Lotus Tenuis Waldst Research Articles

Arbuscular mycorrhizal fungi improve legume seedling performance as the competition with conspecific neighbouring adult plants decreases

In temperate grasslands, the balance between competitive and facilitative interactions between adult plants and conspecific seedlings can be affected by defoliation intensity, soil nutrient deficiency and arbuscular mycorrhizal fungi (AMF). Here, we investigated the effect of AMF on the interactions between Lotus tenuis Waldst. & Kit. seedlings grown in the presence or absence of conspecific adult plants defoliated at different intensities (0, 50 and 75%) in a P-deficient soil of the Salado River Basin (Argentina). Mycorrhizal seedlings grown near defoliated and non-defoliated adult plants produced less shoot dry weight (DW) than non-mycorrhizal counterparts, whereas mycorrhizal seedlings alone showed 258% and 504% more shoot DW and shoot P content, respectively than non-mycorrhizal counterparts. This was associated with higher growth and P uptake of mycorrhizal adult plants than non-mycorrhizal counterparts. The competition index between seedlings and adult plants showed competition interaction in mycorrhizal systems (from −2.6 to −1.9) and neutral interaction in non-mycorrhizal systems (near to zero) despite the defoliation intensity. We propose that moderate defoliation (50%) allows maintaining high mycorrhizal benefits in adult plants (110.1% and 168.8% mycorrhizal growth and P response, respectively), whereas high defoliation (75%) decreases mycorrhizal benefits (27.18% and 80.21% mycorrhizal growth and P response, respectively). We highlight AMF symbiosis as an important strategy of L. tenuis adult plants to regulate the growth of neighbouring conspecific seedlings in a P-deficient 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.

Morphological, Agronomical, Phenological and Stand Persistence Traits of Some Wild Narrowleaf Birdsfoot Trefoil (Lotus tenuis Waldst. & Kit.) Populations

Existing information on the ecology, distribution and plant traits of Lotus taxa is scant for the natural flora of Turkey, which is one of the most important countries in the Mediterranean zone for genetic resources and genetic diversity of these species. Therefore, the aim of this study was to determine (i) morphologic, agronomic, phenologic, stand persistence traits and growth habits of some wild narrowleaf birdsfoot trefoil (NBT; Lotus tenuis Waldst. & Kit.), and (ii) the relationships between these traits and altitude, latitude or longitude of the natural habitats, the samples of which were obtained from diverse natural areas of Black Sea Region, Turkey. The altitudes of sampling sites ranged from 1 to 1510 m. A total of 86 wild NBT were sampled in the study. NBT was present in all ranges of altitude, although its frequency was the highest in altitudes between 1-300 m. On the other hand, considerable variations were determined for the investigated traits, except for growth habit in which all populations had decumbent growth habit. The results of the present study indicate that NBT better adapted to lowlands and studied region offers important genetic resources for further researches and also may serve as a valuable breeding material for new grazing-type and disease resistant NBT varieties.

Assessing the glyphosate tolerance of Lotus corniculatus and L. tenuis to perform rhizoremediation strategies in the Humid Pampa (Argentina)

The broad-spectrum herbicide glyphosate (N – phosphonomethylglicine) is the most common pesticide used in the Humid Pampa, the main agricultural region in Argentina. According to agronomical practices and topogeographical characteristics of the region, rhizoremediation arises as a promising technology to mitigate glyphosate impact on health and agroecosystems. Lotus corniculatus L. (birdsfoot trefoil) and Lotus tenuis Waldst. et Kit. (=Lotus glaber Mill., narrowleaf trefoil) were selected to carry out tolerance studies as the starting point of a rhizoremediation process. L. corniculatus presented the highest root and foliar tolerance to glyphosate, corresponding to 5.0mgkg−1 and 700gha−1 respectively. The enzyme enolpyruvylshikimate-3-phosphate synthase (EPSP synthase) partial cDNA sequence and whole plant shikimate accumulation assay were performed on L. corniculatus in order investigate tolerance mechanisms. No amino acid substitution related to glyphosate tolerance was found on EPSP synthase cDNA sequence. The shikimate accumulation study indicates that limited uptake and/or translocation of the herbicide is the most probable tolerance mechanism. Results obtained in this study, plus the productive and adaptive advantages of L. corniculatus make it a valuable candidate to develop rhizoremediation strategies.

