1. Do Now (5 min.) Directions: Answer in complete sentences in your research journals: • Which solution has a higher buffering capacity, filtered water or HRE water? • Back up your answer with an explanation. • What makes a solution have more Buffering Capacity?

2. HW • Complete your Germination Lab report.

3. How does electrical conductivity relate to plant nutrition? Mr. M. Gonzalez

4. Objectives • I can explain why organisms of the plant kingdom need nutrients. • I can describe the relationship between elements and nutrients. • I can relate electrical conductivity to nutrients.

5. Question? • How can a plant perform photosynthesis? http://www.eoearth.org/files/121601_121700/121668/Irrigation-photosynthesis.gif

6. Make a list of the elements you see on this figure in your notebooks. • Use your table of elements.

7. Question? • Why does a plant perform photosynthesis?

8. Because it needs to make ATP - plant body energy!

9. C = Carbon H = Hydrogen N = Nitrogen O = Oxygen P = Phosphorus S = Sulfur Mg = ? Na = Sodium Cl = Chlorine K = Potassium Ca = Calcium Fe = Iron Cu = Copper Zn = Zinc Others You may have noticed CHNOPS.

10. What element is Mg. • Notice it makes up the heart of this molecule.

11. Proteins Carbohydrates Plants also need to make the 4 organic compounds that make up their body. Which requires ATP Nucleic Acids Lipids

12. So, how does electrical conductivity relate to this? • Electrical Conductivity is a measure of the rate (how fast) at which a small electric current travels through a solution. http://hothardware.com/newsimages/Item15076/Electricity.jpg

13. Molecules & Nutrients • Most plant nutrients (plant food) are made of charged molecules or salts. • The more nutrients (salts) the faster the electricity will travel through the solution.

14. Element + Element = Molecule • When some elements come together they form charged molecules or salts. • Nutrients and plants (+ all living things) are made of molecules!

15. So, in a sense, living molecules (life) needs non-living molecules (nutrients) to keep on living.

16. Question • What will happen to the electrical conductivity if there are a lot of nutrients (salts) in a solution?

17. Answer • If you send a small electrical current through a solution with a lot of nutrients the electricity will travel very fast. • This means you will get a big measurement.

18. Measuring EC • You can use the Hanna Combo Meter to measure EC. • The units that measure EC are “µS” and they appear at the top right-hand portion of the screen. • Press the set button firmly and continuously until it appears. µS

19. Remember • Conductivity is a measure of the rate at which a small electric current flows through a solution. • When the concentration of nutrients is high, the current will flow ________. • When the concentration of nutrients is low then the current will flow ________.

20. Question • Why is measuring EC important?

21. Why is measuring EC important? • Measuring the EC of your solution is important because it will determine if it has enough nutrients to feed your plants.

22. 3 EC Facts • An EC meter shows the reading in microohms per centimeter cubed (µMho/cm3) or microsiemens per centimeter cubed (µS/cm3). • 1 µMho/cm3 = 1 µS/cm3 • High temperatures will affect the EC measurement giving.

23. EC levels for most plants

24. Problems With Nutrients • When a plant uses a nutrient from a chemical “salt” molecule in a nutrient solution, it is actually only using up a part of that molecule. The remaining part of that molecule generally stays in the solution and can eventually reach dangerous levels of concentration. • What needs to be done?

25. Log entry (5 min.) • Explain why organisms of the plant kingdom need nutrients. • Describe the relationship between elements and nutrients. • Explain how electrical conductivity relates to nutrients.

26. HW • Complete your Germination Lab report.

27. Bibliography • Nelson/Pade Multimedia (1999). Hydroponics Guide. 100+p.