Dead Stem Research Articles

Effect of antimicrobial compounds on cut Gerbera flowers: Poor relation between stem bending and numbers of bacteria in the vase water

Gerbera flowers (Gerbera jamesonii) often show stem bending. In four cultivars (Tamara, Liesbeth, Cora, and Mickey), we tested the effects on bending of antimicrobial compounds (chlorine bleach, a slow release chlorine compound, 8-hydroxyquinoline citrate [HQC], silver nitrate, carvacrol and thymol), some combined with sugars. At concentrations used for other cut flowers, inclusion in the vase solution of several of the antimicrobial compounds delayed bending, had no effect, or hastened bending. Hastening of bending was found at higher concentrations. It was accompanied with visible damage on the stem ends. Results with HQC indicated high toxicity as it did not delay bending at any of the concentration tested (100–400mgL−1). At 200mgL−1 HQC induced growth of bacteria that were not found in the controls. The number of bacteria in the vase water showed a low correlation with bending. Visible toxicity on the stem surface was often associated with a high bacteria count. However, at relatively high concentrations of the antimicrobial compounds stem bending was associated with a low count. This indicated an effect other than bacteria. Water uptake was low in stems that bent early. It is hypothesized that material from dead stem cells resulted in a xylem blockage which led to early bending. Sucrose at 15gL−1 in combination with an antimicrobial compound (slow release chlorine, HQC) resulted in the absence of stem damage and produced much less bending than the same concentration of the antimicrobial compounds alone. Sucrose apparently counteracted the toxic effects of the antimicrobial chemicals.

Temporal changes in stem decay and dead and sound wood volumes in the northeastern Canadian boreal forest

Yield tables used for stand-level predictions of standing volume typically do not account for the presence of dead trees and stem decay. Yet, recently dead trees, referred to as dead and sound wood (DSW), could be considered as a valuable supplemental wood source. Conversely, stem decay can cause important losses during product recovery. Accordingly, the general objective of this study was to characterize the patterns of change of stem decay and of DSW as functions of time since the last fire (TSF). The amount of stem decay and of DSW per tree species were measured in two chronosequences of 30 stands each, covering more than 1000 years in the northeastern Canadian boreal forest. Stand-level decay volume increased during the first 150 years following fire and then stabilized. This volume was mainly composed of black spruce (Picea mariana (Mill.) BSP) when TSF <200 years and of balsam fir (Abies balsamea (L.) Mill.) when TSF >200 years. Conversely, the volume of DSW declined rapidly after fire and increased gradually from about 200 years TSF. Hence, the loss of wood volume attributable to stem decay in old-growth stands was cancelled out by the increased availability of DSW, with a slightly positive balance of 3.5 m3/ha. This could be significant considering the large amount of old-growth stands in this part of the boreal forest.

PolydomousCrematogaster pilosa(Hymenoptera: Formicidae) Colonies Prefer Highly Connected Habitats in a Tidal Salt Marsh