Morphological, agronomical, phenological and stand persistence traits of some wild narrowleaf birdsfoot trefoil (lotus tenuis waldst. & kit.) populations

Existing information on the ecology, distribution and plant traits of Lotus taxa is scant for the natural flora of Turkey, which is one of the most important countries in the Mediterranean zone for genetic resources and genetic diversity of these species. Therefore, the aim of this study was to determine i morphologic, agronomic, phenologic, stand persistence traits and growth habits of some wild narrowleaf birdsfoot trefoil NBT; Lotus tenuis Waldst. & Kit. , and ii the relationships between these traits and altitude, latitude or longitude of the natural habitats, the samples of which were obtained from diverse natural areas of Black Sea Region, Turkey. The altitudes of sampling sites ranged from 1 to 1510 m. A total of 86 wild NBT were sampled in the study. NBT was present in all ranges of altitude, although its frequency was the highest in altitudes between 1-300 m. On the other hand, considerable variations were determined for the investigated traits, except for growth habit in which all populations had decumbent growth habit. The results of the present study indicate that NBT better adapted to lowlands and studied region offers important genetic resources for further researches and also may serve as a valuable breeding material for new grazing-type and disease resistant NBT varieties

Geographical Variation in Nutrient Composition of Lotus tenuis (Waldst.&Kit.) Populations from Seeds Collected from Different Locations

To investigate the effect of seed origin on the nutritive value of narrowleaf birdsfoot trefoil (NBT, Lotus tenuis Waldst.&Kit.), seeds of 86 NBT populations were collected from plants spontaneously occurring in natural pastures and rangelands located at different geographical gradients of the Black Sea Region, Turkey. Some nutrient contents of these populations regrown under the same conditions were determined. Minimum and maximum values with regard to the crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), Ca, P, Mg, K and condensed tannin contents, relative feed value, Ca P-1 and K (Ca+Mg)-1 ratios were found as 176.83 and 238.87, 201.00 and 351.61, 307.19 and 435.48, 15.01 and 21.60, 2.18 and 3.77, 3.03 and 4.02, 8.43 and 16.69, 20.00 and 31.50 g kg-1 dry matter, 189.70 and 263.41, 4.73 and 9.57, 0.35 and 0.88, respectively. The effects of seed genotype from different altitudes (Ca P-1), latitudes (digestible dry matter and ADF) and longitudes (CP and Mg) on some nutrient contents and feed values were found significant (P<0.05). The correlations between altitude and NDF, P and Mg or between latitude and P and Mg contents of populations were significant. There were no specific trends in chemical composition and the nutritive value of tested NBT populations due to geographical variation. Thus, the results suggested that all studied geographical populations can be selected to obtain the nutritionally superior forage.

Lotus tenuis Seedling Establishment and Biomass Production in Flooding Pampa Grasslands (Buenos Aires , Argentina)

Biomass and plant density of Lotus tenuis Waldst. & Kit. ex Willd. have been reported in decreasing in grasslands and pastures. Our objective was to determine if L. tenuis biomass and plant density can be increased in grassland through seed addition. Two separated experiments under cattle grazing exclusion were conducted in three paddocks of a Flooding Pampa grassland. The first experiment was from autumn 2004 to autumn 2006 and the second from autumn 2005 to autumn 2007. Different L. tenuis seed additions (0, 57, 229, 917 and 1833 seeds m - ²) were broadcast into experimental plots. In the second experiment, besides seed additions there was a reseeding of approximately 900 seed m - ² from seed rain produced by plants of grassland. Seed density explained the 81% and 19% of the variation in seedling density and L. tenuis biomass, respectively. Seedling emergence occurred mainly between autumn and early spring, while seedling mortality was mainly between late spring and early summer. Lotus tenuis adult plant density and biomass production increased with seed additions. Total biomass production in the plant community varied between 589.94 ± 26.89 and 1042.44 ± 54.39 g m - ² yr -1 and the differences were principally attributed to precipitations. Lotus tenuis biomass contribution was of approximately 10%. The results suggest that L. tenuis seedling and plant establishment and biomass production can be increased through seed addition and/or seed rain through grazing exclusion during reproductive period.

