Nectar defense and hydrogen peroxide in floral nectar of Cucurbita pepo

Daniele Nocentini,Massimo Guarnieri,Chiara Soligo

doi:10.5586/aa.2015.009

Abstract

This study was carried out to investigate some similarities between the nectaries of Nicotiana sp. and Cucurbita pepo, such as starch accumulation in the nectary parenchyma, changes in nectary color during maturation, and the production of a large quantity of sucrose-dominant nectar. The concentration of hydrogen peroxide in C. pepo floral nectar was determined in order to verify the presence of a defense mechanism similar to that found in Nicotiana sp. which protects nectar from yeast and bacteria proliferation. We also tested the eventual accumulation of antioxidants in the nectary of C. pepo as a protection against oxidative stress caused by hydrogen peroxide. The level of hydrogen peroxide found in the floral nectar of C. pepo was much lower than that found in Nicotiana sp. and the male flowers of Cucurbita had a higher concentration than the female flowers. The low oxidative stress induced by this level of hydrogen peroxide caused the accumulation of a low amount of lutein inside the plastoglobules which were contained in amyloplasts. Plastids of the C. pepo nectary are specialized in the accumulation of starch rather than antioxidants.

Highlights

IntroductionThere is a mutual interaction between them: animals are generally rewarded with food, while plants benefit in terms of pollination, seed/fruit dispersal or defense against herbivores [1]
Predation is not the only type of interaction between animals and plants
The concentration of hydrogen peroxide in C. pepo floral nectar was determined in order to verify the presence of a defense mechanism similar to that found in Nicotiana sp. which protects nectar from yeast and bacteria proliferation

Summary

Introduction

There is a mutual interaction between them: animals are generally rewarded with food, while plants benefit in terms of pollination, seed/fruit dispersal or defense against herbivores [1]. Nectar is a plant secretion composed mainly of water and sugars and related to both plant pollination, floral nectar being the reward for pollinators that mediate the dispersal of pollen [2], and the plant’s indirect defense, extra-floral nectar being a reward for ants defending plants against predators [3]. Fermentation changes the sugar profile by reducing the total sugar concentration and lowering the level of sucrose [4,5]. This profound change in the chemistry of nectar may affect the plant–pollinator relationship since the sugar profile of nectar is strictly related

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Discussion

Conclusion