Paspalum Plicatulum Research Articles

Leaf tissue fluxes of Pampa biome native grasses submitted to two grazing intervals

AbstractLeaf tissue fluxes of five Pampa biome grasses (Andropogon lateralis, Aristida laevis, Axonopus affinis, Paspalum notatum and Paspalum plicatulum) were evaluated in a natural pasture under rotational stocking with heifers in the spring and summer from October 2010 to April 2011. The experimental design was completely randomized, with two grazing intervals, defined by thermal sums of 375 and 750 degree‐days, and the five grass species. The evaluated species had a higher growth flux and balance between the fluxes when subjected to a grazing interval of 750 degree‐days and a higher real efficiency of utilization when subjected to grazing interval of 375 degree‐days. Andropogon lateralis showed the highest growth, intake and senescence fluxes: 3·61, 2·37 and 3·04 kg DM ha−1 day−1 respectively. Aristida laevis had the lowest real efficiency of utilization.

Forage performance of Paspalum hybrids from an interspecific cross

ABSTRACT: The goal of this study was to assess the variability of Paspalum plicatulum x P. guenoarum interspecific hybrids in terms of agronomic performance and their tolerance to cold conditions, as well as to estimate the correlation of different phenotypic characters associated with forage production. Twenty hybrids plants were used, besides one access P. guenoarum , one of P. plicatulum and the cultivar 'Pensacola' ( P. notatum ). Assessments were performed on individual plants, in a completely randomized design with five repetitions. Paspalum genotypes presented variability in total dry matter, leaf dry mass, leaf: stem ratio, and tolerance to cold. We suggest selection of the hybrids 08Q01 and 08Q44 for new stages within a forage improvement program. Estimates of phenotypic correlation may aid in the selection of genotypes with better agronomic traits.

Agronomic performance and interspecific hybrids selection of the genus Paspalum

The objective of the study was to analyze the genetic variability at agronomic and molecular level of apomic­tic genotypes of the genus Paspalum obtained by interspecific crosses of Paspalum plicatulum (sexual famale genitor) and Paspalum guenoarum (apomictic male genitor) to predict promising combinations with the sexual genitor using characters related to forage production. The study was conducted in two environ­ments in 2010 and 2011 in Eldorado do Sul and Augusto Pestana, State of Rio Grande do Sul, Brazil. The experiment followed a randomized block design with four replicates at both locations. Seven interspecific hybrids, the two genitors (sexual 4c-4x P. plicatulum and apomictic cultivate Rojas P. guenoarum ) and two native genotypes of Paspalum guenoarum and cultivate Pensacola of P. notatum were used. Analysis done inagronomic and molecular levels were able to detect genetic variability among interspecific hybrids of Paspalum . Moreover, the results suggested that the hybrids H12, H13 and H20 are recommended for further hybridizations with female sexual parent obtaining elite recombinant. Additional keywords: apomixes; forage species; genetic variability; plant breeding.

Inheritance of Aposporous Apomixis in Inter‐specific Hybrids Derived from Sexual Paspalum plicatulum and Apomictic Paspalum guenoarum

ABSTRACTApomictic Paspalum plicatulum Michx. and P. guenoarum Arechav. are promising candidates for forage grass development in tropical regions. From a plant breeding perspective, apomixis provides a unique mechanism for developing superior cultivars and preserving them indefinitely. Therefore, analysis of its inheritance is of great interest in these apomictic species. The objective of this work was to analyze the inheritance and expressivity of apomixis in interspecific families derived from crosses between a sexual colchicine‐induced plant of P. plicatulum and an apomictic P. guenoarum plant. One F1, one F2, and three backcross (BC) populations were created. Amplified fragment‐length polymorphism (AFLP) markers confirmed the hybrid origin of the F1 descendants. Analysis of the reproductive mode of the F1 by flow cytometry seed screen (FCSS) showed a segregation ratio of 1.6:1 sexual vs. apomictic plants. The same analysis in F2 and BC populations showed that in selfing or crosses involving sexual genotypes all progeny reproduced by sexuality, while BC populations involving apomictic hybrids as pollen donors produced offspring that segregated for the reproductive mode. Apomixis can be transmitted by pollen from P. guenoarum to other species of the Plicatula group as a simplex (Aaaa) Mendelian dominant factor, and full sexual reproduction requires the homozygous recessive (nulliplex) condition (aaaa) for the apomixis determinant. Results provided here are of interest for breeding apomictic species of Plicatula and for basic research on the genetic determinants of apomixis. Also, the possibility of creating new apomictic cultivars by traditional breeding methods is presented.