High productivity in salt marshes creates an attractive resource base for terrestrial consumers, but regular tidal inundation creates a harsh environment. numerous terrestrial organisms have adapted to living in salt marshes by timing activity cycles and vertical movements to tidal cycles, while others exhibit physiological adaptations, increasing their tolerance to submersion (Foster 1983; Vaughn & Fisher 1992; petillon et al. 2009). one of the species able to withstand these harsh conditions is the ant Crematogaster pilosa (emery) (Hymenoptera: Formicidae), which has been reported to nest in hollow stems of salt marsh vegetation ranging from Florida to north carolina (davis & gray 1966; mccoy & rey 1987), as well as in trees in mesic forests and within stems of upland plants (teal 1962; Johnson 1988; morgan 2010). little is known about C. pilosa (synonymous with C. clara; Johnson 1988) with the exception of its flexible habitat requirements. the objective of this study was to examine the basic colony attributes and habitat preferences of C. pilosa in a saltmarsh cordgrass [Spartina alterniflora loisel (poales: poaceae)] dominated salt marsh on sapelo island, georgia. connectivity in the S. alterniflora canopy, dead and living stem densities, and maximum stem height were evaluated to examine the influence of habitat structure on ant densities. in october 2011, two marsh transects stretching from the forest edge to the bank of a large tidal creek were demarcated and divided into fourteen 10 × 2 m sections. ant density was sampled in 4 randomly selected 2 m2 quadrats per section by sweep netting for 15 seconds. percent vegetation cover was estimated from photographs taken from ground level and converted to binary sky/ vegetation images using imageJ software. living and dead stem density and tallest stem height were measured in 4 haphazardly placed quadrats (0.25 m2) within a subset of 9 sections. Workers from 15 nests were enumerated, and the presence of eggs or pupae was recorded. to evaluate tidal inundation relative to nest height, 5 fence posts with cups attached at 5 cm intervals covering the lower range of observed nest heights were deployed. Flooded cups were recorded daily for 4 days, which included some of the highest local tides of 2011. the spatial extent and number of colonies examined in this study are small, limiting the potential for generalization to other colonies and habitats. square-root transformed ant densities showed a positive correlation with percent vegetation cover (Fig. 1) when data were averaged over 20 m2 transect sections (r2 = 0.50, p = 0.003). no relationship was found between ant density and living stem density (r2 = 0.21, p = 0.22), dead stem density (r2 = 0.06, p = 0.53), or tallest stem height (r2 = 0.10, p = 0.42). mean nesting stem and entrance heights were 44.6 cm (sd = 14.4) and 35.3 cm (sd = 10.6), respectively. the maximum observed tidal height from substrate was less than 20 cm, and minimum nest entrance height was 21 cm (Fig. 2). nests averaged 242 workers (range: 53-1106, sd = 276), which is conservative because some workers were foraging at the time of collection. eggs and pupae were found in 87% and 46% of the nests, respectively. Workers were observed traveling and carrying eggs among 21 nests within

Allometric Equations for Estimating Carbon Stocks in Natural Forest in New Zealand

Species-specific and mixed-species volume and above ground biomass allometric equations were developed for 15 indigenous tree species and four tree fern species in New Zealand. A mixed-species tree equation based on breast height diameter (DBH) and tree height (H) provided acceptable estimates of stem plus branch (>10 cm in diameter over bark) volume, which was multiplied by live tree density to estimate dry matter. For dead standing spars, DBH, estimated original height, actual spar height and compatible volume/taper functions provided estimates of dead stem volume, which was multiplied by live tree density and a density modifier based on log decay class from field assessments to estimate dry matter. Live tree density was estimated using ratio estimators. Ratio estimators were based on biomass sample trees, and utilized density data from outerwood basic density surveys which were available for 35 tree species sampled throughout New Zealand. Foliage and branch ( < 10 cm in diameter over bark) dry matter were estimated directly from tree DBH. Tree fern above ground dry matter was estimated using allometric equations based on DBH and H. Due to insufficient data, below ground carbon for trees was estimated using the default IPCC root/shoot ratio of 25%, but for tree ferns it was estimated using measured root/shoot ratios which averaged 20%.

Valor nutritivo de perfilhos e componentes morfológicos em pastos de capim-braquiária diferidos e adubados com nitrogênio

Este trabalho foi realizado com o objetivo de avaliar o valor nutritivo de perfilhos e componentes morfológicos em pastos diferidos e adubados com nitrogênio de Brachiaria decumbens cv. Basilisk. Dois experimentos foram realizados em delineamento de blocos casualizados com três repetições e esquema de parcela subdivida. No primeiro experimento, foram realizadas combinações entre doses de nitrogênio (0, 40, 80 e 120 kg/ha) com os componentes morfológicos (folha verde, colmo verde, folha morta e colmo morto) ou com as categorias de perfilhos (vegetativo e reprodutivo) do pasto. No segundo experimento, estudaram-se as combinações entre períodos de diferimento (73, 95 e 116 dias) com categorias de perfilhos (vegetativo e reprodutivo). A adubação nitrogenada aumentou o percentual de fibra em detergente neutro (FDN) nos colmos verdes e o teor de proteína bruta (PB) nas folhas verdes e mortas e no colmo verde. Elevou também os percentuais de PB nos perfilhos vegetativos e reprodutivos, assim como o teor de FDN do perfilhos vegetativos. Maior período de diferimento causou acréscimo no percentual de FDN e redução no percentual de proteína bruta nos perfilhos vegetativos e reprodutivos. A dose de nitrogênio e o período de diferimento alteram o valor nutritivo dos componentes morfológicos e dos perfilhos dos pastos de B. decumbens cv. Basilisk. No diferimento da pastagem, ações de manejo que resultem em maiores percentuais de lâmina foliar verde e perfilho vegetativo no pasto contribuem para melhorar o valor nutritivo da forragem diferida.

