Legume Root Exudates: Their Role in Symbiotic Interactions

Abstract

Legumes are in constant dynamic interactions with rhizobia and arbuscular mycorrhizal (AM) fungi which mutually benefi t the partners. Legumes provide the carbon energy to the microbes, and they in turn provide the nutrients such as nitrogen and phosphorus. The growth of these symbionts largely depends on the secretions of the legume roots which include both high and low molecular weight compounds. These molecules also act as cues in plant-microbe signaling and recognition. A cascade of reactions take place between the legume and the microbe before specifi c refi ned symbiotic partnership manifests mutually benefi ting both the partners. Here, we provide an overview of the functions of legume root exudates with emphasis on the interactions between legume and rhizobia.

The role of abiotic factors modulating the plant-microbe-soil interactions: toward sustainable agriculture. A review

“…Other exudates such as phenolic derivatives, in particular flavonoids, specifically attract rhizobia bacteria, a heterogeneous group of bacteria that includes the genera Rhizobium, Bradyrhizobium, Sinorhizobium, Mesorhizobium, and Allorizhobium (Hernández-Salmerón et al, 2013). In general, rhizobia can form symbiotic associations with legumes and fix atmospheric nitrogen to convert it into ammonium, thereby making nitrogen available for the plant (Biate et al, 2015). Moreover, some exudates are part of the plant defence system, such as phenolic compounds and terpenoids, which have efficient antibacterial and antifungal capacity.…”

Flavones: From Biosynthesis to Health Benefits

“…Other than pathogenic microbes, arbuscular mycorrhiza (AM) fungus and nitrogen fixing bacteria Rhizobium and Frankia provide the most prevalent examples of symbiosis in the plant kingdom [ 118 , 119 ]. Multiple metabolic changes, including the alteration of flavonoid expression in the roots of the host plants, occur before and after the penetration of the host plant’s root by microorganisms [ 120 ].…”

Hormonally active phytochemicals and vertebrate evolution

“…It is likely that products of phenylpropanoid biosynthesis were critical in the evolution of land plants: Lignins provide structural support for terrestrial plants, and some flavonoids are UV protective (Ferrer et al., ; Pollastri & Tattini, ; Tossi, Lombardo, Cassia, & Lamattina, ; Yoo, Lee, & Patil, ). Both saponins and flavonoids function in allelopathy and plant defense against foreign organisms (Biate et al., ; Faizal & Geelen, ; Iriti & Faoro, ; Weston & Mathesius, ); they regulate seed dormancy and germination, root growth and gravitropism, movement of auxin, and root nodulation (Brown et al., ; Buer & Muday, ; Carlsen, Understrup, Fomsgaard, Mortensen, & Ravnskov, ; Faizal & Geelen, ; Jia et al., ; Nair, Safir, & Siqueira, ; Peer, Blakeslee, Yang, & Murphy, ; Peters, Frost, & Long, ). In fact, isoflavonoids involved in recruitment of nitrogen fixing bacteria and root nodulation can account for 9% of the dry weight of red clover (Dornstauder et al., ).…”