Perennial legumes native to Australia: a preliminary investigation of nutritive value and response to cutting

Six Australian native herbaceous perennial legumes (Lotus australis, Swainsona colutoides, Swainsona swainsonioides, Cullen tenax, Glycine tabacina and Kennedia prorepens) were assessed in the glasshouse for nutritive value, soluble condensed tannins and production of herbage in response to three cutting treatments (regrowth harvested every 4 and 6 weeks and plants left uncut for 12 weeks). The Mediterranean perennial legumes Medicago sativa and Lotus corniculatus were also included. Dry matter (DM) yield of some native legumes was comparable to L. corniculatus, but M. sativa produced more DM than all species except S. swainsonioides after 12 weeks of regrowth. Dry matter yield of all native legumes decreased with increased cutting frequency, indicating a susceptibility to frequent defoliation. Shoot in vitro dry matter digestibility (DMD) was high (>70%) in most native legumes, except G. tabacina (65%) and K. prorepens (55%). Crude protein ranged from 21-28% for all legumes except K. prorepens (12%). More frequent cutting resulted in higher DMD and crude protein in all species, except for the DMD of C. tenax and L. australis, which did not change. Concentrations of soluble condensed tannins were 2-9 g/kg DM in the Lotus spp., 10-18 g/kg DM in K. prorepens and negligible (<1 g/kg) in the other legumes. Of the native species, C. tenax, S. swainsonioides and L. australis showed the most promise for use as forage plants and further evaluation under field conditions is now warranted.

Physiological and morphological adaptations of herbaceous perennial legumes allow differential access to sources of varyingly soluble phosphate

The aim of this study was to investigate the capacity of three perennial legume species to access sources of varyingly soluble phosphorus (P) and their associated morphological and physiological adaptations. Two Australian native legumes with pasture potential (Cullen australasicum and Kennedia prostrata) and Medicago sativa cv. SARDI 10 were grown in sand under two P levels (6 and 40 µg P g−1) supplied as Ca(H2PO4)2·H2O (Ca-P, highly soluble, used in many fertilizers) or as one of three sparingly soluble forms: Ca10(OH)2(PO4)6 (apatite-P, found in relatively young soils; major constituent of rock phosphate), C6H6O24P6Na12 (inositol-P, the most common form of organic P in soil) and FePO4 (Fe-P, a poorly-available inorganic source of P). All species grew well with soluble P. When 6 µg P g−1 was supplied as sparingly soluble P, plant dry weight (DW) and P uptake were very low for C. australasicum and M. sativa (0.1–0.4 g DW) with the exception of M. sativa supplied with apatite-P (1.5 g). In contrast, K. prostrata grew well with inositol-P (1.0 g) and Fe-P (0.7 g), and even better with apatite-P (1.7 g), similar to that with Ca-P (1.9 g). Phosphorus uptake at 6 µg P g−1 was highly correlated with total root length, total rhizosphere carboxylate content and total rhizosphere acid phosphatase (EC 3.1.3.2) activity. These findings provide strong indications that there are opportunities to utilize local Australian legumes in low P pasture systems to access sparingly soluble soil P and increase perennial legume productivity, diversity and sustainability.

Root distributions of Australian herbaceous perennial legumes in response to phosphorus placement

