Why do tree leaves turn darker in summer?
Spring in temperate climates is a carnival of colour. As days lengthen and temperatures rise, the electric-green of fresh foliage transforms the dull landscapes of winter. Yet several months later, those bright leaves have turned dark green, giving woods a duller appearance.
Spring foliage is a magnet for a multitude of caterpillars and other insect larvae, which can’t wait to get their jaws on the soft and supple, cellulose-rich leaves. So, to repel this army of leaf-munchers, plants defend themselves by producing dark tannins.
These bitter-tasting chemicals are a natural pest control.
They become activated when the leaf is eaten, and are capable of damaging the mouth and stomach proteins of attacking insects. As summer wears on, the leaves get ever darker and more distasteful as tannins build up to fend off the onslaught.
Things that work well tend to proliferate and endure, which is why the same structures keep appearing in unrelated groups of species, through different periods in the planet’s history. Observing such similarities is one of the great joys of learning about nature. So it is with this deepsea anemone, whose resemblance to the eponymous predatory plants is uncanny. It likewise is a sit-and-wait specialist, unfurling its stinging tentacles to trap morsels of food as they drift past. However, at such depths, most of its meals are scavenged detritus rather than prey.