“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.