English

Five forage crops, namely ruzi (Brachiaria ruziziensis), purple guinea (Panicum maximum), atratum (Paspalum atratum), plicatulum (Paspalum plicatulum), and rhodes grass (Chloris gayana), were experimented for their possibility of ethanol and animal feed utilization. All tested forage crops were harvested 45 and 75 days after being planted. The results indicate the effect of harvesting time on their composition, including the contents of cellulose, lignin, and crude protein, thus affecting the ethanol yield and quality of animal feed. Ruzi grass, harvested 45 days after being planted, was shown to be the most suitable substrate for animal feed due to its highest crude protein content (12.49%), whereas purple guinea and atratum grasses provided highest expected yield of ethanol (2,688.40 and 2,613.20 L/ha/year, respectively).   Key words: Ethanol, animal feed, forage crops.

Genetic response of Paspalum plicatulum to genome duplication.

Paspalum plicatulum is a perennial rhizomatous grass with natural diploid and polyploid cytotypes. In this study, we investigated the occurrence of sequence polymorphisms arising immediately after genome autoduplication in this species. Two mixoploid plants (4C and 7D) were previously obtained through colchicine treatment of seeds generated by open pollination of a diploid plant (H14-2x). Diploid and tetraploid sectors from both mixoploids were dissected to generate two ploidy series (4C-2x/4C-4x and 7D-2x/7D-4x). Molecular fingerprints were generated from the maternal plant H14-2x, both ploidy series (4C-2x/4C-4x and 7D-2x/7D-4x), and a tetraploid plant (C1) produced by selfing 7D-4x. Our results indicate that immediately after polyploidization P. plicatulum suffers genetic rearrangements affecting ~28-38 % of the genome. Band gain and loss were equally prevalent at a statistically significant level. At least 5.62 % of the genome experimented recurrent genetic variation in a non-random basis with a confidence of 94.88 %. A significant proportion of novel bands (36 out of 195; 18.4 %) was detected in the C1 tetraploid plant. Half of these bands were not amplified in either H14-2x or 7D-4x, while the remainders were present in H14-2x but absent in 7D-4x. Our results indicate the occurrence of a considerable number of genetic changes in P. plicatulum immediately after polyploidization, some of which were recurrently detected in different independent events. Moreover, we confirmed that after polyploidization, lost ancestral alleles were spontaneously recovered in further generations, a phenomenon previously reported by other research groups.

Morfogênese de gramíneas nativas do Rio Grande do Sul (Brasil) submetidas a pastoreio rotativo durante primavera e verão

O trabalho objetivou determinar a influência de intervalos de pastoreio rotativo sobre a morfogênese de cinco gramíneas nativas da região central do Rio Grande do Sul (RS), agrupadas segundo uma tipologia funcional, nas estações de primavera e verão. Foram avaliadas taxa de aparecimento, elongação e senescência foliares (TAF/TEF/TSF), filocrono e duração de vida e de elongação foliares (DVF/DEF) em Axonopus affinis, Aristida laevis, Andropogon lateralis, Paspalum notatum e Paspalum plicatulum, sob dois intervalos de pastoreio rotativo, definidos por somas térmicas (°C), 375 e 750 graus-dia, na primavera 2010 e verão 2010/2011. Não houve diferença significativa entre intervalos de pastoreio, mas houve entre espécies e entre estações. Paspalum notatum se destacou por apresentar adaptações bem marcadas ao pastejo. Axonopus affinis e P. notatum foram as espécies com maiores TAF e menores DVF, já A. lateralis apresentou características morfogênicas que contradizem a literatura. Quanto às estações, primavera se caracterizou como a estação de crescimento, e verão, como o início do florescimento. Pastejo afeta a morfogênese de forrageiras, no entanto, os intervalos de pastoreio usados não têm efeito sobre o desenvolvimento das espécies e a influência estacional é marcante no desenvolvimento dessas gramíneas.

