Leaf and Internode


Leaves of different species show wide variation in morphology and anatomy, usually associated with specialized roles in photosynthesis. Formation of leaves, from naive meristematic cells at the growing shoot tip, differs subtly in monocotyledonous and dicotyledonous plants, although it appears to involve conserved gene functions.

Keywords: leaf; leaves; lateral organs; shoot apical meristem; stem

Figure 1.

Parts of the monocot and dicot leaf. (a) A simple leaf of the dicot, Antirrhinum majus (snapdragon). (b) A compound leaf of the dicot Pisum sativum (garden pea). (c) Part of the grass‐like monocot leaf of Zea mays (maize). (d) The broad monocot leaf of Spathiphyllum wallisii.

Figure 2.

Leaf anatomy. (a) A section of the leaf blade of bean (Phaseolus vulgaris) showing adaxial and abaxial epidermal cell layers (e), a single layer of palisade mesophyll cells (pm) and several layers of spongy mesophyll (sm). This picture is of a mature leaf that was frozen and then broken before viewing in a scanning electron microscope. Bar, 50 μm.

(b) The abaxial epidermis of a wheat leaf blade with a pair of stomatal guard cells (gc). The cuticle formed on the leaf surface includes numerous wax crystals. Key: e, epidermal cell; sa, stomatal aperture. Bar, 20 μm.

(c) The abaxial epidermis of an immature bean leaf with both hooked and glandular trichomes. Labelled as in (a). Bar, 100 μm.

(d) A section through a maize leaf showing typical Kranz anatomy associated with C4 photosynthesis. This stained section was made perpendicular to the long axis of the leaf. Key: e, epidermis; m, mesophyll; bs, bundle sheath; v, vascular cells. Bar, 50 μm. Photograph provided by Jane Langdale, University of Oxford.

Figure 3.

Leaf initiation. (a) The shoot apex of the dicot, Antirrhinum majus, showing the shoot apical meristem (SAM) and primordia of leaves formed from it (p). Leaves are produced in opposite pairs and numbered according to increasing age. (b) The apex of the monocot, barley. Leaf primordia (p) are more flattened than those of dicots, produced singly, and encircle the whole meristem. Bars, 100 μm.


Further Reading

Bell A (1991) Plant Form. An Illustrated Guide to Flowering Plant Morphology. Oxford: Oxford University Press.

Esau K (1977) Anatomy of Seed Plants. New York: John Wiley.

Freeling M (1992) A conceptual framework for maize leaf development. Developmental Biology 153: 44–58.

Hetherington AM (ed.) (1994) The Tansley Review Collections. 1: Leaf development and function. New Phytologist 128: 19–507.

Steeves TA and Sussex IM (1989) Patterns in Plant Development. Cambridge, UK: Cambridge University Press.

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How to Cite close
Hudson, Andrew, and Jeffree, Christopher(Apr 2001) Leaf and Internode. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0002056]