Which term refers to plants with an embryo that has a single cotyledon?

The term that refers to plants with an embryo that has a single cotyledon is "Monocotyledon." This classification is fundamental in botany, as it categorizes flowering plants (angiosperms) based on the number of seed leaves or cotyledons present in their embryos. Monocots typically exhibit several defining characteristics, such as parallel leaf venation, floral parts in multiples of three, and a fibrous root system.

Meanwhile, the other terms provided relate to different botanical or ecological concepts. "Monoecious" refers to a plant species that has both male and female reproductive organs on the same individual, which is not connected to cotyledon count. "Node" is a part of a plant stem where leaves, branches, or flowers originate, while "mycelium" refers to the vegetative part of fungi, consisting of a network of fine filaments. Understanding these distinctions is crucial for grasping the diversity within plant biology and ecology.