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. Author manuscript; available in PMC: 2019 Jul 3.
Published in final edited form as: Protoplasma. 2015 Mar 15;253(1):3–14. doi: 10.1007/s00709-015-0787-4

Fig. 6.

Fig. 6

Photograph of the shoot of an etiolated maize (Zea mays) seedling (a) and illustration of the auxin (IAA)-brassinosteroid (BR)-hypothesis of mesocotyl elongation (b). Coleoptile and mesocotyl are separated by the node, which consist of the meristematic tissue of the shoot. In both the coleoptile and the mesocotyl, organ growth is caused by the loosening/elongation of the thickened outer epidermal wall (OEW). This process, which is regulated by IAA (and BRs), depends on (1.) turgor pressure which must be maintained via osmoregulatory processes (2.), O2-fuelled metabolic activity of the cells, and (3.) the presence of growth-limiting proteins (GLPs) (adapted from Niklas and Kutschera 2012)