Depression of legume growth by liming

Summary Early growth or nodulation of certain species was depressed when a Hawaiian Oxisol was limed at rates above 6 tons/ha (pH 6). In 8 legumes, the depression later gave way to positive response. This was evident in plant weights of Desmodium intortum and Glycine wightii var. Cooper, and in pod weights of Phaseolus vulgaris. A transient depression was observed visually in Desmodium canum, Dolichos axillaris, Glycine wightii var. Tinaroo, and Trifolium subterraneum. In Stylosanthes guyanensis and S. fruticosa, the depression persisted throughout the experiment (6 months). Growth was not depressed in Arachis hypogea, Coronilla varia, Glycine max, Leucaena leucocephala, Medicago sativa, Trifolium repens, or Vigna sinensis. Journal Series No. 1953 of the Hawaii Agr. Exp. Station Journal Series No. 1953 of the Hawaii Agr. Exp. Station     

Influence of lime on nitrogen fixation by tropical and temperate legumes

Summary A nitrogen deficient Oxisol which had been fertilized with P, K, Zn and Mo received CaCO₃ at rates which increased continuously from zero to 22 tons/ha. Liming produced a range of pH in the saturation paste from 4.7 to 7.1; a range of calcium in the saturation extract from 0.3 to 3 meq/l; and a significant decline in available manganese. Responses of 9 tropical and 7 temperate legumes were compared across the pH variable.For Stylosanthes spp. nodule numbers and weight and plant yield declined above pH 5.5. Arachis hypogaea and Vigna sinensis, whose yield increased by only 30%, showed no clear improvement in nodulation or nodule effectiveness (acetylene reduction rate per unit nodule weight).Increased nodule effectiveness could account for most of the growth increase in Dolichos axillaris and Glycine max var. Kahala. Both the number and effectiveness of nodules increased for Desmodium intortum, Glycine wightii, Medicago sativa, and Trifolium subterraneum. Nodule size and effectiveness increased for G. max var. Kanrich. Only in one species, Coronilla varia, could increase in nodule numbers alone account for the increased growth associated with liming, although increased numbers of nodules probably accounted for much of the response by Lotus corniculatus, and by Desmodium canum and D. intortum up to pH 5.3.Increased nodulation and plant N contents were consistent with the conclusion that for most species improved N₂-fixation was the cause of growth improvement associated with liming. However, percent N was high in leaves of Vigna and Phaseolus vulgaris at all lime levels. In Phaseolus, variation in nodulation and growth were unrelated. The growth improvement was associated with decline in leaf N, suggesting that something other than N nutrition was limiting.Journal Series No. 1957 of the Hawaii Agricultural Experiment Station.Department of Soils and Plant Nutrition, University of California, Davis.Department of Agronomy and Soil Science, University of Hawaii, Honolulu, Hawaii.     

The effects of lime-pelleting and lime-superphosphate fertilizer on the growth of three annual legumes in an acid sandy soil

Summary Three pioneer pasture legume species,Trifolium subterraneum, Trifolium glomeratum andOrnithopus compressus, were grown in a sandy soil of pH 5.0. The growth and nodulation of each species was examined in the presence and absence of lime pelleting and with superphosphate and lime-superphosphate fertilizer. In each species tested, plant yield, nodule number and nitrogen recovery as maximal where lime pelleting and lime-super were applied together. Plant calcium indicated that the response to lime was due to changes in soil pH rather than to a calcium response. T. glomeratum was the species most responsive to lime application but its growth was at best only half that ofT. subterraneum andO. compressus, which produced equally under both favourable (pH 5.9) and unfavourable (pH 4.4) conditions created by fertilizer applications.     

l-3-(3′-Carboxy-4′-hydroxyphenyl)alanine (3-carboxytyrosine) in seeds of Neonotonia wightii (Glycine wightii) and its possible systematic significance

l-3-(3′-Carboxy-4′-hydroxyphenyl)alanine (3-carboxytyrosine) constitutes 3% of the seeds of Neonotonia wightii (Glycine wightii); it has also been detected in the seeds of 3 species belonging to 2 other genera of the Glycineae. The systematic significance of these findings is discussed.     

