Development of plastids in pollen and tapetum of rye-grass, Lolium perenne L

Proplastids of both tapetal cells and microsporocytes were present early in anther development. Tapetal proplastids differentiated—probably into elaioplasts—at late microspore stage. The tapetal cytoplasm was completely resorbed by early tricellular pollen stage. Microspore proplastids differentiated into amyloplasts at early bicellular stage, and were present in both vegetative and generative cells. In the generative cell, the amyloplasts were ephemeral and apparently degenerated within autophagic vacuoles. Plastids were absent from sperm cells. Vegetative cell amyloplasts increased in number apparently by fission such that one amyloplast produced one amyloplast and one proplastid per division. Mature pollen grains were estimated to contain between 550 and 820 amyloplasts with only one starch granule per plastid.

Comportamento ingestivo e produção de cordeiros em pastagem de azevém anual (Lolium multiflorum Lam.) manejada em diferentes alturas

Realizou-se um experimento na Estação Experimental Agronômica - UFRGS, Eldorado do Sul, objetivando avaliar o desempenho de cordeiros e o seu comportamento ingestivo em pastagem de azevém anual (Lolium multiflorum Lam), estabelecidas por semeadura direta e mantidas em diferentes alturas. O delineamento experimental utilizado foi o de blocos completamente casualizados com quatro tratamentos (5, 10, 15 e 20 cm de altura) e 3 repetições. Foram utilizados cordeiros inteiros em pastejo contínuo com lotação variável. As alturas foram mensuradas através de um bastão medidor graduado. Avaliaram-se parâmetros de desempenho individual dos animais e ganho por área. O comportamento ingestivo dos animais foi determinado através do registro do tempo de pastejo, ruminação e descanso em três ocasiões. As taxas de acúmulo de matéria seca foram estimadas por gaiolas. Amostras de 0.25m2 foram cortadas para estimar a massa de lâminas foliares verdes, colmo, e material senescente. O experimento foi dividido em dois períodos: o período 1, compreendido entre o início do experimento até 14/09, quando as alturas pretendidas estabilizaram-se, e o período 2, compreendido entre os dias 15/09 e 11/11. Os parâmetros de desempenho, por área e por animal, não se mostraram significativos no período 1. O oposto ocorreu no período 2, em que todos os parâmetros de produção, tanto da pastagem quanto animal, mostraram-se significativos resultando em modelos quadráticos em relação à altura da pastagem. As diferentes alturas em que a pastagem foi mantida afetaram a sua produtividade, bem como sua estrutura, o que influenciou diretamente o comportamento ingestivo dos animais.

Efeito de herbicidas na dessecação e germinação de sementes remanescentes de Lolium multiflorum L.

A trial was carried out to evaluate efficacy of different herbicides and spray volumes when sprayed to ryegrass for chemical management and control of remaining seeds. The treatments were: three formulations of glyphosate at 1080 g ha(-1) (Original Round up, Round up Transorb, WG Round Up), paraquat + diuron at 300+500 and 150+250 g ha(-1) and glufosinate ammonium at 400 and 600 g ha(-1). All treatments were used in spray volumes of 200 and 400 l ha(-1). The effectiveness of the desiccation of ryegrass plants was assessed at 1, 3, 7, 14 and 21 days after application. At the last evaluation samples were collected for dry mass production analysis, and also panicles with seeds for germination test. Glyphosate in different formulations and volumes and glufosinate ammonium at 600 g ha(-1) when sprayed with into 400 l ha(-1) provided the best controls regarding ryegrass chemical management. Treatments with gliphosate (Roundup Original) and paraquat + diuron (300 +150 g ha(-1)) in volumes of 400 and 200 L ha(-1), respectively, were the ones that showed the lowest values of dry matter, differing from the control. All the ryegrass seeds were killed by treatments with herbicides (paraquat + diuron) at 500 + 250 g ha(-1) and glufosinate-ammonium at 600 g ha(-1) when used 200 l ha(-1).

