Abstract
In the Cape Fynbos of South Africa, Psoralea
pinnata (L.) plants occur naturally in both wetland and welldrained
soils and yet effectively fix N2 under the two contrasting
conditions. In this study, nodule structure and functioning
in P. pinnata plants from the two habitats were evaluated using
light and transmission electron microscopy (TEM), as well as
the 15N natural abundance technique. The results showed that,
structurally, fully developed P. pinnata nodules were spherical
in shape with six components (namely, lenticels, periderm,
outer cortex, middle cortex, inner cortex, and a central
bacteria-infected medulla region). Morphometric analysis revealed
44 and 84 % increase in cell area and volume of wetland
nodules compared to those from upland. The percentage
area of nodules occupied by the middle cortex in wetland
nodules was twice that of upland nodules. As a result, the size
of the medulla region in wetland nodules was significantly
reduced compared to upland nodules. Additionally, the average
area of medulla occupied by intercellular air spaces in
wetland nodules was about five times that of upland nodules
(about 431 % increase in wetland over upland nodules). TEM
data also showed more bacteroids in symbiosomes of upland
nodules when compared to wetland nodules. However, isotopic
analysis of above-ground plant parts revealed no differences
in symbiotic parameters such as N concentration, ∂15N and %Ndfa between wetland and upland P. pinnata plants.
These results suggest that, under limiting O2 conditions especially
in wetlands, nodules make structural and functional adjustments
to meet the O2 demands of N2-fixing bacteroids.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:tut/oai:encore.tut.ac.za:d1001823 |
| Date | 01 December 2015 |
| Creators | Kanu, SA, Dakora, FD |
| Publisher | Protoplasma |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | |
| Rights | c Springer-Verlag Wien 2015 |
| Relation | ResearchGate |
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