Associate Professor Robert Reid
Associate Professor
Benham Building DP312
School of Earth and Environmental Sciences
University of Adelaide

Personal Website Address: http://www.ees.adelaide.edu.au/people/enviro/rreid01.html
Email robert.reid@adelaide.edu.au

Research Aims

RETURN TO TOP

The Big Question

How do plants control the uptake of solutes? Mechanisms, genes involved, manipulation.

The Short-Term Goals

Finding genes conferring boron tolerance

We have recently found strong evidence that boron tolerance in barley is due to the active efflux from the root. A paper describing this work will appear in Plant Physiology soon. We are now searching for the gene(s) responsible for the efflux. It seems most likely that efflux will be of the borate anion and it is expected that the transporter will be either an anion channel or and anion exchanger. Patch clamp studies are currently under way to investigate the ion channel option.

What causes boron toxicity?

Boron is a difficult element for plants to cope with. It is an essential nutrient but is also the nutrient in which there is the smallest window between deficiency and toxicity. Many agricultural soils in Australia , and particularly in South Australia , have subsoils that contain boron at toxic levels. Using both in vivo and in vitro assays, we have defined the sensitivities to high boron concentrations of a range of essential plant activities to try to identify those processes that are most sensitive. Many activities, including photosynthesis and respiration are only inhibited by very high concentrations of boron, while activities such as root elongation and shoot growth are very sensitive.

Membrane biology & nutrition

The mechanisms by which many nutrients and non-nutrients enter cells are understood for only a very few molecules. This is particularly true for plant micronutrients (Fe, Mn, Cu, Ni, B, Mo, Zn) and for many potentially toxic elements such as Cd, Hg, Pb and Co. We are investigating the factors that determine uptake of various elements and the interactions between elements for uptake and growth. The main areas of current interest are:

Trace metal uptake

Our recent research has indicated that there are a variety of trace metal uptake systems with fairly low specificity for any particular metal species. Therefore, there must exist significant competition between elements for uptake. Additionally, this lack of specificity allows entry to potentially toxic elements. The current investigations focus on describing the general characteristics of trace metal uptake, which has relevance to the increasing interest in understanding the genetic basis for differences between species in their responses to trace metals.

Membrane surface charge

While most physiologists are aware that voltages exist across biological membranes, few appear to appreciate that electrical charges on the surfaces of membranes can create potential differences that impact upon the vast array of activities that occur at, in or through the membrane. We have established that membrane surface charge is a major determinant of the uptake of cations into plants and a major factor in toxicities of many ions.

Phosphorus uptake and phosphorus efficiency

In collaboration with Prof Tetsuro Mimura, Women's University of Nara , Japan , we have been investigating the mechanism of phosphorus uptake and efflux in plants. Under most natural conditions, phosphorus is available at very low concentrations and plants respond to this limited supply by inducing the synthesis of efficient P transporters in their membranes. We have identified a novel mechanism of P uptake in the giant alga Chara, which requires sodium to drive P into the cell. More recently we have characterised the induction of this transporter. Currently experiments are being conducted to ascertain the importance of efflux (or leakage) of P in the overall P nutrition of plants.

There are significant differences in the abilities of plants to grow under low P conditions. Comparative studies with P-efficient and P-inefficient plants have isolated some key physiological and morphological factors that contribute to better performance when P supply is limited. This work is being conducted in collaboration with Prof Yongguan Zhu at the Research Centre of Eco-Environmental Science in the Chinese Academy of Sciences in Beijing , China .

Abiotic Stress

Abiotic stress encompasses a wide range of threats to plant health including nutrient deficiencies, nutrient and non-nutrient toxicites, drought, temperature and salinity stresses. Major topics currently under investigation include:

Aluminium toxicity

Acidic soils are widespread throughout the world, particularly in high rainfall areas. In Australia , soil acidification is becoming a significant problem in some areas. The main consequence of acid soil is the solubilisation of aluminium which is extremely toxic to root growth. The reduction in root mass impacts upon the plants ability to take up nutrients and water and therefore restricts growth. Tolerance to aluminium has been identified in a number of species but the mechanisms are still poorly understood. The cause of toxicity is unknown and is under investigation in collaboration with other groups both locally and overseas.

