Utilizing biostimulants in seed treatment can lead to improved germination rates and overall plant vigor, ensuring that seeds have the best possible start in their growth cycle. Their primary function is to enhance the plant's biological activity rather than restrict or inhibit it, which is the focus of the incorrect options.

Other choices incorrectly describe biostimulants either as harmful chemicals that interfere with growth processes, new seed varieties, or as pesticides, which are designed specifically to control harmful organisms rather than enhance growth. Thus, option B stands out as the only correct representation of what biostimulants are in relation to seed treatment.