Why cannot a farmer use seeds of hybrid plants to raise new crop in the next growing season? 

A farmer cannot use the seeds collected from the hybrid plants. The first-generation hybrid plants (F₁) show hybrid vigour or heterosis, which is the superior performance of the hybrid compared to its parents. However, the seeds produced by the F₁ hybrid plants do not maintain hybrid characters in the progeny. Instead, the progeny will segregate and exhibit traits of either of the parents or a combination of both. Therefore, if a farmer uses seeds from hybrid plants to raise the next crop, the resulting plants will not have the desired traits and may even be inferior to the parents.