Shrub Legumes Research Articles

Origin and ontogeny of the xylopodium in Cerrado legumes: role of the hypocotyl and ecological significance

Bud-bearing underground organs play a role on plant persistence in different fire-prone ecosystems worldwide, but their origin, development and anatomical features are still a matter of inquiry. The xylopodium, for instance, seem to originate from the hypocotyl or primary root, or both, usually associated with tuberous roots. Because this structure is commonly found in legumes across the Brazilian savannas (Cerrado), understanding its formation is important for unveiling its relevance for post-fire resprouting. Here we aimed to investigate the role of the hypocotyl on the development of six Cerrado legume shrubs, as well as histochemical features and ecological implications from seedlings to adult plants in this frequently-burned ecosystem. Seeds of the six study species were collected in central Brazil, set to germinate and cultivated until the stages of four, six, nine, and twelve months. At each stage, the region correspondent to the hypocotyl was delimited and anatomical and histochemical analyses performed. Over time, the hypocotyl region underwent a tuberization process, during which the cortex was progressively replaced by the formation of secondary xylem through intense cambial activity. Before the twelve-month-old stage, all species presented buds, mainly cotyledonary, and reacted to starch, phenols and pectins. Early hypocotyl tuberization drives the formation of the xylopodium from seedlings to adulthood, and the presence of buds and the accumulation of reserves during its formation is a fundamental process driving species’ persistence after fire.

The ‘fertilizer island effect’ cannot eliminate competition between leguminous shrubs and symbiotic herbs in desert ecosystems

The ‘fertilizer island effect’ — a phenomenon engendered by shrubs — promotes the growth of symbiotic herbs and the stabilization of community structures in scrublands. Specifically, leguminous shrubs contribute significantly to the nitrogen input in desert ecosystems. However, the impact of these inputs on the nutrient balance in symbiotic herbs has seldom been explored. To enhance our understanding of the nutrient balance between nitrogen-fixing legume shrubs and symbiotic non-legume herbaceous plants in desert ecosystems, we focused on a typical legume shrub (Eremosparton songoricum) that grows in the Gurbantunggut Desert of northern China. Subsequently, we examined the biomass, ecological stoichiometry, and rhizosphere soil properties of two plant species (annual plant: Ceratocarpus arenarius; and ephemeral plant: Centaurea pulchella) growing across four horizontal distance ranges from E. songoricum. The results indicated that the closer a herbaceous plant was to the leguminous shrubs, the lower was its biomass and nutrient content. In contrast, herbaceous plants growing further away from the shrubs exhibited better growth conditions. The total biomass of Cer. arenarius and Cen. pulchella was greatest at a distance of D4 (90–100 cm), being 3.07, 2.15, and 1.23 times higher for Cer. arenarius and 2.05, 1.18, and 1.26 times higher for Cen. pulchella compared to distances of D1 (0–10 cm), D2 (30–40 cm), and D3 (60–70 cm), respectively. Meanwhile, the physicochemical properties of the rhizosphere root varied inversely with distance, with nutrient levels decreasing horizontally from D1 to D4 and vertically from 0–5 cm > 5–10 cm > 10–20 cm, showcasing a distinct ‘fertilizer island effect’. As the distance increased, the above-ground and below-ground parts of the symbiotic non-leguminous plants started to rely on different types of soil nutrients from different depths to maximize nutrient acquisition. According to the structural equation model, although soil fertility was higher closer to the central leguminous plants, the biomass of nearby herbaceous plants was lower. In summary, in desert ecosystems, the competitive dynamics exerted by leguminous shrubs significantly overshadowed the nutrient provisioning role of the ‘fertilizer island effect’. Furthermore, the utilization of nutrients by symbiotic non-leguminous plants did not exhibit species-specific patterns, and the dominant shrub continued to play a pivotal role. The evidence from this study promotes a deeper understanding of species coexistence mechanisms and ecological stability in desert environments.