Características morfogênicas de gramíneas nativas do Sul do Brasil sob níveis de nitrogênio

Este estudo teve como objetivo avaliar, no outono, as características morfogênicas de oito gramíneas nativas da região central do Rio Grande do Sul, classificadas sob uma tipologia funcional, segundo o teor de matéria seca e a área foliar específica em A, B, C, D: Axonopus affinis (A), Andropogon lateralis (B), Paspalum notatum (B), Paspalum plicatulum (C), Piptochaetium montevidense (C) Aristida laevis (D), Saccharum angustifolius (D) e Sorghastrum pellitum (D); submetidas a dois níveis de nitrogênio (zero e 200kg ha-1 de N). O delineamento experimental foi o inteiramente casualizado com arranjo fatorial 8 (espécies) x 2 (níveis de N) ou 4 (tipos funcionais) x 2 (níveis de N), ambos com três repetições. As plantas foram submetidas a cortes segundo diferentes durações de elongação foliar, definidas por médias das espécies por tipo funcional. As variáveis foram analisadas estatisticamente usando testes de aleatorização com o software MULTIV. Não houve diferença significativa entre os níveis de N, porém houve entre as espécies e entre os tipos funcionais. As variáveis morfogênicas são coerentes com a tipologia funcional utilizada como referência, baseada em atributos foliares. Os níveis de nitrogênio não alteram a morfogênese das espécies na estação do outono, sendo seu uso desaconselhado nesse período.

Morphogenesis of native grasses of Pampa Biome under nitrogen fertilization

Morphogenetic and structural characteristics of the native grasses of the Pampa Biome Andropogon lateralis, Aristida laevis, Axonopus affinis, Erianthus angustifolius, Paspalum notatum, Paspalum plicatulum, Piptochaetium montevidense and Sorghastrum pellitum were evaluated as to the effect of nitrogen (N) fertilization (zero and 100 kg N/ha). The experimental design was of randomized blocks with three replicates in a 8 × 2 (native grasses × N) factorial arrangement. Accumulated thermal sums of 350 and 700 degree days determined the interval between cuts for prostrate and caespitose growth habit species, respectively. Species considered of resource conservation (A. laevis, E. angustifolius, P. plicatulum and S. pellitum) had the highest leaf elongation rate when they received N. For leaf appearance rate, phyllochron, leaf senescence rate, leaf lifespan, number of green leaves and final length of leaf blades, there was difference between the evaluated species.

Interspecific Tetraploid Hybrids between Two Forage Grass Species: Sexual Paspalum plicatulum and Apomictic P. guenoarum

ABSTRACTThe Plicatula group of the grass genus Paspalum contains about 30 species. Most are tetraploid and reproduce by apomixis, though some of them contain sexual diploid races. We crossed a sexual colchicine‐induced autotetraploid plant of brownseed paspalum (Paspalum plicatulum Michx.) with apomictic tetraploid P. guenoarum Arechav., also from the Plicatula group. Crossability was 35% and the progeny showed morphological characteristics intermediate to those of the parents but resembling more the male parent. The random amplified polymorphic DNA (RAPD) analysis showed that the whole progeny amplified bands that were specific of the male parent, confirming its hybrid origin. Meiotic chromosome behavior of hybrids exhibited primarily bivalent and quadrivalent associations similar to those of the two parents. This suggests that natural tetraploid P. guenoarum shares the same basic chromosome set with that of autotetraploid P. plicatulum, and both species probably originate from the same ancestral species. Fourteen out of 23 hybrids reproduced only sexually, while nine were obligate or highly apomictic. Seed set ranged from 11 to 55% among the hybrids. Our results open the possibility of exchanging genes at the tetraploid level in breeding programs of P. plicatulum and P. guenoarum. This possibility is based on their rate of crossability, the degree of fertility among the hybrids, the segregation observed for the reproductive mode in the F1 progeny, and the very simple procedure flow cytometry seed screen (FCSS) used to determine the reproductive mode for each hybrid.

