Floral nectar production and carbohydrate composition and the structure of receptacular nectaries in the invasive plant Bunias orientalis L. (Brassicaceae)

Bożena Denisow,Sebastian Antoń,Marzena Masierowska

doi:10.1007/s00709-015-0902-6

Bożena Denisow, Sebastian Antoń + Show 1 more

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https://doi.org/10.1007/s00709-015-0902-6

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Journal: Protoplasma	Publication Date: Nov 11, 2015
Citations: 16	License type: CC BY 4.0

Affiliation: University of Life Sciences in Lublin

Abstract

The data relating to the nectaries and nectar secretion in invasive Brassicacean taxa are scarce. In the present paper, the nectar production and nectar carbohydrate composition as well as the morphology, anatomy and ultrastructure of the floral nectaries in Bunias orientalis were investigated. Nectary glands were examined using light, fluorescence, scanning electron and transmission electron microscopy. The quantities of nectar produced by flowers and total sugar mass in nectar were relatively low. Total nectar carbohydrate production per 10 flowers averaged 0.3 mg. Nectar contained exclusively glucose (G) and fructose (F) with overall G/F ratio greater than 1. The flowers of B. orientalis have four nectaries placed at the base of the ovary. The nectarium is intermediate between two nectary types: the lateral and median nectary type (lateral and median glands stay separated) and the annular nectary type (both nectaries are united into one). Both pairs of glands represent photosynthetic type and consist of epidermis and glandular tissue. However, they differ in their shape, size, secretory activity, dimensions of epidermal and parenchyma cells, thickness of secretory parenchyma, phloem supply, presence of modified stomata and cuticle ornamentation. The cells of nectaries contain dense cytoplasm, plastids with starch grains and numerous mitochondria. Companion cells of phloem lack cell wall ingrowths. The ultrastructure of secretory cells indicates an eccrine mechanism of secretion. Nectar is exuded throughout modified stomata.

Highlights

Nectar production is generally associated with mutualistic relations with animals that rely on sugar secretions in their nutrition (Simpson and Neff 1981; Nepi et al 2009)
Knuth (1908) reported that Bunias flowers possessed only two nectaries placed on inner sides of short stamens, which could indicate the presence only of lateral glands and a total lack of median glands
The nectarium of B. orientalis is intermediate between two nectary types: the lateral and median nectary type and the annular nectary type sensu Deng and Hu (1995)

Summary

Introduction

Nectar production is generally associated with mutualistic relations with animals that rely on sugar secretions in their nutrition (Simpson and Neff 1981; Nepi et al 2009). Nectaries attract pollinators, protectors (e.g. ants and parasitoids) against herbivores or even prey in carnivorous plants (Heil 2011). These structures occur in different plant organs. Glands located in the flowers are commonly designated as floral nectaries, whereas extrafloral nectaries are present in other parts of the plant. Morphology and structure of the floral nectaries have been described for numerous plant species, and nectary traits are considered highly diverse in angiosperms since those structures appeared independently in many taxa (Vogel 1997; Fahn 2000). The relative location of nectaries within a flower is under pressure to maximize relations with pollinators (Nepi 2007) and to ensure the deposition of pollen on the stigma by pollinators

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