Question

Submersed aquatic plants such as the parrot feather, Myriophyllum aquaticum display highly dissected leaves (A), in contrast to plants with floating leaves such as the water lily (B, Nymphea odorata).
In what way does the dissected leaf structure enable a plant to adapt to a submerged environment?

• A. The dissected structure provides a higher SA/V ratio which allows for a greater ratio of stomata/area for gas exchange.
• B. The dissected structure provides a lower SA/V ratio which limits the amount of osmosis into the submerged leaves.
• C. The dissected structure provides a higher SA/V ratio for purposes of $C{O}_2$ diffusion which compensates for the lower $C{O}_2$ concentration in the freshwater environment.
• D. The dissected structure provides a lower SA/V ratio to cope with the increase in light intensity just beneath the surface of a body of water.

Answer 1

Answer: (C)

The dissected structure provides a higher SA/V ratio for purposes of $C{O}_2$ diffusion which compensates for the lower $C{O}_2$ concentration in the freshwater environment.

The dissected structure provides a higher SA/V ratio as compared to a complete lamina. This is required, as the submerged hydrophytes do not contain stomata. The gaseous exchange will take place only along the surface of the leaf, more over the amount of dissolved Co${}_2$ in water is comparatively less in water than land. So, dissected surface increases surface area.

So, the correct answer is 'The dissected structure provides a higher SA/V ratio for purposes of CO2CO2 diffusion which compensates for the lower CO2CO2 concentration in the freshwater environment'