Estrutura do capim-braquiária durante o diferimento da pastagem

This experiment was performed aiming to evaluate tiller population density, forage mass and its morphological components on pastures of Brachiaria decumbens cv. Basilisk. during deferment. The treatments encompassed four deferred grazing periods (18, 46, 74 and 121 days). A randomized block design with two replications was used. The numbers of vegetative tillers (VT), reproductive tillers (RT) and dead tillers (DT) in the pasture were determined. The masses of green leaf blade (GLBM), dead stem (DSM) and dead forage (DFM) were also determined. There was a reduction in the number of VT (from 1,491 to 944 tiller m-2) during the deferment period. RT and DT numbers were not influenced by the deferment periods. Their averages were 211 and 456 tiller m-2, respectively. Longer deferring periods resulted in an increase in GSM (from 2,965 to 4,877 kg ha-1 of dry mass) and DFM (from 2,324 to 4,823 kg ha-1 of dry mass), but it did not influence GLBM (average of 2,047 kg ha-1 of dry mass). In Viçosa, Minas Gerais State, Brazil, Brachiaria decumbens cv. Basilisk pasture fertilized and deferred in the beginning of March must be kept deferred for about 70 days in order to conciliate both quality and quantity forage production.

Correlações entre número de perfilhos, índice de tombamento, massa dos componentes morfológicos e valor nutritivo da forragem em pastos diferidos de capim-braquiária

Objetivou-se avaliar correlações entre características estruturais e valor nutritivo do pasto diferido de U. decumbens cv. Basilisk. O experimento foi realizado em esquema de parcelas subdivididas, segundo o delineamento em blocos casualizados, com duas repetições. Os tratamentos foram combinações dos períodos de diferimento da pastagem (73, 103, 131 e 163 dias) com os períodos de pastejo (1, 29, 57 e 85 dias). A massa de lâmina foliar verde correlacionou-se positivamente com os percentuais de proteína bruta (PB), fibra em detergente neutro potencialmente digestível (FDNpoD) e matéria seca potencialmente digestível (MSpoD), mas negativamente com os teores de fibra em detergente neutro (FDN) e FDN indigestível. As correlações para colmo morto foram inversas àquelas obtidas para lâmina verde. Para o perfilho vegetativo, as correlações foram positivas com PB e MSpoD e negativas com FDN e FDNi. Para o perfilho morto, constataram-se correlações positivas com os percentuais de FDN e FDNi da forragem, bem como associação negativa com os teores de PB, FDNpoD e MSpoD. O índice de tombamento correlacionou-se de forma negativa com o número de perfilhos vegetativos e de forma positiva com o número de perfilhos reprodutivos e mortos. O índice de tombamento também se correlacionou positivamente com os teores de FDN e FDNi e de forma negativa com os percentuais de PB e MSpoD. As características estruturais do pasto diferido estão associadas ao seu valor nutritivo. Ações de manejo que reduzam a massa de colmo morto e o número de perfilhos mortos e perfilhos reprodutivos contribuem para melhorar a estrutura e o valor nutritivo do pasto diferido.

Relative Contribution of Various Sources of Botrytis cinerea Inoculum in Strawberry Fields in Norway.