The acidophilous taxa of thefestuca varia group in the alps: New studies on taxonomy and phytosociology

The acidophilous taxa of theFestuca varia group appearing in the Alps (F. varia Haenke s.str.,F. scabriculmis (Hack.)K. Richt. subsp.scabriculmis, F. scabriculmis subsp.luedii Markgr.-Dann., andF. acuminata Gaudin) have been investigated with regard to their taxonomy, phytosociology and ecology. Morphometrical analyses of the different taxa confirm that the division of the species group is justified. Moreover three varieties ofFestuca varia s.str. can clearly be distinguished. Apart from the already knownF. varia var.varia and var.handel-mazzettii Krajina a newF. varia var.winnebachensis Wallossek etMarkgr.-Dann. is described. The ploidy levels of 30 samples from all taxa have been determined by means of flow cytometry.Festuca acuminata is diploid (2n=14), although this taxon occurs in ecologically different habitats within an altitudinal range between 200 and 3100 m.Festuca varia var.varia is tetraploid whereas the other varieties occur in hexaploid populations, which can be associated with inter- or post-glacial migration stages. Hexaploidy was also determined for both subspecies ofF. scabriculmis. The phylogenesis of these taxa by allopolyploidy seems possible, as they show a morphologically intermediate position betweenF. acuminata and the basiphilousF. quadriflora Honck. The spatial distribution and separation of the taxa is shown by means of precise area maps. As a result of a numerical classification of 534 relevés, the Alpine variegated fescue grasslands can be subdivided into six independent phytosociological associations of theFestucion variae: the East AlpinePulsatillo albae-Festucetum variae, Gentianello anisodontae-Festucetum variae ass. nov. andSeslerio-Festucetum variae ass. nov. as well as the West AlpineFestucetum scabriculmis, Euphorbio cyparissiae-Festucetum luedii ass. nov. andFestuco scabriculmis-Potentilletum valderiae. The mixture of basiphilous and acidophilous species in theSeslerio-Festucetum variae can be explained by soil heterogeneity with acid and alkaline conditions alternating within a very small space.Festuca acuminata can rather be regarded as a rock plant as it preferably occurs in associations of the allianceAndrosacion multiflorae.     

Chloroplast-DNA variation in the genus Lotus (Fabaceae) and further evidence regarding the maternal parentage of Lotus corniculatus L.

 To resolve the maternal parentage of the tetraploid Lotus corniculatus, restriction-site variation of chloroplast DNA (cpDNA) was studied in several accessions of that species, in the four putative parental diploid species, L. tenuis, L. alpinus, L. japonicus and L. uliginosus, and in four phylogenetically more distant diploid species, L. hispidus, L. edulis, L. ornithopodoides and Tetragonolobus maritimus var. siliquosus. Evidence of cpDNA maternal inheritance was obtained by using reciprocal controlled crosses between plants of L. corniculatus and natural tetraploid individuals of L. alpinus showing very distinct restriction patterns. Interspecific cpDNA variation in the eight Lotus species and T. siliquosus was analysed by comparing cpDNA fragment patterns produced by five restriction endonucleases and totalling 304 distinct fragments. Genetic differentiation in cpDNA was very high between the L. corniculatus group and L. hispidus on the one hand, and the three other species on the other hand. Sixteen restriction-site mutations and eight length polymorphisms were identified among the five species of the L. corniculatus group and L. hispidus, Lotus uliginosus, L. alpinus and L. japonicus showed at least six DNA changes with regard to the molecule of L. corniculatus. Accordingly, these species should be excluded as maternal progenitors of L. corniculatus. Conversely, the cpDNA of L. tenuis differed from that of L. corniculatus by only two small-length mutations. As also suggested previously from an analysis of several nuclear markers, the results reported here show decisively that L. tenuis may be considered as the most probable maternal ancestor of L. corniculatus. Received: 23 February 1997/Accepted: 28 February 1997     

中国甘蔗亚族几个容易混淆物种的订正

通过标本研究和野外考察发现:被鉴定为二色金茅和滇南金茅的国产标本实际均为四脉金茅,且二色金茅和滇南金茅在国内无分布,国内各植物志中该名称下的类群应归入四脉金茅。另发表一新组合E. quadrinervis var. latifolia(Rendle)Y. C. Liu & H. Peng.; 国内各植物志和各大标本馆在描述和鉴定Microstegium ciliatum时,常与M. fasciculatum混淆,并在各种场合错误引证; 在此澄清二者真正的区别。     

PREDICTING HOST RANGE EVOLUTION: COLONIZATION OF CORONILLA VARIA BY COLIAS PHILODICE (LEPIDOPTERA: PIERIDAE)

