seed, race, breed, to plant
种 centers on the idea of a seed or origin that grows into a distinct type: a seed you plant, a breed or race as a biological line, and the act of planting itself.
种 is the modern simplified form of 種. The older form combines 禾 (grain/plant) with 重, which likely contributed the sound and the idea of something heavy or weighty, suggesting seeds as the weighty origin of plants. The modern 中 replacement is a simplification and should not be treated as the original historical component.
The left side is 禾 (grain/plant) and the right side is 中 (middle). Picture a seed being placed right in the middle of the soil to grow a new plant.
For チュウ, imagine planting a seed in the middle of a chew toy: chew -> チュウ, and the seed grows from the center.