II. An Introduction to Plant Morphology: Shoots and Roots!

Learning Objectives:

  • Differentiate between Plant Morphology and Plant Anatomy
  • Define jargon
  • Identify the four repeating units of the shoot

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I. What is Plant Morphology?


    When you look at a plant, what do you see? The leafs, the stem, perhaps some flowers or even roots. These are all parts of the plant's morphology, or the form and arrangement. Plant morphology (from the Greek morphe meaning "form" and -ology meaning "study of") is the study of the form and structure of a plant, often in conversation referring to external structure at the macroscopic level. Plant anatomy is specifically the study of the internal form and structure of plants, usually at the cellular level. Simply put, plant morphology encompasses external and internal form and structure, while plant anatomy specifically refers to internal form and structure. 

In some instances within archaeology and its associated discipline anthracology (the study, analysis, and identification of charcoal based on wood anatomy), archaeological remains of preserved plant material or charcoal relies on these internal structures of wood for plant identification. Aside from these special case scenarios, identifying a plant based on the anatomy is usually not pragmatic. Plant morphology is often the most practical and efficient method for plant identification. Luckily, plants are simple.

Scientific Jargon 

    Disciplines from sociology to quantum physics have specific words or phrases to concisely describe something in that discipline. The specialized, technical language is called jargon. Jargon is abundant in plant morphology as there needs to be a word or phrase to concisely describe an appearance or morphological feature. Much like learning a new language, learning jargon can be overwhelming at first, but over time, it become familiar. As an educator, I believe that it is important use jargon for exposure and scientific completeness. With time, the unfamiliar terms will become frequently used entries in your lexicon. I recognize that there will be a plethora of jargon in the remainder of this section, but is worth noting that this is a distillation of plant morphology; ergo jargon density is high.

II. Roots & Shoots: A Basic Theme of Plant Growth & Development

    It is usually good to start simple and work our way up. Plants can be simplified into two sections: roots & shoots. The root and shoot sections grows from a special set of cells called the apical meristem. From the apical meristem all of the root and shoot structures emerge. In the root, this apical meristem is called the root apical meristem, while in the shoot section it is called the shoot apical meristem. These apical meristems are the primary growing points and contain totipotent cells (i.e. cells that can become any type of cell).

    Roots are typically subterranean structures used for structural support and water and nutrient uptake.  Roots can be classified into two main types. The first type is the tap root- a straight, relatively thick, tapering root that proceeds vertically downward with smaller roots emerging from it called lateral roots. Lateral roots are relatively small roots that proceed from the tap root that strategically grow through the soil to collect water and nutrients. The second type are the fibrous roots- a type of root structure where many relatively small, fibrous root grow from the shoot. Ferns and grasses are examples of plants with fibrous roots, while dandelions and carrots are examples of plants with prominent tap roots.

   Shoots are typically vegetative, superterranean structures made of a repeating unit called a phytomer. The phytomer is comprised of four structures: leaf, axillary bud, node, and internode. A leaf is usually a flattened structure that usually carries out photosynthesis. An axillary bud is a potential growing point for shoot tissue located at the base of a leaf (the base of the leaf is called the axil). A node is a region on the shoot where the leaf and axillary bud arise, while the internode is the shoot tissue between the nodes. These four structures repeat throughout the shoot. All shoot structures are variations on the phytomer, including flowers, which are modified and specialized leaves. The first set of leaves that emerge are called cotyledons, which often have a different shape that the true leaves that emerge at the next node. In some plants cotyledons remain underground and/or act as a source of nutrients for the growing plant. The petiole is the stick part of the leaf that connects it to the stem. Some leaves do not have petioles.

 Above is an "artistic rendering" of a basic plant.
 Below is an outline of the primary layout of the plant followed by a proper diagram of a generalized plant morphology. 

    1. Roots:
            Primary Root (sometimes called Tap Root)
                    Lateral Roots 
            Fibrous Roots (Grasses & Ferns)
    2. Shoots:
                    Axillary Bud

The plant is comprised of two parts: Roots and Shoots

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