Extensive sympatry is currently arising between the common sulfur butterfly, Colias philodice Latreille (Lepidoptera: Pieridae) and a potential leguminous host plant, Coronilla varia (L.). In laboratory trials, larval surviviorship and growth were higher on the primary host, Medicago sativa (L.), than on the nonhost C. varia. However, because females reared from C. varia were on average more fecund than females reared from M. sativa, fitness on C. varia (approximately as survivorship times fecundity) was commensurate with fitness on M. sativa. Thus, it is predicted that selection would favor oviposition on C. varia, if such behavior were to arise. In addition, significant among-family variation exists for several measures of larval performance on both C. varia and M. sativa, indicating that C. philodice can potentially respond to selection for increased performance on each species. Moreover, larval performance was significantly positively correlated across these species, suggesting that selection for increased performance on each species will facilitate, not constrain, evolution of increased performance on the other. It is concluded that behavioral rather than physiological barriers currently account for the absence of C. philodice from C. varia and that, if such barriers are overcome, C. philodice will expand its host plant range to include C. varia.     

Electrophoretic variation of the apogamousDryopteris varia group (Dryopteridaceae)

A total of 35 electrophoretic variants were detected in four apogamous species of theDryopteris varia group: 14 variants inD. bissetiana triploids, 7 inD. sacrosancta triploids, 6 inD. varia triploids, 3 inD. pacifica triploids, and 5 in apogamous diploids. The variants differed from each other in various combinations of a few alleles which were common in some of the variants, suggesting recurrent origin.Dryopteris insularis var.insularis (2x) and var.chichisimensis (3x), other members of the group, were electrophoretically monomorphic, suggesting single origin. Banding patterns infer that triploids ofD. bissetiana andD. sacrosancta may have originated from hybrids whose parent is the sexualD. saxifraga, whereas this species was not involved in the origin of the other apogamous triploids and the apogamous diploids. The other parent was also discussed and we proposed a hypothesis that diploid offsprings fromD. pacifica triploids hybridized withD. saxifraga giving rise to triploids ofD. bissetiana andD. sacrosancta.     

青羊湖林场不同林分物种多样性与水源涵养能力的研究

通过群落调查和林下土壤及枯落物特性的分析,研究了青羊湖林场南酸枣（Choerospondias axillaris）林、未抚育马尾松（Pinus massoniana）林、抚育马尾松林、马尾松-南酸枣混交林4种林分的物种多样性及水源涵养能力。结果表明：（1）4种林分共有维管束植物135种,隶属58科97属,其中南酸枣林物种相对较丰富(88种),混交林次之(76种),抚育马尾松林较少(64种),未抚育马尾松林则相对最少(55种);（2）林分类型对物种多样性有重要影响,南酸枣林和混交林草本物种多样性较两种针叶林高,而灌木物种多样性则较低;（3）DCA排序结果显示,南酸枣林和混交林物种相似性程度较高,两种马尾松林与南酸枣林、混交林差异明显;（4）林分类型对水源涵养能力有重要影响,相比两种马尾松林,南酸枣林和混交林的林下枯落物蓄积量分别降低10.1%和15.2%,最大持水量降低34.1%和44.7%,而且0～10 cm土壤容重降低14.7%和7.4%,10～20 cm土壤容重降低14.1%和4.0%,20～30 cm土壤容重降低8.7%和4.9%,但总储水量增加15.8%和4.5%,即南酸枣林和混交林具有较高的水源涵养能力。研究认为,生态抚育增加了马尾松林的水源涵养能力。     

Genome relationships among Lotus species based on random amplified polymorphic DNA (RAPD)

The ability of random amplified polymorphic DNA (RAPD) to distinguish among different taxa of Lotus was evaluated for several geographically dispersed accessions of four diploid Lotus species, L. tennis Waldst. et Kit, L. alpinus Schleich., L. japonicus (Regel) Larsen, and L. uliginosus Schkuhr and for the tetraploid L. corniculatus L., in order to ascertain whether RAPD data could offer additional evidence concerning the origin of the tetraploid L. corniculatus. Clear bands and several polymorphisms were obtained for 20 primers used for each species/accession. The evolutionary pathways among the species/accessions presented in a cladogram were expressed in terms of treelengths giving the most parsimonious reconstructions. Accessions within the same species grouped closely together. It is considered that L. uliginosus which is most distantly related to L. corniculatus, may be excluded as a direct progenitor of L. corniculatus, confirming previous results from isoenzyme studies. Lotus alpinus is grouped with accessions of L. corniculatus, which differs from previous studies. With this exception, these findings are in agreement with previous experimental studies in the L. corniculatus group. The value of the RAPD data to theories on the origin of L. corniculatus is discussed.     