Controle de invasão biológica por capim-anonni em margem viária mediante a introdução de gramíneas

Objetivou-se avaliar o controle da invasão biológica por Eragrostis plana Nees (capim-anonni) em margens de rodovia com a introdução de gramíneas concorrentes associada a práticas de preparo do solo e adubação. O delineamento experimental foi em blocos casualizados com parcelas subdivididas e três repetições. Nas parcelas, foram avaliadas duas práticas de preparo do solo: solo subsolado e gradeado com aplicação de calcário e fósforo; e solo apenas subsolado, e nas subparcelas, as espécies de gramíneas: capim-mombaça (Megathyrsus maximus (Jacq.) B. K. Simon & S. W. L. Jacobs); capim-kazangula (Setaria sphacelata (Schumach.) Stapf & C. E. Hubb. ex M. B. Moss); mistura de sementes de três gramíneas nativas, grama-de-forquilha (Paspalum notatum Alain ex Flüggé), macega-do-banhado (Paspalum regnelli Mez) e capim-das-roças (Paspalum urvillei Steud.); avaliadas em comparação a uma subparcela de exclusão (testemunha). Nos levantamentos florísticos, realizados em 8 de janeiro de 2005, e após o plantio, em 26 de janeiro e 25 de junho de 2006, observou-se alta riqueza florística, com 86 espécies botânicas distribuídas em 29 famílias e 21% de espécies exóticas. O solo subsolado, gradeado, corrigido e adubado, associado às introduções de M. maximus e S. kazungula, foram as alternativas que mais contribuíram para reduzir a cobertura de E. plana. As gramíneas nativas presentes na vegetação do acostamento, Paspalum plicatulum Mitchx, Piptochaetium montevidense (Spreng.) Parodi e a espécie nativa introduzida (Paspalum urvillei) têm potencial para controlar a invasão de E. plana.

Mode of Reproduction of Colchicine‐Induced Paspalum plicatulum Tetraploids

Paspalum plicatulum Michx. is a wild forage grass species. The common races are tetraploid and apomictic, while sexual diploid representatives have been reported sporadically. Objectives of this study were to induce sexual 4x individuals from sexual diploids, determine the capacity for hybridization with other apomictic 4x species closely related with P. plicatulum, and thus create a tetraploid sexual material cross compatible with apomictic 4x species of the Plicatula group of Paspalum. Two induced tetraploid plants were recovered from germinating 2x seeds treated for 24 h with colchicine. Bivalent and quadrivalent chromosomes were the most common association at meiosis in these autotetraploids. Embryological analysis and progeny tests using molecular markers revealed that both induced tetraploids reproduced sexually. Single‐seed screening by flow cytometry confirmed full sexual reproduction. These plants retained the high self‐incompatibility system of the diploids, but set seed after reciprocal crosses and when crossed with pollen of apomictic 4x P. guenoarum Arechav. of the Plicatula group. Both sexual 4x plants constitute the foundational material for plant improvement through gene exchange and selection in apomictic 4x P. plicatulum and possibly in several apomictic species of the Plicatula group.

