Transcript Diapositivo 1

Salinity-induced effects on transpiration rate,
stomatal conductance and leaf area of three
olive (Olea europaea L.) varieties
Renato Coelho1,3, Mário Moitas2, Ana Elisa Rato1, Margarida Vaz1
1ICAAM,
Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal; 2Graduation student, Universidade de Évora. Portugal; 3 [email protected]
INTRODUCTION
Soil salinity may become a serious issue for
olive orchards in southern Portugal, where
irrigation with groundwater is becoming the
ordinary practice.
Aim of this work
The objective of this work was to
(1) test a non-destructive method for whole-plant
leaf area determination, and
(2) observe how soil salinity affected leaf area,
leaf transpiration and stomatal conductance of
young olive trees.
RESULTS
Table 1. Relation between canopy area (m2) of
trees and their actual leaf area, for each of the
three varieties of olive trees. For details, see Fig.1.
variety leaves
Arbequina 0,139
Cobrançosa 0,098
Galega 0,136
canopy leaves/canopy
0,100
0,068
0,110
1,40
1,43
1,24
mM NaCl
0,3
0
80
200
0,2
MATERIALS AND METHODS
Three olive varieties, Arbequina, Cobrançosa
and Galega (18 trees per variety) were grown in
soil irrigated with three levels of salt (0, 80 or
200 mM NaCl) for about 90 days. After that, leaf
area and transpiration rate were assessed.
Determination of whole-plant leaf area
0,1
a
0,0
a
a
a
a
b b b
b b b
Cobrançosa
Galega
b b
Arbequina
a
Figure 3. Leaf area (m2) of olive trees after
exposure to salt in the irrigation water for three
months. Bars show mean plus standard error (n =
6). Different letters indicate statistical difference
between means (p < 0,05, Tukey’s test).
1st
10 cm
canopy
= 0,110 m2
2nd
mM NaCl
0
80
200
2,0
1,5
10 cm
leaf area / canopy area = 1,24
Figure 1. Schematic representation of the
determination of whole-plant leaf area. The shoot
of one tree of each variety was photographed from
a side and its total area (canopy area) was measured
with ImageJ software. On the same tree, leaves
were removed and photographed allowing for an
accurate measurement of actual leaf area (leaf
area). For each variety, a correlation was obtained
for the leaf area/tcanopy area which was then used
to determine leaf area of all other plants based on
the photograph of the whole shoot.
Determination of whole-plant transpiration
rate (E) and stomatal conductance (gS)
Figure 2. Determination
of transpiration rate (E)
and stomatal conductance (gS). The
plant and its pot were weighed
around 10 am and later at 5 pm.
The soil in the pot was covered with
plastic to avoid evaporation.
Transpiration rate was calculated
7 328 g
from the weight loss, the time lapse
and the estimated leaf area (Fig. 1).
Simultaneously, stomatal conductance (gS) was
measured with a porometer (Delta-T).
1,0
a
0,5
0,0
a
b b
c c
Arbequina
a
b
c
Cobrançosa
c c
Galega
Figure 4. Transpiration rate (mmol m-2 s-1) of olive
trees after exposure to salt in the irrigation water
for three months. Bars show mean plus standard
error (n = 6). Different letters indicate statistical
difference between means (p < 0,05, Tukey’s test).
gS (measured)
3rd
leaf area
= 0,136
m2
100
50
porometer
gS (calculated)
0
0
50
100
Figure 4. Relation between the stomatal
conductance (gS) measured with a porometer and
gS calculated from the transpiration rate and the
difference in molar fraction between the leaf and
the atmosphere. Each point represents the average
of 6 measurements. The regression equation is
gS (measured) = 0,967 × gS (calculated); R2 = 0,837
CONCLUSIONS
Three month irrigation with salt slightly decreased leaf area of olive trees, but greatly reduced
transpiration rate of all three olive-tree varieties investigated in this work.
Calculated and measured values of stomatal conductance showed a close relation between them which
indicates this non-destructive method to determine whole-plant leaf area to be reasonably accurate.
Acknowledgements: the authors thank Roberta Lima and Gracieli Manfrin da Silva for their help on the preparation of this poster.