Physical and biochemical characteristics of tropical grass and legume pastures grazed by lambs

AbstractLarge areas of tropical grass pastures are not grazed by lambs because of the difficulties in managing high growth rate swards with high selective animals. The objective of this study was to evaluate the physical and biochemical characteristics of tropical pastures offered to lambs in continuous grazing. An upright grass and a shrub legume were set out in three pasture types and grazed by lambs: (1) aruana grass monoculture (AG—Panicum maximum Jacq. cv. IZ‐5), (2) pigeon pea monoculture (PP—Cajanus cajan [L.] Millsp. cv. Anão) and (3) contiguous swards (CS), half of the paddock with AG (CSAG) and half with PP (CSPP). The pastures were evaluated for structural characteristics, production, nutritional composition and antioxidant concentrations in four periods over 92 days of continuous grazing by lambs. Hand plucking samples, similar to animal diet, were collected for chemical analysis. Regarding height, the PP legume monoculture after 42 days of grazing had uncontrollable growth by the lambs, reaching 1.2 m in height. This same legume but as a CS beside AG (CSPP) was maintained at a lower and similar height throughout the experimental periods. In general, the leaf:stem ratio of the different pastures decreased over the experimental periods from 0.7 to 0.2. In most periods, the CS showed intermediary nutritional quality compared to AG and PP. The alpha‐tocopherol content was similar among swards, with an average of 137.2 ± 13.67 mg/kg of green matter (p > .05). Pigeon pea showed the highest levels of total tannin and condensed tannin at 63 and 92 days (p < .05). The use of tropical grass together with a legume provides a better physical structure of the pigeon pea for grazing lambs than when monoculture of this species.

Cratylia argentea – review of a tropical shrub legume: Biology and agronomy

Cratylia argentea – review of a tropical shrub legume: Biology and agronomy

Cratylia argentea – review of a tropical shrub legume: Quality and utilization

Cratylia argentea – review of a tropical shrub legume: Quality and utilization

The native distribution of a common legume shrub is limited by the range of its nitrogen-fixing mutualist.

Plant-microbe mutualisms, such as the legume-rhizobium symbiosis, are influenced by the geographical distributions of both partners. However, limitations on the native range of legumes, resulting from the absence of a compatible mutualist, have rarely been explored. We used a combination of a large-scale field survey and controlled experiments to determine the realized niche of Calicotome villosa, an abundant and widespread legume shrub. Soil type was a major factor affecting the distribution and abundance of C. villosa. In addition, we found a large region within its range in which neither C. villosa nor Bradyrhizobium, the bacterial genus that associates with it, were present. Seedlings grown in soil from this region failed to nodulate and were deficient in nitrogen. Inoculation of this soil with Bradyrhizobium isolated from root nodules of C. villosa resulted in the formation of nodules and higher growth rate, leaf N and shoot biomass compared with un-inoculated plants. We present evidence for the exclusion of a legume from parts of its native range by the absence of a compatible mutualist. This result highlights the importance of the co-distribution of both the host plant and its mutualist when attempting to understand present and future geographical distributions of legumes.

Gamma Irradiation Doses reduce Cooking time and Improve Nutritional Profile of selected Pigeon pea [Cajanus cajan (L.) Millsp] Genotypes in Nigeria

Pigeon Pea (Cajanus cajan L.) is a self-pollinating perennial legume shrub with over 30,000 accessions deposited world-wide. Despite the nutritional importance of pigeon peas, its detrimental traits such as its long cooking time, has led to low cultivation of the crop and inhibit its consumers’ request. Concerted efforts to improve both the quality and quantity of this crop through mutation breeding informed this research. It was based on this premise that the study was aimed to evaluate gamma irradiation influences on the nutrient quality and cooking duration of selected pigeon pea varieties in Nigeria. Four accessions of pigeon peas (‘NG/SA/11/08/108’, ‘NG/AO/MAY/00/021/01’, ‘TCC-2’ and ‘NG/SA/07/191’) were obtained from National Centre for Genetic Resources and Biotechnology (NACGRAB), Ibadan. They were irradiated at the Oncological Department ABU Teaching Hospital, Shika, Zaria, using Cobalt-60 (60CO) irradiation source. Standard procedures were followed to determine the effects of the irradiation on cookability and nutritional profile of the M1 plants and their respective controls. It was established that all the parameters tested were irradiation dose dependent. In NG/AO/MAY/00/021/01, 100 Gy produced the highest protein (20.40 %) and highest carbohydrate (68.93 %) contents. Anti-nutritional factors such as cyanide were lower (48.83, 46.22, 43.65 and 44.75 mg/kg in NG/AO/MAY/00/021/01, NG/SA/11/08/108, NG/SA/07/191 and TCC-2) at 400 Gy than those of their respective controls (54.83, 56.83, 53. and 53.55 mg/kg). The amount of Magnesium increased with higher doses of gamma irradiation (1.37 g/100 g for 200 Gy NG/AO/MAY/00/021/01; 1.03 g/100g for 400 Gy NG/SA/11/08/108 and 1.13 g/100 g for TCC-2). There were significant reductions in cooking time in 400 Gy treatments for all the genotypes. The differences between the control and the least cooking time in 400 Gy were 11, 16, 22 and 15 minutes for NG/AO/MAY/00/021/01, NG/SA/11/08/108, NG/SA/07/191 and TCC-2, respectively. It was therefore concluded that these variations could be exploited for further improvement of the crop for food security. Keywords: Cooking time, Mutation breeding, Gamma irradiation, Cookability, Dose dependent