To identify the most important sources of inoculum of Botrytis cinerea (causal agent of gray mold) in commercial strawberry (Fragaria × ananassa) fields in Norway, soil and overwintered plant material were collected from planting beds and alleys at five locations in 2000 to 2002 (13 samples altogether). Plant material was sorted by category (e.g., leaves, stems, mulch, and weeds). After subsamples of each material were incubated for 5 days at 20°C at high humidity, conidiophores of B. cinerea growing from mycelia and sclerotia were counted. Overwintered plant debris within planting beds yielded more than 96% of total conidiophores counted, the remainder originating from plant debris collected from alleys or soil. Overwintered strawberry plant debris produced 98% of the conidiophores within planting beds and 80% of the conidiophores in the alleys, while the remaining was produced by weeds. Senescing and dead leaf laminae produced 45% of the conidiophores while stem residues (i.e., petioles, stolons, inflorescences, and unidentifiable stem parts) produced 50% and mummified fruit produced 5% within planting beds. The contribution of sclerotia, compared with mycelia, to conidiophore production varied greatly between fields and years. Overall, 47% of the total number of conidiophores produced in plant material within planting beds originated from sclerotia. More than 90% of the conidiophores from sclerotia were found in dead stem residues.

Características estruturais e índice de tombamento de Brachiaria decumbens cv. Basilisk em pastagens diferidas

Objetivou-se avaliar o efeito dos períodos de diferimento e de pastejo sobre a densidade populacional de perfilhos, a massa dos componentes morfológicos da forragem e o índice de tombamento em pastagens de Brachiaria decumbens cv. Basilisk. Dois ensaios foram conduzidos: o primeiro denominado ano 1 e, o segundo, ano 2. Adotou-se o esquema de parcelas subdivididas, segundo o delineamento em blocos casualizados, com duas repetições para cada combinação dos períodos de diferimento da pastagem com os períodos de pastejo. No ano 1, os períodos de diferimento foram 103, 121, 146 e 163 dias; e no ano 2, foram 73, 103, 131 e 163 dias. Os períodos de pastejo foram 1, 29, 57 e 85 dias. O aumento do período de diferimento elevou a densidade populacional de perfilhos reprodutivos (ano 2: de 37 para 304 perfilhos/m²) e reduziu a de perfilhos vegetativos (ano 1: de 1.253 para 889 perfilhos/m²; ano 2: de 1.235 para 627 perfilhos/m²). Durante o período de pastejo, ocorreu diminuição no número de perfilhos vegetativo (ano 1: de 988 para 868 perfilhos/m²) e reprodutivo (ano 1: de 216 para 0 perfilhos/m²; ano 2: de 203 para 0 perfilhos/m²) e aumento no número de perfilhos mortos (ano 1: 463 para 1.088 perfilhos/m²; ano 2: de 341 para 1.010 perfilhos/m²). Pastagens sob maiores períodos de diferimento e de pastejo apresentaram maior massa de colmo morto (6.093 e 3.819 kg/ha de MS nos anos 1 e 2, respectivamente) e menor massa de lâmina foliar verde (341 e 177 kg/ha de MS nos anos 1 e 2, respectivamente). Pastos de Brachiaria decumbens cv. Basilisk, submetidos a longos períodos de diferimento e de pastejo possuem características estruturais desfavoráveis à produção animal.

Methylation of<I>H19</I>gene in ES mice and embryonic stem cells

To investigate the relationship between the methylation status of imprinted gene H19 and the development of mice derived completely from Embryonic stem cells (ES) by tetraploid embryo complementation. The methylation status of two loci at 5'UTR region in imprinted gene H19 in normal adult control mice, 22 adult ES mice, 8 newborn dead ES mice and embryonic stem (ES) cells with different passage number were detected by using of methylation-sensitive restriction endonuclease-PCR technique. The results indicated that the methylation status of the imprinted gene H19 in adult ES mice were identical to that of adult control mice. However, some significant differences in the methylation status of the imprinted gene H19 were found among newborn dead ES mice, adult ES mice and normal adult control mice. Furthermore, the methylation status of the imprinted gene H19 in ES cells were probably different from that of adult ES mice and normal adult control mice.

