Lotus tenuis and Schedonorus arundinaceus co-culture exposed to defoliation and water stress

The present study aimed to investigate the effect of defoliation frequency (low and high) and water stress (excess or deficit) on biomass production, P and N nutrition, and symbiosis with native soil microorganisms on a Lotus tenuis and Schedonorus arundinaceus co-culture in a pot experiment. Combined effects of defoliation frequency and water stress affected plant accumulated shoot biomass. L. tenuis root biomass decreased in response to defoliation and water stress, while S. arundinaceus root biomass was similar between non-defoliated and defoliated plants, at all water levels. Low and high frequencies of defoliation in a waterlogged soil can be considered the most stressful scenario for L. tenuis and S. arundinaceus co-culture. Colonization of arbuscular mycorrhizal fungi in L. tenuis roots and dark septate endophytes colonization in S. arundinaceus roots were affected by both factors, whereas arbuscular mycorrhizal colonization in S. arundinaceus was affected only by water stress. Both plants tolerated defoliation and water stress due to the interaction between the translocation of nutrients and carbon compounds from roots to shoots, and P and N absorption (plus N2 fixation in L. tenuis). Highlights: Both plants tolerated defoliation and water stress due to the interaction between the translocation of nutrients and carbon compounds from roots to shoots, and P and N absorption (plus N2 fixation in tenuis). Low and high frequencies of defoliation in a waterlogged soil can be considered the most stressful scenario for tenuis and S. arundinaceus co-culture. Defoliation frequency increased AM colonization in plant roots under well watered and water deficit conditions. arundinaceus roots were co-colonized by AM fungi and DSE. Promoting the presence of tenuis through low defoliation frequency would improve forage yield and quality with the maintenance of AM symbiosis in legume–grass communities.

Biological Nitrogen Fixation, Carbon assimilation and plant performance of Lotus tenuis, contribute to define a strategic role in the lowlands in the Salado River Basin (Argentina)

Background and AimsForage production constitutes a great challenge for the Salado River Basin (Argentina), the major area devoted to livestock in the country. The successful naturalization of the European legume Lotus tenuis has been a productive and environmental relevance for the region. This study aims to evaluate its strategic contribution, reporting for the first time the B value for this species in these marginal environments for agriculture.MethodsThe 15N natural abundance method was used to evaluate the BNF of L. tenuis at soil plots and non-leguminous weed species in the same plots were utilized as reference plants. The assays included determinations of the 13C isotope, as well. Simultaneously, evaluations were carried out in the greenhouse for the determination of the B value of L. tenuis and the relative reproducibility of the field experiments.ResultsThe results obtained demonstrated that the L. tenuis promotion is accompanied by an increase in forage quality, due to the predominance of this C3 legume species, over C4 species. Moreover, its contribution to N inputs to the system, through the BNF with native rhizobia demonstrated to be about 80%, a highly relevant percentage for these constrained agroecosystems.ConclusionsThis work supports the hypothesis that L. tenuis promotion plays a strategic role in the sustainability of the ecosystem, especially in soil constrained areas. Joined with data previously published, the results obtained contribute to support the criteria that define the naturalized legume playing a strategic role in the sustainability of agriculture marginal soils.

Impact of Water Level on Species Quantity and Composition Grown from the Soil Seed Bank of the Inland Salt Marsh: An Ex-Situ Experiment

The near elimination of inland salt marshes in Central Europe occurred throughout the 19th and 20th centuries, and the currently remaining marshes exist in a degraded condition. This work examines the impact of groundwater level on the growth of plants from a seed bank obtained from a degraded salt marsh in proximity to still existing one through an ex-situ experiment. An experimental tank was set up with the sample seed bank experiencing differing levels of water level. There were 1233 specimens of 44 taxa grown from the seed bank, of which 5 species were abundant, and 10 species are considered as halophytes. Only Lotus tenuis from halophytes was more abundant, and only five species of halophytes were represented by more than three individuals. The water level has a significant impact on the number of species (based on linear regression analysis) as well as species distribution among different water level treatments (a non-metric multidimensional analysis (nMDS) followed by linear regression). The results show a strong negative relationship between the average water level and the number of species. The water level did not affect the species composition of halophytes, but differences in individual species abundances were found among the halophytes. The species Bupleurum tenuissimum, Crypsis schoenoides, Melilotus dentatus, and Plantago maritima grew on the drier and non-inundated soils. Tripolium pannonicum, Spergularia maritima, and Lotus tenuis grew on both wet and dry soils. Trifolium fragiferum and Bolboschoenus maritimus were found in places with water stagnant at the soil level. Pulicaria dysenterica grew in inundated soil.