Establishment of an Efficient and Rapid Regeneration System for a Rare Shrubby Desert Legume Eremosparton songoricum.

Eremosparton songoricum (Litv.) Vass. is a rare and extremely drought-tolerant legume shrub that is distributed in Central Asia. E. songoricum naturally grows on bare sand and can tolerate multiple extreme environmental conditions. It is a valuable and important plant resource for desertification prevention and environmental protection, as well as a good material for the exploration of stress tolerance mechanisms and excellent tolerant gene mining. However, the regeneration system for E. songoricum has not yet been established, which markedly limits the conservation and utilization of this endangered and valuable desert legume. Assimilated branches derived from seedlings were cultured on several MS mediums supplemented with various concentrations of TDZ or 6-BA in different combinations with NAA. The results showed that the most efficient multiplication medium was MS medium supplemented with 0.4 mg/L 6-BA and 0.1 mg/L NAA. The most efficient rooting medium was WPM + 25 g/L sucrose. The highest survival rate (77.8%) of transplantation was achieved when the ratio of sand to vermiculite was 1:1. In addition, the optimal callus induction medium was MS + 30 g/L sucrose + 2 mg/L TDZ + 0.5 mg/L NAA in darkness. The E. songoricum callus treated with 100 mM NaCl and 300 mM mannitol on MS medium could be used in proper salt and drought stress treatments in subsequent gene function tests. A rapid and efficient regeneration system for E. songoricum that allowed regeneration within 3 months was developed. The protocol will contribute to the conservation and utilization of this rare and endangered desert stress-tolerant species and also provide a fundamental basis for gene functional analysis in E. songoricum.

Genetic Divergence Studies among Indigenous Accessions of Cassia auriculata (L.) Roxb., through Screening and Utilization for Chambal Ravine Rehabilitation

Background: Cassia auriculata, L., is an imperative medicinal and traditional neutral colour leaf hair dye yielding in India. This is a multipurpose and indigenous, perennial leguminous shrub and widely used as traditional medicine to cure diabetics by the rural peoples. Tanner’s cassia is also used as neutral henna and its yields natural golden blonde colouring to hair through the dried leaf powder. Young buds are used for yellow colour dye extraction by textile industries. Screening of high tolerance and best performing genotypes is highly essential in this imperative woody legume shrub to rehabilitate the mass erosion prone gullied and ravine lands for productive purpose of the wasteland and degraded lands. Methods: Thirty different accessions of Cassia auriculata were assembled and numbered from CA-1 to CA-30 from arid and semi-arid regions of Rajasthan (India). The experimental trial was conducted at ICAR-IISWC, Research Centre, Kota-Rajasthan, India during 2019-2022. After evaluation, CA-4 genotype was selected as an elite genotype. The elite genotype was used for high density plantation development with resource conservation for green cover development in non-arable ravine lands. Result: Genetic variation studies of Cassia auriculata indicated that considerable and significant variability, abundant morphometric variations in assembled genotype progenies. Further, genetic divergence analysis was also revealed that nine clusters segregated from 30 genotypes. Thirty genotypes were grouped into nine clusters according overall performance with geographical identity. Finally, C. auriculata (CA-4) genotype was identified and selected as an elite genotype based on its overall superiority in terms of plant growth, higher green biomass, leaf litter biomass, more number branching behaviour and plant coppicing ability which are directly relevant and imperative in soil erosion control, resource conservation and potential rehabilitation effect in resource poor dry regions of non-arable lands.

