Positive root pressure and xylem repair

tomaat fruit

The main aim of this project is to further our understanding of the conditions under which positive root pressures develop in the tomato plant, and to test the hypothesis that the ability to generate positive root pressure enhances drought-resistance.

Dr. Frederic Lens

Senior researcher
Understanding Evolution

frederic.lens@naturalis.nl
+31 (0)71 7519320

Climate change is predicted to strongly influence rainfall patterns across the globe, with
potentially disastrous consequences for crops and human food production. Recent work has
greatly improved our understanding of plant function during drought, but has focused mostly on
woody plants. There is therefore an urgent need to study herbaceous plants that comprise most
of the world’s crops. In particular, it has been hypothesized that positive root pressure could
play a crucial role in the survival of herbaceous species during drought, by removing gas
bubbles (‘embolisms’) formed in the water conducting vessels due to severe drought stress, a
process called ‘xylem repair’. While generation of positive root pressure has been verified in
some species (including in the tomato plant, Solanum lycopersicum), its potential role xylem
repair and in providing drought-tolerance is controversial in many cases and untested in herbs.

Objectives and goals


The main aim of this project is to further our understanding of the conditions under which
positive root pressures develop in the tomato plant, and to test the hypothesis that the ability to
generate positive root pressure enhances drought-resistance by “refilling” embolized xylem
vessels. The project also involves interacting with the tomato industry (Rijk Zwaan) to obtain
different genotypes of tomato and provide feedback regarding the development of positive root
pressure and any benefits during drought or fruit development (root pressure has been
associated to damage fruits by bursting them open).

 

Material tasks and approach


Different varieties of tomato plants will be grown under well-watered conditions. A subset of
plants will be subjected to increasing levels of drought, and drought stress will be monitored
daily by measuring soil water-content, leaf water-potential and gas-exchange parameters.
After rewatering the droughted plants, we will monitor stem diameter variation and sap-flow, to
estimate root pressure (following De Swaef et al. 2013). To visualize xylem refilling, these plants
will be brought to the X ray scanning facility in Ghent University (Belgium), where they will be
repeatedly scanned after rewatering to observe a direct link between positive root pressure and
refilling. Vulnerability curves will assess differences in embolism resistance, by scanning plants
at different levels of drought stress and measuring the area of embolized vessels relative to the
area of total initially functional xylem.


Requirements


We are looking for a student with an interest in plant hydraulics and modelling.

Period and duration


Ca. 6 months, project can start now


Study and level


MSc project