Floral Scents in Bee-Pollinated Buckwheat and Oilseed Rape under a Global Warming Scenario

Abstract

Many wild plants and crops are pollinated by insects, which often use floral scents to locate their host plants. The production and emission of floral scents are temperature-dependent; however, little is known about how global warming affects scent emissions and the attraction of pollinators. We used a combination of chemical analytical and electrophysiological approaches to quantify the influence of a global warming scenario (+5 °C in this century) on the floral scent emissions of two important crop species, i.e., buckwheat (Fagopyrum esculentum) and oilseed rape (Brassica napus), and to test whether compounds that are potentially different between the treatments can be detected by their bee pollinators (Apis mellifera and Bombus terrestris). We found that only buckwheat was affected by increased temperatures. Independent of temperature, the scent of oilseed rape was dominated by p-anisaldehyde and linalool, with no differences in relative scent composition and the total amount of scent. Buckwheat emitted 2.4 ng of scent per flower and hour at optimal temperatures, dominated by 2- and 3-methylbutanoic acid (46%) and linalool (10%), and at warmer temperatures threefold less scent (0.7 ng/flower/hour), with increased contributions of 2- and 3-methylbutanoic acid (73%) to the total scent and linalool and other compounds being absent. The antennae of the pollinators responded to various buckwheat floral scent compounds, among them compounds that disappeared at increased temperatures or were affected in their (relative) amounts. Our results highlight that increased temperatures differentially affect floral scent emissions of crop plants and that, in buckwheat, the temperature-induced changes in floral scent emissions affect the olfactory perception of the flowers by bees. Future studies should test whether these differences in olfactory perception translate into different attractiveness of buckwheat flowers to bees.

Phytochemical profiling of red raspberry (Rubus idaeus L.) honey and investigation of compounds related to its pollen occurrence

“…What is already well acknowledged is that olfactory signals are very important to bees to make flower choices because olfactory cues are easily learned and remembered by pollinators 90 and act in synergy with the reward and other floral features such as colour and the shape to attract specific pollinators 74 . Most studies showed that just a limited number of substances have a direct key function in attracting pollinators 61‐91 . Many substances appear almost universally present in the scent of flowers pollinated by honeybees, such as linalool and its analogues (found also in our studies), while others are characteristic of one or a few species.…”

“…Another aspect to consider is that nicotinaldehyde was found in plants not included in the fruit or bush trees, such as buckwheat nectar 66 and buckwheat honey, 67 in tobacco aroma, 68 and in linden honey 69 . In this last case it was not yet mentioned among the typical compounds of linden (otherwise called lime‐tree).…”