Resource selection by grazing herbivores on post-fire regrowth in a West African woodland savanna

The preference of grazing herbivores to feed on grass regrowth following savanna fires rather than on unburnt grass swards is widely recognised. However, there is little information on which factors govern patterns of resource selection within burnt areas. In this study, we attempted to disentangle the effects of different habitat and grass sward characteristics on the utilisation of post-fire regrowth by nine species of ungulates in a fire-dominated woodland savanna in north Cameroon. We used resource-selection functions based on logistic regression. Overall, the resource-selection functions identified the time elapsed since burning as the most influential parameter in determining probability of use by ungulates, as most species strongly selected swards that were recently burned. This pattern might be related to nutrient levels in the grass sward. In addition, most species selected areas with high grass cover and avoided grass swards with high amounts of dead stem material. This is likely to increase bite mass and, hence, intake rates. The avoidance of high tree cover by some species may suggest selection for open areas with good visibility and, hence, reduced risk of predation. Body mass seemed to have no effect on differential selection of post-fire regrowth, irrespective of feeding style.

An experimental study of bamboo ants in western Amazonia

Numerous ant taxa naturally inhabit stems of live and dead Guadua bamboo (Bambusoidea, Poaceae) in western Amazonia. In an experiment at the onset of the wet season in Peru’s Manu National Park, we augmented potential nest sites in stems of live bamboo, dead bamboo and dead cana brava (Gynerium sagittatum, another woody grass) at five stations within each of ten bamboo patches and ten control areas outside those patches. Each experimental stem possessed three vacant and available internodes, pre-drilled with, respectively, large, small and linear holes, mimicking the range of forms of surveyed natural entrances. After 24 days, approximately 13% of 798 available internodes had been colonized, the majority by fragments of existing colonies. Ignoring entrance type, which did not affect colonization for any species or species group, and censoring non-independent internodes of the same stem, we used individual stems as independent sample units in other tests. One specialist in live bamboo (Camponotus longipilis), and a likely specialist in dead bamboo (Camponotus depressus), were identified based on overrepresentation in bamboo habitat and disproportionate occurrence in live or dead bamboo stems. A third species, Camponotus (Pseudocolobopsis sp.) was more abundant in bamboo areas but colonized both dead bamboo and dead cana. Relatively high abundance of standing dead stems in Guadua forests may account for the presence of a dead stem specialist. The experiment missed detecting specialization in one live culm specialist (Camponotus mirabilis), likely due to its failure to simulate conditions required for the species’ unique modes of colony establishment and spread into new culms. Most opportunistic stem nesters colonized dead bamboo at significantly greater rates than dead cana, but were either equally well represented in bamboo and control areas, or underrepresented in bamboo habitat. Given low colonization rates overall, underrepresentation in bamboo cannot be attributed to competition from bamboo specialists for nesting space. Rather, it may be due to combined effects of seasonal flooding of bamboo habitat, and greater importance of food limitation, relative to nest site limitation, in that habitat.

A comparison of epifaunal communities associated with the stems of salt marsh grasses Phragmites australis and Spartina alterniflora

The invasion of Phragmites australis (common reed) into Spartina alterniflora (cordgrass) salt marshes along the northeastern coast of the United States has recently been of concern. Numerous studies have evaluated the effects of P. australis on marsh nekton and infauna, but its effects on the distribution of stem-dwelling epifaunal communities has not been investigated previously. Standing living and dead plants of both species were collected periodically during three growing seasons (2000–2002) from brackish and salt marshes in New Jersey and Long Island, and the abundance, composition, and diversity of epifaunal communities associated with the stems of the two plant species were compared. Spartina alterniflora, particularly dead S. alterniflora, supported a higher density of animals than P. australis in 12 of the 19 samplings. When communities on standing live and dead stem were considered separately, higher abundances were found on dead S. alterniflora stems. Nematodes and harpacticoid copepods were the dominant taxa, with mites, annelids, and insects comprising minor components. Taxon-specific abundances tended to be higher on S. alterniflora stems, and community diversity was generally greater on this species as well. Between-site and between-year variation was observed. Relative to data recorded from sub-tropical salt marshes, the epifaunal communities in our samples were less abundant and diverse. Differences in the epiphytic communities associated with the two species, along with differences in stem structure, may explain why S. alterniflora stems support more epifaunal animals than P. australis stems overall.

