Replacement with color figures: The 2,4-D-induced wheat para-nodules are modified lateral roots with structure enhanced by rhizobial inoculation

• Published in: Plant and soil 1994-02, Vol.159 (2), p.121-129
• Main Authors: FRANCISCO, PERIGIO B., AKAO, SHOICHIRO
• Format: Article
• Language: English
• Subjects: Inoculation; Legumes; Nitrogen fixation; Nodules; Plant roots; Plant tissues; Plants; Rhizobium; Seedlings; Wheat
• ISSN: 0032-079X; 1573-5036

Nodular outgrowths (para-nodules or p-nodules) on the roots of wheat (Triticum aestivum L.) cv. Miskle seedlings were induced by treatment with 0.3 and 0.6 mg L⁻¹ 2,4-dichlorophenoxyacetate (2,4-D). When co-inoculated with Rhizobium trifolii strain ATCC 14480, more p-nodules were formed at these levels and p-nodulation occured at 0.1 mg L⁻¹ indicating that inoculation enhances 2,4-D-induced p-nodulation. Similar to lateral roots, the p-nodules arose from the pericycle opposite the phloem tissues and were free from the cortical cells of the parental root at all stages of development. Structurally, the p-nodules exhibited tissue differentiation. They possessed a highly organized central vascular cylinder connected to that of the parent root, an endodermis, a cap, and an apical and lateral meristems. P-nodules formed by 2,4-D treatment alone were irregularly lobed due to uncoordinated activity of the apical meristem, while those in the combined 2,4-D and inoculation treatment were more globose. The results of the present study indicate that the 2,4-D-induced wheat p-nodules are modified lateral roots, the structure of which is enhanced by rhizobial inoculation.