Additional Hosts for the Ring Nematode,Criconemella xenoplax

Some common legumes and weeds indigenous to peach orchards in South Carolina were tested in greenhouse experiments to determine their host suitability for Criconemella xenoplax. Legumes that were hosts for the nematode were dwarf English trefoil (Lotus corniculatus var. arvensis), big trefoil (L. uliginosis), birdsfoot trefoil (L. corniculatus), narrowleaf birdsfoot trefoil (L. tenuis), ball clover (Trifolium nigrescens), rose clover (T. hirtum), subterranean clover (T. subterraneum), striate lespedeza (Lespedeza striata), and partridge pea (Cassiafasciculata). Most nonleguminous plants tested did not support population increases, but small increases were observed on orchardgrass (Dactylis glomerata), broadleaf signalgrass (Brachiaria platyphylla), purslane (Portulaca oleracea), and Carolina geranium (Geranium carolinianum). Results indicate that leguminous plants probably should not be used as ground cover or rotation crops for plants that are injured by C. xenopax.     

Effect of oxygen availability on nitrogen fixation by two Lotus species under flooded conditions

The pasture legumes Lotus uliginosus (Schk.) and Lotus corniculatus (L.), known to differ in their tolerance to flooding, were inoculated with Rhizobium loti and flooded for 60 d while subjected to two levels of dissolved pO2: 0.241 and 0.094 mol ml^-1. L. uliginosus showed significantly greater growth (shoot and root) and N2 fixation under both pO2s, compared to L. corniculatus, although growth and N2 fixation by L. corniculatus was not affected by the low pO2. Surprisingly, in L. uliginosus., growth, nodulation and N2 fixation were all increased by low pO2 while nodulation of L. corniculatus where low pO2 plants showed a significant increase over that of the higher pO2 plants while L. uliginosus plants showed a decline. Root porosity of L. uliginosus doubled in the low pO2-treatment from a mean of 14.5% in high pO2 roots to 28.5%, whereas that of L. corniculatus was relatively unaffected by pO2, being 7% and 9% for high and low pO2 plants, respectively. The structure of nodules differed little between species and treatments, although nodules/nodulated roots from the L. uliginosus plants had particularly profuse lenticels and aerenchyma. However, L. corniculatus nodules, especially those grown in the lower pO2 showed signs of early senescence with vacuolation of infected cells and green coloration when cut open. Leghaemoglobin (Lb) concentrations in nodules from both species were unaffected by low pO2, although that of L. corniculatus nodules, regardless of pO2, was significantly greater than L. uliginosus. Concentrations of the intercellular glycoprotein recognized by the monoclonal antibody MAC265 were significantly reduced in nodules from the low pO2 treatment in both species. Immunogold labelling showed that the MAC265 antigen was localized primarily within intercellular spaces within nodule cortices from both Lotus species. A marked decrease in deposition of the MAC265 antigen within the cortices of L. uliginosus nodules grown in the lower pO2, is discussed in terms of the relative abilities of the two Lotus spp. to maintain an O2 supply to the N2-fixing bacteroids within submerged nodules.Keywords: Lotus uliginosus, Lotus corniculatus, N2 fixation, flooding, oxygen.      

Extract of Ocimum canum lowers blood glucose and facilitates insulin release by isolated pancreatic β-islet cells

Aqueous extract of Ocimum canum Sim, (Lamiaceae) is used by some Ghanaians to manage diabetes mellitus. In vivo modulation of levels of fasting blood glucose by 0. canum extract was evaluated in type-II diabetes mellitus using the C57BL/KsJ db/db genetically diabetic animal model, and its effects on glucose-stimulated insulin release in vitro were monitored using isolated rat pancreatic beta-islet cells. The results showed that fasting blood glucose levels and body weight decreased significantly (p < 0.05) in diabetic and non-diabetic C57BL/KsJ mice, which were administered aqueous extract of 0. canum. In vitro, the 0. canum extract significantly enhanced insulin release from isolated rat pancreatic beta-islet cells. Insulin release was found to be dependent on glucose concentration and increased with increasing O. canum concentration in the incubation medium up to an optimum extract concentration of 0.03 mg/ml. Release of the hormone decreased beyond this concentration of extract in the medium. Addition to the medium of Desmodium adscendens, a plant preparation used to manage inflammatory disorders, did not increase but rather inhibited insulin secretion by the pancreatic beta-islet cells. These results could explain the use of 0. canum in Ghanaian folk medicine to manage diabetes mellitus.     

