Grant Agreement number: 226646 -CP- 1- 2005-1-IE-COMENIUSC21(2005-3264)

Photosynthesis and Plant Respiration

Subject: Biology Grade level: Upper secondary Schools Anticipated time: 8 hours (lessons and outdoor activities)

Developers: Institution: Country:

L. Brancaleoni, O. De Curtis, U. Thun Hohenstein, M.C. Turrini Dipartimento di Biologia ed Evoluzione – Ferrara University Italy

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Grant Agreement number: 226646 -CP- 1- 2005-1-IE-COMENIUSC21(2005-3264) CENTRAL IDEA AND DRIVING QUESTIONS: What is the trend of photosynthesis and respiration in plants? How the photosynthesis and respiration change at different temperatures and humidity levels? Can the plants help in solving the problem of the Earth heating? PEDAGOGICAL FRAMEWORK Photosynthesis is recognised by most teachers as one of the most problematic concepts in biology (Çapa, 2000; Eisen & Stavy, 1992). Like for all the scientific processes, in particular when they are difficult and complex, students develop ideas and misconception before to receive a science education (Amir & Tamir, 1994). For its abstract nature, photosynthesis is difficult both to teach and to learn at all levels of schooling (Storey, 1989; Bahar, Johnstone, & Hansell, 1999) but this process, with the plant respiration, is a fundamental/indispensable prerequisite for ecological studies. In fact, photosynthesis and plant respiration have a central role in the living systems: through photosynthesis and respiration the energy of the sun is made available to support metabolic processes in all livings (Anderson, Sheldon & DuBay, 1990). Besides, both for the importance of the argumentation and for their difficult, it is important to find alternative teaching approaches in their teaching. Computers and technological tools can and must be used for this educational goal. This module proposes the study of the photosynthesis and respiration as concrete processes developed by the plants in relation to the environmental factors. The approach followed here involves the direct measurements of the gas exchanges inside a leaf chamber, allowing the comparison between the courses of CO2 and O2 from high and low plants, of different organs or different phenological stadiums (buds, mature leaves, etc.). The experiment also studies the effects of the environmental variables, particularly of the temperature and humidity of the air, on the gas exchanges. The graphic visualization of the carbonic anhydride trend will allow the students to understand the strong influence of the environment on the living organisms and on the biological processes. PREREQUISITE KNOWLEDGE: This lesson is appropriate for students with basic knowledge of plants and leaves morphology, CO2 and O2 features, environmental variables (temperature and humidity). BACKGROUND KNOWLEDGE The superior and inferior plants absorb the light energy of the sun and, in presence of water and carbonic anhydride, they convert it in chemical energy of sugars and oxygen. With the photosynthesis therefore the CO2 absorbed from the atmosphere is transformed in organic carbon compounds, particularly sugars and free oxygen. Since the aerobia life consumes oxygen and free carbonic anhydride, the photosynthetical process balances the respiration continually supplying the atmosphere of O2. The earth’s green plants absorb CO2 from the air through the openings on the leaves, the stomata, while the aquatic plants (particularly the algae) absorb the CO2 dissolved in the water. Through the stomata the carbonic anhydride penetrates in the leaf and in presence of humidity it is dissolved in order to enter in the cells. The process of fixation of the CO2 is expressed by the equation: CO2 + 2H2O → (CH2O) + O2 + H2O 2

