Aroidendron, The Keeper of the Gate
The Keeper of the Gate, Aroidendron heterophyllum, is the largest organism on Aroidia. This tree reaches heights of 3000 feet, and is found only at the north and south polar regions of the planet.
While plants on Earth require two gametes, male and female, to produce a zygote and then seeds, Aroidendron requires five different gametes joined together to produce a semmule that will grow into a new Aroidendron plant. These five gametes come from five different plants found on Aroidia; these plants are obligate gametophytes and never produce seeds of their own. One of these obligate gametophytes turns out to be Pinnatidendron altissimum.
One must wonder what the "Gate" is that Aroidendron is the Keeper of; the answer is that the Gate is the access to the planetwide communications network for the global organism. Aroidendron is the transmitting/receiving station for all communications to and from the global organism, while the Pinnatidendron plants serve as repeater stations for the network.