WHERE DOES A PLANT’S MASS COME FROM* AnsKey

Name: ________________________________________ Period: ____ Date: ____ WHERE DOES A PLANT’S MASS COME FROM* AnsKey 1. For each hypothesis in the cartoon, write a T if you think the hypothesis is true or an F if you think the hypothesis is false. F F T F CO2 enters the stoma ( plural is stomata) or holes found on the upper and / or lower surface of the leaves. https://www.youtube.com/watch?v=IlmgFYmbAUg Structure and working of stomata In this activity, you will learn more about each of these hypotheses. 2. Plants are made up of two types of molecules: water and organic molecules (e.g. sugars, cellulose, starch and proteins). So, our first question is how much of a plant’s mass is water and how much is organic molecules. To find out, you can weigh a plant, then dry the plant in an oven to remove all the water, and then weigh the dried plant. This table shows representative results for a small plant. Complete the second and third columns of the table by putting a check mark on the correct answer. Weight % of plant’s mass Total mass of plant 5.6 grams 100% Mass of dried plant = mass of organic molecules in plant = biomass 1.4 grams 25%__ or 75%__ Mass of water in plant before it was dried 4.2 g 25%__ or 75%__ The results in the data table are found for smaller plants and larger plants. Actively growing tissues as root tips and leaves are ~75-90% water, and woody parts such as tree trunk are ~ 45-60% water. BIOMASS = dry mass of a plant = mass of organic molecules For plants, ~ 96% of the dry mass consists of organic molecules. To understand how plants make their organic molecules, we need to begin with photosynthesis. This chemical equation summarizes how photosynthesis makes the sugar, glucose. sunlight 6 CO2 + 6 H2O C6H12O6 + 6 O2 3a. Can the energy in sunlight be converted to the C, H or O atoms in the glucose molecules that are made by photosynthesis? YES ___ NO ___ How do you know? According to the Law of Conservation of Matter and Energy, matter and energy are transformed from one form to another but neither are created or destroyed. Energy is not matter and matter is not energy. 3b. Where do the C, H and O atoms in the glucose C6H12O6 molecules come from? sunlight 6 CO2 + 6 H2O C6H12O6 + 6 O2 C and O of the glucose molecule must come from CO2 since H2O does not have C. 2 Experiments using isotopes of O have shown that O in the O2 produced by photosynthesis comes from H2O. https://goo.gl/ph3GbW isotopes of O https://goo.gl/Ajb6BB C isotope 3