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depends on total conductance (stomatal conductance + mesophyll conductance) of
leaf. As water stress occurs, the stomatal closure restricts the entry of both CO
2
and
water fl uxes from surrounding atmosphere to leaf, but mesophyll conductance remains
same and transpiration reduces disproportionately to stomatal conductance. The mag-
nitude of LWUE (
mol CO
2
fi xed per mmol H
2
O transpired) increased from RDI
0
to
RDI
50
and then decreased at FI. The higher LWUE was with RDI
50
treatment, due to
the marginal decrease in P
n
value associated with the higher decrease in T
r
value under
this treatment over other treatments.
μ
19.3.6 PLANT VEGETATIVE GROWTH
The irrigation treatments significantly influenced the different growth parameters (PH,
STGD, SGD and CV) of plants (Table 5). The minimum incremental of PH, STGD,
SGD and CV was observed with rain-fed plants, whereas the maximum values were
with fully irrigated plants. The higher vegetative growth under higher irrigation re-
gime was probably due to better leaf photosynthesis rate and higher metabolic activi-
ties of fully irrigated plants under favorable soil water condition in the root-zone in
this treatment. However, the increase in growth was more in 2011 than 2010, probably
due to larger rainfall amounts and other weather parameters, which favored better
plant growth in former year than the latter year. Earlier study by García-Tejero et al.
[9] showed the similar findings of decrease in vegetative growth of deficit-irrigated
'Salustiano' orange plants in Spain.
TABLE 5
Annual increment of plant growth parameters of 'Kinnow' mandarin under various
irrigation treatments in 2010 and 2011.
Annual increment of plant growth parameters
Treat-
ments
2010
2011
Mean
PH
*
(m)
STGD
**
(mm)
SGD
+
(mm)
CV
++
(m
3
)
PH
*
(m) STGD
**
(mm)
SGD
+
(mm)
CV
++
(m
3
)
PH
*
(m)
STGD
**
(mm)
SGD
+
(mm)
CV
++
(m
3
)
RDI
0
28.31
a
17.14
a
24.64
a
0.66
a
22.16
a
15.21
a
21.75
a
0.57
a
25.23
a
16.17
a
23.20
a
0.62
a
RDI
50
37.90
b
20.81
a
29.91
b
0.79
b
30.72
b
19.90
a
25.22
b
0.69
b
34.31
b
20.36
a
27.57
b
0.74
b
FI
40.72
c
26.22
a
48.74
e
0.86
c
36.05
c
25.64
a
32.35
c
0.78
c
38.39
c
25.93
a
40.54
c
0.82
c
*
PH: Plant height;
**
STGD: Stock girth diameter;
+
SGD: scion girth diameter;
++
CV: canopy volume.
Data in one column followed by different letter are signifi cantly different at
P <
0.05
,
as per separation by Duncan's
multiple range test.
RDI
0
= No irrigation at early fruit growth period (EFGP); RDI
50
= Irrigation at 50% crop evapotranspiration at EFGP.
19.3.7 FRUIT YIELD AND WATER USE EFFICIENCY
Table 6 presents the fruit harvested (number of fruits tree
-1
, average fruit weight and
total fruit yield) and irrigation water use efficiency under different irrigation treat-
ments. The number of fruits harvested and total fruit yield increased with increase in
irrigation regime from no irrigation to FI. Conversely, the highest fruit weight was
recorded with RDI
50
followed by FI. The lower fruit weight in FI treatment over RDI
50
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