Section 3: The Basic Parts of a Plant

Glossary

Lesson 4: The Leaves



          Plant leaves come in a huge variety of shapes and sizes. Most often, they are
          thin and green with a large surface area, although there are exceptions to
          this.
          The leaves of a plant are positioned so as to best catch sunlight to provide
          the energy for producing food for the plant.
          Leaves are also important as a way of identifying plants and trees.


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When talking about leaves, it's important to know the names of the different parts of the leaf. The main parts of the leaf, are defined as follows:
The broad portion of a leaf that contains chloroplasts (subunits of plant cells) which hold chlorophyll, a substance that absorbs sunlight. Sunlight provides the energy for producing food for the plant. Chlorophyll gives leaves their green colour.
The veins are transport vessels that contain xylem and phloem tubes that carry water and nutrients into the leaf which distributes the plant food from the leaves to the different parts of the plant. The central main vein is called the midrib.
The thin stalk that attaches the leaf to the stem, allowing for continuous transport of liquids to and from the leaves.
Pores in the epidermis, that allow the plant to release or retain gases.


Leaves are generally arranged and angled on the plant for maximum light absorption. This allows each leaf to better carry out its functions, which are as follows:

  • receiving water and nutrients from the soil, through the stem

  • taking in carbon dioxide from the air through small openings, called stomata ( stoma is singular)

  • absorbing sunlight and using this light energy to produce food for the plant in a process called photosynthesis

  • releasing oxygen and water vapor into the air through the stomata; oxygen and water vapour are the by-products or "left-overs" produced by photosynthesis.


 
So far, we have studied the roots, stems, and leaves of a plant.  These parts comprise the vegetative parts, which can be used for non-sexual plant propagation.
The next three parts of this section, you will study the flowers, fruit, and seeds of a plant.  These are the reproductive parts, which are functional in sexual plant propagation.