Seasonal variation of soluble carbohydrates and starch in Echinolaena inflexa, a native grass species from the Brazilian savanna, and in the invasive grass Melinis minutiflora

Echinolaena inflexa (Poir.) Chase is an abundant C3 grass species with high biomass production in the Brazilian savanna (cerrado); Melinis minutiflora Beauv. is an African C4 forage grass widespread in cerrado and probably displacing some native herbaceous species. In the present work, we analysed seasonally the content and composition of soluble carbohydrates, the starch amounts and the above-ground biomass (phytomass) of E. inflexa and M. minutiflora plants harvested in two transects at 5 and 130 m from the border in a restrict area of cerrado at the Biological Reserve and Experimental Station of Mogi-Guaçu (SP, Brazil). Results showed that water soluble carbohydrates and starch amounts from the shoots of both species varied according to the time of the year, whilst in the underground organs, variations were observed mainly in relation to the transects. Marked differences in the pattern of the above-ground biomass production between these two grasses relative to their location in the Reserve were also observed, with two peaks of the invasive species (July and January) at the Reserve border. The differences in carbohydrate accumulation, partitioning and composition of individual sugars concerning time of the year and location in the Reserve were more related to the annual growth cycle of both grasses and possibly to specific physiological responses of M. minutiflora to disturbed environments in the Reserve border.

Silicon distribution and accumulation in shoot tissue of the tropical forage grass Brachiaria brizantha

Silicon (Si) accumulation in organs and cells is one of the most prominent characteristics of plants of the family Poaceae. Many species from this family are used as forage plants for animal feeding. The present study investigates in Brachiaria brizantha (Hochst. ex A. Rich.) Stapf. cv. Marandu: (1) the dry matter production and Si content in shoot due to soil Si fertilizations; (2) the Si distribution among shoot parts; and (3) the silica deposition and localization in leaves. Plants of B. brizantha cv. Marandu were grown under contrasting Si supplies in soil and nutrient solution. Silica deposition and distribution in grass leaf blades were observed using light microscope and scanning electron microscope equipped with an energy dispersive X-ray spectrometer (SEM-EDXS). Silicon concentration in the B. brizantha shoot increased according to the Si supply. Silicon in grass leaves decreased following the order: mature leaf blades > recently expanded leaf blades > non-expanded leaf blades. Silicon accumulates mainly on the upper (adaxial) epidermis of the grass leaf blades and, especially, on the bulliform cells. The Si distribution on adaxial leaf blade surface is non uniform and reflects a silica deposition exclusively on the cell wall of bulliform cells.

Seed dormancy mechanisms in warm season grass species

Available evidence suggests that there are at least two locations for dormancy mechanisms in primary dormant seeds: mechanisms based within the embryo covering structures, and mechanisms based within the embryo. Mechanisms within the covering structures may involve mechanical, permeability and chemical barriers to germination. Mechanisms within the embryo may involve the expression of certain genes, levels of certain plant growth regulators, the activity of important respiratory pathways or the mobilisation and utilisation of food reserves. In addition, some embryos may be too immature to germinate immediately and must undergo a further growth phase before germination is possible. An individual species could have one or several of these various dormancy mechanisms and these mechanisms need to be understood when selecting treatments to overcome dormancy. The way in which certain dormancy breaking agents are thought to work is discussed and practical applications of such agents in field situations are explained.

Effect of nitrogen fertilization, grass species and cultivar on sod production on Valkeasuo peat bog - a case study

Selostus: Typpilannoituksen, kasvilajin ja lajikkeen vaikutus siirtonurmikon tuotanto-ominaisuuksiin Valkeasuon turvetuotannon jättöalueella

Recovery of Trichostrongylus colubriformis infective larvae from three grass species contaminated in the autumn

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relationships between functional traits and inorganic nitrogen acquisition among eight contrasting European grass species

