Boreal Pop Sprout

The Boreal Pop Sprout split from its ancestor the Salt Sprout and spread into the waterways throughout the Dixon-Darwin Boreal. They can be found in seeps, creeks, bogs, and snow melts, pretty much any reliably moist area whether with surface water or not. They are a short lived perennial, surviving for about 5 years, and during which producing billions of hydrophobic airborne spores and potential progeny.

The Boreal Pop Sprout begins life in the air as either an asexual spore or fertilized spore in spring or summer. It will passively drift down to the ground, if lucky it will be a nice wet spot that the spore lands on. From that point the organism gets it's first footing in the world. Beginning as a tiny spore it starts off with very little material of it's own to work with and must immediately set out to gather nutrients and light to survive. There are not many options for the initial structure of something starting out as a spore, and the simple method is to begin life trying to achieve the form of a thin filamentous film of cells hardly bigger than half a centimeter across.

Once the film of cells begins passing the 5 mm mark for their diameter the organism will begin to thicken. As the body of the Boreal Pop Sprout gains mass it takes the rough shape of a ball, no bigger than a small Earth pea. The surface grows to be more tightly bound together, rather than a loose filamentous form, and three indentions appear giving away the mature trilobed form of the future. It's insides at this point move away from the filamentous form of the mat as well and take on a loose mash of undifferentiated parachyma, which continues to grow across the body with no defined growth layers. This tissue in turn organizes itself to form many choppy air labyrinths, unconnected to one another. This organization is a standard means of getting air to reach the deep tissue of its body. This maze of pockets can become water logged, and then must be cleared via uptake by the surrounding tissue. A preventative development against this is the growth of several layers of densely woven but porous hydrophobic fiber. However, regardless of these internal changes there remains to be no well developed phloem, nutrients and energy remain being passed cell to cell in a radiating manner from sources outward similarly to how it is in the mat stage.

Another shift the parachyma takes is the formation of roots and vascular fibers. Parachyma on the ventral side of the Boreal Pop Sprout, just behind the epidermal layer, arrange themselves in circles of four or six, which themselves are formed in large circular clusters of various number, but no fewer than 12. These tiny disks then begin to grow, both outward to push through the epidermal layer, and inward to push into the surrounding parachyma. The growth point pushing inward and upward stimulates parachyma to form a binding sheath one cell thick around it to act as a support and as a separating structure between the two tissues. The growth point pushing outward and downward enlisted several layers of parachyma cell sheaths, one layer of which continues a single strand of air labyrinth down the length of the root. a thin layer of epidermal cells for protection when growing out of the body is also brought along as the beginnings of a root develops.

Reduced to 20% of original (3479 x 3119) user posted image Simplified diagram of the growth stages of root and vascular fibers.

Between these two growth points the cell ring formations begin to expand and hollow out. Each ring expands to form a tube with walls one cell thick, they are similarly continual hollow tubes like the individual "funnel-like hairs" of their ancestral Bank Balgae. However, unlike that relative lost in time, the vascular fibers grown by the Boreal Pop Sprout are bound together into stronger larger structures. The walls of each tube are butted up against one another, and tiny pores, filled with loose fibers, are formed between them so what they carry may be exchanged across tubes.

As the roots reach out into the wet soil they begin to drag water into themselves through the thin and porous epidermis, and across the several layers of filtering sheaths of parachyma, the final vascular sheath playing a role similar to the casparian strip on Earth, though less effective. The surface of these roots lack any roothair structure. Water fills the void growing in the vascular fibers and is drawn up the long tubes via capillary action and into the tissues of the body where it passively spreads through the intercellular spaces. Because water moves through the Boreal Pop Sprout so passively it can more easily desiccate than members of the related Orange Spore Stalk lineage, which instead actively take advantage of the evaporation process to move water up their bodies. This prevents them from spreading to drier areas, essentially they must remain in damp soil during their active periods, as water so easily passes back out of them either through evaporation. Their dark pigmentation can put any not submerged tissues at risk of drying out when exposed to direct sun for long periods, resigning their populations to shadier areas and dappled light.

Reduced to 20% of original (3120 x 3451) user posted image Simplified cross section of nearly mature Boreal Pop Sprout displaying various distinct tissues.

With its body forming distinct tissues, and eventually a thick beard of roots digging into the soil, the Boreal Pop Sprout will be established well enough by the beginning of winter to survive the cold period using the dormancy behavior it inherited from its ancestor. Its dark pigments help lessen the chill effect from the air. During this first dormancy its sporangium begins maturing. The sporangium can take up to half the body mass of the Boreal Pop Sprout. The creases between the three lobes deepens, and the parachyma inside differentiates to cells that will give rise to spores as well as those tissues that support them during development. One thing that has changed is that the structure of the lobe has gained another layer across its inner surface, a bulwark membrane, so that spore development is not exposed if the sporangium opens prematurely.

When spring comes, and snow begins to melt, the sporangium will be dense with spores. The lobes will fill a length of tissue along the concave length of their curve with water resulting in expansion and the inversion of the lobe shape. This inversion movement splits the bulwark membrane down it's length, and after dying and drying the membrane gives in an instant and spores are released with a pop. Once popped open the tissues in the lobes will continue to produce spores for a few weeks, eventually petering out and closing beck up to heal and replenish their parachyma tissue for the winter. The first year spores released are always sexual spores, convergent in function and structure to those produced by the Salty Sunstalk lineage. Spores produced the following years will all be asexual.

Reduced to 19% of original (3596 x 2813) user posted image Enlarged cross section diagram of an asexual spore and sexual spore.

The cylindrical, septatic or multicellular, asexual spores are roughly the same as ancestral asexual spores. Their inner portion comprises of a large zygote which is slightly off center, and smaller support cells. These perform various roles both during the true spore phase and the initial divisions of the zygote, including buffering from the environment as well as a food source. The outermost cells are flat, tight against each other forming a casing, and produces hydrophobic rodlets, convergent with earth fungi, across the surface of the spore to prevent clumping from water and granting them their orange color.

Sexual spores are more complex in structure, and convergent with the airborne sexual spores of the other black flora lineages. They share the characteristic support cells of the asexual spores, but rather than a zygote they carry a very large gamete. The gametes lack any sexual dimorphism, each contributing an equal portion of material to their resulting zygote. The gamete, like the zygote in the asexual spore, is off center, with the asymmetry distinguishing a top and bottom with distinct parts. The bottom contains aforementioned support cells. The top comprises of a cap, hooks, and retracting cells. The cap seals the top of the casing and prevents exposure to the elements during initial release from the sporangium. It also keeps the hooks inside and prevents immediate fusion with spores of the same sporangium before and during initial release, as there are no distinct mating types between gametes.

After a brief span of time in the air a ring of rodlet cells holding the cap in place dies and releases it, a set of cells underneath begin drying, their oblong shape retracting and unfurling the hook structures above them. These hooks, made of exposed support cells, slowly over the course of days thins and desiccates. This act of drying causes them to gradually curl more and more, increasing their hook structure and causing strain between them, the retracting cells underneath facilitate this movement as well. While airborne in this state the spore will mesh hooks with another spore, both of their hooks continuing to curl and shorten the distance between them. Eventually the tension across the top of the respective spores will be too great, and the germ pores in their centers will rupture to expose the gametes to one another at which point they will merge to form a zygote and develop a fibrous mat. However, if a spore reaches this state before latching onto another it will simply die.