Many Australian plant species have specific root adaptations for growth in phosphorus-impoverished soils, and are often sensitive to high external P concentrations. The growth responses of native Australian legumes in agricultural soils with elevated P availability in the surface horizons are unknown. The aim of these experiments was to test the hypothesis that increased P concentration in surface soil would reduce root proliferation at depth in native legumes. The effect of P placement on root distribution was assessed for two Australian legumes, Kennedia prorepens F. Muell. and Lotus australis Andrews, and the exotic Medicago sativa L. Three treatments were established in a low-P loam soil: amendment of 0.15 g mono-calcium phosphate in either (i) the top 50 mm (120 µg P g–1) or (ii) the top 500 mm (12 µg P g–1) of soil, and an unamended control. In the unamended soil M. sativa was shallow rooted, with 58% of the root length of in the top 50 mm. K. prorepens and L. australis had a more even distribution down the pot length, with only 4 and 22% of their roots in the 0–50 mm pot section, respectively. When exposed to amendment of P in the top 50 mm, root length in the top 50 mm increased 4-fold for K. prorepens and 10-fold for M. sativa, although the pattern of root distribution did not change for M. sativa. L. australis was relatively unresponsive to P additions and had an even distribution of roots down the pot. Shoot P concentrations differed according to species but not treatment (K. prorepens 2.1 mg g–1, L. australis 2.4 mg g–1, M. sativa 3.2 mg g–1). Total shoot P content was higher for K. prorepens than for the other species in all treatments. In a second experiment, mono-ester phosphatases were analysed from 1-mm slices of soil collected directly adjacent to the rhizosphere. All species exuded phosphatases into the rhizosphere, but addition of P to soil reduced phosphatase activity only for K. prorepens. Overall, high P concentration in the surface soil altered root distribution, but did not reduce root proliferation at depth. Furthermore, the Australian herbaceous perennial legumes had root distributions that enhanced P acquisition from low-P soils.

The diversity of arbuscular mycorrhizas of selected Australian Fabaceae

Members of the Australian native perennial Fabaceae have been little explored with regard to their root biology and the role played by arbuscular mycorrhizal (AM) fungi in their establishment, nutrition and long-term health. The ultimate goal of our research is to determine the dependency of native perennial legumes on their co-evolved AM fungi and conversely, the impact of AM fungal species in agricultural fields on the productivity of sown native perennial legume pastures. In this paper we investigate the colonisation morphology in roots and the AMF, identified by spores extracted from rhizosphere soil, from three replicate plots of each of the native legumes, Cullen australasicum, C. tenax and Lotus australis and the exotic legumes L. pedunculatus and Medicago sativa. The plants were grown in an agricultural field. The level and density of colonisation by AM fungi, and the frequency of intraradical and extraradical hyphae, arbuscules, intraradical spores and hyphal coils all differed between host plants and did not consistently differ between native and exotic species. However, there were strong similarities between species in the same genus. The three dominant species of AM fungi in rhizosphere soil also differed with host plant, but one fungus (Glomus mosseae) was always the most dominant. Sub-dominant AM species were the same between species in the same genus. No consistent differences in dominant spores were observed between the exotic and native Fabaceae species. Our results suggest that plant host influences the mycorrhizal community in the rhizosphere soil and that structural and functional differences in the symbiosis may occur at the plant genus level, not the species level or due to provenance.

Variation in morphological and physiological parameters in herbaceous perennial legumes in response to phosphorus supply

Change in morphological and physiological parameters in response to phosphorus (P) supply was studied in 11 perennial herbaceous legume species, six Australian native (Lotus australis, Cullen australasicum, Kennedia prorepens, K. prostrata, Glycine canescens, C. tenax) and five exotic species (Medicago sativa, Lotononis bainesii, Bituminaria bituminosa var albomarginata, Lotus corniculatus, Macroptilium bracteatum). We aimed to identify mechanisms for P acquisition from soil. Plants were grown in sterilised washed river sand; eight levels of P as KH2PO4 ranging from 0 to 384 μg P g−1 soil were applied. Plant growth under low-P conditions strongly correlated with physiological P-use efficiency and/or P-uptake efficiency. Taking all species together, at 6 μg P g−1 soil there was a good correlation between P uptake and both root surface area and total root length. All species had higher amounts of carboxylates in the rhizosphere under a low level of P application. Six of the 11 species increased the fraction of rhizosphere citrate in response to low P, which was accompanied by a reduction in malonate, except L. corniculatus. In addition, species showed different plasticity in response to P-application levels and different strategies in response to P deficiency. Our results show that many of the 11 species have prospects for low-input agroecosystems based on their high P-uptake and P-use efficiency.

