A structural and histological description of nodules of Tribulus terrestris L. and the infecting microorganisms
2004
Mahmood, A. | Athar, M. (Karachi Univ. (Pakistan). Dept. of Botany)
The present paper is a histological study of the nodules or nodule- like swellings found on the roots of Tribulus terrestris L., a xerophytic nonleguminous plant of the angiosperms. Anatomically the nodules found on this species show similarities to the tissue pattern of non-leguminous nodules. They had a central vascular system and the infected tissue occupying the cortical cells on both sides of the stele. The cytology of the proliferated tissue is described. Two types of endophytes were observed in the cortical cells of the nodules. Cells of the outer cortex were bigger showing large intercellular spaces in which clumps of rhizobia (Bradyrhizobium sp.) could be seen. The invasion pathway of bacteria appears to be "crack entry" and their cell to cell movement was both intercellular and intracellular. Cells of the inner cortex were smaller, compact and did not show intercellular spaces. These cells were heavily colonized by cyanobacterium. This has been described as a new toxin and is designated as Newmania karachiensis Mahmood and Athar gen. nov et sp. nov. The occurrence of a blue green alga as endophytes in the root nodules of an angiosperm is being reported for the first time.
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