Viewing Plant Systematics through a Lens of Plant Compensatory Growth

By Rea, Roy V.; Massicotte, Hugues B. | The American Biology Teacher, November-December 2010 | Go to article overview

Viewing Plant Systematics through a Lens of Plant Compensatory Growth


Rea, Roy V., Massicotte, Hugues B., The American Biology Teacher


[ILLUSTRATION OMITTED]

An important objective of most college and university plant systematics courses, and of thematic lesson units on plants in some high school science classes, is to teach students how to effectively use dichotomous keys for the purpose of identifying plants. The language of most keys is quantitatively descriptive and, as such, provides students the explanatory terms and measurements required to determine the fit of their "plant-in-hand" in the order, family, genus, and finally species to which it belongs.

Dichotomous keys are generally designed as a series or sequence of paired questions that, when answered, allow the student to move to the next set of paired questions. Answering questions in sequence ultimately enables students to identify the organism of interest. These questions are often framed in a way that requires students to determine answers and make decisions based on the presence or absence of structures or on some measurement (or range of measurements) for certain plant components, such as leaf blade length or width, thorn or petiole length, or plant height (e.g., Figure 1). Although dichotomous keys provide a useful range of measurements and attributes for each species in question, these measurements are often regional and derived from averages. They do not always account for the large plasticity exhibited by plants.

The term plant compensatory growth refers to exaggerated vegetative growth that results from mechanical damage to plants (e.g., cutting, animal browsing, or breakage from snow) as a physiological consequence of an increase in the root-to-shoot ratio following the loss of aboveground biomass (McNaughton, 1983). When aboveground tissues are damaged or removed, more root reserves are allocated to relatively fewer buds, which produce fewer but larger shoots and leaves (Millington, 1963; Danell et al., 1997).

All of the examples of plant compensatory growth that we have documented (see Figure 2) exceed (sometimes by one or two orders of magnitude) the size ranges described for the species in dichotomous keys. Consequently, it has been our experience that students who are attempting to use dichotomous keys are often confused when they encounter samples of exaggerated leaf and shoot growth; they may simply disregard these atypical forms or may confront the instructor, asking why their "plant-in-hand" does not fit the key Seeking a simple explanation, instructors may answer that "Plants are variable and no keys are perfect" or "Botany is a science of exceptions to the rule," instead of proposing a response that helps students to understand why such variability can occur in nature. Here, we present several ideas for how instructors can turn these seeming conundrums into teachable moments.

At the University of Northern British Columbia (UNBC), we began to realize that our Plant Systems (Forestry 201) students were challenged each fall when attempting to key out plants during their laboratory exercises. Plants often came from areas such as river banks, where river-ice scouring sheared plants; ungulate winter ranges, where plants were heavily browsed by moose; road and trail sides, where plants were compensating from brush-cutting; and parks and city streets, where ornamental hardwoods are routinely pruned.

To help students understand ranges of variability in nature and concepts such as phenotypic plasticity (the ability of an organism to modify its morphology in response to a changing environment), and to prepare them for discrepancies between key descriptions and what they might observe in the field and in class, we now initiate discussions early in the semester on the concept (and consequences) of plant compensatory growth. We choose striking examples from the field that visually illustrate how imbalances in the root:shoot ratios can change plant morphology and phenology (e.g., how events such as bud burst or time of flowering are affected by climate). …

The rest of this article is only available to active members of Questia

Sign up now for a free, 1-day trial and receive full access to:

  • Questia's entire collection
  • Automatic bibliography creation
  • More helpful research tools like notes, citations, and highlights
  • Ad-free environment

Already a member? Log in now.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this article

This article has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this article

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited article

Viewing Plant Systematics through a Lens of Plant Compensatory Growth
Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Full screen

matching results for page

Cited passage

Style
Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

"Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

"Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

"Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited passage

Welcome to the new Questia Reader

The Questia Reader has been updated to provide you with an even better online reading experience.  It is now 100% Responsive, which means you can read our books and articles on any sized device you wish.  All of your favorite tools like notes, highlights, and citations are still here, but the way you select text has been updated to be easier to use, especially on touchscreen devices.  Here's how:

1. Click or tap the first word you want to select.
2. Click or tap the last word you want to select.

OK, got it!

Thanks for trying Questia!

Please continue trying out our research tools, but please note, full functionality is available only to our active members.

Your work will be lost once you leave this Web page.

For full access in an ad-free environment, sign up now for a FREE, 1-day trial.

Already a member? Log in now.