Xenosuliphytes and Other Plant Life

 Most photosynthetic life on Xenosulia belongs to the kingdom Xenosuliphyta, which most notably includes the divisions Cardiophyta, characterised by the presence of muscular hearts, and Iculophyta, which most grass-like plants belong too. There are also numerous groups of algae, including air algae, although there are also numerous algae taxa outside of this kingdom. 

Cardiophytes

Cardiophytes are divided into multiple different taxa, with most tree-like cardiophytes belonging to the clade Pilophyta. The defining features of this clade are the presence of exoskeletons, red, yellow or yellow-green feathery leaves, and motile larvae with bilateral symmetry. Like other cardiophytes, larvae have exoskeletons, but they have moved away from their ancestral pentaradial symmetry as they became more active. Muscles are retained in adults, which in addition to powering their hearts allow the organisms to curl up their leaves and branches to avoid heavy winds; this can also be used to protect against predation, but it’s hardly an effective strategy. The presence of an exoskeleton provides support that allows them to grow taller than other plants, allowing pilophytes to dominate the “tree” niche on Xenosulia. 

Due to the unchanging position of the sun, many pilophytes have developed bilaterial symmetry. Since light can dependably come from the same direction, a bilateral body plan maximises surface area facing the sun, with trees flattened in the sunward direction. This is more common further from the sub-stellar point, where the sun is lower on the horizon; in places where the sun is directly overhead, plants tend to be tall and have broad leaves concentrated at the top. It is also less common in more forested areas, where there isn’t always such a direct path from the sun; here, it is advantageous to gather light from every direction. 

Among the most successful bilateral pilophytes are the Arthroales, owning their success to their flexible trunks. This allows them to tolerate stronger winds much better, since they flex rather than snap, with jointed overlapping exoskeleton plates that can slide over each other, rather than the single solid shell present in most groups. 

Iculophytes

Icolophytes consist of small needle-like structures and are usually dark red in colour, serving the role of the planet’s grass, although some form larger bushes. Unlike cardiophytes, they only retain their muscles as larvae, losing the ability to move in their photosynthetic stage. Their larvae consist of a seed-like shell with a worm-like structure inside, used to move the organism to a suitable location to grow. Compared to cardiophytes the larval phase takes up a much smaller fraction of the plant’s total lifespan, and some larvae have developed a much smaller size and start off as aerial plankton. 

Air algae

Xenosulia is noteworthy for the abundance of air algae, which is likely facilitated by the strong winds and high carbon dioxide concentrations. Not all air algae are xenosuliphytes, with a large portion of air algae belonging to the kingdom Allophyta (from the domain Allocaryota). Patches of the sky are often coloured by high concentrations of algae, which can vary in colour but are often purple, leading to the appearance of coloured clouds. Certain species use bioluminescence to signal to each other and form colonies, which can result in a phenomenon resembling the northern or southern lights, especially near the sub-stellar point where air algae is more common.