Seasonal extrafloral nectar production by Laguncularia racemosa (L.) C.F. Gaertn (combretaceae) in Southeast Brazil

Abstract

The aim of this study was to quantify the nectar production of extrafloral nectaries by Laguncularia racemosa leaves. Extrafloral nectaries are nectar-secreting glands not directly related with pollination and which attract diverse nectarivorous arthropods but most especially ants. During two years we investigated if the extrafloral nectaries of Laguncularia racemosa were morphologically variable and if the production of nectar was seasonal. Branches with five pairs of leaves of L. racemosa each were collected out in the mangrove of River Guaratuba (Bertioga, SP, Brazil; 23°45′12″S; 45°53′45″W) in five samplings from May 2008 to April 2010. Samples received only diffuse light and were analyzed 24 h after collection, when the presence or not of liquid in all five pairs of leaves per branch was recorded. The extrafloral nectaries near apical leaves produced nectar more frequently compared to other leaf pairs. There was a sharp decrease in the frequency of extrafloral nectar production from autumn to summer. The visitation of ants was recorded and could explain the observed seasonality of nectar production by Extrafloral nectaries because the fall is the period of flight dispersal of several herbivorous insects. This work demonstrated clearly that Extrafloral nectaries in L. racemosa are functional nectar-secreting structures that are able to attract nectarivorous insects such as ants and flies. © 2011 Asian Network for Scientific Information.