SVERIGES LANTBRUKSUNIVERSITET - Epsilon Open Archive - SLU
SVERIGES LANTBRUKSUNIVERSITET - Epsilon Open Archive - SLU
SVERIGES LANTBRUKSUNIVERSITET - Epsilon Open Archive - SLU
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
46<br />
CONTENTS<br />
PLANT WATER RELATIONS<br />
APPROACHES AND MEASUREMENTS<br />
Page<br />
SUMMARY .......................................... 1<br />
INTRODUCTION ...................................... 2<br />
WATER POTENTIAL AND WATER CONTENT ................ 2<br />
THE SOIL-PLANT-AIR CONTINUUM (SPAC) .............. 5<br />
MEASUREMENT OF PLANT WATER STATUS<br />
AND GAS EXCHANGE ............................... 11<br />
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11<br />
Water content ................................. 11<br />
Water potential ................................ 11<br />
Components of water potential ..................... 13<br />
Pressure volume curves . . . . . . . . . . . . . . . . . . . . . . . . . .. 15<br />
Measurement of stomataI conductance and gas exchange .. 15<br />
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16<br />
SUMMARY<br />
Plant water deficits are described by relative water content (RWC), water<br />
potential (1/J), and its components osmotic potential (1/J7r)' and turgor<br />
potential (1/J p )' The shape of the curves describing their interrelationship<br />
in the Höfler diagram, is determined by the bulk tissue elastic modulus ( € ).<br />
The relation between plant water status and gas exchange is illustrated.<br />
Water transport in the soil-plant - atmosphere continuum (SPAC) is<br />
described by Ohm's law analogy as ratios of potential differences and<br />
resistances connected in series. The threshold in soil hydraulic conductivity<br />
limiting water uptake and methods in calulating 1/J at the root surface are<br />
discussed.<br />
Current techniques for measuring RWC, 1/J, 1/J 7r and 1/J p are described and<br />
the derivation of pressure volume (PV) curves is given in details. The PV<br />
technique both give the most rigerous determination of water relation<br />
parameters and the greatest amount of information. However, the PV<br />
technique is rather time consuming.<br />
Finally, for field use the measurements of stomataI conductance and gas<br />
exchange of water vapour and CO 2 by porometer technique are mentioned.
Change language