Calcium carbonate solubilization through H-proton release from some legumes grown in calcareous saline-sodic soils

Increasing levels of CO2 and H+ proton in the rhizosphere from some legumes may play an important role in calcite dissolution of calcareous salt affected soils. Soils planted with white and brown varieties of cowpea (Vigna unguiculata L.) and hyacinth bean (Dolichos lablab L.) relying on either fertilizer N (KNO3) or N-fixation were compared against soils to which gypsum was applied and a control without plants and gypsum application to study the possibility of Ca2+ release from calcite and Na+ leaching. As compared to plants relying on inorganic N, leachates from all pore volumes (0·5, 1·0, 1·5, 2·0 pore volume) in lysimeters planted with N-fixing hyacinth bean contained significantly higher concentrations of HCO with lower concentrations from lysimeters planted with white cowpea relying on N-fixation. However, the lowest concentrations of HCO were recorded in the gypsum and control treatments. In initial leaching, lysimeters planted with N-fixing plants maintained similar leachate Ca2+ and Na+ concentrations compared to gypsum amended soils. However, gypsum amended soils were found to have a prolonged positive effect on Na+ removal. It might be concluded that some legumes that are known to fix N in calcareous salt affected soils may be an alternative ameliorant to the extremely expensive gypsum through calcite solubilization and a consequent release of Ca2+.

'Roman' or 'native' bodies in Britain: the evidence of late Roman nail-cleaner strap-ends

This paper reviews late Roman `nail-cleaner strap-ends', a group of objects first discussed by Hawkes and Dunning (1961). The precise function of these objects is unclear as their shape suggests use as toilet instruments but the split socket suggests that they were part of belt-fittings. We suggest a detailed typology and discuss the dating evidence and the spatial distribution of the type. Regardless of their precise function, it is argued in this paper that nail-cleaner strap-ends of this type are unique to late Roman Britain and thus represent a distinct regional type. The use of nail-cleaner strap-ends can be viewed in the context of gender associations, military status and religious beliefs.

In vitro degradability of mature and immature leaves of tropical forage legumes differing in condensed tannin and non-starch polysaccharide content and composition

A study was designed to examine the relationships between protein, condensed tannin and cell wall carbohydrate content and composition and the nutritional quality of seven tropical legumes (Desmodium ovalifolium, Flemingia macrophylla, Leucaena leucocephala, L pallida, L macrophylla, Calliandra calothyrsus and Clitotia fairchildiana). Among the legume species studied, D ovalifolium showed the lowest concentration of nitrogen, while L leucocephala showed the highest. Fibre (NDF) content was lowest in C calothyrsus, L Leucocephala and L pallida and highest in L macrophylla, which had no measurable condensed tannins. The highest tannin concentration was found in C calothyrsus. Total non-structural polysaccharides (NSP) varied among legumes species (lowest in C calothyrsus and highest in D ovalifolium), and glucose and uronic acids were the most abundant carbohydrate constituents in all legumes. Total NSP losses were lowest in F macrophylla and highest in L leucocephala and L pallida. Gas accumulation and acetate and propionate levels were 50% less with F macrophylla and D ovalifolium as compared with L leucocephala. The highest levels of branched-chain fatty acids were observed with non-tanniniferous legumes, and negative concentrations were observed with some of the legumes with high tannin content (D ovalifolium and F macrophylla). Linear regression analysis showed that the presence of condensed tannins was more related to a reduction of the initial rate of gas production (0-48 h) than to the final amount of gas produced or the extent (144h) of dry matter degradation, which could be due to differences in tannin chemistry. Consequently, more attention should be given in the future to elucidating the impact of tannin structure on the nutritional quality of tropical forage legumes. (C) 2003 Society of Chemical Industry.