Increasing defoliation frequency constrains regrowth of the forage legume Lotus tenuis under flooding. The role of crown reserves

Repeated defoliation and flooding trigger opposite plant morphologies, prostrated and erect ones, respectively; while both induce the consumption of carbohydrate reserves to sustain plant recovery. This study is aimed at evaluating the effects of the combination of defoliation frequency and flooding on plant regrowth and levels of crown reserves of Lotus tenuis Waldst. & Kit., a forage legume of increasing importance in grazing areas prone to soil flooding. Adult plants of L. tenuis were subjected to 40 days of flooding at a water depth of 4 cm in combination with increasing defoliation frequencies by clipping shoot mass above water level. The following plant responses were assessed: tissue porosity, plant height, biomass of the different organs, and utilization of water-soluble carbohydrates (WSCs) and starch in the crown. Flooding consistently increased plant height independently of the defoliation frequency. This response was associated with a preferential location of shoot biomass above water level and a reduction in root biomass accumulation. As a result, a second defoliation in the middle of the flooding period was more intense among plants that are taller due to flooding. These plants lost ca. 90% of their leaf biomass vs. ca. 50% among non-flooded plants. The continuous de-submergence shoot response of frequently defoliated plants was attained in accordance to a decrease of their crown reserves. Consequently, these plants registered only 27.8% of WSCs and 9.1% of starch concentrations with respect to controls. Under such stressful conditions, plants showed a marked reduction in their regrowth as evidenced by the lowest biomass in all plant compartments: shoot, crowns and roots. Increasing defoliation frequency negatively affects the tolerance of the forage legume L. tenuis to flooding stress. Our results reveal a trade-off between the common increase in plant height to emerge from water and the amount of shoot removed to tolerate defoliation. When both factors are combined and defoliation persists, plant regrowth would be constrained by the reduction of crown reserves.

Drought-tolerant naturalized populations of Lotus tenuis for constrained environments

A perennial forage legume species tolerant to water stress would be useful to improve pasture and animal productivity in the central zone of Chile. The growth, dry-matter (DM) production, and drought tolerance of twelve accessions of Lotus tenuis Waldst & Kit, Syn. L. glaber, naturalized in Chile were evaluated with the objective to select contrasting genotypes, tolerant and sensitive to drought, for future breeding programmes. The accessions were sown in pots of 1.3 L containing a volcanic soil (Andisol). A completely randomized design with all combinations of Lotus accessions and four water treatments [100, 70, 40, and 10% of soil water availability (SWA)] was used. The relative rate of stem elongation (RRSE), the shoots and roots DM production, the relative water content (RWC), and the specific leaf area (SLA) were measured. A drought-sensitivity index (DSI) and the interaction genotype×environment were calculated. The RRSE, the DM production, RWC, and SLA all showed a significant reduction (P<0.05) in the treatment with the higher water restriction (10% SWA). There were significant differences (P<0.05) within RRSE and DM production genotype means, but the RWC and SLA did not differ among populations. The DSI varied broadly among genotypes, from 0.49 to 1.34, and was correlated negatively with DM production under water stress (10% SWA). It was concluded that the Lotus tenuis populations showed water-stress tolerance genetic variability, with accessions Lt14 and Lt4 the most contrasting. These findings will permit us to identify chromosomal regions associated with drought-tolerant genotypes which will allow us to accelerate the development of cultivars adapted to water-restricted environments.

