Effects of boron and calcium nutrition on the establishment of the Rhizobium leguminosarum–pea (Pisum sativum) symbiosis and nodule development under salt stress

Abstract

The effects of modifying boron (B) and calcium (Ca2+) concentrations on the establishment and development of rhizobial symbiosis in Pisum sativum plants grown under salt stress were investigated. Salinity almost completely inhibited the nodulation of pea plants by Rhizobium leguminosarum bv. viciae 3841. This effect was prevented by addition of Ca2+ during plant growth. The capacity of root exudates derived from salt‐treated plants to induce Rhizobium nod genes was not significantly decreased. However, bacterial adsorption to roots was highly inhibited in plants grown with 75 mM NaCl. Moreover, R. leguminosarum 3841 did not grow in minimal media containing such salt concentration. High Ca2+ levels enhanced both rhizobial growth and adsorption to roots, and increased nodule number in the presence of high salt. Nevertheless, the nodules developed were not functional unless the B concentration was also increased. Because B has a strong effect on infection and cell invasion, these processes were investigated by fluorescence microscopy in pea nodules harbouring a R. leguminosarum strain that expresses green fluorescent protein. Salt‐stressed plants had empty nodules and only those treated with high B and high Ca2+ developed infection threads and exhibited enhanced cell and tissue invasion by Rhizobium. Overall, the results indicate that Ca2+ promotes nodulation and B nodule development leading to an increase of salt tolerance of nodulated legumes.

Comparative symbiotic performance of native rhizobia of the Flooding Pampa and strains currently used for inoculating Lotus tenuis in this region

“…In this way, salt concentrations that decrease symbiotic performance are usually different to those that affect growth of each symbiotic partner (Bordeleau and Présvost 1994;El-Hamdaoui et al 2003). In agreement with these observations and in spite that all the isolates hereby studied tolerated 200 mM NaCl in free-living conditions, the symbiotic performance of two strains (BSA2.8 and BSA1.6) from saline soils was considerably impaired under 100 mM NaCl.…”

Boron Increases the Growth and Yield of Mungbean

“…It increases the yield and growth of plants by increasing the leaf area expansion, 1000 seed weight, nodule formation, seed yield and biological yield. It influences the major cellular functions and metabolic activities in plants and required for cell differentiation at all growing tips of plants (meristems) where cell division is active (El-Hamdaoui et al, 2003). Kaisher et al (2010) studied the effect of boron on pulses and concluded that it is important for protein synthesis and improved protein content.…”

The pleiotropic effects of extract containing rhizobial Nod factors on pea growth and yield

“…Among other strategies, enhancement of symbiotic nitrogen fixation efficiency has been investigated [1,2], an approach that is wellfounded both economically and ecologically. Biological nitrogen fixation is of significant importance to various crop and pasture legumes, as this additional nitrogen source often meets more than half of a plant's requirement for nitrogen [3].…”