Abstract:
Expansion of apple growing to dry areas requires re
liable approaches to select
genotypes tolerant to water stress. We have simulat
ed apple tree transpiration (Ec) from
different commercial orchards and compared it with
actual transpiration (Ea) derived
from sap flow measurements. The modelling approach
lies in rearranging a
parameterized P–M Equation and incorporating in it
a stomatal conductance model
derived from meteorological variations. The model u
ses diurnal courses of variables
instead of commonly used daily means. We then wrote
a complex P–M Equation which
already includes the canopy conductance as the func
tion of radiation and vapour pressure
deficit. For model calibration, an extensive experi
mental dataset of tree transpiration was
collected from 2011 to 2013 in various sites of Alb
ania and Kosovo, ranging from very
warm to temperate. The daily pattern of canopy cond
uctance for water vapour at canopy
level provided by the model offers an unprecedented
insight into rapid response to
humidity of different cultivars as well as their li
ght saturation levels. The satisfactory
performance of this functional model should improve
the precision of current empirical
approaches followed to compute fruit tree water req
uirements and can be a promising
tool for early and quick evaluation of water stress
tolerance in apple genotypes.
Keywords:
Irrigation, Modelling, Sap flow, Stomatal kinetics
.
