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Keywords:

  • carbon metabolism;
  • environmental stresses;
  • hydraulics;
  • leaf development;
  • leaf growth;
  • mechanics

Contents

 Summary349
I.Leaf growth: volume, structures, water and carbon349
II.Coupling water and carbon limitations through the Lockhart model?350
III.ABA signalling pathway as a hub to coordinate water and carbon relations353
IV.Leaf venation: just a two-way pipe network?354
V.Leaf ontogeny orchestrates the actors involved in the control of leaf growth355
VI.The growing leaf in a changing world360
VII.Conclusion361
 Acknowledgements362
 References362

Summary

Leaf growth is the central process facilitating energy capture and plant performance. This is also one of the most sensitive processes to a wide range of abiotic stresses. Because hydraulics and metabolics are two major determinants of expansive growth (volumetric increase) and structural growth (dry matter increase), we review the interaction nodes between water and carbon. We detail the crosstalks between water and carbon transports, including the dual role of stomata and aquaporins in regulating water and carbon fluxes, the coupling between phloem and xylem, the interactions between leaf water relations and photosynthetic capacity, the links between Lockhart's hydromechanical model and carbon metabolism, and the central regulatory role of abscisic acid. Then, we argue that during leaf ontogeny, these interactions change dramatically because of uncoupled modifications between several anatomical and physiological features of the leaf. We conclude that the control of leaf growth switches from a metabolic to a hydromechanical limitation during the course of leaf ontogeny. Finally, we illustrate how taking leaf ontogeny into account provides insights into the mechanisms underlying leaf growth responses to abiotic stresses that affect water and carbon relations, such as elevated CO2, low light, high temperature and drought.