Rice is a semi-aquatic model
crop grown widely in regions of seasonal rainfall. Therefore, submergence is
one of the most common abiotic stresses that result in reduced oxygen supply for
respiration at night. This in turn reduces the rate of respiration at night
resulting in decreased survival of rice plants.
So rice plants adapted to
use the oxygen released during underwater photosynthesis, which forms a gas
film layer around these submerged leaves. This physiological adaptation is
supported by the super-hydrophobic leaves that have a thicker cuticle with
increased permeability. These two traits enhance oxygen exchange to submerged
shoot regions at night.
In this specific study, the
influence of gas film layer on the rate of oxygen transport and resistance to
oxygen transport was measured against variabilities in stomatal
characteristics, cuticle permeability and thickness of diffusive boundary layer
(standing water or bulk water). The use of 3D simulation modelling for this
study is a very novel experimental approach and highlights a turning point in
plant physiological studies.
The scientists concluded from
the hypothetical results that there is a 22 fold reduction in the resistance
against oxygen transport rate due to the presence of gas film layers in
submerged rice leaves with high cuticle permeability and fully open stomata. This
model also predicted the direction of oxygen transport through open stomata to
be perpendicular and through closed stomata to be oblique.
Hence these adaptations confirm
that rice crop have better survival strategy in regions with seasonal
inundation problem and thus can serve as the crop of choice for rotation during
wet season.
Reference: VERBOVEN,
P., PEDERSEN, O., HO, Q. T., NICOLAI, B. M. and COLMER, T. D. (2014), The
mechanism of improved aeration due to gas films on leaves of submerged rice.
Plant, Cell & Environment, 37: 2433–2452. doi: 10.1111/pce.12300
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