Avaliação do controle de azevém (Lolium multiflorum) nas condições de cana crua em Louisiana/EUA e dinâmica dos herbicidas na palha

Pós-graduação em Agronomia (Agricultura) - FCA

Influência do glyphosate no perfil bioquímico e fisiológico de populações de azevém (Lolium multiflorum) suscetíveis e resistentes ao herbicida

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Manejo de azevém (Lolium multiflorum Lam.) resistente ao glyphosate com o uso de diferentes herbicidas

Pós-graduação em Agronomia (Proteção de Plantas) - FCA

Leaves of Lolium multiflorum 'Lema' and tropical tree species as biomonitors of polycyclic aromatic hydrocarbons

This study extends the current knowledge regarding the use of plants for the passive accumulation of anthropogenic PAHs that are present in the atmospheric total suspended particles (TSP) in the tropics and sub-tropics. It is of major relevance because the anthropic emissions of TSP containing PAHs are significant in these regions, but their monitoring is still scarce. We compared the biomonitor efficiency of Lolium multiflorum 'Lema' and tropical tree species (Tibouchina pukka and Psidium guajava 'Paluma') that were growing in an intensely TSP-polluted site in Cubatao (SE Brazil), and established the species with the highest potential for alternative monitoring of PAHs. PAHs present in the TSP indicated that the region is impacted by various emission sources. L. multiflorum showed a greater efficiency for the accumulation of PAH compounds on their leaves than the tropical trees. The linear regression between the logBCF and logKoa revealed that L. multiflorum is an efficient biomonitor of the profile of light and heavy PAHs present in the particulate phase of the atmosphere during dry weather and mild temperatures. The grass should be used only for indicating the PAHs with higher molecular weight in warmer and wetter periods. (C) 2012 Elsevier Inc. All rights reserved.

Analysis of the chlorophyll catabolism pathway in leaves of an introgression senescence mutant of Lolium temulentum

igments, proteins and enzyme activity related to chlorophyll catabolism were analysed in senescing leaves of wild-type (WT) Lolium temulentum and compared with those of an introgression line carrying a mutant gene from stay-green (SG) Festuca pratensis. During senescence of WT leaves chlorophylls a and b were continuously catabolised to colourless products and no other derivatives were observed, whereas in SG leaves there was an accumulation of dephytylated and oxidised catabolites including chlorophyllide a, phaeophorbide a and 132 OH-chlorophyllide a. Dephytylated products were absent from SG leaf tissue senescing under a light-dark cycle. Retention of pigments in SG was accompanied by significant stabilisation of light harvesting chlorophyll-proteins compared with WT, but soluble proteins such as Rubisco were degraded during senescence at a similar rate in the two genotypes. The activity of phaeophorbide a oxygenase measured in SG tissue at 3d was less than 12% of that in WT tissue at the same time-point during senescence and of the same order as that in young pre-senescent WT leaves, indicating that the metabolic lesion in SG concerns a deficiency at the ring-opening step of the catabolic pathway. In senescent L. temulentum tissue two terminal chlorophyll catabolites were identified with chromatographic characteristics that suggest they may represent hitherto undescribed catabolite structures. These data are discussed in relation to current understanding of the genetic and metabolic control of chlorophyll catabolism in leaf senescence.

Efecto fitotóxico de Baccharis ulicina sobre la germinación y crecimiento inicial de Avena sativa, Lolium perenne y Raphanus sativus

