Dr. Lew Feldman, Garden Director

As you walk through the UC Botanical Garden and observe the diversity in form, shape, and size of plants, it is easy to conclude that plants must be made up of many different types of parts (organs). But in fact, the construction of plants is amazingly simple, consisting of only a few visible parts:

  1. Stems, which are divided into nodes (where the leaves are attached) and internodes (the parts of the stem between where leaves are attached)
  2. Leaves, divided usually into a flat portion, the blade, and a region connecting the blade to the stem, known as the petiole
  3. Branches, growing from the node
  4. Flowers, if the plant is reproductive and is a flowering plant
  5. Fruits or their seeds

That’s it…you’ve learned all the parts which typically make up the above-ground portion of the plant. What this means is that for most of the flowering plants that are growing in the Garden, all the variety in shape and form you observe during your walk comes from only five parts or organs. But how can only five parts account for all the diversity in plant form and shape?

The field of morphology is the study of plant form and shape. Morphologists investigate the developmental steps that an enlarging organ undergoes in order to arrive at a particular final shape and size. Underlying these steps and processes is the assumption that the final form of an organ (or of the whole plant) adapts the plant to grow in particular environments or habitats.

A good example to familiarize you with the thinking of a morphologist is shown by water plants growing in the Aquatic Display pools located along the road between the Arid House and the Orchid, Fern and Carnivorous Plant House. Notice that some plants are totally submerged, whereas other plants are partly submerged with their stems growing out of the water into the air. Use the diagram in this article to help you notice the differences between the leaves on the submerged versus the aerial portions of the stem.

Consider how these differences in leaf form could be adaptive, depending on whether the leaf is above or under the water. In other words, what’s different in the environments of totally submerged plants compared to plants only partly submerged?

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