Plant Respiration and Gas Exchange PDF

Do plants breathe? Stomata facilitate gas exchange in plants.  CELLULAR RESPIRATION AND GAS EXCHANGE Instructor: Louise Gwynne S. Quirante (Plants)  Respiration Respiration is the process by which energy from organic molecules such...

Do plants breathe? Stomata facilitate gas exchange in plants.  CELLULAR RESPIRATION AND GAS EXCHANGE Instructor: Louise Gwynne S. Quirante (Plants)  Respiration Respiration is the process by which energy from organic molecules such as carbohydrates is released to be used in the different life processes in an organism. Cellular respiration refers to the breakdown of carbohydrates in the cells as shown: Figure 1. The equation for cellular respiration.  Respiration Respiration is the process by which energy from organic molecules such as carbohydrates is released to be used in the different life processes in an organism. It is opposite of photosynthesis which has the following reaction: glycolysis 2 pyruvate molecules  Cellular Respiration in Plants Figure 2. Overview of cellular respiration. https://www.youtube.com/watch?v=rvrao5V89nE  Gas Exchange in Plants Plants do not need respiratory organs like animals do because all their oxygen requirements are met by photosynthesis which occurs in the chloroplasts. Thus, oxygen is directly released into the plant cells and minimal transport of gases from one plant part to another occurs. For small plants such as bryophytes, gas exchange occurs easily by diffusion since the leaves and other structures are very thin. For more complex plants, gas exchange can occur through the stomata and the lenticels. Bryophytes (mosses, liverworts, and hornworts)  Gas Exchange in Leaves Gas exchange in plants occurs mostly through the leaves Stomata facilitate gas exchange in plants. Figure 3. A stylised cross-section of a euphyllophyte plant leaf, showing the key plant organs involved in gas exchange by McKenna (2006, January 31)  Gas Exchange in Leaves Figure 4. Openings called stomata (singular: stoma) allow a plant to take up carbon dioxide and release oxygen and water vapor. The (a) colorized scanning-electron micrograph shows a closed stoma of a dicot. Each stoma is flanked by two guard cells that regulate its (b) opening and closing. The (c) guard cells sit within the layer of epidermal cells. (credit a: modification of work by Louisa Howard, Rippel Electron Microscope Facility, Dartmouth College; credit b: modification of work by June Kwak, University of Maryland; scale-bar data from Matt Russell) Plant respiration occurs 24 hours per day, but night respiration is more evident since the photosynthesis process ceases.  Gas Exchange in Stems As the plant matures, the stems and woody parts become covered with layers of dead cells, or cork, that contain suberin. Suberin is a waxy substance that is waterproof and airproof. Gas Exchange in Stems However, gas exchange in stems occurs through lenticels, which are non-suberized pores on mature roots and woody stems. Figure 5. Lenticels on the bark of this cherry tree enable the woody stem to exchange gases with the surrounding atmosphere (credit: Roger Griffith) Figure 6. Cross section of Sambucus stem (magnification: 100x) by OpenStax (2020, August 15) showing a lenticel by Berkshire Community College Bioscience Image Library (2014, February 10) Can gas exchange occur in roots?  Gas Exchange in Roots Plant roots not only absorb water from the soil but they also obtain oxygen needed for cellular respiration from the air spaces in the loose soil. In other words, root cells need oxygen to carry out respiration and release energy for their own use. Root hairs are small extensions of root cells that enhance gas exchange by increasing surface area for oxygen absorption from the soil. Figure 7. Plant root with root hairs by Clark, Douglas & Choi (2018, March 28).  How does gas exchange occur in roots? Root hairs are in contact with the air in the soil particles, allowing oxygen from the air in soil particles to diffuse into the root hairs towards the root cells for respiration. Carbon dioxide produced in the cell during respiration diffuses out through the same root hairs by the process of diffusion. If the soil is waterlogged, the roots will not be able to take up oxygen and metabolic processes will be affected. Figure 4. Gas Exchange in the Roots GAS EXCHANGE IN PLANTS Plants do not only perform photosynthesis, they also undergo cellular respiration especially when there is no sunlight. Cellular respiration is the process by which all organisms obtain energy to maintain metabolic processes. Plants exchange respiratory gases with the atmosphere through the stomata and lenticels and by diffusion through thin epidermal cells.  FA: Short Quiz! 1. Which of the following 3. The table below shows a comparison of the structures DOES NOT function plant processes, photosynthesis and respiration. for respiration? Write the word produces/releases or uses in the A) mitochondrion appropriate space. B) stomata C) cork cells D) root hairs E) lenticels 2. How many pyruvate molecules can be formed from one glucose molecule?