The leaf

The leaf is the main organ for photosynthesis in the plant, and its cells are organized in a way that provides maximum efficiency. The upper epidermis is transparent enough to allow the transmission of light into the lower leaf tissues. The sausage-shaped palisade mesophyll cells are packed together, pointing downwards, under the upper epidermis. The sub-cellular chloroplasts within them carry out the photosynthesis process. The absorption of light by chlorophyll occurs at one site and the energy is transferred to a second site within the chloroplast where it is used to build up carbohydrates, usually in the form of insoluble starch. The spongy mesophyll, below the palisade mesophyll, has a loose structure with many air spaces. These spaces allow for the two-way diffusion of gases. The carbon dioxide from the air is able to reach the palisade mesophyll; and oxygen, the waste product from photosynthesis, leaves the leaf. The numerous stomata on the lower leaf surface are the openings to the outside by which this gas movement occurs. The numerous small vascular bundles (veins) within the leaf structure contain the xylem vessels that provide the water for the photosynthesis reaction. The phloem cells are similarly present in the vascular bundles, for the removal of sugar to other plant parts. Figure 8.8 shows the

Palisade with many chloroplasts

Palisade with many chloroplasts

Ligustrum Leaf Cross Section
Figure 8.8 Cross-section of Ligustrum leaf showing its structure as an efficient photosynthesizing organ

structure of the leaf and its relevance to the process of photosynthesis. A newly expanded leaf is most efficient in the absorption of light, and this ability reduces with age. The movement of the products of photosynthesis is described in Chapter 9.

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Responses

  • cornelia twofoot
    What is ligustrum leaf vascular tissue?
    7 years ago
  • kaiden
    Does ligustrum have chloroplast?
    7 years ago
  • saradas greenhand
    What are the parts of a cross section of a leaf?
    7 years ago

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