Interested in understanding how plants grow? Check out the latest two Focus Issues of Plant Physiology. The January issue is on Cellular Dynamics, the February issue on Energy: Light and Oxygen Dynamics. Combined they have provide excellent resources for the recent updates on light-mediated growth control and the cellular mechanisms required for growth.
Charlotte Gommers and Elena Monte explain how the transition of seedlings from dark to light reprograms the organism and its growth, partially involving PIF proteins and  various photoreceptors. Kasper van Gelderen et al-a review that these photoreceptors are distributed over the entire plant body, including the roots that do not typically see light, but do respond to light information from the shoot. Our recent paper in Plant Cell (van Gelderen et al-b) shows the molecular mechanism of root responses to shoot-derived phytochrome signals. The latest insights phytochrome regulation of PIFs (Phytochrome-Interacting Factors) are discussed by Vinh Ngoc Pham et al. Johanna Krahmer et al give an overview on how these phytochromes then regulate not just cellular growth but also metabolism. Interestingly, not just photoreceptors, but also the chloroplasts have a light signaling function and these retrograde signaling pathways are reviewed by Tamara Hernández-Verdeja and Åsa Strand.
Most of growth responses require the photosensory pathways to control cell wall-associated factors, such that the wall can be remodeled to yield to turgor pressure and allow the cells to expand. Daniel Cosgrove gives an excellent overview of cell wall modification mechanisms during cell growth and Carlisle Bascom et al review how growth involves interplay between between the cell wall, cytoskeleton and ion homeostasis, which is further underlined with a review on cortical microtubule dynamics by Andrew Elliott and Sidney Shaw.

Links to the papers mentioned:
Bascom et al: http://www.plantphysiol.org/content/176/1/28
Cosgrove: http://www.plantphysiol.org/content/176/1/16
Elliott & Shaw: http://www.plantphysiol.org/content/176/1/94
van Gelderen et al-a: http://www.plantphysiol.org/content/176/2/1049
van Gelderen et al-b: http://www.plantcell.org/content/early/2018/01/09/tpc.17.00771
Gommers & Monte: http://www.plantphysiol.org/content/176/2/1061
Hernández-Verdeja & Strand: http://www.plantphysiol.org/content/176/2/967
Krahmer et al: http://www.plantphysiol.org/content/176/2/1039
Pham et al: http://www.plantphysiol.org/content/176/2/1025