Grant Agreement number: 226646 -CP- 1- 2005-1-IE-COMENIUSC21(2005-3264) It reguards a reduction process in which the products C, H, O have the proportion of the glucose and the free O2 originates from one of the two molecules of water. The light produces a series of reactions in which the energy available in the shape of phosphoric bonds of the ATP, is made with the release, from the water, of oxygen and of protons and electrons that reduce the glucose CO2 (CH2O). Inside the cell, the photosynthesis happens in the chloroplasts where the chlorophyll and the accessory pigments carry the energy produced by the light from the reaction centres to the chains of chemical reactions. In fact, the photosynthesis is a complex process that consists of two kinds of reactions. The reactions of the light phase in need of light occur on the tilacoidis of the chloroplasts and they produce ATP (energy) and NADPH (electron transporters). The reactions of the dark phase of the cycle of Calvin, without direct intervention of the light, occur in the stroma of the chloroplast and they use the ATP and the NADPH to fix the carbonic anhydride, converting it in sugars. The cycle of Calvin fixes one molecule of CO2 at the time and it is necessary to complete it 6 times to produce a sugar with 6 atoms of carbon as the glucose: 6CO2 + 12H2O → (C6H12O6) + 6O2 + 6H2O Besides, respiration is the oxidation of substrates by enzymes with the release of Carbon dioxide. Respiration is an essential life process in plants. It is necessary for the synthesis of essential metabolites including carbohydrates, amino acids and fatty acids, as well as for the transport of minerals and other solutes between cells. It consumes between 25 and 75% of all the carbohydrates produced in photosynthesis at ordinary growth rates (Lambers et al., 2005). MATERIALS - LabQuest - LoggerPro 3.6 Software - CO2 gas sensor with a portable chamber - A dark cloth to create a “dark chamber” for respiration measurements - Thermo-hygrometer - Small bags to collect plants or leaves used in the experiments - GPS CONTEXT The study of the photosynthesis can be carried out in the garden of the school or in a public park, everywhere plants are present. This is a very important aspect that makes the module a very flexible tool for teachers who can use it in different sites, depending on the requirements of the class and where the school is located. However we suggest to develop this experiment in a forest, because in this kind of environment there are trees, shrubs and grass, so it is possible to compare different kind of plants. The Santa Giustina woodland in the first Station of the Po Delta Regional Park was chosen as heritage site where to test the module. This wood is situated in the southern area of the Po Delta, between the “Po di Goro” and the “Po di Volano” rivers, in the province of Ferrara. The Santa Giustina woodland (also known as the Fasanara Wood) develops on ancient dunes and covers more than 200 Ha. It is the residue of a complex larger woodland originated since around the year 1000. The vegetation is characterized by Mediterranean species with Quercus ilex (evergreen oak) as dominant tree in the arboreal layer, associated with pines, white hornbeam and 3

Grant Agreement number: 226646 -CP- 1- 2005-1-IE-COMENIUSC21(2005-3264) peduncolate oak. The shrubby layer is composed principally by junipers, butcher's broom, wild asparagus and phyllireas shrubs. The wood is populated by numerous chaffinches, thrushes and ringdoves. The non-migratory birdlife is mainly represented by pheasants and blackbirds. Mammals include hares, badgers and weasel. INSTRUCTIONAL ACTIVITIES Lesson 1: In (Preparatory) Duration: 3 hours Goals: the students acquire basic knowledge about photosynthesis, handled technologies and heritage site. - Students study the principal reactions that happen during the photosynthesis and the mechanisms at the base of this process, with the aid of a scientific video-tape or dvd. - Students have an introduction to the use the LabQuest interface with CO2 gas sensors. - The teacher explains the characteristics of the environment that will be visited: geographical position, naturalistic features, peculiarity of the protected area, also by a visit to the website of the area, if it exists. - The teacher remarks the correct behaviour for avoiding trouble and safety notions for potential danger (e.g. presence of poisonous plants and dangerous bugs). Lesson 2: Out (of Classroom) Duration: 3 hours Goals: The students join the heritage site and start to collect photosynthesis and respiration data. the different trend of gas exchange will be useful to understand the health of plants in relation to the temperature and humidity of the air. If the module takes place in protected areas the teacher must ask the income permission and/or the permission to pick up the samples. Once arrived at the woodland the students will take note of the flora, the fauna and the geological and geomorphological features of the area (ground, rivers, etc). The teacher remind the correct behaviour to keep in a protected area. Procedure: The students are divided in small groups, so that each of them is charged of one specific task. First of all the sample position has to be localized by GPS and the temperature and the humidity of the air are recorded. Then three different plants in the different layers are chosen: a tree, a shrub, a grass. With the LabQuest interface and the sensors, every group takes note of the gas exchanges measurements of different plants in the vegetational layer. The students will first use the sensor called “light” chamber to take the values of photosynthesis and then the “dark” chamber for those of the respiration. Before, during and after the measurements it is important to record the course of the air temperature and humidity. After samples are taken and recorded, the teacher leads students into a brief discussion and analysis of the data collected. Do the plants react in the same way? How does it change the photosynthesis and respiration trend? Does the temperature affect the photosynthesis and respiration? 4

