Botany 431 - Physiological Plant Ecology


These notes are to give students in the course some background on the pedagogical basis behind this course.


There is a consensus amongst educators that what a student does is more important in determining what is learned than what the teacher does. The learner is central in the creation of meaning, not the teacher, as the transmitter of knowledge. Learners arrive at meaning by actively selecting, and cumulatively constructing, their own knowledge through both individual and social activities. The implication is that teaching should focus on the learner and the learner's world.

Teaching therefore should:

  1. provide instructional situations that elicit activities appropriate to the subject studied.
  2. view learners' conceptions from their perspective.
  3. see 'errors' as reflecting the learners level of development.
  4. recognise that substantive learning occurs through periods of conflict, surprise, over periods of time and through social interactions.


It is to be anticipated that learners develop their cognitive abilities over time. If assessment exercises only deal in low level cognitive activities, e.g. by testing rote learning, then learning will be constrained by assessment at a low level.

It is most desirable that learners are assessed for higher level cognitive abilities and that they have some control over that assessment. In part because the ability to define what is wanted from a learning situation is an important generic skill to use after leaving the formal educational environment. The ability to be able to undertake lifelong learning is much talked about but not assessed.

What can research tell us about the development of learners.


Piaget defined five stages in the development of the ability to learn. We would hope that people graduating from university would be functioning at the fifth level.

  1. Pre-operation 1 (4 to 6 years).

    Associations made on the basis of emotion, personal preference and an egocentric view of the world.

  2. Early Concrete (7 to 9 years).

    Learners can use one, but only one, relevant operation. They cannot coordinate two operations as is necessary in making judgments about the area of a surface.

  3. Middle Concrete (10 to 12 years).

    Learners can think by using several relevant operations. They acquire the concepts of conservation, transitivity and reversibility (click on the hightlighted term for footnotes).

  4. Concrete Generalization (or Early Formal) (13 to 15 years).

    Learners can generalize from their own concrete experiences but only within the context of that experience. They cannot hypothesize about possible concepts or work with abstract variables.

  5. Formal (16 years onward).

    Learners are capable of purely abstract thought. Rules can be combined to obtain quite novel results that are beyond the individual's own experience. Scientists do this when they hypothesize about possible conclusions from theory, and then design experiments to test those not-yet-experienced hypotheses.


  1. Stages proceed in an irreversible sequence (formal may never be reached).

  2. Stages are stable. Having reached a stage, thinking is characteristic of that stage and not earlier ones. This may not be valid as a student may be formal in thinking one week and concrete the next.

  3. The best way to predict how a student will behave in a given task is to observe them perform other logically relate tasks. This may not be valid as other factors like motivation and prior knowledge have an influence. Most people function well below their potential maximum.

  4. Exceptions to points 2 and 3 occur. Décalage is where a learner performs one task but cannot perform another task of similar structure. e.g., can do 6 +7 = ? but not 600 + 700 = ?.

  5. The learner labelled at one stage will remain at that stage until reaching the next one.

    It follows that it is pointless to instruct or evaluate a subject that requires thinking at a higher stage than that at which the student is capable of thinking. Are the students ready for the instruction? For first year University students this usually involves the difference between the concrete and formal stages. Many first year students may not yet be formal thinkers or not yet formal thinkers about biological sciences. It is hoped that biology majors would be before they graduate.

    An answer to some of these dubious assumptions is to shift the label of the student's thinking ability from the students themselves to the quality of their response to a particular task like responding to an exam or quiz question. The Structure of the Observed Learning Outcomes (SOLO) Taxonomy was designed to do that, but it can only describe a particular performance at a particular time and must not be used to overgeneralize.


Biggs and Collis modified Piaget's scheme to identify five stages of a learner's development. The stages are based on an analysis of written work submitted by learners in assessment exercises.

The response stages of the SOLO Taxonomy are paralleled by the human stages of cognitive development of Piaget (in parenthesis).

  1. Prestructural (Pre-operational).
    The learner does not understand the point of a question.

  2. Unistructural (Early concrete).
    One or a few aspects of a task are picked up and used.

  3. Multistructural (Middle Concrete).
    Several aspects of a task are learned but are treated separately.

  4. Relational (Concrete generalization).
    Parts are integrated into a coherent whole, with each part contributing to the overall meaning.

  5. Extended Abstract (Formal).
    An integrated whole at the relational level is reconceptualised at a higher level of abstraction. This may allow generalisation to a new topic or area.

To illustrate how these response stages might operate, sample answers to a question will be given. Even though a particular individual may be in graduate school, he or she may still answer at a lower level than they are capable of. The SOLO taxa can be applied to any skill level or age cohort of people.


What modifications of plant structure and function would help a plant resist drought stress in a desert environment?


  1. Prestructural.

    Plants don't grow in the desert.

  2. Unistructural.

    1. Plants have a very thick cuticle.

    2. Plants absorb water any time they can get it.

  3. Multistructural.

    1. Desert plants have reduced leaves in the form of spines and their roots spread out to absorb as much water as they can.

    2. Desert plants have CAM photosynthesis and very thick cuticles.

  4. Relational.

    1. Carrying out CAM photosynthesis involves opening the stomate at night when the desert air is cool. The result is that when the stomata open to admit CO2 there is a lower rate of water loss than there would be if the stomate were open during the hot day.

    2. By having roots that go very deep into the desert a plant may be able to find hidden reserves of water. By also having a thick cuticle to restrict water loss from the shoot the plant is able to conserve enough water to survive.

  5. Extended abstract.

    Because the plant has to balance the opposing fluxes of water and CO2 when stomate are open, it is advantageous to open the stomate at a time when it is less likely that water will be lost because CO2 will always be available. That would be at night when the desert air is cooler or in the day when excess water is temporarily available. Because carbon fixation by Rubisco can only occur in the light, an additional means of CO2 fixation is needed. That is provided by PEP carboxylase in the CAM photosynthesis dual fixation process. With excess water, stomata may open during the day and rely exclusively on Rubisco fixation. As the greenhouse effect causes a warmer and dryer global climate it could be expected that plants showing these adaptations will increase their geographical range in the future.

It is obvious that the extended abstract answer is richer and more well rounded showing evidence of thought well beyond the narrow confines of the question.


Learning outcomes will be stated for all parts of the course. Students in the course will be invited to select some of the evidence used to decide whether they have achieved the learning outcomes or not. That material will be assembled by each student into a portfolio. In part, this forces each student to reflect on what they want out of each part of the course and how they are going to get what they want.


Conservation - quantitative aspect of material. Not changed or affected by transformation of material.

Transitivity - if x if related to y and y is related to z then x must be related to z. Unidirectional relationships are transitive. e.g. taller than, multidirectional relationships are not.

Reversibility - a series of operations where the reverse order gives the original state. A requirement for conservation.

Much of the theoretical material above is lifted verbatim from Biggs J.B. and K.F. Collis (1982) Evaluating the Quality of Learning. Academic Press, London.

See also: Biggs,J. (1996) Enhancing teaching through constructive alignment. Higher Education 32:347-364.

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