The pulvinus, structure responsible for slow or fast leaf movements answering to outside or endogenous stimulus, constitutes a remarkable feature of leguminous species. The leaf position adjustments represent an efficient mechanism that allows the photosynthesis maximization under adverse conditions. In the available literature, the majority of the information about pulvinus structure refers to few leguminous species, especially those with fast movements. In this work the primary pulvinus anatomy of nine leguminous species from Brazilian "cerrado" with different kinds and velocity of leaf movement is described, attempting to identify patterns and to point structural peculiarities. The primary pulvinus of the studied species show uniseriate epidermis recovered by thick cuticle, large parenchymatous cortex, central vascular system and reduced or absent pith. The outer cortex cells are wider and show phenolic compounds, except in Zornia diphylla Pers.; in the inner cortex, the cells are juxtaposed and do not have phenolic content. The collateral vascular bundles are surrounding by a septate fibers sheath. The general anatomy organization pattern is common to the pulvini of the studied species, independently of the subfamily they belong. The observed peculiarities are possible related to the kind and velocity of leaf movement.
anatomy; Fabaceae; leaf movement; pulvinus
