Morphoanatomy, patterns of development and types of feijoa (Acca sellowiana) flower buds in tropical and subtropical climates.

Abstract

Main conclusion: Two distinct patterns of bud ontogenesis and development were found under subtropical and tropical climates, pointing to the potential plasticity under climatic variations. Acca sellowiana flourishes and sprouts in spring in subtropical climates (STC), its center of origin and diversity, but throughout the year in the tropics (TC). We hypothesized that the flower and vegetative buds could have distinct patterns of origins and development. Thus, this study aimed to identify the origin of floral buds in feijoa under STC and TC, as well as the relationship between flowering development and seasonality. Stages from the genesis of flower buds to flowering, from samples collected in orchards under TC (Colombia) and STC (Brazil), were morpho-physiological characterized and analyzed in light and scanning electron microscopy. It was found two patterns of bud development: (i) in STC: pseudoterminal and axillary flower buds were evident, but a vegetative bud can originate in the same axilla, independent of the development of current year branches; (ii) in TC: flower buds showed common base with vegetative buds that originate new branches but formed in the alternate nodes; flower and vegetative epicormic buds, recorded in different accessions and types, were grew along bowed branches. Climatic conditions can have different effects on the development of floral buds of feijoa. Other factors also affected the genesis of floral buds, highlighting cultivation practices and biotic factors. Flowering of feijoa adjusts to the most favorable climate, revealing the potential plasticity under climatic variations that have been occurring. Distinct bud development patterns can also be a signal of incipient speciation between Brazil and Uruguay feijoa populations, such as the cultivated one in Colombia.