SVERIGES LANTBRUKSUNIVERSITET - Epsilon Open Archive - SLU
SVERIGES LANTBRUKSUNIVERSITET - Epsilon Open Archive - SLU
SVERIGES LANTBRUKSUNIVERSITET - Epsilon Open Archive - SLU
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model can be used as a research too l to lead to new ideas for<br />
experimentation, and to provide a link between plant physiol<br />
ogy in the laboratory and problems in the field. Thirdly, the<br />
model could be used by researchers in analyzing their own<br />
field data. Being simple to use, the models are suitable for<br />
those who have not time to develop their own models and/or<br />
are not experienced in using simulation modeIs. The main<br />
emphasis has been to develop so called interactive computer<br />
programs, which are easy to use, include various type of<br />
help facilities and have possibility to show results in<br />
graphical form.<br />
Water movement in Soil-Plant-Atmosphere-Continuum<br />
Water movement in the plant can be considered to be<br />
driven by differences in water potential and flow is restric<br />
ted by some resistances within the system. Water will flow<br />
from a point of high water potential to the direction of<br />
decreasing water potential. In the soil-plant-atmosphere<br />
system the water potential in a well-watered soil may be on<br />
the order of -0.01 MPa (equivalent to -100 cm or pF 2). In<br />
plant leaves midday values of the water potential are gene-<br />
rally around -0.5 ... -2.5 MPa (-5000 ... -25000 cm). In the air<br />
the water potential is very low (-30 ... -100 MPa depending on<br />
vapour pressure deficit of the air). Comparison of these<br />
potentials show that general ly there is a continuous stream<br />
of water from the soil to the plant and from plant to the<br />
atmosphere. The magnitude of flow is influenced by resistan<br />
ces at various parts (see Fig. 1): from the soil to the plant<br />
roots, from the roots to the leaves (plant resistance), from<br />
the intercellular spaces to the atmosphere (stomataI and<br />
boundary layer resistances) .<br />
Description of the computer programs<br />
Various type of computer programs have been developed<br />
mainly to be used as research and educational tooIs. The<br />
value of mathematical models depends on the nature of the<br />
problem. Some points of general significance are given<br />
below:<br />
. modeling can stimulate new ideas and experimental<br />
approaches