Effects of Sago Palm Pith as Replacement for Corn Grain on Intake, Rumen Fermentation Characteristics and Microbial N Supply of Cattle Fed Paspalum plicatulum Hay

To investigate the effects of sago palm pith (SPP) substitution of corn in the diets on intake, digestibility, rumen fermentation characteristics, nitrogen balance and microbial N Supply, five ruminally fistulated Southern indigenous cattle (mean initial BW = 226±5 kg) were randomly assigned to a 5x5 Latin Square Design to receive five diets, T 1 = concentrate with 0% SPP, T 2 = 25% SPP, T 3 = 50% SPP, T 4 = 75% SPP and T 5 = 100% SPP, of dietary dry matter, respectively. Plicatulum hay (PH) was offered ad libitum as the roughage. A metabolism trial lasted for 21 days during which liveweight changes and feed intakes were measured. Based on this experiment, there were no significant differences (p>0.05) among treatments groups regarding total DM intake (OMI, NDFI and ADFI) and digestion coefficients of nutrients (DM, OM, CP, NDF and ADF), while total DM intake (% BW) was significantly (p 0.05), whereas NH 3 -N, blood urea nitrogen and molar proportion of propionate concentrations were significantly (p<0.05) higher as higher levels of SPP were incorporated into diets. The amount ofN absorption, N retention and microbial protein synthesis were similar among treatments. These results indicate that SPP can be included in diets for Southern indigenous cattle to supply up to 100% of supplemental corn when fed with PH without negative impact on animal performance and it was a good approach in exploiting the use of local feed resources for beef cattle production.

Comparative studies on dry matter intake, digestibility and nitrogen metabolism between Thai native (TN) and Anglo Nubian × TN bucks

Metabolic experiments were conducted for each Thai native (TN) and Anglo Nubian–TN 50% (AN × TN) bucks, 26.5–38 kg BW and 35–52 months of age, by assigning the following concentrate diets, which had four levels of CP concentrations, T1: 14%, T2: 21%, T3: 28% and T4: 35%, on a DM basis. The animals were fed the concentrates at a rate of 1% of their BW and had ad libitum access to Paspalum plicatulum hay. As the CP level increased, digestibility of CP, N excretion in urine and N retention increased ( P < 0.01). No significant differences of DM digestibility among the CP levels of diet and between the breeds of bucks were observed. The AN × TN had higher DM intake than TN ( P < 0.05, 40.9 g/(kg BW 0.75 day) versus 36.0 g/(kg BW 0.75 day)), thus N intake of AN × TN was higher than that of TN ( P < 0.01, 0.99 g/(kg BW 0.75 day) versus 0.90 g/(kg BW 0.75 day)). Digestibility of CP and blood urea N concentrations of TN were higher than those of AN × TN ( P < 0.05, 69.8% versus 64.0% and 32.2 mg/dl versus 26.7 mg/dl, respectively). The AN × TN tended to retain more N than TN in the higher CP feeding condition of T3 (0.19 g/(kg BW 0.75 day) versus 0.11 g/(kg BW 0.75 day)) and T4 (0.25 g/(kg BW 0.75 day) versus 0.17 g/(kg BW 0.75 day)). Digestibility of NDF and ADF, and TDN of TN were higher than those of AN × TN ( P < 0.05, 61.1% versus 55.9%, 49.6% versus 43.5% and 65.8% versus 62.4%, respectively). The overall mean DE was 109 kcal/(kg BW 0.75 day), and no significant difference of DE among CP levels nor breeds of bucks was observed. Thai native was superior to AN × TN in digestibility of N and fiber fractions at the maintenance level of DE, which might have overcome inferiority of TN to AN × TN in amount of N and energy intake caused by the lower DMI. It is likely that TN goats are well adapted to fodder shortage condition due to their efficient utilization of nutrients.