Germinación de semillas de Lotus tenuis: efecto del tratamiento pregerminativo, tiempo de almacenamiento y rol de la cubierta dura a largo plazo

Se evaluó el efecto de la escarificación mecánica en dos momentos luego de la cosecha sobre la germinación de semillas de 23 genotipos de Lotus tenuis Waldst et Kit almacenadas en condiciones de laboratorio sin escarificar y el rol de las cubiertas duras sobre dicha respuesta a largo plazo. Se usó un DCA con tres factores [genotipos, tratamiento pregerminativo (E=escarificado; NE=ausencia de escarificado) y tiempo de almacenamiento (t1=0,25 años; t2=22,5 años)] (n=4). Se calculó el porcentaje de germinación acumulada (Gac%) y de semillas duras (Sd%). Para t2 se calculó el índice de velocidad germinativa (IVG). Se aplicó ANOVA no paramétrico (Kruskal-Wallis) y comparación de medianas. Para t2 se analizaron correlación y regresión simple. La interacción triple resultó significativa (p ≤0,01) para ambos parámetros. Gac% tuvo valores mayores en el tratamiento E en t1 y menores en NE en t2. El factor genotipo resultó significativo (p≤0,01) para el E en t2. Sd% tuvo valores mayores en el tratamiento NE en t1 y menores en E independientemente del tiempo de almacenamiento. El factor genotipo resultó significativo (p≤0,01) para NE en t2. La correlación Sd% vs. Gac% e IVG resultó significativa (p≤0,01) y positiva. Las regresiones simples Sd% vs. Gac% e IVG resultaron significativas (p≤0,01). El estudio demostró que la escarificación y el tiempo de almacenamiento afectan de manera positiva y negativa, respectivamente, al comportamiento germinativo de los genotipos estudiados, que el ablandamiento de la cubierta dura es variable entre genotipos y que dicha cubierta estaría vinculada con la conservación de la capacidad germinativa en el largo plazo.

Forage biomass yield and arbuscular mycorrhizal symbiosis in a legume and C3 and C4 grasses under increasing soil phosphorus availability

Phosphorus (P) is the main limiting factor for forage production in grasslands. It is important to determine levels of available P in soil that optimise production with minimum impact on arbuscular mycorrhizal (AM) symbiosis. We investigated the effects of increasing P availability on biomass production, root morphology, AM symbiosis and P acquisition of a forage legume (Lotus tenuis), a C3 grass (Schedonorus arundinaceus) and a C4 grass (Panicum coloratum) growing on a P-deficient soil in pots with P applied at rates of 0–160 mg kg–1 dry soil. The three forage species responded strongly to addition of P, with 90% of maximum shoot growth reached at available P levels of 24.3 mg kg–1 for L. tenuis, 14.4 mg kg–1 for P. coloratum and 11.2 mg kg–1 for S. arundinaceus. Lotus tenuis and P. coloratum produced higher yields of shoot biomass than S. arundinaceus. Root dry weight was higher in the legume than in the grasses, with the root-mass fraction being lowest in P. coloratum. AM colonisation was higher in L. tenuis roots than in grass roots, and decreased with increased soil P availability, especially in grasses. Low to moderate additions of P did not affect, and could even improve, AM colonisation in L. tenuis roots. For L. tenuis, it is possible to increase forage yield while maintaining high values of AM colonisation at 10–20 mg kg–1 of available P, but for grasses, especially S. arundinaceus, it is difficult to achieve both objectives. The presence of L. tenuis in grasslands or pastures may contribute to maintaining the native AM inoculum under a wide range of soil P availability in regions such as the Salado River basin of Argentina.