Aroids of the imagination IV - Branching up to the heightsBy LariAnn Garner (LariAnn)
January 21, 2008
While Amorphophallus species on Earth send up a leaf that terminates in a single tier of branches, Triklados trikladum on Aroidia grows a three-tiered structure, with a gargantuan inflorescence as the third tier. This plant is one of those that must form a dendrostyle, or woody core, to support this massive vegetative growth form. The base of this plant is also heavily buttressed, much like the base of Pinnatidendron. In fact, along with Pinnatidendron, these plants often contribute to the root base that forms the substrate of the biological archipelagos.
Triklados trikladum pollenoids are among the most unusual of any plant on Aroidia. While at first glance they may look like some kind of bee, a close inspection reveals that they are unlike any bee on Earth. Their mode of flying involves small retractable "parachutes" and their vision consists of both "eyes" and ion sensor antennae. Eyes and antennae are present in groups of three, unlike Earth insects, which have them in pairs.
These pollenoids possess what appear to be legs, but which are actually attachment points to help them in adhering to the receptive areas of the inflorescence. Each "leg" has touch-sensitive ends that close on contact with the pistilloid ridges. A pollen exit port, located between the two groups of three legs, opens and releases a single large pollen grain upon successful attachment. The pollenoid then detaches and hovers around the spadix to locate another receptive pistilloid ridge. In this manner each pistilloid receives a single pollen grain, not multiple grains as in pollination seen on Earth.
The parachute-like appendages, alternately retracted and deployed, provide an improbable means of flight. Scientists would undoubtedly consider them physically unable to fly, just as had been thought about bumblebees on Earth. Yet, just like bumblebees, they fly nonetheless, without approval from the scientists!
At above, left, can be seen a side view of the T. trikladum pollenoid, while at right is a frontal view, showing the three-eyed "head" and the six "legs". The large bulblike growths on the "abdomen" are the pollen receptacles. No mouth is present, of course, as Aroidian pollenoids have no need to eat. Remember that these are not animals, but are plant derived motile entities.
More bizarre specimens
From the sublime to the bizarre, the genus Triklados was full of surprises. This next specimen is named Triklados disjunctus; an example can be seen in the picture below, left. The plant is relatively diminutive, growing only about 3 feet tall by Earth measurements, but what it lacks in size it makes up for in sheer strangeness. Growth begins with a tuberlike underground structure, but instead of sending up a vertical shoot, it sends out three horizontal shoots in a "y" pattern. These shoot grow for about a foot, then stop and swell into tuberlike growths which produce one vertical shoot each. These shoots do not grow straight up; instead, they grow at about a 45 degree angle in towards each other until they actually meet. There they fuse together and form a structure with three "leaves" in a "y" arrangement above, with a tripartite inflorescence hanging down below! The spathe is divided into three lobes and the spadix is three-lobed as well, although these three lobes are fused into one.
But the most bizarre aspect of this plant may be the pollenoids. These are like tripedal insects walking on spring-loaded stilt legs. They do not fly up to the inflorescence as many other Aroidian pollenoids do, but instead walk until they are directly underneath the inflorescence. The pollenoids then jump up repeatedly until they stick onto the receptive pistilloid area of the spadix.
T. disjunctus produces berries whose seeds germinate after a year of dormancy. This allows storms and shifting tides to move the seeds to locations other than right next to the parent plant.
Another Giant of the archipelago
Triklados dendrostylum is the type specimen in the group producing the woody cores known as dendrostyles. A massive grower with a heavily buttressed base, this plant produces only one tier of branches before blooming with a large, but relatively inconspicuous, terminal inflorescence. Growth starts from a feathered semmule that produces a bulbous base upon germination. Within the bulbous base, a dendrostyle begins as a small woody rod that is enlarged as growth proceeds. As the dendrostyle enlarges, the basal tuber becomes first cup-shaped, then trilobed, with the base of the dendrostyle set right in the midst of what will become three growing points. When the three growing shoots reach the top of the dendrostyle, they end up engulfing it completely so that it is entirely surrounded and embedded within the living plant tissue.
With age, the dendrostyle becomes somewhat triangular in cross section. Each of the straighter sides forms with a slight concavity or channel. Each spring, the shoots grow up the concavities, meet at the upper end of the dendrostyle, then fuse together to form the meristematic zone that gives rise to the main branches and the inflorescence.
During the growing season, as the plant matures, another woody layer is added to the dendrostyle. This is why, when viewed in cross section, the dendrostyle shows rings much as in woody tree trunks on Earth. Were it to be harvestable for lumber, the dendrostyle would yield perfect wood boards with no knots at all!
Revisiting T. trikladum
This brief introduction to the diversity of the genus Triklados ends with an overall look at a specimen of T. trikladum (see image, below right). At the base is a human figure added for scale; note the extreme surprise being displayed! Also observe the dotted lines indicating the monstrous tripartite tuberous growth that sustains the plant during dormant periods. Like T. dendrostylum, the semmules of T. trikladum germinate to form a bulbous single-leaved plant. This juvenile develops a small dendrostyle internally. As the plant continues growing, the dendrostyle becomes seated within a thick cup-shaped tuber. The tuber gradually becomes tripartite and develops three growing points prior to the production of a double-decker branching structure, signaling maturity.
The double- or triple-decker versions of these plants are normally found only in the subpolar and polar northern and southern latitudes of Aroidia. This is due to the presence of severe ground-level wind shear and turbulence in the equatorial regions during the annual storm season. Consequently, the best examples of this genus are seen in the northern and southern polar regions, where the storm winds are not fierce enough to damage vegetation growing there.
After visualizing this strange and wonderful genus, I pondered about what other marvels awaited me as I continued my imaginary exploration of Aroidia. For example, the idea of plants whose entire vegetative structure was floral in nature intrigued me. My wondering bore fruit when I envisaged some of the most cryptic of the Aroidian flora . . .
(Continued in Part V: Cryptic Flowers, Hidden Foliage)
Picture credit: LariAnn Garner, Aroidia Research