Agriculture Reference
In-Depth Information
Lara
Panegine20
0
80
0
80
)
70
70
m
r
-1
f
r
l
)
-1
m
r
)
f
r
l
)
60
60
-2
-2
50
50
u
-3
40
-3
40
e
30
30
-4
-4
e
20
20
-5
10
-5
10
-6
0
0
-0.1
-0.5
-0.75
-1
-1.5
-2
-6
0
0
-0.1
-0.5
-0.75
-1
-1.5
-2
Medium water potential (MPa)
Medium water potential (MPa)
Chandler
Serr
0
80
0
80
e
m
r
)
)
70
70
)
f
r
l
)
-1
m
r
(
-1
60
60
f
r
l
-2
-2
50
50
-3
40
-3
40
e
30
30
-4
-4
20
20
-5
-5
10
10
-6
0
-6
0
0
-0.1
-0.5
-0.75
-1
-1.5
-2
0
-0.1
-0.5
-0.75
-1
-1.5
-2
Medium water potential (MPa)
Medium water potential (MPa)
Figure 2.
Patterns of predawn leaf water potential (♦), midday leaf water potential (■)and soil available water (▲)
measured in walnut seedlings during drought treatments [Lotfi et al., 2010].
MPa decline in Ψπp as a result of both increased solute content and increased leaf tissue
elasticity. Seedlings of a New York source showed no detectable osmotic adjustment [214].
They concluded that in roots, decreased Ψπo (osmotic potential at full hydration) and Ψπp
were observed under drought. Sources that exhibited significant leaf osmotic adjustment also
generally showed a similar response in roots. Tissue elasticity and Ψπo of roots were higher
than those of shoots, whereas Ψπp of the two organs was similar for most sources. Because of
greater elasticity, roots exhibited a more gradual decline in turgor and total water potential
than did leaves as tissue relative water content decreased [214].
Cochard et al. [29] focused their analysis on some of the endogenous physiological parameters
likely to be altered during a water stress and reported in the literature to be associated with
stomatal responses. These parameters are the Ψ
soil
(soil water potential), the R
soil
(soil resist‐
ance), the R
root
(root hydraulic resistances), and the R
shoot
(shoot resistance); all of these
parameters are strongly correlated under natural drought conditions. The experiments were
designed to alter Rplant in very different ways, which probably had a primary influence on
different parts of the pathway.
Soil dehydration provoked mainly a drop in Ψ
soil
and an increase of R
soil
. The resistance of the
interface between the soil and the root, probably increase during drought stress [87]. When
R
root
modified to the extent that the radial flow into the root xylem altered. R
shoot
probably not
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