Advancing Science and Engineering through Laboratory Learning Stomata on leaves Key words and phrases: Plants, Biology, Epidermis, cuticle, Biological sciences, Observation, Water loss, Regulation, Gasses, Exchange, Atmosphere, leaves, stomata, respiration, transpiration, photosynthesis. Brief Introduction From: ​
National Gardening Association, 2001 Concentrated on the lower leaf surfaces are tiny openings called stomata* (stow­MAH­tuh; Gr. stoma = mouth) that allow gases to pass into and out of the leaves. The stomata are surrounded by guard cells that collapse and swell to close and open the stomata, depending on the plant's needs. Students can tear a leaf with a waxy cuticle (jade, calla lily, or philodendron, for example) to expose the lower epidermis. Using a microscope, they can count the number of stomata that are open and closed. In most plants, the stomates open in the light and close in the dark. However, the plant faces a tradeoff. In order for photosynthesis to take place, the leaf must consume carbon dioxide. So, when the sun comes up, the stomates open and carbon dioxide enters the leaf. Whenever the stomates are open, the leaf is also losing water in the form of water vapor (because of transpiration). Therefore, the plant must balance the need for carbon dioxide with the avoidance of dehydration and regulate the stomata accordingly. plural ​
stomata​
or ​
stomates​
; singular ​
stomate​
or ​
stoma Curriculum links Stage Year Australian Curriculum NSW VIC Stage 4 Year 7 ACSSU111 LW1 VCSSU092 ­ f ACSSU149 LW2 ­ c, f Year 8 VCSSU094 ACSSU150 LW3 ­ b, e Year 9 ACSSU175 VCSSU117 VCSSU121 Year 10 LW1 ­ a, b Stage 6 Years 11/12 ACSBL055 ACSBL059 8.2.2​
(pdf) 8.3.4​
(pdf) 9.2.3​
(pdf) Unit 1, Area of study ​
2 (pdf) Unit 3, Area of study 1 (pdf) Stage Year Australian Curriculum NSW VIC Stage 4 Year 7 There are differences within and between groups of organisms; classification helps organise this diversity. Year 8 Multi­cellular organisms contain systems of organs carrying out specialised functions that enable them to survive and reproduce Cells are the basic units of living things and have specialised structures and functions. Multicellular organisms contain systems of organs that carry out specialised functions that enable them to survive and reproduce Cells are the basic units of living things and have specialised structures and functions. Multicellular organisms contain systems of organs that carry out specialised functions that enable them to survive and reproduce Multicellular organisms rely on coordinated and interdependent internal systems to respond to changes in their environment. Multicellular organisms rely on coordinated and interdependent internal systems to respond to changes to their environment. Ecosystems consist of communities of Stage 5 Stage 5 Year 9 Multi­cellular organisms rely on coordinated and interdependent internal systems to respond to changes to their environment Stage 6 Year 10 Years 11/12 The specialised structure and function of tissues, organs and systems​
can be related to cell differentiation and cell specialisation. In plants, gases are exchanged via stomata and the plant surface; their movement within the plant by diffusion does not involve the plant transport ​
system​
. interdependent organisms and abiotic components of the environment; matter and energy flow through these systems Identify some adaptations of living things to factors in their environment . Outline the transport system in plants, including: stomates and lenticels Plants and animals regulate the concentration of gases, water and waste products of metabolism in cells and in interstitial fluid The structural, physiological and behavioural adaptations that enhance an organism’s survival and enable life to exist in a wide range of environments The purpose of cellular respiration. Stage 4 Discussion In this activity students are encouraged to plan their own experiment and compare of stomata from different leaves, and how this relates to other factors such as colour of leaves, size of leaves etc. Students may find there are many ways to conduct this experiment ­ it about opening the field so that they may come up with their own research question. During the course of the experiment, students may: ­
Test a number of different leaves ­
Measure the size and density of stomata ­
Identify other parts of the organism Science inquiry questions ­
­
­
­
­
What else could affected by the application of nail polish on the leaves? What other observations can you make about the leaves and stomata? Does the number of stomata matter? What other questions could you ask with this investigation? How could you improve this investigation to get better results Stage 5 Discussion Students in late Stage 5 may begin to question what affects the rate of photosynthesis in leaves due to the stomata and identifying the links between different structures and functions biological systems. Relationships between different cells is to be investigated in terms of adaptations and environment changes. Science inquiry questions List the variables and the steps you took to measure those variables. Control variable Independent variable Dependant variable Variable Measurement ­
­
­
­
­
How can you measure the rate of photosynthesis? Can you feel a temperature change? If so, how could we measure the change? How does the temperature change affect the rate of photosynthesis? What other questions could you ask with this investigation? How could you improve this investigation to get better results Stage 6 Discussion
In this activity students move beyond the observation of respiration to more complex analysis of how all these systems work together in an organism. Student in stage 6 will be asked to understand the history, nature and practice of biology, the applications and uses of chemistry and implications of chemistry for society and the environment. Science inquiry questions ­
Compare density of stomata and amount of photosynthesis in different type of leaves. This can take the form of a first hand investigation. ­
Conduct a risk analysis filling out the following table. List three risks to do with this investigation, and in an industry based on biological sciences. What are the consequences of those risks and your mitigation techniques, or precautions from stopping those risks come about. Rank each risk in terms of likelihood and impact and make a judgement about whether the experiment is safe or not. Risk Consequence Precaution Classroom Industry ­
­
What other questions could you ask with this investigation? How could you improve this investigation to get better results The experiment: Here is the investigation as it is presented at an ASELL workshop Stomata on Leaves
Key Concepts ●
●
Plants generally have an impermeable epidermis and a waxy cuticle to prevent uncontrolled water loss. Stomata provide a way for the plant to (a) exchange gases to and from the cells and (b) control their release of water to the atmosphere. Summary In Part 1 students will look at an impression of a leaf’s surface under a microscope. They will make a connection between structure and function of stomata. In Part 2 students will design a new experiment to investigate whether Australian native plants show adaptations for the Australian climate with respect to their stomata. Part 1 Experiment Materials and Equipment ●
●
●
●
●
●
●
●
●
●
Microscope Microscope slides Clear Sellotape Clear quick­dry nail polish Freshly picked leaf Microscope Microscope slides Clear Sellotape Clear quick­dry nail polish Freshly picked leaf Procedure 1.
2.
3.
4.
5.
Collect a leaf from a plant. Get a 2cm piece of tape and fold over the top 2­3mm and stick it to itself. Stick the tape on the underside of your leaf. Take the nail polish and paint on a thin coat covering an area equivalent to a 20c piece. Note­ Half the nail polish should be on the tape and half on the leaf itself. When the nail polish is completely dry and not tacky carefully and slowly peel off the tape the layer of nail polish should come with it. Without touching it, place the layer of dried nail polish on the microscope slide. Results Draw a picture of what you see in the field of the microscope. (what is visible through the eyepiece on high magnification without moving the slide). Are the stomata open or closed? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ Describe the arrangement of the stomata on your leaf? Do you think other plants might have different arrangements? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ What do you think is the purpose of stomata on leaves of plants? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ Part 2 Design and carry out an experiment that will address the following question. Do Australian native plants show adaptations for the Australian climate with respect to their stomata? You will need to include a hypothesis Notes Contact Contact ASELL to come to an ASELL workshop [email protected] Support material ­
Comments from teachers Data Some data on this experiment ­ coming soon