One process all multicellular organisms undergo is development.  Starting as a single haploid or diploid cell, they are all the result of a complex series of events known as morphogenesis and differentiation in which one becomes many and a simple fertilized egg divides and multiplies into a mosaic of cells with structures and functions as different from the original as they are from each other.  You are such an organism, growing from a zygote in your mother's womb to the full-sized adult you are today, and along the way, your cells also left behind the features of that first cell and took on those of  the specialized cells that make up human tissues like nerve and skin.
    Plants too are multicellular organisms, and they undergo the morphogenic and differentiation process as well.  There are many similarities between the way plants and animals like yourself do these tasks, and therefore, they make excellent creatures for you to study the cycle of growth and development.
    Specifically, you will be looking at the relationship between the differentiating parts of a plant and their respective metabolic rates.  All cells burn oxygen in reaction with sugar, creating CO₂, H₂O, and usable energy as by-products (C₆H₁₂0₆ + 0₂ --> C0₂ + H₂0 + ATP).  Since energy production takes place in those parts of a plant where growth and development are taking place the most, measuring and comparing cellular respiration rates from these locations allows one to sequence the events taking place and, thus, to know what is occurring and where.  Hence, you can study the developmental process in plants by testing differences in metabolic activity as determined by how much the cells in specific areas respire.
   The way scientist do this is with a tool known as a respirometer.  These are simply closed systems (most often a flask or test tube) that can be used to measure changes in either gas pressure or volume.  Normally, if an organism is placed in such a situation, any carbon dioxide released during cell respiration essentially replaces the oxygen consumed, but if the CO₂ is removed (usually by reacting with KOH to form non-gaseous K₂CO₃), then any additional O₂ used up causes both the pressure (P) and volume (V) n the contained system to drop since as the ideal gas law informs us, mass (n) is directly proportional to pressure and volume (PV=nRT).  These drops, in turn, are easily quantified.

    Your assignment will be to choose one of the questions below about plant development and hypothesize an answer to it based on your current understanding of the life cycle of flowering plants.  You will need to design an experiment to test your hypothesis, and after you perform it, collecting and interpreting your data, you will need to determine whether your original hypothesis is valid. You may assume access to the basic protocol system for respirometers described below when designing your procedures as well as all the materials listed (your teacher will tell you whether you will be using CBLs or the water-displacement apparatus).
    But all other elements (controls, variable, etc.) are up to you.  It is your experiment.
    Good luck!
 

A. Problems:
 

• Is there a difference between the respiration rates of different parts of the germinating or sprouting seed?
• Within specific regions of the developing seed (such as the radicle) are there localized differences in metabolic rates?
• If you believe the answer to the last question is yes, do the rates of individual areas (such as the apical radicle) change as a seed sprouts and develops?
• Within a species of plant, does the respiration rate change over time as it grows and differentiates?
• Do different species of plant respire at different rates during development?
• Pick two embryonic plant structures and decided an interesting question you want to ask about their respective developmental metabolic rates (be sure to check it with your teacher to be sure it is okay).

        3 125-ml respirometers                           either:
        3 600-ml beakers                                         TI-82 or TI-83 calculator
        1 100-ml graduated cylinder                         Venier Bio-Software Package or equivalent
        1 250-ml graduated cylinder                         Venier Biology Gas Pressure Sensor
        1 thermometer                                                    (0-10 kpasc) or equivalent
         balances & weigh boat                            or:
         non-absorbent cotton                                   water-displacement apparatus
         absorbent cotton
         1-L 15% KOH
         forceps or tweezers
         an assortment of germinating seeds:
                kidney beans
                great northern beans
                alaskan snow peas
                corn

C. Respirometer Construction:

    Take a #4 rubber stopper containing a graduated pipette and a 124-ml flask provided by your teacher and  place a 2 cm layer of absorbent cotton in the bottom of the flask.  Use an eyedropper to saturate the cotton with fresh 15% KOH and cover this layer with 2-3 cm of non-absorbent cotton to protect any living samples from the KOH.  Place the samples inside the flask and seal with the pipette-stopper.