Which type of stem reproduces asexually above ground?

The correct answer, a stolon, is a type of stem that grows horizontally above the ground and can produce new plants at its nodes. Stolon formation is a common method of asexual reproduction in many plants, allowing them to spread and colonize new areas. As the stolons extend, they develop roots and shoots at intervals, creating new independent plants that connect back to the parent plant through the stolon.

In contrast, rhizomes, which are horizontal underground stems, reproduce asexually but do so below the soil surface. They also serve to store nutrients and can give rise to new shoots and roots. The culm refers to the main stem of grasses and some other plants; while it supports leaves and reproductive structures, it does not serve the purpose of asexual reproduction in the same way as stolons. An internode is simply the segment of the stem between two nodes and doesn't participate in reproduction directly. Therefore, among these options, stolons are unique for their above-ground growth and asexual reproductive capabilities.