Levantamento das pastagens naturais da região de Santa Maria-RS, Brasil

Este trabalho foi realizado com o intuito de se obter um levantamento das pastagens naturais da região de Santa Maria, a qual foi subdividida, para este objetivo, em quatro localidades: Dilermando de Aguiar, Pains, Santa Flora e São Martinho. O levantamento utilizou estimativas visuais da freqüência de espécies através do método BOTANAL e permitiu a identificação de 61 espécies, dentre as quais 45 apresentaram contribuição significativa para a biomassa aérea da vegetação. No distrito de Pains, encontrou-se maior freqüência das espécies Axonopus affinis, Eragrostis plana, Desmodium barbatum e Aristida spp.. Em Dilermando de Aguiar, houve maior contribuição de Calamagrostis viridiflavescens, Schizachyrium microstachyum e Paspalum notatum a qual foi, também, uma espécie abundante em Santa Flora, assim como Desmodium incanum. As espécies mais freqüentes em São Martinho foram: Baccharis trimera, Paspalum plicatulum e Erianthus angustifolius. O teste de aleatorização mostrou que, em todas as localidades, ocorreu diferença significativa na sua composição florística (P= 0,0058), evidenciando a inexistência de associação entre os tipos fisionômico-florísticos e os tipos de solo. A partir disto, este levantamento permite que se estabeleçam prioridades quanto à pesquisa e manejo das pastagens naturais dos diferentes grupos fisionômico-florísticos da região.

Sweating of panicoid tropical pasture grass seeds

Sweating, the practice of holding freshly cut seed heads of tropical pasture grasses in covered heaps for periods of about three days before separating and drying the seed, was investigated. Its course was recorded with seed crops of various cultivars of Panicum maximum, Setaria sphacelata, Brachiaria decumbens. Paspalum plicatulum and Urochloa mosambicensis. Seed viability, genmination, dormancy and storage characteristics were compared with the equivalent properties of seed that had not been sweated. Temperatures inside sweating heaps rose rapidly over the first day to a peak that often exceeded 50°C, probably due to the respiration of the still metabolically active seed. Temperatures than declined, but tended to rise again later as fungal activity increased. Carbon dioxide levels in the internal atmosphere rose as high as about 20% and oxygen tended to be depleted. Sweating hastened abscission, with over 80% of pure seed being detached within 3 days. Seed remaining attached was mostly immature and inferior. Sweated seed was normally of superior quality to seed that had been quickly dried immediately after harvest, but did not differ consistently from unsweated seed that load been kept moist but well-ventilated for three days before active drying was begun. Contrary to common belies sweating neither broke dormancy nor led to accelerated deterioration in subsequent storage Sweating conditions are inherently variable and, taken to extremes, may damage seed. For example, deliberate prevention of gas exchange rapidly caused tolyl seed death, as did spontaneous healing to greater than 60°C of unventilated combine-harvested seed. Nevertheless, it conducted with care, sweating provides a valuable alternative to machine-threshing in minimally mechanised or small scale seed harvesting systems and can be practised without measurable detriment to seed quality.

Cerebella andropogonis . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Cerebella andropogonis . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Although Cerebella andropogonis apparently produces a disease in spikelets of grasses, it is actually a saprobe on sugary secretions of members of the ascomycete family Clavicipitaceae , and therefore by itself not a real trouble for the plants on which it grows. HOSTS: Parasitic on members of the Clavicipitaceae ( Claviceps maximus, C. paspali, Claviceps sp.) growing on the following grasses: Andropogon annulatus, Andropogon sp., Anthaenantia sp., Anthisteria sp., Cenchrus sp., Cynodon sp., Dichantium annulatum, Digitaria sp., Heteropogon sp., Hyparrhenia sp., Ischaemum sp., Melinus minutiflorus, Molinia sp., Panicum maximum, P. purpurascens, Panicum sp., Paspalum plicatulum, Paspalum sp., Setaria sp., Sorghastrum sp., Sorghum sp., Spartina sp., Tricholaena sp., Trichopteryx sp. ( Gramineae ). GEOGRAPHICAL DISTRIBUTION: Cosmopolitan. AFRICA: Ghana [as Gold Coast], Kenya, Malawi, Mauritius, Senegal [as French West Africa], Sierra Leone, South Africa, Sudan, Tanzania, Uganda. NORTH AMERICA: USA. CENTRAL AMERICA: Cuba, Dominican Republic, Jamaica, Puerto Rico. SOUTH AMERICA: Brazil, Colombia, Paraguay, Venezuela (LANGDON, 1955). ASIA: Myanmar [as Burma], Sri Lanka, India, Philippines. AUSTRALASIA: Australia, Papua New Guinea. TRANSMISSION: By air-borne conidia.