Natural re-colonization of experimental gaps by terricolous bryophytes in Central European pine forests

In northeastern German pine forests we studied re-colonization patterns of experimental gaps by four dominant bryophyte species (Dicranum scoparium, Hypnum jutlandicum, Pleurozium schreberi and Scleropodium purum) over three years. Both vegetation and litter layer were removed on 1 m(2) plots within +/- pure colonies of the experimental species, while the humus layer was left intact. All plots were vegetatively re-colonized by the species which was dominant before gap creation. Three mechanisms of re-colonization occurred and interacted: (1) advance of surrounding shoots from the edge into the gaps by clonal growth, (2) dispersal of detached single shoots as well as larger clumps of multiple shoots into the plots, resulting in new colonies by continuing growth, and (3) regeneration from a soil diaspore bank consisting of seemingly dead stem fragments in the humus layer of the gaps. Scleropodium purum, which occurs at locations with good water and nutrient supply, displayed the most rapid growth. Here, some plots were completely recovered after three years. Despite lower rates of advance from the edge, colonization of Hypnum jutlandicum was faster than and of Dicranum scoparium as fast than that of Pleurozium schreberi because of a larger diaspore bank. Thus, each bryophyte species was characterized by a different habitat occupation strategy. The different clonal colonization strategies account for the high competitive capacity and regeneration potential of the investigated bryophyte species in pine forests despite of the lack of generative reproduction. Experimental disturbance resulted in a temporary increase of bryophyte diversity, because short-lived Colonists with a low competitive capacity colonized the gaps, before they will be overgrown by the dominant Perennials

Modeling dead wood in Fennoscandian old-growth forests dominated by Norway spruce

If equilibrium is assumed in unmanaged forests, the volume of coarse woody debris (CWD), VCWD, may be calculated from (i) the volume of living trees, Vliving, (ii) average volume of a dead stem in relation to when it was alive, k, (iii) tree mortality rate, m, and (iv) residence time of CWD, t, by the equation VCWD = Vlivingkmt. We parameterized this equation with data from Norway spruce (Picea abies (L.) Karst.) dominated forests in Fennoscandia. The Vliving was assumed to be directly proportional to forest productivity. Tree mortality data were from the National Forest Inventory, while it was difficult to find quantitative data on k and t. The predicted amounts (74–138 m3/ha, with larger amounts in the south) and size distribution (a negative exponential distribution of the number of stems) of CWD corresponded fairly well to averages from field inventories. By using a computer simulation program, the variability in tree mortality, density of living trees, and residence time of CWD were considered. In the simulations, the amount of CWD varied widely between 1-ha plots, especially for individual decay classes. Therefore, this model could be used to predict averages from larger landscapes unaffected by large disturbances, while no model can predict the amount of CWD at individual plots.

Avaliação de pastagem diferida de Brachiaria decumbens Stapf: 1. Características químico-bromatológicas da forragem durante a seca

Verificaram-se, durante o período seco, as composições químico-bromatológicas da forragem colhida em pastagem diferida de Brachiaria decumbens por dois métodos, forragem total (FT) e extrusa (EXT); as composições químico-bromatológicas; e as frações de proteína e carboidratos dos componentes folha verde (FV), caule verde (CV), folha seca (FS) e caule seco (CS). A FT apresentou proteína bruta (PB) inferior a 2,5%; a fibra em detergente neutro (FDN), superior a 78%; a lignina, superior a 8,7% na MS; e a digestibilidade in vitro da matéria seca (DIVMS), de 43,5%. A EXT apresentou maior DIVMS e maiores teores de PB, proteína insolúvel em detergente neutro e ácido, cinzas e fósforo e menores teores de fibras, carboidratos totais (CHT) e magnésio, quando comparado com FT. Verificaram-se maiores DIVMS e teores de PB, carboidratos não fibrosos (CNF), fósforo e potássio no componente FV e maiores teores de CHT e FDN nos componentes CV, FS e CS. Observaram-se altos valores da fração A da PB nos componentes FV e CV, baixos valores em FS e CS e altos valores da fração C da PB em CV, FS e CS. As concentrações das frações potencialmente digestíveis da PB, com exceção da fração B1, e de CNF, correlacionaram-se com o teor protéico nos componentes FV, CV, FS e CS. Em relação aos CHT, verificaram-se baixos valores de CNF e altos da fração C nos componentes CV, FS e CS.

