You Are Going to Complete Four Different Investigations

Student activity AB1.10.1 Book links: Page 32 Lesson reference: B1.10 Controlling Specification links: B1.2.3 a–d plant growth

Investigating plant hormones

Equipment required per group: Petri dishes with soaked filter paper and germinated cress seedlings Shoebox and scissors Geranium plant, plastic bag, string or sticky tape to seal it Small, clean plant pots Potting compost and trowel (or old large spoons) Hormone rooting powder Scalpel, knife, or scissors for taking cutting Measuring cylinders Balance pH paper Three ripe bananas, two bowls, eight unripe tomatoes (hard and pale red) Health and Safety notes:  Wash your hands at the end of the practical.

Getting started You are going to complete four different investigations. i) Investigating phototropism 1 You will have two Petri dishes containing cress seedlings. 2 Keep one exposed to light all around it, and put the other in a shoebox with a slit in the side. These seedlings get light from only one direction. You are using the same type of seedlings in each case and they were germinated at the same time. 3 Make sure that each has the same volume of water and try to keep them at the same temperature. 4 Examine both after a few days.

Thinking about A Write down what you see and explain what has happened.

Asking questions A What is the stimulus? B What was the response made by the cress seedlings in the shoebox? C Higher tier only: How did plant hormones make this response happen? ii) Investigating geotropism

Practical activities have been checked for health and safety advice by CLEAPSS. All users will need to review the risk assessment information and may need to adapt it to local circumstances. 67 © Oxford University Press 2011 This document may have been altered from the original. Your teacher may do this as a demonstration. 1 Water a potted geranium plant well and wrap a polythene bag around the pot to keep the compost moist. 2 Lay the pot on its side. 3 Examine it each day to see if the shoot tip starts to bend upwards and grow away from the pull of gravity.

Thinking about A Why is it useful to the plant if its shoot grows away from the pull of gravity? iii) Investigating fruit ripening Place some unripe tomatoes in a bowl with some very ripe bananas. Place an equal number of unripe tomatoes in a bowl without any bananas. Examine the tomatoes each day and note how long each group of tomatoes takes to become deep red and soft.

Thinking about A How do ripe bananas alter the rate of ripening of the tomatoes? iv) Investigating rooting powder 1 Grow two geranium cuttings. Your teacher will show you how to take a cutting. 2 Dip one cutting in rooting powder. 3 Put each cutting in a pot and give them the same conditions. Keep them watered over the next few weeks. 4 Monitor their growth and examine how their new roots are forming.

Thinking about A Does rooting powder help cuttings to make more roots? B What is the advantage to the new plant if it makes more roots quickly?

Spreading the word Record your results and share them with the class. A Do you all get similar results? Are the data reliable? B What can you say about rooting powder and how it helps cuttings to grow? C What conditions did you keep the same? Was your investigation valid?

Plenary Plants and touch Watch your teacher demonstrate how a Venus Flytrap plant can catch flies. Touch a sensitive plant and watch what happens.