Poster19: Tolerance to waterlogging in Brachiaria genotypes: the role of root aerenchyma development
Roots of plant species adapted to waterlogging usually display
characteristics that enable them to withstand the adverse conditions in
water-saturated soils, of which aerenchyma is the most obvious
adaptive one. Aerenchyma are cortical airspaces that provide a low
resistance internal pathway for the movement of O2 from the shoots to
the roots, where it is consumed in respiration and could also partially
oxidize the rhizosphere. The present work explores the extent to
which aerenchyma formation occur under well drained and
waterlogged conditions in Brachiaria genotypes with contrasting levels
of tolerance to poorly drained soils.
A pot experiment was performed in January, 2009 at the Forages
patio area (CIAT, Cali, Colombia).
B. humidicola CIAT 6133, B. humidicola CIAT 679 (tolerant);
B. brizantha CIAT 26110, B. decumbens CIAT 606 (moderately
tolerant); B. brizantha CIAT 6294, B. ruziziensis Bruz 44-02,
B. hybrid Mulato 2 CIAT 36087 (sensitive).
Two stem cuttings per pot were sown and allowed to grow for 50
days in 3,1kg of a fertilized top oxisoil from Santander de Quilichao.
The experiment was a Randomized complete block with 4 replications.
Waterlogging treatment was imposed by applying excessive water
to the pots (5 cm over soil surface) for 21 days. Plants without
waterlogged soils and maintained at field capacity were used as a
Root anatomy: Freehand sections were taken every 5cm and
photographed with a digital camera connected to a Leitz Orholux II Fig. 1. Root anatomy of contrasting Brachiaria genotypes grown under field capacity
microscope. Cross sectional area and aerenchyma within each (CONTROL) and waterlogged conditions. Sections were taken at the distance of 150
capture were measured using ImageJ software. mm from the root tip.
Fig. 2. Percentage of
aerenchyma of roots
• For all genotypes, a 21 day waterlogging treatment grown in an oxisoil
maintained at field
increased the area of aerenchyma when compared to capacity or waterlogged
the control (Figures 1 and 2). for 21 days. * denotes a
* * * statistically significant
CIAT 679 CIAT 26110 Bruz 44-02 * *
difference at 95%
confidence level (LSD)
between columns of a
• Differences in aerenchyma formation between two moderately tolerant
( C I AT 2 6 11 0 a n d C I AT 6 0 6 ) a n d t h r e e s e n s i t i v e
(Bruz 44-02, CIAT 6294 and CIAT 36087) were not significant.
• Although moderately tolerant and sensitive genotypes genotypes had significant increase of aerenchyma formation under
waterlogged conditions, it was not possible to establish the role of aerenchyma in their differential tolerance to waterlogging.
• All genotypes responded to waterlogging by increasing the formation of root aerenchyma.
• The higher percentage of aerenchyma in two accessions of the tolerant B. humidicola (CIAT 6133 and CIAT 679) should be of
adaptive advantage at the offset of and during waterlogging.
• The moderate level of waterlogging tolerance observed for CIAT 26110 and CIAT 606 may not be related to aerenchyma formation.
This work is supported with a grant from FONTAGRO: “Desarrollo de genotipos de Brachiaria adaptados a suelos con drenaje deficiente para aumentar producción
bovina y adaptar sistemas de pastoreo al cambio climático en América Latina”.