Effects of solution pH and bicarbonate on the growth and nodulation of a range of grain legume species

Abstract

Defining plant adaptation to soil conditions is critical for the successful introduction of grain legume species into farming systems. This nutrient solution study examined the effects of pH (4, 5, 6, 7 and 8) and bicarbonate (5 mM KHCO3) on the growth and nodulation of 14 grain legume species supplied with N or reliant on N2-fixation. Species included Pisum sativum L., Cicer arietinum L., Lens culinaris Med., and a range of Lupinus, Vicia and Lathyrus species.Species differed greatly in response to solution pH. For both N-fertilized and N2-fixing plants, shoot growth of L. culinaris was very sensitive to low pH (pH < 7), whereas shoot growth ofLupinus angustifolius L. and Lupinus albus L. was sensitive to higher pH (pH > 6). Other species had a broader optimal pH range for growth when supplied with N, but were generally sensitive to low pH (pH < 7 for C. arietinum and Vicia sativa L., pH < 6 for P. sativum, Vicia faba L., Lathyrus sativus L. and Lathyrus eicera L., and pH < 5 for Vicia benghalens& L. and VicM narbonensis L.) when reliant on N2-fixation. For these other species, symbiotic Ne-fixation appeared to be more sensitive than host plant growth to low pH. This finding was supported by lower nodule numbers and mass, and lower N concentrations in shoots of sensitive species at low pH relative to higher pH. For L. culinaris, nodule numbers and mass were relatively unaffected by pH 5-8, N concentrations in shoots were high at low pH and plants developed symptoms relating to H + toxicity at pH as high as 7. These results indicate that host plant growth of L. eulinaris is more sensitive to low pH than the Rh&obium symbiosis. For L. albus and L. angustifolius, both host plant growth and symbiotic N2-fixation appeared to be equally sensitive to pH _> 6. Lupinus pilosus Murr. was more tolerant of high pH than the other Lupinus species. At pH 4, two genotypes of C. arietinum had better early nodulation than other species. Vicia ervilia L. nodulated poorly at all levels of solution pH, indicating that the commercial Group E inoculum (Rhizobium leguminosurum bv. viceae SU303) may not be effective for this species in solution culture.Addition of bicarbonate decreased shoot growth, nodulation and N concentrations in shoots of most species. Early nodulation (nodule number) ofLathyrus ochrus (L.) DC was not affected by the bicarbonate treatment.Abbreviations: MES-2-(N-morpholino)ethane-sulfonic acid, TES-N-tris(hydroxymethyl)methyl-2-aminoethane-sulfonic acid.

Natural variation for Fe-efficiency is associated with upregulation of Strategy I mechanisms and enhanced citrate and ethylene synthesis in Pisum sativum L.

“…Only healthy and uniform seedlings were transplanted to solution culture. A basal nutrient solution (Tang and Thomson 1996) was used with the following nutrient concentrations (lM): NH 4 NO 3 (400), Ca(NO 3 ) 2 (1,600), KH 2 PO 4 (80), K 2 SO 4 (2,400), MgSO 4 (800), CaCl 2 (2,400), FeEDDHA (40), H 3 BO 3 (20), Na 2 MoO 4 (0.12), ZnSO 4 (3.0), MnSO 4 (4.0), CuSO 4 (0.8) and CoSO 4 (0.8). Target pH values were obtained by titrating the basal solution with KOH or H 2 SO 4 .…”

“…Both genotypes were grown in the presence of 10 mM 1-aminoisobutyric acid which is known to block ethylene biosynthesis. Fe chelate reductase activity and chlorophyll score were measured 5 days after Fe deficiency was imposed in the nutrient solution (Tang and Thomson 1996).…”

An Insight into the Legume–Rhizobium Interaction

“…Like rhizobial species, the legume species also differ in their response to low pH (Tang and Thomson 1996 ). Muthukumar et al ( 2014 ) suggest three possible mechanisms that enable plants to tolerate acidic conditions: (1) exclusion of toxic ions (such as Al and Mn) from the root apex, (2) tolerance to toxic levels of Al and Mn through detoxifi cation in the plant symplasm and (3) enhanced effi ciency in the uptake of limiting nutrients from acid soils (Kochian et al 2005 ;Bhalerao and Prabhu 2013 ).…”

“…Taylor et al ( 1991 ) suggested that at low pH, the rhizobial population decreases. However, not all the strains exhibit pH sensitivity, and rhizobia appear to be more tolerant to alkalinity and acidity and then do their legume hosts, thus host legume is considered to be a limiting factor for creating rhizobium-legume symbiosis (Tang and Thomson 1996 ;Graham et al 1994 ;Zahran 1999 ). Bradyrhizobium (slow-growing strain) is more tolerant to low pH than the fast-growing strains of rhizobium, with the exception of R. loti and R. tropici .…”

“…In both tropical and temperate areas, the acidic pH limits the growth and survival of rhizobium strains in soil and nodulation and ultimately constrains nitrogen fi xation of legumes (Graham et al 1994 ). In a study by Tang and Thomson ( 1996 ), they studied the effects of pH (4, 5, 6, 7 and 8) and bicarbonate (5 mM KHCO 3 ) on the growth and nodulation of 14 grain legume species supplied with N or reliant on N 2 fi xation. Species shows a broader optimal pH range for growth when supplied with N, but showed sensitivity at low pH when reliant on N 2 fi xation.…”