The Old World species of Pouzolzia (Urticaceae, tribus Boehmerieae). A taxonomic revision

The Old World species of the genus Pouzolzia have been revised and 24 species and 13 infraspecific taxa recognised. Worldwide, the genus now totals 36 species and 17 infraspecific taxa. Pouzolzia sect. Memorialis Bennett & Brown (including the genera Gonostegia Turcz. and Hyrtanandra Miq.) is maintained here as a section of Pouzolzia. The characters used to separate Pouzolzia from Boehmeria are found to work worldwide. In the Old World, the genus ranges, west to east, from Senegal to Japan and the Solomon Islands, and, north to south, from China, the Himalayas and Yemen to South Africa, Madagascar, Australia and the Lord Howe, Norfolk and Kermadec Is. Some species are common and occur almost throughout tropical Indomalesia or are widespread in Africa; others are rare and with a narrow range, for example restricted to one or a few oceanic islands. Each of the taxa occurring in the Old World is described and illustrated, habitats and geographical ranges are indicated, conservation status is discussed on the basis of our impression of old and new collecting activity, and distributions are mapped. The following new taxa are described: P. tsaratananensis Friis & Wilmot Dear from Madagascar, P. herpetophyton Friis & Wilmot‐Dear from the Comoro Is., and P. zeylanica subsp. calcicola Friis & Wilmot‐Dear and P. thailandica Friis & Wilmot‐Dear, both from southern Thailand. A new name, P. variifolia Friis & Wilmot‐Dear, is proposed for P. heterophylla (Blume) Wedd., nom. illeg. The following new combinations are published here: P. australis (Endl.) Friis & Wilmot‐Dear, P. sanguinea (Blume) Merr. var. formosana (Li) Friis & Wilmot‐Dear, P. sanguinea (Blume) Merrill var. cinerascens (Blume) Friis & Wilmot‐Dear, P. mixta Solms var. shirensis (Rendle) Friis & Wilmot‐Dear, P. hirta (Blume) Hasskarl var. parvifolia (Wight) Friis & Wilmot‐Dear, P. pentandra (Roxb.) Benn. & R. Br. subsp. wightii (Benn. & R. Br.) Friis & Wilmot‐Dear. and subsp. wightii (Benn. & R. Br.) Friis & Wilmot‐Dear var. gracilis (Miq.) Friis & Wilmot‐Dear. The following taxa are reduced to synonymy for the first time: Pouzolzia argenteonitida W.‐T. Wang, P. bracteosa Friis, P. calophylla W.‐T. Wang & C.‐J. Chen, P. guineensis Benth. var. seyrigii Leandri, P. guineensis Benth. var. madagascariensis Wedd., P. baronii Leandri, and P. auriculata Wight.     

The comparative phosphorus requirements of some temperate perennial legumes

The phosphorus (P) responses of seven temperate perennial pasture legumes and two species of lupins were compared in a field trial over a range of nine P rates, from 0 to 800 kg ha^-1. The two lupins produced more than 5 t ha^-1 of dry matter in the absence of added P and showed no response to the fertiliser. In contrast, the pasture legumes initially failed to grow without added P and responded to applications of between 200 and 800 kg ha^-1. At the higher rates of P, dry matter production of the pasture legumes was equivalent to that of the lupins.In the first 2 years of the trial; the most productive pasture legume species at the higher rates of added P were also the most productive at the lower rates. Phosphorus requirements for 90% of maximum yield varied greatly between species, but were closely related to maximum yield. Thus species with low P requirements for maximum yield were not necessarily P-efficient species. In the third and subsequent years of the trial Lotus corniculatus performed better than the other pasture legumes at the lower rates of added P. In contrast to other studies Lotus pedunculatus showed no ability to outyield Trifolium repens at low rates of P. Critical P concentrations of the pasture species for the late spring-early summer period declined in the order Trifolium repens (0.34%) > Lotus pedunculatus (0.30%) > Triofolium pratense (0.28%) > Trifolium hybridum (0.27%) > Trifolium ambiguum (0.26%) > Lotus corniculatus (0.23%).Mineralisable nitrogen (N) levels were determined in soils under three species in the 7th year of the trial. At the lowest rates of added P, mineralisable N levels were much higher under Lupinus polyphyllus than under Trifolium repens or Lotus corniculatus. With increasing P rate, levels under the latter species increased, and at 100 kg P ha^-1 were equivalent to those under the lupin with no added P.     