Leaf carbon isotope tracks the facilitation pattern of legume shrubs shaped by water availability and species replacement along a large elevation gradient in Trans-Himalayas.

Understanding patterns and mechanisms of nurse plant facilitation is important to predict the resilience of arid/semi-arid ecosystems to climate change. We investigate whether water availability and nurse species turnover interact to shape the facilitation pattern of widespread legume shrubs along a large elevation gradient. We also investigate whether leaf δ13C of nurse plants can track the facilitation pattern. We measured the relative interaction index (RII) of the number of species within and outside the canopy of two widespread legume shrub species (Caragana gerardiana and Caragana versicolor) alternatively distributed along a large elevation gradient in the Trans-Himalayas. We also assessed the proportional increase of species richness (ISR) at the community level using the paired plot data. To determine site-specific water availability, we measured the leaf δ13C of nurse shrubs and calculated the Thornthwaite moisture index (MI) for each elevation site. Elevational variations in RII, ISR and δ13C were mainly explained by the MI when the effects of soil nitrogen and plant traits (leaf nitrogen and shrub size) were controlled. Variations in RII and ISR across the two nurse species were explained better by δ13C than by smoothly changing climatic factors along elevation. At the transition zone between the upper limit of C. gerardiana (4100 m) and the lower limit of C. versicolor (4200 m), RII and ISR were much higher in C. versicolor than in C. gerardiana under a similar MI. Such an abrupt increase in facilitation induced by nurse species replacement was well tracked by the variation of δ13C. Water availability and nurse species replacement are crucial to shaping facilitation patterns by legume shrubs along a large elevation gradient in dry mountainous regions, such as the Trans-Himalayas. Turnover in nurse species under global change might significantly alter the pattern of nurse plant facilitation associated with water availability, which can be well tracked by leaf δ13C.

High Diversity of Bradyrhizobial Species Fix Nitrogen with Woody Legume Spartocytisus supranubius in a High Mountain Ecosystem.

The symbiosis between rhizobia and legumes is of pivotal importance in nitrogen-poor ecosystems. Furthermore, as it is a specific process (most legumes only establish a symbiosis with certain rhizobia), it is of great interest to know which rhizobia are able to nodulate key legumes in a specific habitat. This study describes the diversity of the rhizobia that are able to nodulate the shrub legume Spartocytisus supranubius in the harsh environmental conditions of the high mountain ecosystem of Teide National Park (Tenerife). The diversity of microsymbionts nodulating S. supranubius was estimated from a phylogenetic analysis of root nodule bacteria isolated from soils at three selected locations in the park. The results showed that a high diversity of species of Bradyrhizobium and two symbiovars can nodulate this legume. Phylogenies of ribosomal and housekeeping genes showed these strains distributed into three main clusters and a few isolates on separate branches. These clusters consist of strains representing three new phylogenetic lineages of the genus Bradyrhizobium. Two of these lineages belong to the B. japonicum superclade, which we refer to as B. canariense-like and B. hipponense-like, as the type strains of these species are the closest species to our isolates. The third main group was clustered within the B. elkanii superclade and is referred to as B. algeriense-like as B. algeriense is its closest species. This is the first time that bradyrhizobia of the B. elkanii superclade have been reported for the canarian genista. Furthermore, our results suggest that these three main groups might belong to potential new species of the genus Bradyrhizobium. Analysis of the soil physicochemical properties of the three study sites showed some significant differences in several parameters, which, however, did not have a major influence on the distribution of bradyrhizobial genotypes at the different locations. The B. algeriense-like group had a more restrictive distribution pattern, while the other two lineages were detected in all of the soils. This suggests that the microsymbionts are well adapted to the harsh environmental conditions of Teide National Park.

