Leaf architecture of terrestrial and epiphytic ferns from an Araucaria forest in southern Brazil

Studies of angiosperms have associated the mechanical design of petioles with leaf form and the occurrence of simple and compound leaves. Petiole anatomy can respond differently, according to different leaf forms, to maintain plant architecture. The present study evaluated whether this premise applies to fern leaf architecture. Leaves of five ferns (Blechnum binervatum (Poir.) C.V. Morton &amp; Lellinger, Ctenitis falciculata (Raddi) Ching, Megalastrum connexum (Kaulf.) A.R. Smith &amp; R.C. Moran, Microgramma squamulosa (Kaulf.) de la Sota, and Serpocaulon catharinae (Langsd. &amp; Fisch.) A.R. Sm.) from a remnant of an Araucaria Forest in southern Brazil were collected and their morphological and anatomical traits were analyzed. Results indicate that the biomechanical patterns of these terrestrial and epiphytic ferns are similar to those reported for angiosperms, except for the presence of subepidermal sclerenchyma in fern petioles. Independently of leaf form, the rigid structure of fern petioles appears to be an important adaptation to biomechanically support leaf position for maximum light interception in forest understories. </jats:p