Late Summer Management Can Improve Forage Yield Distribution and Nutritive Value in Temperate Grassland

Chemical defoliation (glyphosate spraying) at the end of summer and fertilization are practices proposed to improve winter forage availability in native grasslands of the Flooding Pampa of Argentina. However, there is no preceding work comparing the effect of either practice on the yield and botanical composition of these grasslands. In 2002 and 2003, three defoliation treatments were applied in mid‐February: control (C) without summer defoliation; severe summer defoliation (D) to 2‐ to 3‐cm stubble height and glyphosate, isopropylamine salt of N‐[phosphonomethyl] glycine, G, applied at 2.2 kg a.i. ha−1. Additionally, the effect of three rates of N, 0, 35, and 70 kg N ha−1and P, 0, 11, and 22 kg P ha−1 applied in combination with the three late summer defoliation treatments were researched. Early changes during fall in the biomass components ryegrass (Lolium multiflorum Lam.), warm‐season grasses (WSG), dead matter, and litter were evaluated after defoliation treatments. The effect of defoliation treatments along with N and P fertilization was followed on seasonal and annual forage yield, botanical composition, in vitro dry matter digestibility (IVDMD), and crude protein (CP). Glyphosate application increased annual ryegrass contribution while reducing WSG and legumes, mostly narrow leaf trefoil (Lotus tenuis Waldst &amp; Kit.) and annually yielded 29% less forage dry matter (DM) than the intense mechanical defoliation. Forage IVDMD and CP were increased by D and G in fall the first year. In the second year CP was low in G in winter and spring. Changes in botanical composition can explain the differences observed in quality DM traits. Fertilizer increased forage yield 2 to 10 kg DM per kg N and 8 to 24 kg DM per kg P applied. Severe defoliation applied in late summer increased fall and winter forage availability and quality without the negative effect on legumes observed with glyphosate that had a negative impact on DM accumulation and quality in spring.

Condensed Tannin Concentrations of Three Lotus Species Grown in Different Environments

A B S T R A C T Condensed tannins (CT) present in Lotus spp., depending on their concentration in the plant, can prevent bloating and improve protein absorption in ruminants. With the objective to know the variability of this characteristic, the CT concentration (% dry matter basis) was determined by the butanol-HCl procedure in 13 cultivars of Lotus corniculatus L. (Lc) introduced from North and South America and Oceania, 11 accessions of Lotus tenuis Waldst. & Kit. ex Willd. (Lt), and 22 accessions of Lotus uliginosus Schkuhr (Lu) collected in Chile, from 32° to 38° S and 36° to 46° S, respectively. The field experiments, with two randomized complete blocks, were established in autumn 1998, in five different environments in the central-southern zone of Chile (clay soil, sandy soil, and three volcanic soils with different levels of water availability). The herbage sampling was conducted in spring-summer 1999-2000, when the plants were in full flowering. Significant differences between cultivars or accessions were found within each site, in total CT and/or in extractable or protein or fiber bound fractions of CT concentrations. The Lc and Lu genotypes showed high variability, with a range of 4.7 to 8.7% and 6.3 to 11.0%, and means of 6.1 and 8.2%, respectively, of total CT. The Lt general mean was 4.8%, considerably higher than the figures reported in the literature, and had low variability. This information will contribute to select genotypes for the improvement of this species by selection and breeding.

