Influence of shoot inclination on irradiance and morphophysiological leaf traits along shoots in cerrado trees with distinct leaf deciduousness

Abstract

This study investigated the relationship among shoot inclination, irradiance and morphophysiological traits of basal (BL) and distal (DL) leaves in six cerrado trees with distinct leaf deciduousness. Deciduous species showed plagiotropic shoots (44°) and larger leaf area than semideciduous and evergreen species, which showed orthotropic shoots (56° and 63°, respectively). Despite larger leaf area, irradiance at shoot base in deciduous was around 85% in relation to full irradiance, while in semideciduous and evergreen only 23% of irradiance reached on BL. Likewise, maximum net photosynthesis (Pnmax) was similar between BL and DL in deciduous. Contrastingly, semideciduous and evergreen showed significant decreasing of Pnmax in BL. Plagiotropic shoots of deciduous allow similar irradiance along shoots, resulting in similar Pnmax along shoot. On the other hand, orthotropic shoots of semideciduous and evergreen resulted in shading and decreasing of Pnmax on BL. However, considering BL and DL together, there was not significant difference of leaf-life-span or Pnmax among deciduous, semideciduous and evergreen. Therefore, shoot inclination and shading among leaves on same shoot should be significant influencing leaf morphophysiological traits along shoots in cerrado trees. On the other hand, similar leaf-life-span among phenological groups resulted in absence of Pnmax differences when BL and DL were considered together.