Grant Agreement number: 226646 -CP- 1- 2005-1-IE-COMENIUSC21(2005-3264) Lesson 3: In (Follow-up) Duration: 3 hours Goals: data interpretation to understand the central idea of the module and answer the driving question. The collected data allow to reconstruct the course of the photosynthesis and the respiration in a part of the woodland for the chosen plants and in the conditions of temperature and humidity of the air during the measures. Objective The students will be able to know: - The function of the photosynthesis in different vegetable organisms and under different environmental conditions; - How to understand the photosynthesis and respiration processes by way of real measurements graphs; - How to interpret the collected data; - The direct influence of the environment on the gas exchanges; - The use of technologies (datalogger and environmental sensor) to collect data in the field; - How to compare and discuss the data they have collected from different plants or parts of plants. POSSIBLE EXTENSIONS The wood of Santa Giustina is well structured in the different arboreal, shrubby, grassy and mosses layers. For this reason the measurement of the gas exchanges can be carried out in plants with different biological forms: in high plants (trees, shrubs, grasses) and low plants (mosses and lichens), in plants with different phenological stadiums, in the leaves at the shade (sciaphilous) and at the sun (eliophilous) of the ivy, in the young (more tenderly) and adult (harder) leaves of the oak. The gas exchange can also be measured in the mushrooms to see that they do not have photosynthesis but only respiration as they are not plants. The measurements can be taken in different moments of the day (e.g. morning and afternoon); during days with different weather or in different seasons to point out the influences of the climatic variables on gas exchange. The same measurements can be taken also only with the O2 gas sensor or both (CO2 and O2 sensors) to better understanding and simplify the measurements. The teacher can easily work with other science teacher: i.e. - Geography: construct maps using the coordinates recorded with the GPS; - Physics: study the resistences inside/outside the leaves blocking the flows of CO2 and O2; - Mathematic: how can we construct different kind of graphs? ASSESSMENT In small groups, students will present their results to the class in order to demonstrate: - their ability and facility to use calculator and sensors; - their understanding of the complex interactions among a plant, the biological processes and the environment. To check the individual preparation the teacher can: 5

Grant Agreement number: 226646 -CP- 1- 2005-1-IE-COMENIUSC21(2005-3264) - ask for the interpretation of the graphic that the student has drawn from the data recorded in the field; - stimulate hypothesis on the possible trend of the graphic in stress conditions, e.g. elevated summer temperatures or elevated concentration of polluted gas in the air (SO2); - ask for repeating the experiment into the classroom on leaves picked at the moment in the garden of the school; - stimulate hypothesis about factors limiting the gas exchanges and about plants adaptations; - submit a final test.

Bibliography Anderson C.W., Sheldon, T.H. & DuBay J. 1990. The effect of instruction on college nonmajors’ conceptions of photosynthesis and respiration. Journal of Research in Science Teaching 27(8): 761–776. Amir R. & Tamir P. 1994. In-depth analysis of misconceptions as a basis for developing research-based remedial instruction: the case of photosynthesis. The American Biology Teacher 56(2): 94–100. Çapa Y. 2000. An analysis of 9th grade student’s misconceptions concerning photosynthesis and respiration in plants. Unpublished Master Dissertation, Middle East Technical University, Turkey. Eisen Y. & Stavy R. 1992. Material cycles in nature, a new approach to teaching photosynthesis in junior high school. The American Biology Teacher, 54(6): 339–342. Lambers, H. & Ribas-Carbó, M. eds. (2005), Plant Respiration: From Cell to Ecosystem (Advances in Photosynthesis & Respiration), Kluwer Academic Publishers, Dordrecht.

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