Field of Science

Peculiar "forest" caption

Congratulations to everyone who recognized this was a kelp forest.

COVER ILLUSTRATION: Kelps use a basal growth strategy that positions younger tissue at the base of the blade. This younger tissue is more fl exible and extensible than older tissue at the blade’s distal end. In contrast, red algae have an apical meristem that produces new tissue at the distal end of the blade, positioning older tissue near the blade’s base. In “Divergent growth strategies between red algae and kelps infl uence biomechanical properties” on pp. 1938–1944, Krumhansl et al. hypothesize that the location of older tissues relative to the blade’s attachment point to the substratum infl uences the species’ performance in wave-swept habitats. The authors propose that the positioning of younger, more fl exible and extensible tissue at the blade base in kelps may contribute to their ability to obtain large blade sizes and dominate in hydrodynamically stressful environments (Laminaria setchellii). (Photo credit: Kyle W. Demes.)
What this means is that unlike apical growth brown seaweeds have an intercalary meristem at the base of their stipes (stem-like part) next to the holdfast (root-like anchoring organ). As juvenile tissue, the cell walls are thinner and more flexible, so the stipes bend without breakingor buckling, a useful trait when growing in a heavy wave zone what with a lot of water washing to and fro. As you can see in the image posted on the previous blog, this Laminaria has pretty broad blades, a lot of surface area for water to push against. However in filamentous green algae, anchored filaments in zones of moving water have apical growth while filamentous green algae growing in still water have intercalary growth. The first form is stronger at the base, but slower growing.  The second form has weak zones where ever the cells have divided, but it grows faster. This difference in comparison to the brown algae is probably due to limited structural strength to a filament to a multicellular stipe.

1 comment:

William Connolley said...

You're right, that was interesting :-).