VIAS ALTERNATIVAS DE HIDRATAÇÃO PERMITEM A EXPRESSÃO DE MÚLTIPLOS TRAÇOS FLORAIS EM ESPÉCIES DO CERRADO QUE FLORESCEM EM DIFERENTES CONTEXTOS CLIMÁTICOS

Abstract

The emergence of floral organs revolutionized the distribution of plant species around the globe and represents one of the main innovations that explain the great success of angiosperms. However, despite the great impact that the variation of water availability can have on the expression of floral traits, little is known about the costs and benefits associated with morphoanatomical and physiological variations of flowers along water availability gradients. Therefore, the main objective of this work was to investigate the structural and functional divergence in flowers of Cerrado species that bloom between the dry and rainy seasons. In general, despite the great variability between species, seasonality did not exert significant effects on key parameters associated with morphology (ex. size (Aflor), relative investment (MFE) and modulus of elasticity (ɛ)], longevity (LF), water relations (residual transpiration (gflor-res), capacitance (Cmass) and point of turgor loss (ΨPPT-flower)] and reproductive hydraulic safety margins (MSHR). This absence of variation in structural and functional characteristics was explained by contrasting hydration mechanisms. In fact, for the vast majority of the studied species (83%), and regardless of the season, phloem was the preferred route of hydration of floral organs. In this regard, the results of the present study provide a new perspective on the wide diversity of strategies associated with water use conservation in flowers of Cerrado species, and strongly suggest that such variations are directly associated with the use of alternative hydration pathways.