Interspecific hybridization between diploid species of Lotus (Leguminosae)

An interspecific hybridization study has been carried out between seven diploid species of Lotus (L. alpinus Schleich., L. japonicus (Regel) Larsen, L. filicaulis Dur., L. schoelleri Schweinf., L. krylovii Schischk. and Serg., L. tenuis Waldst. et Kit., and L. corniculatus var. minor Baker) closely related to L. corniculatus L. A total of 139 interspecific hybrids were produced in 16 combinations of the 7 species. Nine of these crosses were produced for the first time and four were obtained by means of embryo-culture. The growth habit, number of florets per umbel, flower color expression, HCN reaction and 15 metrical traits were compared between parents and hybrids. The relative case with which some hybrids were produced suggested that during the early evolutionary history of the genus species diversification could have originated through interspecific hybridization and subsequent gene differentiation. In some crosses, the hybrids resembled one parent more closely than the other. This close morphological affinity between the hybrids and one of their parents would make it extremely difficult to detect such hybrids in natural populations and probably aceounts for the prevailing belief that there is little or no hybridization in nature.     

PHYLOGENETIC IMPLICATIONS FROM CUTICULAR WAX ANALYSES IN EPILOBIUM SECT. ZAUSCHNERIA (ONAGRACEAE)

Analysis of n-alkane constitutents of the leaf cuticle have been utilized to elucidate phylogenetic relationships within Epilobium section Zauschneria. Specimens representing 136 populations were greenhouse-grown under the same conditions. Crosses were made between representatives of all taxa within the section. The resulting F₁ generations were also grown under the same conditions. Cuticle samples were removed in chloroform, purified with column chromatography and analyzed using gas chromatography and mass spectrometry. Resultant data were computer analyed using discriminant function analysis. Based on percent composition of 12 n-alkanes, each population and taxon can be characterized by a distinctive wax profile. Results suggest that the tetraploids E. canum subsp. canum and E. canum subsp. latifolium have been derived from the anastomosis of two distinct diploid genomes, E. canum subsp. canum “angustifolium” and E. septentrionale. Biochemical evidence from extant populations of E. canum are in agreement with geographic positions and ranges of the diploid species involved. Greenhouse hybridizations between the respective diploids, E. canum subsp. canum “canum” and E. septentrionale, result in F₁ progeny possessing phenotypes similar to naturally occurring tetraploid E. canum populations. Wax compositions of the natural tetraploid populations are intermediate between diploids and vary depending on geographical proximity to diploid species. Past taxonomic treatments of the genus have placed the tetraploid Zauschneria arizonica within the species Z. californica (now E. canum). Analysis of wax compositions now suggets that Z. arizonica had an independent origin which involved, at least in part, the diploid species E. canum subsp. garrettii from Utah.     

A palynological study and molecular analysis of the Desmodium procumbens group (Leguminosae-Papilionoideae) in Mexico

Desmodium diversity has been mainly classified using fruit characters, and because of variability in these and other characters, the taxonomy has sometimes been problematic and thus, there is a need for clarification and taxonomic reassessments. This is the case for the Desmodium procumbens group, where several infraspecific taxa have been named. The phylogenetic relationships among taxa referred to this group is unknown, and the taxonomic status has been recently revised only for some of the taxa. In this study, pollen morphology and ultrastructure of D. neomexicanum, D. procumbens var. procumbens, D. procumbens var. exiguum, D. procumbens var. longipes and D. procumbens var. transversum, belonging to the Mexican Desmodium procumbens group, were examined using light, phase-contrast, scanning electron and transmission electron microscopy, in order to establish palynological characters that might contribute to a better taxonomic resolution. Pollen grains are tricolporate, radiosymmetric, oblate spheroidal to prolate spheroidal shape, with lalongate endoapertures and rugulate exine with foveolae between rugulae. The exine is tectate with a columellate and/or granulate structure. The absence of a fastigium, features of exine sculpture, a colpus membrane and infrastructure mainly dominated by granules differentiate the pollen grains of the varieties exiguum and transversum from the other taxa studied. Pollen traits and sequence data provide evidence for separating D. neomexicanum from species D. procumbens. In general, the result from the pollen analysis is congruent with results obtained from a preliminary molecular analysis of this group.