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Do plants dynamically regulate nectar features through sugar sensing?

Nectar properties (volume, concentration, viscosity) change dynamically in time. As stated by Pedersen some decades ago (1958), “Nectar is not a static product remaining outside the plant once produced but is in close contact with the plant system.”1 It is now evident that secretion may occur concomitantly with resorption and that the latter process sometimes continues after secretion has ended. The rate of the two processes may be modified dynamically by the plant in response to ecological and physiological constraints, maintaining a relatively constant nectar concentration to ensure pollinator visits (nectar homeostasis) and reallocating resources, especially during development of the ovules and pericarp after fertilization. We suspect that nectar resorption is under-estimated as a phenomenon, because it requires detailed information on the dynamics of nectar production throughout the life of the flower that is seldom available or taken into consideration. The cytological and molecular mechanisms involved in nectar resorption are almost completely unknown. Sugar sensing may have a fundamental role in nectar resorption and homeostasis. Due to direct contact with sugar solutions, nectaries may offer wide scope for insights into this phenomenon which has attracted interest as part of plant signalling systems. Addendum to: Nepi M, Stpiczyńska M. The complexity of nectar: Secretion and resorption dynamically regulate nectar features. Naturwissenschaften 2008 95:177-84.