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Article Addendum

Canopy Light Gradient Perception by Cytokinin

Alex Boonman and Thijs L. Pons

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We have recently identified cytokinin as an important xylem-carried signal involved in the photosynthetic acclimation of plants to light gradients in dense canopies. Lower leaves become shaded in a dense canopy and consequently have reduced transpiration rates. Our measurements have shown that this results in a reduced delivery of cytokinins carried in the transpiration stream to shaded leaves, as compared to light-exposed leaves. Cytokinins are involved in the regulation of photosynthetic acclimation to the light gradient by stimulating the expression of photosynthetic enzymes in light-exposed leaves. In shaded leaves, the low delivery rate of cytokinin leads to reduced photosynthetic capacity and ultimately senescence. We show evidence for this role of cytokinin, as part of a complex of signaling pathways where other regulatory mechanisms are also involved. A model is presented depicting the regulation of photosynthetic acclimation by cytokinin delivery to leaves dependent on the irradiance they receive.

Authors

Alex Boonman

Utrecht University and University of Amsterdam; Utrech/Amsterdam, The Netherlands

Thijs L. Pons

Utrecht University; Utrech, The Netherlands

Purchase article for $19

Subscribe to this journal for $79/year