Plant Tissues

Abstract

Higher plants are organized into three tissue layers: the epidermis, the ground tissue and the vascular system. The three tissue layers are established in the meristems and they are largely maintained as separate tissues throughout plant development. The L1 layer forms the epidermis responsible for plant protection and gas exchange. The L2 layer develops into subepidermal tissues generating most photosynthetically active tissues. The L3 layer generates the vascular system required for long‐distance transport of water and metabolites. Despite the clonal origin the differentiation of cells depends on the developmental context. Experiments in which single tissue layers were genetically manipulated revealed the relative importance for overall plant growth and development for each tissue layer. Central questions are: which layer determines the shape of organs, how are the cell division rates coordinated among the different tissue layers, how can the different cell layers communicate with each other and in particular what is the importance of hormonal control? The current knowledge of the underlying molecular principles are discussed.

Key Concepts:

  • Plant organs develop from three meristematic layers that are largely kept separate throughout development because of the periclinal division patterns.

  • The outermost meristematic L1 layer forms the epidermis that serves as a protection shield against the environment and regulates the gas exchange.

  • The second meristematic L2 layer generates the ground tissue which may adopt various functions including photosynthesis, storage, reproduction and mechanical support.

  • The innermost meristematic L3 layer produces the vascular system that governs the long‐distance water and metabolite transport.

  • Each tissue layer has distinct roles in the regulation of organ shape, cell division rates that seem to be dependant on the genetic pathway and the plant species.

  • Intercellular communication is mediated by receptor ligand systems and controlled transport through plasmodesmata.

Keywords: dermal tissue; ground tissue; vascular tissue; cell determination; tissue layers

Figure 1.

Origin of tissue layers. Tissue layers originate from the three cell layers of the meristem: the L1, the L2 and the L3. (a) Section of an apical meristem. Modified after Raven et al.. (b) Schematic drawing of (a) with L1, L2 and L3 cell layers marked. (c) Schematic drawing of an apical meristem with the general direction of cell divisions of the three meristematic cell layers during further development indicated by arrows. Although L1 cells almost always divide by periclinal divisions, L2 and L3 cells also frequently divide anticlinally. (b) and (c) Modified after Sitte et al..

Figure 2.

Role of tissue layers in the regulation of morphogenesis. Periclinal chimaeras revealed that leaf shape in tomato is controlled by the L2 layer, whereas trichome development depends on the L1 layer. (a) Lycopersicum esculentum has compound leaves and is hairy. Below, a schematic presentation of the three‐layered meristem is shown in grey for the genotype L. esculentum. (b) Solanum luteum has simple leaves and few hairs. Below, the three‐layered meristem is shown in black for the S. luteum genotype. (c) Periclinal chimaera with a L. esculentum L1 and a S. luteum L2 and L3 layer. The epidermis is hairy as in L. esculentum and the leaf form is simple as in S. luteum. (a–c) Modified after Jorgensen and Crane .

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Further Reading

Howell SH (1998) Molecular Genetics of Plant Development. Cambridge, UK: Cambridge University Press.

Leyser O and Day S (2003) Mechanisms in Plant Development. Oxford, UK: Wiley‐Blackwell.

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How to Cite close
Hülskamp, Martin, and Schnittger, Arp(Jun 2012) Plant Tissues. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0002070.pub2]