Roles of tree and shrub legume leaves as protein sources for cattle raised by small farmers in Bangkalan Regency

Inclusion of tree or shrub legume leaves in the ration of beef cattle improved quality and the main indicators are the increase in crude protein content and digestibility. The present study was done from March to September 2023 involving 30 farmers in Bangkalan regency who raised madura cattle and the information gathered were type and number of feeds offered daily. Tree and shrub legume leaves such as Gliricidia, Moringa, Indigofera, and jackfruit are the most common protein sources used to supplement field grass or straws. Samples of forage were taken and the following rations were formulated to simulate cattle feed: A (grass only); B (60% grass + 40% gliricidia); C (60% grass + 40% moringa); D (60% grass + 40% Indigofera); E (60% grass + 40% jackfruit) leaves. Parameters measured using an in vitro gas production technique showed that supplementation with tree and shrub legume leaves on field grass basal diet improved dry matter digestibility (DMD) and organic matter (OMD) values and this was closely related to improvements of rumen NH3 concentration which also contributed to efficiency of microbial protein synthesis (ESPM) value improvement. It can be concluded that tree and shrub legume leaves have shown important roles in improving the quality of field grass based diet for Madura cattle.

Carbon versus nitrogen release from root and leaf litter is modulated by litter position and plant functional type

Abstract Litters of leaves and roots of different qualities occur naturally above‐ and below‐ground, respectively, where they decompose in contrasting abiotic and biotic environments. Therefore, ecosystem carbon (C) and nitrogen (N) dynamics can be strongly affected by the combination of litter position and quality. However, it is poorly understood how C versus N turnover of litters depend on the interplay among plant functional type (PFT), organs, traits and litter position. In a semi‐arid inland dune, soil surface and buried leaf litters and buried fine roots of 25 species across three PFTs (herbs, legume shrubs and nonlegume shrubs) were incubated for 3, 6, 9, 12, 18 and 24 months to investigate litter decomposition and C and N dynamics. Morphological and chemical (nutrient and NMR carbon) traits of initial litters of leaves and fine roots were determined. The litter decomposition rates (k values) of surface leaves and buried fine roots did not differ, but buried fine roots and buried leaf litter decomposed faster than surface leaf litter. Ratios of k values of surface leaves to buried leaves decreased with leaf C:N ratio. Herbs and legume shrubs decomposed faster than nonlegume shrubs for buried fine roots, but not for leaves. At given C loss, buried fine roots had higher N loss than leaf litters; legume shrubs with relatively higher N or lower C:N ratio had higher N loss than nonlegume shrubs. Stronger positive relationships between C and N losses were shown in leaves and legume shrubs than in fine roots and nonlegume shrubs respectively. Synthesis. The generality of faster N release of legume litters at given C release highlights the importance of legumes in N cycling in semi‐arid ecosystems where N is the limiting factor. The dynamics and coordination of C versus N release as a function of litter quality are modulated by litter position and PFT. These findings have important implications for the development of process‐based models on C and N cycles in the context of on‐going global change potentially altering the functional composition of plant communities and the relative quantities and qualities of above‐ground versus below‐ground litter.

Seasonal Effect on Bacterial Communities Associated with the Rhizospheres of Polhillia, Wiborgia and Wiborgiella Species in the Cape Fynbos, South Africa.

The Cape fynbos biome in South Africa is home to highly diverse and endemic shrub legumes, which include species of Aspalathus, Polhillia, Wiborgia and Wiborgiella. These species play a significant role in improving soil fertility due to their ability to fix N2. However, information regarding their microbiome is still unknown. Using the 16S rRNA Miseq illumina sequencing, this study assessed the bacterial community structure associated with the rhizospheres of Polhillia pallens, Polhillia brevicalyx, Wiborgia obcordata, Wiborgia sericea and Wiborgiella sessilifolia growing at different locations during the wet and dry seasons in the Cape fynbos. The results showed that the most dominant bacterial phylum was Actinobacteria during both the dry (56.2–37.2%) and wet (46.3–33.3%) seasons. Unclassified bacterial genera (19.9–27.7%) were the largest inhabitants in the rhizospheres of all five species during the two seasons. The other dominant phyla included Bacteroidetes, Acidobacteria, Proteobacteria and Firmicutes. Mycobacterium and Conexibacter genera were the biggest populations found in the rhizosphere soil of all five test species during both seasons, except for W. obcordata soil sampled during the dry season, which had Dehalogenimonas as the major inhabitant (6.08%). In this study plant species and growth season were the major drivers of microbial community structure, with W. obcordata having the greatest influence on its microbiome than the other test species. The wet season promoted greater microbial diversity than the dry season.

