Potential carbon gain of shingle leaves in juveniles of the vine Monstera tenuis (Araceae) in Costa Rica.

The amount of light intercepted by vertically oriented, shingle leaves of juvenile Monstera tenuis vines growing in forest understory was compared to the amount of light the leaves would intercept if they were horizontal. Light levels were monitored using quantum sensors and hemispherical photography. Shingle leaves absorb less light than they would if the leaves were horizontal at the same positions, and the difference increases with height in the forest. Modeling based on measured photosynthetic light responses and light interception suggests that at 1 m height, 75% more carbon could be gained if leaves were horizontal instead of vertical. Because the vertical leaf orientation reduces light interception, other selective factors are likely of greater importance in favoring the evolution of the shingle-leaved growth form.