Naturespeak A naturalist's view of the world

August 11, 2009

The Lotus Effect

Filed under: Uncategorized — wykes @ 9:09 pm

The American Lotus is a spectacular plant. With their giant blossoms, expansive circular leaves, and larger than life look they are inspirational (see here). Over the course of their lengthy summer bloom period they prompt us to spout poetry or to take artsy photos using non-artsy cameras. They elicit “wows” and silent admirational stares in equal measure. They even inspire “superheros” such as the downriver resident called the Blue Lotus who wields a large blue plastic sword, carries a parasol, and draws her special water powers from the lotus. People have eaten, worshipped, or channeled these incredible water plants for centuries, so it should be of little wonder that I feel compelled to bring up a few more Lotus related issues.

I’m not even going to mention the Lotus flower in this discussion, but will instead concentrate on the huge circular leaves. Unlike the Blue Lotus Lady, these magnificant structures have real supernatural powers over water. This feature is alluded to in an ancient poem entitled “The Virtuous Man,” where the chaste man is “not enslaved by any lust whatever, by the stain of passion he is not soiled. As in the water, yet unwet by the water, is the lotus leaf.”Before you react by saying “What the heck does that mean,” the lotus leaf’s water resistant powers are legendary. It is near impossible to get one of these leaves wet even though they are aquatic plants.  They are, in the parlance of science, “superhydrophobic.”

A drop of water instantly beads up like quicksilver when striking the surface of a leaf. All it takes is the gentle motion of the wind (or a hand) to swirl the bead about and pour it off without leaving any residue see the short video here. This water shedding ability, called the Lotus Effect, is caused by nano-sized wax papillae on the upper side of each epidermal cell. In simpler words, this means that the upper side of the leaf is covered with very tiny wax-covered bumps that force the liquid water to congeal and roll. The apparent purpose of this magical effect is to remove dust, dirt, and fungal particles from the leaf. This self-cleaning leaf  is indeed a pure and chaste leaf.

A lotus leaf submerged, like the poem says, remains resistant to water. When held under, the leaf surface takes on the look of a finely polished mirror and reflects the face of the virtuous man or woman pressing it down. When so submerged, the leaf also reveals yet another one of its fascinating traits – they breath the same virtuous air we do. The pale center spot on each leaf (see above) is a porous breathing hole where the plant exchanges gas with the air. This fact becomes clear when you observe a submerged leaf  and see a procession of bubbles issue from that location (see below and the short video here ). In the video example, I watched a steady stream of  18 equal sized bubbles pop out over the course of 20 seconds. This is air exhaled by the tubers deeply buried in the sediment.

The stem of the lotus is perforated with dozens of long air tubes (see here) which feed oxygen rich air down to the buried rootstocks, aka rhizomes or tubers, some 4 to 5 feet below.  Aquatic plant “roots” need air just like terrestrial ones do. Oxygen rich air is taken in through the surface of the leaf and sent down through one or two of the stem tubes. The spent air is returned to the atmosphere via another set of tubes which dead end at the porous surface of the center spot. This is the air that is seen bubbling out. So, in a primitive sort of way, the plant is breathing in and out.

In case you are wondering,  lotus plants can drown if deprived of air- that is unless the Blue Lotus Lady intervenes.

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