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Plant Gene and Trait, 2013, Vol.4, No.4, 17
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The soluble protein content of the leaf, being a
measure of RuBP carboxylase activity was considered
as an index for photosynthetic efficiency. There were
reports that RuBP-case enzyme forms nearly 80 per
cent of the soluble proteins in leaves of many plants
(Joseph et al., 1981). Diethelm and Shibles (1989)
opined that the RUBISCO content per unit leaf area
was positively correlated with that of souble protein
content of the leaf. Soluble protein content was
estimated in order to find out the photosynthetic
capacity of banana cultivars under water deficit
situations. In the present study, water deficit caused a
significant reduction in soluble protein content of
leaves of all the banana cultivars. Among the cultivars
studied, Karpuravalli, Karpuravalli × Pisang jajee,
Saba and Sannachenkathali maintained higher soluble
protein content with 9 per cent reduction over control,
followed by cultivars of Poovan, Ney Poovan,
Anaikomban and Anaikomban × Pisang jajee with 15
per cent reduction. However, the cultivars of Matti,
Matti × Anaikomban, Matti × cultivar rose and Pisang
jajee × Matti recorded the lowest soluble protein
content with higher reduction of 19 per cent than
control. The mechanism of reduction in soluble
protein content due to water deficit by reduction in
RUBISCO enzyme activity leads to lower CO
2
assimilation. These findings were in accordance with
the results of Wahad et al. (2000) who observed a
significant reduction in soluble protein content of
banana plants grown under drought stress conditions.
Besides these results, Martignone et al. (1987) observed
that in soybean soluble protein content was the first
nitrogenous compound affected under stress conditions,
which at severity got denatured and lost the activity. It
was further explained that soluble protein, world’s
most abundant protein containing the enzyme RUBISCO,
is involved in CO
2
assimilation; therefore, the reduction
in soluble protein might have a direct adverse effect
on photosynthesis. Hsio (1974) reported that the
decrease in the protein level in water stressed plants
could be attributed to decrease in protein synthesis,
the decreased availability of amino acids and
denaturation of the enzymes involved in amino acid
and protein synthesis, perhaps at the ribosomal level.
3.3 Bunch yield (kg/bunch)
Bunch yield of banana is considered as the major
contributing factor for the final plant yield, generally
expressed in kg per bunch. In the present study,
comparing bunch weight of all the twelve cultivars of
banana as affected by water deficit, significant variations
could be observed. The cultivars of Karpuravalli,
Karpuravalli × Pisang jajee, Saba and Sannachenkathali
produced the mean bunch weight of 17.5 kg/bunch,
15.5 kg/bunch, 14.5 kg/bunch and 14.5 kg/bunch
followed by Poovan, Ney Poovan, Anaikomban and
Anaikomban × Pisang jajee recording 14.0 kg/bunch,
9.5 kg/bunch, 6.0 kg/bunch and 5.5 kg/bunch, whereas
Matti, Matti × Anaikomban, Matti × cultivar rose and
Pisang jajee × Matti produced lower bunch yield of 4
to 4.5 kg/bunch due to water deficit (Figure 1).
Besides these cultivar variations due to water deficit
exhibited their significant inhibitory effect on bunch
yield. The tolerant cultivars had lesser effect on bunch
Figure 1 Effect of water stress on bunch weight (kg/bunch) of
banana cultivars and hybrids at different growth stages