Outcomes of the search for new perennial and salt tolerant pasture plants for southern Australia

The potential adaptation of a range of perennial pasture species to recharge environments in southern Australia is reviewed based on their performance in 20 field nurseries in a nationally coordinated project. Species were also evaluated for their suitability to discharge sites where salt and waterlogging are major restraints. Species are ranked according to their potential to be incorporated into farming systems and the scope for further breeding and selection. Medicago sativa L. (lucerne) was the most persistent of the perennial legumes across a diversity of recharge environments. Lotus corniculatus L. (birdsfoot trefoil) showed the most promise on soils prone to waterlogging. Other legumes that showed potential included Cullen australasicum (Schltdl.) J.W. Grimes (tall verbine) and Lotononis bainesii Baker (lotononis). The herb Chicoriyum intybus L. was superior to M. sativa on more acid soils. Phalaris aquatica L. (phalaris) and summer dormant cultivars of Dactylis glomerata L. (cocksfoot), Festuca arundinacea L. (tall fescue) and Lolium perenne L. (perennial ryegrass) were among the most persistent and productive of the perennial grasses. Further exploitation of temperate perennial grass germplasm with increased summer dormancy should be a priority to increase the role of these grass species in lower rainfall, summer-dry environments. Although difficult to establish, the indigenous grasses Austrodanthonia caespitosa (Gaudich.) H.P. Linder (wallaby grass) and A. richardsonii (Cashmore) H.P. Linder were persistent and showed good recruitment. They should be a priority for low rainfall, low input environments. Other grasses that showed promise were Chloris gayana Kunth (Rhodes grass), Secale montanum Guss. (mountain rye), Microlaena stipoides (Labill.) R. Br. (weeping grass), Ehrhata calcycina Sm. (veldt grass) and Bromus stamineus E. Desv. (grazing brome). For discharge environments, Melilotus siculus (Turra) Vitman ex B.D. Jacks. was one of the most salt tolerant legumes and should be a priority for further development. Medicago polymorpha L. (burr medic) appears underutilised in discharge environments. Increasing the waterlogging tolerance of this moderately salt tolerant species would further enhance its potential. Trifolium michelianum Savi. (balansa clover) owed its success in discharge areas more to ‘salt avoidance’ rather than salt tolerance per se. Melilotus sulcatus Desf., T. tomentosum L. and Lotus tenuis Waldst. &amp; Kit. ex Willd. also had traits that may prove advantageous for discharge environments. Within the pasture grasses, Puccinellia ciliata Bor (pucinellia) was superior at sites prone to waterlogging whereas T. ponticum performed better in moderately drained saline sites.

Deficit and excess of soil water impact on plant growth of Lotus tenuis by affecting nutrient uptake and arbuscular mycorrhizal symbiosis

The impact of deficit and excess of soil water on plant growth, morphological plant features, N and P plant nutrition, soil properties, Rhizobium nodulation and the symbiosis between arbuscular mycorrhizal (AM) fungi and Lotus tenuis Waldst. & Kit. were studied in a saline-sodic soil. Water excess treatment decreased root growth by 36% and increased shoot growth by 13% whereas water deficit treatment decreased both root and shoot growth (26 and 32%, respectively). Differences between stress conditions on shoot growth were due to the ability of L. tenuis to tolerate low oxygen concentration in the soil and the sufficiency of nutrients in soil to sustain shoot growth demands. Water excess treatment decreased pH, and increased available P and labile C in soil. Water deficit treatment decreased available P and also increased labile C. In general, N and P acquisition were affected more by water excess than water deficit. The number of nodules per gram of fresh roots only increased in water excess roots (97%). Under both stress conditions there was a significant proportion of roots colonized by AM fungi. Compared to control treatment, arbuscule formation decreased by 55 and 14% under water excess and water deficit, respectively. Vesicle formation increased 256% in water excess treatment and did not change under water deficit treatment. L. tenuis plants subjected to water deficit or excess treatments could grow, nodulated and maintained a symbiotic association with AM fungi by different strategies. Under water excess, L. tenuis plants decreased root growth and increased shoot growth to facilitate water elimination by transpiration. Under water deficit, L. tenuis plants decreased root growth but also shoot growth which in turn significant decreased the shoot/root ratio. In the present study, under water excess conditions AM fungi reduced nutrient transfer structures (arbuscules), the number of entry points and spore, and hyphal densities in soil, but increased resistance structures (vesicles). At water deficit, however, AM fungi reduced external hyphae and arbuscules to some extent, investing more in maintaining a similar proportion of vesicles in roots and spores in soil compared to control treatment.