Physiological, morphological, and biochemical characterization of <i>Cratylia argentea</i> (Desv.) Kuntze seeds

Cratylia argentea is a shrub legume native to tropical regions of South America where it is used for animal feed and green manure. In the absence of germination guidelines, the key aim of this study was to define the most suitable temperature for conducting germination and accelerated aging tests. The biochemical attributes of seeds were also assessed. Seeds with 10% moisture from 4 different seed lots were germinated using the between paper method in a germinator at temperatures of 20, 25, 30 and 35 °C and alternating temperatures of 20/30 °C (16 h:8 h), with daily counting until germination was stable (seven days without germination). For the accelerated aging test, two temperatures (41 and 45 °C) and six aging periods (0, 24, 48, 72, 96 and 120 h) for seeds with between 10–40 % moisture content were used. Carbohydrates (%), ethereal extract (%), crude protein (%) and macro and micronutrient contents of the seeds were measured. Results showed that C. argentea seeds consist predominantly of starch (22.67 %) and protein (26.45 %) reserves with a low percentage of lipids. For the germination test, the temperature of 30 °C is recommended, allowing greater percentage and speed of germination, with seedling evaluation at 10 and 20 days. For the accelerated aging test, aging for 48 h at 41 °C is recommended to discriminate C. argentea seed lots in terms of quality.

Genome-wide investigation of AP2/ERF gene family in the desert legume Eremosparton songoricum: Identification, classification, evolution, and expression profiling under drought stress.

Eremosparton songoricum (Litv.) Vass. is a rare leafless legume shrub endemic to central Asia which grows on bare sand. It shows extreme drought tolerance and is being developed as a model organism for investigating morphological, physiological, and molecular adaptations to harsh desert environments. APETALA2/Ethylene Responsive Factor (AP2/ERF) is a large plant transcription factor family that plays important roles in plant responses to various biotic and abiotic stresses and has been extensively studied in several plants. However, our knowledge on the AP2/ERF family in legume species is limited, and no respective study was conducted so far on the desert shrubby legume E. songoricum. Here, 153 AP2/ERF genes were identified based on the E. songoricum genome data. EsAP2/ERFs covered AP2 (24 genes), DREB (59 genes), ERF (68 genes), and Soloist (2 genes) subfamilies, and lacked canonical RAV subfamily genes based on the widely used classification method. The DREB and ERF subfamilies were further divided into A1–A6 and B1–B6 groups, respectively. Protein motifs and exon-intron structures of EsAP2/ERFs were also examined, which matched the subfamily/group classification. Cis-acting element analysis suggested that EsAP2/ERF genes shared many stress- and hormone-related cis-regulatory elements. Moreover, the gene numbers and the ratio of each subfamily and the intron-exon structures were systematically compared with other model plants ranging from algae to angiosperms, including ten legumes. Our results supported the view that AP2 and ERF evolved early and already existed in algae, whereas RAV and DREB began to appear in moss species. Almost all plant AP2 and Soloist genes contained introns, whereas most DREB and ERF genes did not. The majority of EsAP2/ERFs were induced by drought stress based on RNA-seq data, EsDREBs were highly induced and had the largest number of differentially expressed genes in response to drought. Eight out of twelve representative EsAP2/ERFs were significantly up-regulated as assessed by RT-qPCR. This study provides detailed insights into the classification, gene structure, motifs, chromosome distribution, and gene expression of AP2/ERF genes in E. songoricum and lays a foundation for better understanding of drought stress tolerance mechanisms in legume plants. Moreover, candidate genes for drought-resistant plant breeding are proposed.

Diversity of availability of feed plant on sub optimal land in Karangasem Regency, Bali

The development of forage crops in Indonesia is directed at lands that are less productive for food crops, marginal land, and critical land, known as sub-optimal land. The research was carried out in Karangasem Regency: West Seraya, Seraya, and East Seraya Village which are Karangasem District, and Dukuh, Sukadana, and Tianyar Village, which are Kubu District. The number of respondents involved in this study were 20 farmers in each village, so the total number were 120 people. The data obtained were presented and analyzed descriptively. From the observations, it was found that the botanical composition of native pasture for the Seraya location found the presence of Panicum maximum grass that spreads on farmers' arable land and rudera areas. The types of shrub legumes used as hedgerows are Gliricidia sepium, Leucaena leucocephala, and Calliandra calothyrsus. The proportion of feed availability of shrub legumes, especially on hedgerows, is dominated by G. sepium. It can be concluded that the diversity of forage on sub optimal land is a potential in efforts to provide and fulfill bali cattle feed throughout the year, and the development of bali cattle and the availability of forage is dominated by shrub legumes, especially G. sepium and tree species.

