Microscopic evidence on how iron deficiency limits nodule initiation in Lupinus angustifolius L.

Abstract

SUMMARYLupins (Lupinus angustifolius L. cv. Yandee), grown in solution culture, have been used to study the sites and process of infection by Bradyrhizobium sp. (Lupinus) and the impairment of nodulation by iron deficiency.Infection leading to nodulation occurred in an area of epidermal cells either lacking root hairs or with very young root hairs at the time of inoculation. Cells aged 13 h or over appeared not to be infected. Infection was initiated in the outer cortex. Rare, short infection threads were evident on day 4 after inoculation, 2 d after the initial division of cortical cells resulting from the bradyrhizobial inoculation. Bacteria had been released into the cytoplasm of cortical cells within 5 d after inoculation. Bacteroids multiplied in the cytoplasm, segregated passively and spread in the infection zones by repeated division of the invaded cells.Under iron deficiency, initial cell division occurred in the outer cortex of host roots, as in iron-sufficient plants after inoculation. Iron deficiency then limited further division of cortical cells. Only a few surviving infection sites developed nodules with normal structure but development was much slower than in iron-sufficient plants.

Development of N2‐fixing nodules on the wetland legume Lotus uliginosus exposed to conditions of flooding

“…This second mode of infection appears to occur where there are no root hairs and follows a pattern similar to that observed within roots of Sesbania rostrata, Lupinus angustifolius, Mimosa scabrella and Mimosa pellita (Ndoye et al, 1994 ;Tang et al, 1992 ;De Faria et al, 1988 ;Loureiro et al, 1998). For example, like S. rostrata (Ndoye et al, 1994) and L. angustifolius (Tang et al, 1992), nodule initiation can occur in the region of the lateral root that lies within the tap root cortex, far from the region of root hair development. Furthermore, as with M. pellita (Loureiro et al, 1998), it appears that enlarged cells comprising the aerenchyma on flooded roots are most susceptible to infection.…”

Mogelijke oorzaken van een dalende opbrengst van witte klaver (Trifolium repens L.) in de tijd

“…Daardoor is de Fe-behoefte van de wortelknolletjes groter dan de Fe-behoefte van de plant zelf (Abdelmajid et al 2008). Een Fe-tekort heeft niet direct een negatief effect op het begin van de infectie met Rhizobium-bacteriën, maar vooral op het vervolg, waaronder de vermenigvuldiging van de bacteriën (Tang et al 1992). Fe-tekort bij leguminosen leidt tot een verminderde wortelknolletjesvorming en N-binding (O'Hara et al 1988;Tang et al 1991) en treedt vooral op bij een te hoge pH.…”

“…In Nederland kan Fe-gebrek daardoor mogelijk voorkomen op jonge zeeklei. Opheffen van Fe-tekort door Fe-bemesting via het blad (via de bodem is niet zinvol) is waarschijnlijk niet direct een optie, omdat Fe niet bij alle gewassen (b.v. bij lupine) van het blad naar de wortelknolletjes wordt getransporteerd (Tang et al 1992). …”

Metal Transport in the Rhizobium-Legume Symbiosis

“…For instance, the effect of low iron levels ranges from the inhibition of the nodulation to the loss of the capability to fi x nitrogen (Tang et al 1990, Tang et al 1992, O'Hara 2001. This is due to the high number and relevance of metalloproteins involved in symbiotic nitrogen fi xation.…”