The Scientific Name of Narrow‐Leaf Trefoil

The narrow‐leaf trefoil is a widely used forage plant in temperate and subtemperate areas. It is the object of extensive improvement programs and research, which has generated a large body of literature. A few decades ago it was discovered that its traditional scientific name, Lotus tenuis Waldst. &amp; Kit. ex Willd., had to be superseded by an older name, L. glaber Mill. It was then proposed to permanently reject the name L. glaber, thus allowing L. tenuis to continue in use for the narrow‐leaf trefoil. The rejection proposal for the name L. glaber was finally accepted by the 17th International Botanical Congress (IBC) in July 2005, so L. tenuis is now the scientific name for the narrow‐leaf trefoil.

Segregation by morphological analyses of trisomy types inLotus tenuis(Fabaceae)

Two autotetraploids (2n = 4x = 24) were produced by colchicine treatment of dry seeds of Lotus tenuis Waldst. et Kit. Triploids (2n = 3x = 18) were obtained by backcrossing the tetraploids to normal diploid plants. Primary trisomies (2n = 12 + 1) were obtained by selfing the triploids. A morphological comparison was made between a randomly selected diploid, a tetraploid, and five trisomic plants. The trisomics could be distinguished distinctly from the diploid and tetraploid using 12 quantitative phenotypic traits. Two traits, bract index and number of flowers per umbel, were not significantly different between all three cytotypes (2x, 2x + 1, 4x). By means of morphological analyses it was possible to select trisomic plants for presumably different trisomes prior to detailed cytological analyses of individual chromosomes. Key words: aneuploidy, tetraploids, Fabaceae, Lotus tenuis, morphological traits, triploids, primary trisomics.

Post-Burn Recovery in the Flooding Pampa: Impact of an Invasive Legume

Winter burning of Paspalum quadrifarium Lam. stands (pajonales) promotes colonization of denuded spaces by several alien species. Lotus tenuis Waldst et Kit. (lotus), a recent invader of the region, is able to reach very high densities between the resprouting bunches of the dominant species. Results of a removal experiment performed to evaluate the impact of natural establishment of lotus on post-born colonization of pajonal stands are reported. Seedlings of lotus were removed shortly after their emergence between burned bunches of P. quadrifarium. Eighty days after burning, approximately 30% of the soil surface remained uncovered within removal plots, whereas canopy cover was complete within controls. Furthermore, final (137 days post-burn) total aboveground biomass was 2.7 times higher in control than in removal plots. Removal of lotus significantly (p<0.05) increased the cover of an annual native grass (Phalaris angusta Nees, ex Trin.) and the final biomass of an alien thistle (Carduus acanthoides L). A spatial association analysis provided additional evidence about the negative impact of lotus on colonization success of C. acanthoides. Weed colonization may be reduced, if not prevented, by managing the colonization processes of other new and useful invaders.

Increase in forage yield in narrowleaf birdsfoot trefoil (Lotus tenuis Waldst & Kit ex Willd) in a permanent pasture with foliar applied gibberellic acid (GA3), and phosphorus