Effect of condensed tannins from tropical legumes on the activity of fibrolytic enzymes from the rumen fungus Neocallimastyx hurleyensis

A study was conducted to assess the effect of condensed tannins on the activity of fibrolytic enzymes from the anaerobic rumen fungus, Neocallimastix hurleyensis and a recombinant ferulic acid esterase (FAE) from the aerobic fungus Aspergillus niger. Condensed tannins were extracted from the tropical legumes Desmodium ovalifolium, Flemingia macrophylla, Leucaena leticocephala, Leucaena pallida, Calliandra calothyrsus and Clitoria fairchildiana and incubated in fungal enzyme mixtures or with the recombinant FAE. In most cases, the greatest reductions in enzyme activities were observed with tannins purified from D. ovalifolium and F macrophylla and the least with tannins from L leucocephala. Thus, whereas 40 mu g ml(-1) of condensed tannins from C. calothyrsus and L. leucocephala were needed to halve the activity of N. hurleyensis carboxymethylcellulase (CMCase), just 5.5 mu g ml(-1) of the same tannins were required to inhibit 50% of xylanase activity. The beta-D-glucosidase and beta-D-Xylosidase enzymes were less sensitive to tannin inhibition and concentrations greater than 100 mu g ml(-1) were required to reduce their activity by 50%. In other assays, the inhibitory effect of condensed tannins when added to incubation mixtures containing particulate substrates (the primary cell walls of E arundinacea) or when bound to these substrate was compared. Substrate-associated tannins were more effective in preventing fibrolytic activities than tannins added directly to incubations solutions. It was concluded that condensed tannins from tropical legumes can inhibit fibrolytic enzyme activities, although the extent of the effect was dependent on the tannin, the nature of its association with the substrate and the enzyme involved. (c) 2005 Elsevier Inc. All rights reserved.

The impact of Solanum elaeagnifolium, an invasive plant in the Mediterranean, on the flower visitation and seed set of the native co-flowering species Glaucium flavum

We examined the effect of the invasive Solanum elaeagnifolium (Solanaceae) on flower visitation patterns and seed set of the co-flowering native Glaucium flavum (Papaveraceae). We observed flowering G. flavum plants in invaded and uninvaded sites and found that G. flavum flowers in uninvaded sites received significantly more total visits. In addition, we hand-pollinated flowers on plants of G. flavum with (i) pure conspecific pollen, (ii) pure S. elaeagnifolium pollen and (iii) three different mixtures of the two types of pollen (containing 25, 50 and 75% invasive pollen). As a control, flowers were left unmanipulated or were permanently bagged. Seed set did not differ significantly between flowers receiving pollen mixtures and pure conspecific pollen. However, in the open pollination treatment, seed set was significantly lower than in the 100% conspecific pollen treatment, which suggests pollen limitation. Bagged flowers had very low seed set. G. flavum was generally resilient against the deposition of S. elaeagnifolium pollen.

Do all tannins have similar nutritional effects? A comparison of three Brazilian fodder legumes

Three tropical legumes, namely Leucaena leucocephala, Sesbania sesban and Cajanus cajan, were subjected to chemical analysis plus in vitro, in situ and in vivo evaluations. Three different assays were used to determine total tannins: adsorption to polyvinyl pyrrolidine (PVPP-tannins), radial diffusion (RD-tannins) and protein precipitation capacity (BSA-tannins). Total phenols, total tannins and condensed tannins were highest for Sesbania. RD-tannins were correlated with total phenols (r(2) = 0.93), PVPP-tannins (r(2) = 0.92) and condensed tannins (r(2) = 0.99). The protein precipitation capacity of Sesbania, Leucaena and Cajanus were 25.9, 6.13 and 4.05 mu g BSA/g DM, respectively. Gas production at 24h was negatively correlated with total phenols (r(2) = 0.99), PVPP-tannins (r(2) = 0.99) and condensed tannins (r(2) = 0.91). The RD-, PVPP-tannins and the response to polyethylene glycol (PEG) in the gas production assay appeared to be useful as a first screen for tannins. In situ degradability did not reflect any adverse effects of tannins. However, in vivo experiments showed that the apparent DM digestibility of Sesbania and Leucaena was lower than the basal diet. The apparent protein digestibility was lower for all legumes compared to the basal diet. Most treatments caused a negative nitrogen balance. The problems associated with browse feeding were not only related to tannin contents, other factors such as inherently poor digestibility and low energy intake may also have lead to the poor animal performance on these diets. We propose, given the limitations of current tannin assays, that it is not possible to predict beneficial or harmful nutritional effects from total tannin concentrations per se. (C) 2004 Elsevier B.V. All rights reserved.