Backgrounds and Aims Leaf functional traits have been used as a basis to categoize plants across a range of resource-use specialization, from those that conserve available resources to those that exploit them. However, the extent to which the leaf functional traits used to define the resource-use strategies are related to root traits and are good indicators of the ability of the roots to take up nitrogen (N) are poorly known. This is an important question because interspecific differences in N uptake have been proposed as one mechanism by which species coexistence may be determined. This study therefore investigated the relationships between functional traits and N uptake ability for grass species across a range of conservative to exploitative resource-use strategies.Methods Root uptake of NH4+ and NO3-, and leaf and root functional traits were measured for eight grass species sampled at three grassland sites across Europe, in France, Austria and the UK. Species were grown in hydroponics to determine functional traits and kinetic uptake parameters (Imax and Km) under standardized conditions.Key Results Species with high specific leaf area (SLA) and shoot N content, and low leaf and root dry matter content (LDMC and RDMC, respectively), which are traits associated with the exploitative syndrome, had higher uptake and affinity for both N forms. No trade-off was observed in uptake between the two forms of N, and all species expressed a higher preference for NH4+.Conclusions The results support the use of leaf traits, and especially SLA and LDMC, as indicators of the N uptake ability across a broad range of grass species. The difficulties associated with assessing root properties are also highlighted, as root traits were only weakly correlated with leaf traits, and only RDMC and, to a lesser extent, root N content were related to leaf traits.

Index to grass species,

Mode of access: Internet.

The invasion risk in the Pacific Northwest of two closely related grass species in the Genus Cortaderia

Thesis (Master's)--University of Washington, 2016-08

The superior re-sprouting performance of exotic grass species under different environmental conditions: the study case of Paspalum atratum (Swallen) and Urochloa brizantha (Hochst. ex A. Rich. - Stapf.).

2016

Sulphuric acid scarification effects on Brachiaria brizantha, B. humidicola and Panicum maximum seed dormancy release

Most tropical forage grass species have dormant seeds, which reduce percentages in germination tests. The objective of this study was to evaluate H2SO4 scarification effects on seed dormancy releasing, through germination time (T50) and variability among germination test replicates, in 630, 94 and 82 seed samples of B. brizantha, B. humidicola and P. maximum, respectively, tested at the Central Seed Testing Laboratory, Campinas, Brazil, from 1991 to 1999. Germination tests used two 4 x 100 replicates of intact and scarified seeds (15-, 10-, 5-minute treatments, respectively). Mean germination time (T50) and variability among germination replicates were also analysed. Statistical analysis was performed by t-test paired samples for means. Scarification promoted general decreases in T50, while variability among germination test replicates was reduced in B. brizantha. Scarification increase germination in B. brizantha and P. maximum, but is deleterious in B. humidicola.

Recuperação de larvas de Trichostrongylus colubriformis em diferentes estratos de Brachiaria decumbens E Panicum maximum

The purpose of the experiment was to evaluate infective Trichostrongylus colubriformis larvae vertical migration in two forage grass species. Experimental modules formed by eight plots, established with Brachiaria decumbens cv. Australian and Panicum maximum cv. Aruana, were used in the study, totaling four plots for each grass species. Each plot was divided into six 30 x 30 cm subplots. Larval migration was evaluated in the four seasons of the year, in different plant strata (0-7, 7-14, 14-21, 21-28 and above 28 cm). Four feces deposits were made, one in each season of the year, in the middle of 30-cm tall forage. The feces were collected from the forage ten days after each feces deposit in the experimental subplots. Grass height was measured in each of the strata immediately before the collections. The forage of the different strata was cut from an area measuring 10-cm in radius. The feces were collected manually from the subplots. There was a grass species and grass stratum interaction in the deposit made in autumn (P < 0.05). During that season, most of the larvae were recovered from the Brachiaria grass base; meanwhile, at the forage apex, the biggest average was registered in the aruana grass. Infective larvae (U) recovery was similar among the different strata during spring. In springtime, the biggest L3 recovery occurred at the 21-28 cm stratum from both forage species. No L3 was recovered from any of the No L3 was recovered from any of the grass strata during winter and summer. Study results show that migration of T colubriformis larvae was more influenced by weather conditions Than by forage species.

Sobrevivência e migração vertical de larvas infectantes de Trichostrongylus colubriformis em gramíneas, nas diferentes estações do ano

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)