“Making plants grow in salty soil”

 

Dr Ian Newman

Visiting Fellow in Biophysics,
School of Mathematics and Physics,
University of Tasmania

 

Tuesday, 27 July 2004, 8:00 P.M.

Physics Lecture Theatre 1

University of Tasmania, Sandy Bay

 

Abstract:

How can it be done? For a sustainable future, Australian agriculture needs to know.

In saline soils, sodium leaks into root cells as they take up essential nutrients, but too much sodium makes cells sick. What can a root cell do with this sodium? Pump it out again? Stuff it away in the cupboard? Make it “somebody else’s problem” and forget about it?

Answers are coming through the use of a wide range of sciences: mathematics, physics, chemistry and biology. All cells have an outer membrane that separates the living interior from the outside. Nutrients taken up by plants must first pass through the membranes of root cells. This process depends on electric fields and the change of energy of the electrically charged nutrient “ions”. The chemical concentrations and reactions of the nutrients also matter. Because the nutrients diffuse through the soil or hydroponic solution to the root, the mathematics of diffusion is needed to work out how fast they go. The nutrient pathways through the membrane are actually large protein molecules, and molecular genetics has worked out the detailed structure of some of them.

All this is not rocket science – it is actually more complicated! However we can pick out the main ideas, to get a picture of what plants do in salty soils. This illustrated talk is about current research here and overseas on an interesting topic that is important for our society and industry. It is designed for the public, science teachers and year 11/12 students. It centres on the biophysics of an “exchange transporter” that pumps sodium out of cells by swapping it for hydrogen. Our Tasmanian MIFE research suggests that another transporter, for potassium, may also be important. At the end, we can see how the ideas work in a genetically modified tomato plant that can actually grow in salt water. Its tomatoes look good. Are there problems with them? How will they taste?  

The speaker

Ian Newman is a mathematics and physics graduate from Sydney University who came to Tasmania to study biophysics. He began with an interest in why plants bend towards the light. His PhD in 1965, on electric effects of growth hormone transport in oat seedlings, gave rise to two Letters in the journal Nature.

He turned to photoperiodism – how plants know the length of a day – and was the first to demonstrate membrane related electric changes within 10 seconds of the transformation of the pigment phytochrome by light.

He developed and commercialised the MIFE system for non-invasive measurement of nutrient ion movement through the surface of roots or other tissues bathed in solution. MIFE studies are going on in several laboratories around the world contributing to understanding how membrane transport proteins work. The ionic movements responsible for the electric changes he observed several decades ago are now beginning to be identified. He is presently collaborating with Dr Sergey Shabala in the School of Agricultural Science in a study of plant responses to salinity.

For many years he has been a strong supporter of science teachers in years 11 and 12. He is active in the Australian Institute of Physics, of which he is a Fellow.