Clam Daisies

300 million years post-establishment, life is now difficult for most living things outside a few lingering, low-lying refugia. Toward the equators, life is hot but tolerable, thanks to the life-giving seas. Toward the polar regions are now cold, glaciated lands once more, while deserts now spread across the lands in between, overtaking grasslands especially in the north, with rapidly growing drier and prone to drastic swings of temperature from day to night. But for one new group of final stretch plants, the spreading deserts are just the sort of place that they need to thrive. 

Clam Daisies are a group of centipedeweed relatives, part of the razorgrass clade of sunflowers, which have become highly specialized toward life in this increasingly cold, arid, and radiated world. They are descended from small, carnivorous plants which clung to the edges of the last sky islands. At some point in the later hothouse, their ancestors evolved motor cells to close their leaves around small prey animals, allowing them to become active predators. Now, however, these descendants that have moved down from the abandoned mountains and onto the plains, are benign. Back onto solid ground, they find nitrogen more available in the soil, and hunting is less necessary. Now, their roots dig into the ground to find nutrients and sparse water. They now get all of their energy from sunlight, but have had to evolve many new strategies to get it this far along in time. With Serina's volcanism extinct, its magnetosphere is lost, and its atmosphere grows thinner as a result. Without the magnetic field to protect it, the sun's radiation now hits the surface of the moon with greater intensity, causing severe sunburns and cancers in organisms that spend too long exposed. Now, plants like the clam daisies have to find ways to still collect the necessary spectrum of sunlight for photosynthesis without roasting in its harshest rays, or freezing to death in the long, chilly nights as the sun's daily heat rapidly dissipates into space without as much of an atmosphere to insulate it. The solution to all of these problems that has been found by the clam daisies is particularly innovative. 

The primary allying characteristic of the clam daisy family is a single set of very large, stone-like leaves which persist for the lifetime of the plant, slowly growing outwards from the base. These huge leaves are protected by a layer of precipitated mineral deposts up to two inches thick, which lends them a rock-like look and strength. The original structure of these protective leaf covering was silica, a mineral utilized in the tissues of all grasses. Clam daisies also utilize calcium for further strength, specifically in the form of aragonite, which helps bind the silica particles on each leaf into one solid, protective covering. The inner side of each leaf is soft, unprotected, and photosynthetic, using clear silica-infused membranes to filter light down several inches into its structure, which at close magnification resembles a labrynth of tiny rooms, each filled with chloroplasts. For many animals, this would make a delightful meal, but the clam daisies are named for their remarkable defensive strategy. Motor cells at the base of each leaf, similar to those which allow a Venus fly-trap to rapidly seal shut on insect prey, are triggered into action by cold, the beginning of sunburn on its interior tissues, or aggressive interactions with a grazing animal and most species can completely seal their leaves together in as little as three minutes - an astonishing speed for a plant that, in the case of the giant clamflower, can weigh almost 400 pounds (not counting its root system.) The notched edges of the leaves link together, like teeth, and prevent even large animals from prying it open again.

Most clam daisies grow above ground, and their growth is very slow, for they can only open up and photosynthesize for a few hours each day, at dawn and dusk, when conditions are just right. Young plants survive long, vulnerable infancy by merit of being very rare in their environments, and hiding from grazers among fields of like-colored desert stones. Growth to full size can take more than a century, and lifespans may exceed 700 years. Flowers - still resembling those of ancient sunflowers, albeit minute in size - are born in the center of the plant when conditions are most suitable, and are pollinated by small flying insects or wind - if pollination does not occur, most can self-fertilize and still bear seeds. Seeds are dispersed on the wind with small hair-like parachutes to carry them, and surely only a very small number manage to land somewhere sheltered enough to support them through their most vulnerable seedling stages. For all of these reasons, there is no species of clam daisy that could be considered common, and even in ideal habitat, the most numerous species may only occur one to every ten square miles. But this is how they survive, for being so rare, they are typically overlooked by animals that might learn to eat them, if they could more easily find them.

The most specialized clam daisies are the sunchambers, which have lost the ability to fully close their leaves, and have instead sealed them together at their tips with a membrane of clear silica particles suspended in a protein film. These plants burrow backwards into the ground as they grow, until only this "window" remains at surface level. The way the minerals are arranged in the membrane filters out most UV light, while allowing the visible spectrum to reach their chloroplasts. Thus, sunchambers can photosynthesize all day long, rather than only at sunrise and dusk. This allows them to achieve more rapid growth, reaching an adult size of some 300 pounds in as little as 20 years. Large spiked growths on their leaves help hold them down in the soil in the rare event some large animal, or simple weathering and erosion, attempts to dig them up. The only time that these plants dissolve their protective membrane is during flowering, to allow insects access inside, and later during seed dispersal, when the seed heads grow up and out of the plant on long, wiry stalks that blow away in the breeze. 

Some clam daisies show unexpected streaks of bright red or violet coloration within their mostly green tissues. This is from symbiotic cyanobacteria which many of them cultivate in their own bodies, taking advantage of the higher photosynthetic capacity of another pigment, phycoerythrin, which only they can produce. In exchange for a safe, moist place to live in a world otherwise not conducive to their survival, the cyanobacteria share some of their excess sugars with their host plant, allowing it to grow a little bit faster. Spores of these symbiotes are dispersed throughout the plant's tissues, even within the endosperm of the plants' seeds, and so are also introduced into the new seedling's first leaves as it metabolizes its energy stores and germinates.