Lotus tenuis is a perennial legume with a good adaptation to infertile, heavy and waterlogging soils. It can replace alfalfa in these sites with a similar feeding value. An important constraint is its weak competitive capacity with other graminae and weed species in permanent pastures, having consequently a poor forage yield. The objective of the present research is to overcome this disadvantage, enhancing its competitive ability with foliar applications of GA3 (GA) and phosphorus (P), increasing L. tenuis forage yield. Field experiments were conducted during 1994 with foliar application of GA (50 mg.l-1) and during 1995 with foliar application of GA (25 and 50 mg.l-1), phosphorus (8 kg.ha-1, as P2O5) and their combinations, in permanent pastures with L. tenuis and other companion grasses. In 1994 GA 50 increased significantly L. tenuis dry matter (DML) in 64.6% but not the dry matter of graminae fraction (DMG) and in consequence the total dry matter of the pasture (TDMP) was increased. In 1995 all GA treatments and their combinations with phosphorus enhanced DML but not DMG. In this sense GA 25 + P was the most effective treatment with a 151% increment of DML. Consequently TDMP was significantly increased due to a larger participation of L. tenuis in the forage yield. This increase was achieved due to a greater length and diameter of L. tenuis branches, with a logical modification in leaf:stem ratio. Moreover GA treatments reduced L. tenuis flower number. Phosphorus treatment, applied alone, showed an increase in the DML. GA treatments did not modify the feeding value of the forage in L. tenuis and graminae fractions, except GA 50 and GA 50 + P in acid detergent fiber (ADF), neutral detergent fiber (NDF) and crude protein (CP), respect to the control. The total crude protein (CP.m-2) was enhanced in all GA and GA + P treatments. Foliar GA3 and phosphorus spray applications increased the competitiveness of trefoil for light, on account of morphological changes in the spatial disposition of L. tenuis stems reaching faster the top of the pasture canopy. This practice can be an adequate alternative to increase the forage yield and total crude protein in permanent and cultivated pastures with a low cost-benefit ratio.

Emergence and Seedling Survival of Lotus Tenuis in Festuca Arundinacea Pastures

Emergence and survival of seedlings of lotus or narrowleaf trefoil (Lotus tenuis Waldst.) were monitored in 4 grazed pastures dominated by tall fescue (Festuca arundinacea Schreb.) for 2 successive years. The objective was to detect patterns and environmental conditions promoting successful seedling establishment of lotus. Emergence followed a seasonal pattern each year, with most emergence occurring towards the end of winter. Seedling emergence occurred mainly in heavily grazed sites which occupied 45 to 90% of each pasture. Seedling emergence was greatest, but seedling survival was poorest in the wettest year. Competition resulting from climatic conditions favoring growth of established pasture plants was detrimental to establishment of lotus seedlings. In contrast, heavily grazed areas provided microsites that enhanced survival of new recruits during the spring growing season. Dense seedling stands emerging on feces were overcrowded and suffered the highest mortality, thus, they contributed little to recruitment of lotus. However, dispersal of lotus was enhanced by the presence of seeds in livestock feces.

Cytology of 2N pollen formation and pollen morphology in diploid lotus tenuis (fabaceae)

Two genotypes of Lotus tenuis Waldst &amp; Kit. ex Willd. PI 204882, a diploid (2n = 2x = 12), were identified as producing 2n pollen (maximum = 6%). The objectives of this research were: (1) to determine the mechanism(s) of 2n pollen formation in the L. tenuis genotypes and (2) to morphologically describe n and 2n pollen using light and scanning electron microscopy. Meiotic studies revealed that 2n pollen resulted from tripolar spindles during anaphase II of microsporogenesis. The 2n pollen germinated well, although abnormal pollen tubes were observed. The genetic constitution of 2n pollen resulting from tripolar spindles is equivalent to first division restitution (FDR) of meiosis. Fresh and air‐dried pollen samples exhibited differences in size and shape under light and scanning electron microscopy. The size of diploid (2n) pollen was larger than that of haploid (1n) pollen. Normal haploid (1n) pollen was globose‐prolate in shape, while diploid (2n) pollen was tetrahedral in shape.

Identification of Lotus tenuis (Waldst et Kit.) flavonoids

Flavonoid metabolism was investigated in Lotus tenuis Waldst. et Kit. (birdsfoot trefoil). This species is dominant during spring and summer in the native grasslands of the Province of Buenos Aires (Argentina). Flavonoid compounds were studied during a whole life cycle of the plant in four different developmental stages. The presence of free kaempferol, kaempferol-3-O-glucoside and kaempferol-3-O-glucosyl-7-O-rhamnoside was detected. Qualitative and quantitative differences in relation to these compounds were observed.