Baccharis ulicina es una maleza ampliamente distribuida en los pastizales de la zona semiárida argentina. A fin de evaluar sus posibles efectos alelopáticos, se utilizaron extractos acuosos de B. ulicina (hoja, tallo, raíz y planta entera) a dos concentraciones (50 y 150 g tejido/L agua) sobre la germinación y crecimiento inicial de Avena sativa, Lolium perenne y Raphanus sativus. Para cada especie se regaron 100 semillas y se mantuvieron a 25°C y oscuridad. Se registraron la germinación de las semillas y la longitud de coleóptilo / hipocótile (C/H) y radícula (R). Con los datos obtenidos se determinó: porcentaje de germinación, coeficiente de velocidad de germinación, vigor de la germinación, inhibición de la germinación, inhibición de la longitud de la radícula y del coleóptilo / hipocótile e índice de vigor de radícula y de coleóptilo / hipocótile. Los extractos con alta concentración redujeron la germinación en promedio 65% mientras que inhibieron la longitud en 58,8% (C/H) y 93,3% (R) para A. sativa; 71,5% (C/H) y 87,9% (R) para L. perenne, y 93,8% (C/H) y 94,5% (R) para R. sativus. Se registró un evidente efecto fitotóxico de B. ulicina sobre las especies evaluadas, indicando que la alelopatía sería una estrategia ecológica de la especie.

Long-Day Up-Regulation of a GAMYB Gene during Lolium temulentum Inflorescence Formation

Long-day exposure of the grass Lolium temulentum may regulate flowering via changes in gibberellin (GA) levels. Therefore, we have examined both GA levels and expression of a MYB transcription factor that is specific to the GA signal transduction pathway in monocots. This MYB gene from L. temulentum shows over 90% nucleotide identity with the barley and rice GAMYB genes, and, like them, gibberellic acid (GA3) up-regulates its expression in the seed. Furthermore, cDNAs of both the barley and L. temulentum GAMYB show the same simple patterns of hybridization with digests of L. temulentum genomic DNA. Compared with vegetative shoot apices of L. temulentum, the in situ mRNA expression of LtGAMYB does not change during the earliest steps of “floral” initiation at the apex. However, by 100 h (the double-ridge stage of flowering) its expression increased substantially and was highest in the terminal and lateral spikelet sites. Thereafter, expression declined overall but then increased within stamen primordia. Prior to increased LtGAMYB expression, long-day exposure sufficient to induce flowering led to increased (5- to 20-fold) levels of GA1 and GA4 in the leaf. Thus, increases first in GA level in the leaf followed by increased expression of LtGAMYB in the apex suggest important signaling and/or response roles in flowering.

A taxonomic revision of the genus Lolium,

Bibliography: p. 44-45.

Rhizodeposits of Trifolium pratense and Lolium perenne: Their comparative effects on 2,4-D mineralization in two contrasting soils

Rhizosphere enhanced biodegradation of organic pollutants has been reported frequently and a stimulatory role for specific components of rhizodeposits postulated. As rhizodeposit composition is a function of plant species and soil type, we compared the effect of Lolium perenne and Trifolium pratense grown in two different soils (a sandy silt loam: pH 4, 2.8% OC, no previous 2,4-D exposure and a silt loam: pH 6.5, 4.3% OC, previous 2,4-D exposure) on the mineralization of the herbicide 2,4-D (2,4-dichlorophenoxyacetic acid). We investigated the relationship of mineralization kinetics to dehydrogenase activity, most probable number of 2,4-D degraders (MPN2,4-D) and 2,4-D degrader composition (using sequence analysis of the gene encoding alpha-ketoglutarate/2,4-D dioxygenase (tfdA)). There were significant (P < 0.01) plant-soil interaction effects on MPN2,4-D and 2,4-D mineralization kinetics (e.g. T pratense rhizodeposits enhanced the maximum mineralization rate by 30% in the acid sandy silt loam soil, but not in the neutral silt loam soil). Differences in mineralization kinetics could not be ascribed to 2,4-D degrader composition as both soils had tfdA sequences which clustered with tfdAs representative of two distinct classes of 2,4-D degrader: canonical R. eutropha JMP134-like and oligotrophic alpha-proteobacterial-like. Other explanations for the differential rhizodeposit effect between soils and plants (e.g. nutrient competition effects) are discussed. Our findings stress that complexity of soil-plant-microbe interactions in the rhizosphere make the occurrence and extent of rhizosphere-enhanced xenobiotic degradation difficult to predict.