Histological and in vitro seed culture studies on Biancaea sappan (L.) Tod. (Caesalpiniaceae)

Establishment of a tissue culture protocol for clonal regeneration is an essential prerequisite for the potential and economically important plant species Biancaea sappan (L.) Tod. (syn. Caesalpinia sappan L.; Caesalpiniaceae). This plant is a valuable dye-yielding legume shrub native to Indomalayan and is used in India by the local people of Kerala and Tamil Nadu States for its biological potential. The present study evaluated seed development both in vivo and in vitro through histological analysis. The mature seed was used as explants and cultured on modified Murashige and Skoog (MS) medium supplemented with 2, 4-D, BAP, GA3 and IBA. The cultures showed direct regeneration of shoots from nodular structures in the shoot apical meristem (SAM) region. During in vitro regeneration, the callus cells exhibited ballooning of cells, and the morphogenetic seed developed parenchymatous, polygonal cells filled with polyphenols. Histological studies indicated that in vitro plant regeneration involved the organogenic pathway that leads to de novo shoot primordia development.

Soil nitrogen regulates symbiotic nitrogen fixation in a legume shrub but does not accumulate under it

AbstractLegumes in dryland ecosystems face the challenge of maintaining energetically costly symbiosis with N2‐fixing rhizobia, in a water‐ and nutrient‐limited environment. Controlled experiments showed a strong reduction in symbiotic N2fixation in response to elevated levels of nitrogen availability, but this regulation of N2fixation was not found in dryland field settings. Here, we ask whether regulation of N2fixation occurs in the field and what are the possible consequences for dryland soil nitrogen. We measured plant investment in root nodules and rates of bacterial activity, in seedlings and adults of a common N2‐fixing shrub,Calicotome villosa,in five field sites naturally varying in soil nitrogen and phosphorus availabilities. Additionally, we measured nitrogen concentrations and availabilities in the soil underC.villosaand a reference non‐fixing shrub. Biomass investment in root nodules was significantly reduced in response to elevated levels of soil nitrate in adult shrubs, but no such effect was found for seedlings. Soil nitrogen concentration underC.villosashrubs was low compared to the soil under a non‐fixing reference shrub. We provide evidence that symbiotic N2‐fixing plants in drylands tightly regulate their investment in symbiotic N2fixation, therefore controlling nitrogen inputs into the soil. These findings challenge the long‐held notion that the growth of N2‐fixing plants necessarily leads to the accumulation of soil nitrogen in their surroundings over time.

Ecological adaptation and phylogenetic analysis of microsymbionts nodulating Polhillia, Wiborgia and Wiborgiella species in the Cape fynbos, South Africa

Polhillia, Wiborgia and Wiborgiella species are shrub legumes endemic to the Cape fynbos of South Africa. They have the ability to fix atmospheric N2 when in symbiosis with soil bacteria called ‘rhizobia’. The aim of this study was to assess the morpho-physiological and phylogenetic characteristics of rhizobia associated with the nodulation of Polhillia, Wiborgia and Wiborgiella species growing in the Cape fynbos. The bacterial isolates from root nodules consisted of a mixture of fast and intermediate growers that differed in colony shape and size. The isolates exhibited tolerance to salinity (0.5–3% NaCl) and pH (pH 5–10) and different antibiotic concentrations, and could produce 0.51 to 51.23 µg mL−1 of indole-3-acetic acid (IAA), as well as solubilize tri-calcium phosphate. The ERIC-PCR results showed high genomic diversity in the rhizobial population and grouped them into two major clusters. Phylogenetic analysis based on 16S rRNA, atpD, glnII, gyrB, nifH and nodC gene sequences revealed distinct and novel evolutionary lineages related to the genus Rhizobium and Mesorhizobium, with some of them being very close to Mesorhizobium australicum. However, the phylogenetic analysis of glnII and nifH genes of some isolates showed incongruency.