The role of within plant variation in nectar production: an experimental approach.

Nectar, a plant reward for pollinators, can be energetically expensive. Hence, a higher investment in nectar production can lead to reduced allocation to other vital functions and/or increased geitonogamous pollination. One possible strategy employed by plants to reduce these costs is to offer variable amounts of nectar among flowers within a plant, to manipulate pollinator behaviour. Using artificial flowers, we tested this hypothesis by examining how pollinator visitation responds to inter- and intra-plant variation in nectar production, assessing how these responses impact the energetic cost per visit.We conducted a 2 × 2 factorial experiment using artificial flowers, with two levels of nectar investment (high and low sugar concentration) and two degrees of intra-plant variation in nectar concentration (CV = 0 and 20%). The experimental plants were exposed to visits (number and type) from a captive Bombus impatiens colony, and we recorded the total visitation rate distinguishing geitonogamous from exogamous visits. Additionally, we calculated two estimators of the energetic cost per visit and examined whether flowers with higher nectar concentrations (richer flowers) attracted more bumblebees.Plants in the variable nectar production treatment (CV = 20%) had a greater proportion of flowers visited by pollinators with higher rates of total, geitonogamous and exogamous visitation, compared to plants with invariable nectar production. When assuming no nectar reabsorption, variable plants incurred a lower cost per visit compared to invariable plants. Moreover, highly rewarding flowers on variable plants had higher rates of pollination visits compared to flowers with few rewards.Intra-plant variation in nectar concentration can represent a mechanism for pollinator manipulation, enabling plants to decrease the energetic costs of the interaction while still ensuring consistent pollinator visitation. However, our findings did not provide support the hypothesis that intra-plant variation in nectar concentration acts as a mechanism to avoid geitonogamy. Additionally, our results confirmed the hypothesis that increased visitation to variable plants is dependent on the presence of flowers with nectar concentration above the mean.© The Author(s) 2023. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Citation

Michelle Maldonado, Juan Fornoni, Karina Boege, Rubén Pérez Ishiwara, Rocío Santos-Gally, César A Domínguez. The role of within plant variation in nectar production: an experimental approach. Annals of botany. 2023 Jul 07

PMID: 37419457

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