Group (laboratory ) Members

RETURN TO TOP

• Dr Julie Hayes
• Dr Uri Yermiyahu (1 year from July 2004)
• Jack Askew (PhD)
• Matthew Freeman (PhD)

Funding

RETURN TO TOP

Current

• Biophysical analysis of nutrient acquisition in plants - ARC Linkage International
• Mechanisms of tolerance to boron toxicity in plants - ARC

Applications submitted or planned

• Physiological mechanisms of plant responses to hostile soils - ARC Linkage International (submitted)
• Isolation and functional analysis of genes conferring tolerance to metal toxicities in plants - ARC Discovery (to be submitted March 2004)
• Isolation and characterisation of genes involved in tolerance to boron toxicity in plants - ARC Discovery (to be submitted March 2004)

Techniques in the Laboratory

RETURN TO TOP

Currently active

• Polyvalent cation flux measurement
• Measurement of apoplastic pH and ion concentrations by confocal fluorescence microscopy

In development

• Isolation of plant vacuoles for transport studies

Main areas of expertise

RETURN TO TOP

Top three areas of knowledge

1. Micronutrient uptake systems in plants
2. Surface charge and membrane transport
3. Plant toxicities on acid soils

Recent Publications

RETURN TO TOP

• Hayes J, Reid R (2004) Boron tolerance in barley is mediated by efflux of B from the roots. Plant Physiology xxx , provisional acceptance

• Reid R, Hayes J, Post A, Stangoulis JCR, Graham RD (2004) A critical analysis of the causes of boron toxicity in plants. Plant Cell and Environment xxx , submitted

• Reid R, Liu J (2004) Measurement of trace metal influx in plants: a case study using Co. Functional Plant Biology xxx , submitted

• Reid R, Hayes J (2003) Mechanisms and control of nutrient uptake in plants. International Review of Cytology 229 , 73-114.

• Reid RJ, Dunbar KR, McLaughlin MJ (2003) Cadmium loading into potato tubers: the roles of the periderm, xylem and phloem. Plant Cell and Environment 26 , 201-206.

• Dunbar KR, McLaughlin MJ, Reid RJ (2003) The uptake and partitioning of cadmium in two cultivars of potato (Solanum tuberosum L.). Journal of Experimental Botany 54 , 349-354.

• Reid RJ, Smith FA (2002) The cytoplasmic pH stat. In 'Handbook of Plant Growth: Ph as the Master Variable' pp. 49-71)

• Mimura T, Reid RJ, Ohsumi Y, Smith FA (2002) Induction of the Na+/Pi cotransport system in the plasma membrane of Chara corallina requires external Na+ and low levels of Pi. Plant Cell and Environment 25 , 1475-1481.

• Haslett BS, Reid RJ, Rengel Z (2001) Zinc mobility in wheat: Uptake and distribution of zinc applied to leaves or roots. Annals of Botany 87 , 379-386.

• Holdaway-Clarke TL, Walker NA, Reid RJ, Hepler PK , Overall RL (2001) Cytoplasmic acidification with butyric acid does not alter the ionic conductivity of plasmodesmata. Protoplasma 215 , 184-190.

• Liu WH, Fairbairn DJ, Reid RJ, Schachtman DP (2001) Characterization of two HKT1 homologues from Eucalyptus camaldulensis that display intrinsic osmosensing capability. Plant Physiology 127 , 283-294.

• Reid RJ (2001) Mechanisms of micronutrient uptake in plants. Australian Journal of Plant Physiology 28 , 659-666.

• Stangoulis JCR, Brown PH, Bellaloui N, Reid RJ, Graham RD (2001) The efficiency of boron utilisation in canola. Australian Journal of Plant Physiology 28 , 1109-1114.

• Stangoulis JCR, Reid RJ, Brown PH, Graham RD (2001) Kinetic analysis of boron transport in Chara. Planta 213 , 142-146.

• Zhang Q, Smith FA, Sekimoto H, Reid RJ (2001) Effect of membrane surface charge on nickel uptake by purified mung bean root protoplasts. Planta 213 , 788-793.

• Taylor GJ, McDonald-Stephens JL, Hunter DB, Bertsch PM, Elmore D, Rengel Z, Reid RJ (2000) Direct measurement of aluminum uptake and distribution in single cells of Chara corallina. Plant Physiology 123 , 987-996.

• Reid RJ, Mimura T, Ohsumi Y, Walker NA, Smith FA (2000) Phosphate uptake in Chara: membrane transport via Na/Pi cotransport. Plant Cell and Environment 23 , 223-228.

• Reid RJ, Smith FA (2000) The limits of sodium/calcium interactions in plant growth. Australian Journal of Plant Physiology 27 , 709-715.

• Liu J, Reid RJ, Smith FA (2000) The mechanism of cobalt toxicity in mung beans. Physiologia Plantarum 110 , 104-110.

• Owens G, Ferguson VK, McLaughlin MJ, Singleton I, Reid RJ, Smith FA (2000) Determination of NTA and EDTA and speciation of their metal complexes in aqueous solution by capillary electrophoresis. Environmental Science & Technology 34 , 885-891.