Investigations with immobilised algae Paul BeaumontJenny Edrich Science

Investigations with immobilised algae Paul Beaumont/Jenny Edrich Science & Plants for Schools Homerton College, Cambridge

Background Debbie Eldridge A novel approach to photosynthesis practicals School Sci. Rev. (2004), 85, 37 -45.

Photosynthesis - problems l understanding experimental procedures – l controlled experiments with conditions or materials missing followed by iodine test for starch. with motivation – pupils have ‘done it before’ or see plants as tedious.

Photosynthesis - problems l obtaining data – – l difficulty getting enough reliable data to illustrate change in rates Elodea bubbling rates notoriously unreliable. keeping a range of photosynthetic organisms in school for use over the year.

New practical ideas l l Photosynthetic organisms easy to grow and culture. The ability to be able to measure – – l either oxygen evolution or carbon dioxide uptake so that rates can be determined. A novel species.

Algae Scenedesmus quadricauda

Enthusing the next generation A report on the bioscience curriculum by a working group established by the Biosciences Federation

Hydrogencarbonate indicator • Used to measure [CO 2]. • Orange/red in air. • Increasingly yellow as [CO 2] increases. • Orange red magenta deep purple as [CO 2 ] decreases.

Hydrogencarbonate indicator

Light Sources

£ 30 each from: Ring Lighting, Ring House, Gelderd Road, Leeds LS 12 6 NB Tel: 0113 2767565

What might you observe?

Dark control 60 -90 min irradiation

Variables? Colour of light Light Intensity • • Distance from lamp Neutral density experiment Number of balls Ball size Concentration of algae Temperature

Colour of light

100% Red Green Blue 0%

Light Intensity I

Light Intensity II

Transmission data Filter No %T 298 Absorbanc e 0. 15 209 0. 30 50 210 0. 60 25 211 0. 90 12. 5 299 1. 20 6. 25 71

100% 71% 50% 25% 12. 5% 6. 25%

Dark control 60 -90 min irradiation

Filters LEE Filters – range of filters • Different colours available • Neutral density options • LEE Filters, Central Way, Walworth Industrial Estate, Andover, Hants SP 10 5 AN. • Tel 01264 366245; www. leefilters. com

Can we quantify the colour change? • By measuring the absorbance using a colorimeter • By comparing the colours to a range of prepared buffer solutions.

Colorimeter Direction of Beam R = Reference T = Test

Hydrogencarbonate indicator No access to a colorimeter?