Citocininas nos processos anatômicos, citológicos e fisiológicos durante o cultivo in vitro e aclimatização de Annona glabra L.

Abstract

Annona glabra L. is one of the most important wild annonaceae with a high potential to produce fruits and pharmacological compounds. In vitro cultivation is a viable alternative for large scale production of plantlets of this species, overcoming the natural constraints for its propagation. However, its use in a broad form has been limited by the difficulty to induce various shoots in explants, high rate of leaf abscission and reduced plant survival index during the acclimatization phase. Among the factors that control the in vitro morphogenesis of this species, cytokinins affect diverse morphological responses. However, a better understanding of the action of these substances on the morphogenetic process of the annonaceae is still necessary, in spite of its broad use on in vitro cultivation of plant tissues. Therefore this paper evaluated the effect of four cytokinin sources, one natural and three syntheticis, on leaves and shoots anatomy, delay in leaf senescence, development of autotrophism and mineral accumulation in plants of A. glabra. Among the cytokinin sources tested, 6-benzilaminopurine (BAP) and kinetin induced an expressive increment in palisade and spongy parenchyma thickness, higher retention on leaf area, higher chloroplast differentiation and higher photosynthetic rate in shoots. The use of BAP and kinetin during the multiplication phase promoted a higher dry matter accumulation, higher development of leaf area and higher plant survival rate during the acclimatization and rooting phases. All the sources of cytokinin used stimulated a higher nitrogen and boron accumulation in shoots and lower accumulation of calcium. Thidiazuron (TDZ) promoted a disorganization in the chloroplast lamellar system, reducing the chlorophyll "a" level and photosynthetic leaf potential.