Aroids of the imagination VII - Butterflies, Crimson Melons and Chains
Building a Base
Monsteroides catenifolium, the Chain Vine, is a very patient plant. On germination, it forms a rosette of leaves and remains as a rosette until it senses a climbable structure or plant nearby (see picture at right). Often, the appearance of such a suitable support may take one or many seasons of growth. The Chain Vine continues to grow patiently in rosette form as plants around it increase in height and maturity. As soon as one of them reaches a size that would support the mature vining stage, the Chain Vine changes its growth habit and leaf structure abruptly and begins climbing.
The Chain Ascends
Once climbing starts, the growth rate of this plant accelerates markedly. The Chain Vine must reach flowering maturity in the same year as it begins climbing because the winds of the annual storm season will rip the vine off its support and destroy it. Should the vining plant fail to reproduce within that time frame, the process will have to begin again with another seedling somewhere else next season. M. catenifolium has no axillary buds, so the destruction of the apical meristem of this vine is, essentially, the destruction of the entire plant. So as patient as the plant was before, it becomes equally impatient to reach maturity once it begins vining!
In the picture at left, you can see the complete transformation of the leaf structure from rosette leaves to vining leaves. The chain-like segmented leaves are what gives this plant its name; they can be described as catenately divided.
On Earth, many plants show changes in leaf morphology from juvenile to mature stages. Monstera deliciosa is one vining aroid that shows this behavior. The young leaves are entire, looking like those on a common cordate Philodendron. On reaching a more mature stage, however, the leaves develop numerous splits and holes that give this vine its common name, "Swiss Cheese Plant".
M. catenifolium can be understood as one of the few plants on Aroidia that is a "biennial" in the sense that it cannot survive from one season to the next unless it is in the rosette form. However, this is not always accurate because the plant can remain in rosette form for several years before a suitable support for the climbing stage grows large enough nearby. In fact, an old enough specimen in the rosette form could be mistaken easily for a species of Macroalocasia.
Success at last!
At right can be seen a mature inflorescence of M. catenifolium. The spadix remains partially enclosed by the spathe, leaving some openings for access by the pollenoids.
Inflorescences are borne terminally and usually in groups of one to three, each maturing in succession. The ripening of the infructescences occurs just before the onset of the storm season, affording the semmules an excellent opportunity for wide dispersal.
Butterflies in the Tree
The Chain Vine grows in the same habitat as another Aroidian plant with very unusual leaves. This next wonder is closely allied with the titanic Pinnatidendron that is so ubiquitous on the biological archipelagos. Pinnatidendron lepidopterophyllum, or the "Butterfly Palm", is not nearly as common on Aroidia, but it is unmistakable when it is found.
Unlike its much larger cousin, P. lepidopterophyllum has only two leaflets per leaf. Each pair is attached to the end of a wire-thin flexible petiole that can be up to 5 feet long on mature specimens. The plant produces a head of 30 or more of these leaves, all with different petiole lengths that vary with their maturity. But the most striking characteristic these leaflets have is that they flutter gently during the daytime, like a group of emerald butterflies! This movement is not driven by wind, but by pulvinoids at the base of each leaflet.
On Earth, rapid movement of leaflets is not unheard of. One well-known plant that shows this is Mimosa pudica, which is also known as the Sensitive Plant or Touch-Me-Not. This is because, when touched, the leaflets close rapidly, due to the action of a pulvinus at the base of each leaflet and at the joints of each leaf.
On Aroidia, the leaflet movement on P. lepidopterophyllum is nearly continuous because it occurs not from touch, but as a result of temperature differences between the upper and lower surfaces of the leaflets. When the upper surface is warmer than the lower surface, the pulvinoids activate and the leaflets close. As the concealed and shaded upper surfaces cool, the leaflets open again.
The activity of these leaflets is not the only attraction this plant has to offer. When in bloom, the inflorescences cannot be missed because they appear as bright crimson melons nestled amongst the bases of the long petioles. The inflorescence is about the size and shape of a small honeydew melon, with the spathe an intense crimson color and the spadix a dark maroon-red. The spathes open just enough to allow pollenoids an entry; thus adding to the melon-like appearance.
P. lepidopterophyllum is found growing right at the water's edge, where the ripe berries can fall and be carried away by currents to other suitable habitats.
Even more bizarre and beautiful discoveries awaited me as I continued my visionary exploration of Aroidia . . .
Picture credit: LariAnn Garner, Aroidia Research
(Continued in Part VIII: Bananas and Aroids)