The Glowcap family is a family of plants found in Pikmin and Pikmin 2. Both variants shed light and are found only underground. Like most plants, their only purpose is as scenery but they do contribute dim light.
Rather than actual plants, Glowstems are LEDs with either a green or orange light. If touched, the light will flicker for a moment, and then return to normal. They are found in caves with metallic scenery.