Patterns of calcium oxalate crystals in young tropical leaves: a possible role as an anti-herbivory defense

Calcium oxalate crystal formation and leaf toughness were measured and comp ared in five species, (Cyclanthus subpalmata, Pandanus leram, Crinum amabil e, Heliconia longiflora and Guzmania zahnii) pre selected for known leaf ra phide production and toughness. Nine to eleven representative individuals f rom each species were randomly selected for the same microenvironment. The study was conducted in Las Cruces, Costa Rica. Leaves from each species wer e classified as two age classes: young and mature. Leaf crystal number was quantified by light microscopy. Leaf toughness was measured with a penetrom eter. For all five species, the number of crystals was highest in young lea ves and lowest in mature leaves. In addition, crystal formation was inverse ly related both to the leaf age class and to leaf toughness. It is proposed that crystal formation may be an alternative plant defense to toughness in young leaves.