Biology Reference
In-Depth Information
Chapter 4
NECTAR PRODUCTION AND PRESENTATION
ETTORE PACINI and MASSIMO NEPI
Department of Environmental Sciences, University of Siena, Via Mattioli 4, 53100 Siena, Italy
1
INTRODUCTION
Nectar secretion is complicated to study from the ultrastructural point of
view because it is a dynamic process involving many tissues simultaneously.
Study may also be affected by artefacts created by chemical fixation proce-
dures, although this problem can be overcome by freeze-drying and freeze-
substitution techniques (Zhu & Hu, 2002; Stpiczyńska et al., 2005b). Previous
research has focused on the ultrastructure of secretory cells, especially
secreting trichomes (Robards & Stark, 1988), and a general model of nectary
function as a whole is still lacking.
Nectar is secreted with particular rhythms and can be reabsorbed over the
life of the flower. The temporal patterns of secretion, cessation, and reabsorp-
tion, if any, define nectar production dynamics. This parameter is usually
linked to the foraging behaviour of visiting animals (see also Nicolson, 2007,
Chapter 7 in this volume) whose activity, together with changing environ-
mental parameters, is responsible for the amount of nectar found in a flower
at a certain moment, known as nectar standing crop (Galetto & Bernardello,
2005). Knowledge of all these parameters is fundamental to understanding
the reproductive biology of plant species, and complex, interdependent
plant-animal relationships.
This chapter also highlights the relationship between the ecological fea-
tures of nectar and the cyto-physiological characters of nectaries that were
considered in earlier literature. The ultrastructure of nectary parenchyma
cells is closely related to the manner and rate of nectar secretion. Búrquez
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