Nectary structure in four melliferous plant species native to Chile

Abstract

Floral nectary is specialized structure mostly locating in flowers secreting nectar, a sugar-rich liquid involved in the mutual interactions of pollination and the main resource used by honey bees, Apis mellifera, to produce honey. The objective of this study is to provide detailed examination of the floral nectary in four plant species native to Chile: Quillaja saponaria, Eucryphia cordifolia, Escallonia pulverulenta and Gevuina avellana, all visited by wide diversity of insects including honeybees. These plants are responsible for the main production of monofloral honey in Chile. The descriptions were based on direct and microscopic observation of several histological sections of the flowers. The nectary of the four studied species, have very different structures, forming differentiated tissues. Our observations indicated that E. cordifolia and Q. saponaria have the highest nectary volume. On the other hand, E. pulverulenta and Q. saponaria have thick cuticles and nectar stomata. The secretory tissue in nectary of E. cordifolia was rich in starch, while E. pulverulenta, Q. saponaria and G. avellana were rich in tanniferous cells. With the exception of G. avellana, vascular bundles were always present in the sub-nectary parenchyma. The four studied species have exposed nectary and their flowers exhibit similar morphological characteristics, such as colour, and petal coherence. The large number of floral visitors in our studied species, including A. mellifera might be associated with these nectary features and flower traits, among others. This research, contribute to the knowledge of floral biology in Chilean flora, which would be useful for studies in the field of apiculture and plant-pollinator interactions.