Abstract:

Background & Aim: Floral nectar is the reward and energy resource many flowers provide to pollinating animals. It plays a key role in constructing the plant–pollinator interaction which strongly influences ecosystem function and food security. Under the current global change situation, plant–pollinator networks are seriously impacted, consequently, floral nectar is getting more and more attention due to its importance to pollinator health. In this review, we systematically summarize the current progresses of floral nectar secretion patterns, specifically focusing on nectar dynamic, the cost to a plant of producing nectar, and the regulation of nectar attributes. 

Progresses: Previous research suggests that floral nectar is a plant behavior responding to pollination environments and a trade-off in reproductive resource allocation. Floral nectar attracts pollinators to visit flowers and manipulates floral foraging behaviors of pollinators to achieve pollination. Nectar secretion is highly dynamic at spatial and temporal scale, and it is influenced by the eco-physiology of the plant itself and environmental factors. Nectar production is an essential cost for the plant, however, the evidence to support nectar production cost is limited. Nectar reabsorption is an important mechanism to optimal allocation of floral resources. Moreover, plants may use the processes of nectar secretion and absorption, possibly simultaneously, to regulate floral nectar attributes. However, the mechanisms and ecological function of such regulation is largely unknown. 

Outlook: In the future, we suggest focusing on these basic questions involving floral nectar: (1) To explore the mechanism of floral nectar production behavior and uncover how nectar production and absorption homeostatically regulate floral nectar attributes. (2) To investigate how floral nectar influences and manipulates pollinators’ behavior and shapes pollination syndromes. (3) To understand the cost of nectar production to a plant, the energy translocation and floral resource allocation during plant reproduction. (4) To study the distribution and movement of nectar resources at the landscape level and how such changes influence plant–pollinator interactions and food production. This research will enrich our understanding of plant–pollinator interaction and predict the response of pollination to global change.

Key words: plant-pollinator interaction, floral nectar, secretion dynamic, cost, regulation