The Importance of Neighbors, Soil pH, Phosphorus, and Nitrogen for the Growth of Two C4Grasses

In the coastal prairies of Texas, C4 grasses dominate. However, reasons for spatial differences in composition of these prairies are uncertain, and the reasons for codominance of Schizachyrium scoparium and Paspalum plicatulum are unexplained. We completed a greenhouse experiment that examined the effects of neighbors, soil pH, added P, and N on the growth of P. plicatulum and S. scoparium, two C4 grasses. Intraspecific competition was essentially equal to interspecific competition, and soil factors seem to control dry mass of these two species. For P. plicatulum, addition of P to native soil increased above- and belowground dry mass 1.8-2.5 times, while P and N together increased dry mass 2.9-6.5 times. The response was pH dependent, with the greatest dry mass at low pH. Root: shoot ratios changed from 0.3 to ca. 1.0 as the pH decreased in native soil regardless of the P level. When N was added, ratios were ca. 0.3 across all pH and P treatments. For S. scoparium in native soil, there was little change in aboveground dry mass when P was added; however, belowground dry mass was augmented 1.5-1.9 times, with the greatest dry mass at pH 7.0. Additions of P and N increased aboveground dry mass 2.2-2.7 times, with the greatest dry mass at pH 7.0. N additions caused reductions of 79%-89% in belowground dry mass compared with that of native soil, at all levels of P and pH. Root: shoot ratios were 5-10 times higher in the native soil compared with N addition treatments and increased to 1.0 as pH decreased. Ratios were about 15% higher with P added to native soil and remained constant at ca. 0.1 in all the N addition treatments. These two C4 grasses seem to be competitively equal. Their growth was not determined by the presence of neighbors but by levels of soil resources and soil pH.

Cytoembryology of Paspalum chaseanum and Sexual Diploid Biotypes of Two Apomictic Paspalum Species

This study was undertaken to determine the cytology, method of reproduction, and flowering behaviour of three Paspalum species. Paspalum plicatulum has long been considered a segmental allotetraploid that reproduces by obligate apomixis with the type being apospory followed by pseudogamy. Paspalum simplex is an apomictic autotetraploid species, while P. chaseanum is a rare species for which no information regarding cytology and reproduction is available. This investigation concerns diploid cytotypes (2n = 2x = 20) of P. plicatulum and P. simplex that were recently collected in subtropical South America. In addition, two accessions of P. chaseanum were also recorded and both had 2n = 2x = 20 chromosomes. Meiosis showed regular bivalent chromosome pairing. Embryological observations indicated that the three species reproduce sexually at the diploid level. Pollen–pistil interaction following self-pollination suggested the presence of a self-incompatibility system responsible for allogamy. The results indicate that P. plicatulum and P. simplex complexes consist of diploid sexual allogamous cytotypes in addition to the known tetraploid apomictic cytotypes. Diploid strains constitute a source of sexuality for plant improvement. Chromosome doubling will likely produce sexual tetraploids to be used as females in crosses with natural apomictic tetraploid biotypes. Since diploid self-incompatible sexual Paspalum plants usually have apomictic tetraploid co-specific counterparts, the self-incompatible diploid P. chaseanum described in this study warrants further exploration for its apomictic counterpart.

Effects of Phosphate Concentration and Soil pH on the Growth of Schizachyrium scoparium and Paspalum plicatulum, Two Co-Occurring C 4 Grasses

Effects of Phosphate Concentration and Soil pH on the Growth of Schizachyrium scoparium and Paspalum plicatulum, Two Co-Occurring C 4 Grasses