Document: BIL-3-19-6

Soil drying and atmospheric stress can combine to affect shoot growth and functioning through chemical signalling.

DAVIES, B.* and S.WILKINSON

Lancaster University, Bailrigg, Lancaster, LA1 4YQ, United Kingdom ¹

Abstract:
It has now become clear that growth and functioning of plants in drying soil can be regulated by both chemical and hydraulic influences. It has been suggested that plants may use chemical signalling between roots and shoots to 'measure' such variables as the availability of water in the soil. There are some circumstances where hydraulic signalling has a dominant influence but many others where changes in the delivery to shoots of potent chemical species will result in the regulation of plant functioning. This can mean that shoot water relations are regulated along with growth and gas exchange. It is often difficult to ascribe particular plant responses to variations in fluxes of particular chemical signals but some hormones seem to have a key role. In addition, variation in the flux of inorganic ions through the xylem and/or the pH of the xylem sap can also be important. This paper will emphasise the subtle nature of chemical regulation of growth and gas exchange in response to soil perturbations. This regulation may involve no net increase in the synthesis of particular regulators. We will also consider ways in which information moving from the roots to the shoots may be modified by the influence of climatic factors such that shoots can achieve an appropriate response to a combination of stress factors.

Keywords: Chemical signalling, plant hormones, inorganic ions, xylem pH, growth, gas exchange

This abstract is being presented at: 9:15 AM in session:
Symposium # 9: The Water Limitation: Issues in Plant, Community, and Ecosystem Water Use.