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Keywords:

  • growth coordination;
  • organ growth;
  • organ identity;
  • organ shape;
  • organ size

Contents

 Summary319
I.Introduction320
II.The cell biology and biophysics of growth320
III.Timing is everything: what determines when proliferation gives way to expansion?323
IV.Anisotropic growth and the importance of polarity325
V.How does organ identity and developmental patterning modulate growth behaviour?326
VI.Coordination of growth at different scales327
VII.Conclusions329
 Acknowledgements329
 References330

Summary

The growth of plant organs is under genetic control. Work in model species has identified a considerable number of genes that regulate different aspects of organ growth. This has led to an increasingly detailed knowledge about how the basic cellular processes underlying organ growth are controlled, and which factors determine when proliferation gives way to expansion, with this transition emerging as a critical decision point during primordium growth. Progress has been made in elucidating the genetic basis of allometric growth and the role of tissue polarity in shaping organs. We are also beginning to understand how the mechanisms that determine organ identity influence local growth behaviour to generate organs with characteristic sizes and shapes. Lastly, growth needs to be coordinated at several levels, for example between different cell layers and different regions within one organ, and the genetic basis for such coordination is being elucidated. However, despite these impressive advances, a number of basic questions are still not fully answered, for example, whether and how a growing primordium keeps track of its size. Answering these questions will likely depend on including additional approaches that are gaining in power and popularity, such as combined live imaging and modelling.