Avaliação de pastagem diferida de Brachiaria decumbens Stapf. 2. Disponibilidade de forragem e desempenho animal durante a seca

Verificaram-se as disponibilidades de forragem total, forragem verde e morta e dos componentes folha verde, caule verde, folha seca e caule seco em pastagem diferida de Brachiaria decumbens. A pastagem foi vedada à entrada dos animais de dezembro de 1996 a junho de 1997 e avaliada, sob pastejo contínuo, durante a estação seca, nos meses de julho a outubro de 1997. Também foram estudadas correlações entre características do relvado e ganho de peso de tourinhos Limousin-Nelore com 19 meses e 374 kg de peso. O diferimento da pastagem de Brachiaria decumbens proporcionou disponibilidade média de forragem (DMST) de 7.568, forragem verde (DMSV) de 3.834 e morta (DMSM) de 3.734 kg de matéria seca (MS)/ha em julho, antes do período de pastejo. A utilização contínua da pastagem diferida durante o período seco, com lotação animal de 0,75 UA/ha, não afetou a DMST, média de 7.902, e DMSM, média de 4.637 kg/ha, mas afetou a DMSV e a disponibilidade de folhas verdes (DMSFV). A DMSV e a DMSFV apresentaram taxas crescentes em julho e outubro e diminuíram a taxas crescentes em agosto e setembro. No final de setembro, as pastagens apresentaram a menor DMSV, 2.540 kg/ha. A DMSFV e a proporção de folhas verdes no relvado foram maiores no início de agosto, respectivamente, 1.517 kg/ha e 18,5%, e menores no final de setembro, 480 kg/ha e 5,7%, respectivamente. O diferimento da pastagem permitiu a manutenção dos animais e apenas pequeno ganho de peso durante a seca, média de 104 g/dia. Em setembro, os animais nas pastagens perderam peso. O ganho de peso vivo médio diário correlacionou-se linear e negativamente com DMSM e linear e positivamente com as relações [DMSV/DMSM] e [DMSFV/(DMSM + DMSCV)], em que DMSCV é a disponibilidade de matéria seca de caule verde. Não foram verificadas correlações entre ganho de peso e as variáveis DMSV, DMSFV, pressão de pastejo e oferta diária de forragem.

ROOTING OF KIWIFRUIT (Actinidia deliciosa Lang et Ferguson cv. Bruno)CUTTINGS IN THE FOUR SEASONS OF THE YEAR

A propagação de kiwizeiro ou kiwifruit (Actinidia deliciosa A. Chevallier (C. F. Lang et A. R. Ferguson)) normalmente ocorre pela enxertia das copas sobre porta-enxertos originados de sementes. Tendo em vista o tempo de formação dos porta-enxertos e posterior enxertia, este trabalho visa uma alternativa para a propagação da espécie, utilizando a estaquia direta das copas como técnica de maior rapidez e eficiência. Diferentes concentrações das auxinas exógenas ácido indol-butírico (IBA) e ácido naftaleno-acético (NAA) foram aplicadas em solução e em talco, na base de estacas caulinares da cultivar Bruno, coletadas nas quatro estações do ano (outono/2001, inverno/2001, primavera/2001 e verão/2002) em Porto Amazonas - PR. As estacas foram preparadas com comprimento de aproximadamente 12 cm e tiveram suas bases imersas por 10 segundos em soluções concentradas contendo fitorreguladores e nos tratamentos em talco, conforme segue: T1: água destilada; T2: 2500 mg.L-1 IBA (solução); T3: 5000 mg.L-1 IBA (solução); T4: 2500 mg.L-1 NAA (solução); T5: 5000 mg.L-1 NAA (solução); T6: talco inerte; T7: 2500 mg.Kg-1 IBA (talco); T8: 5000 mg.Kg-1 IBA (talco); T9: 2500 mg.Kg-1 NAA (talco); T10: 5000 mg.Kg-1 NAA (talco) e foram mantidas em tubetes utilizando vermiculita como substrato, permanecendo em casa-de-vegetação com nebulização intermitente. As avaliações foram realizadas depois de 70 dias, sendo observadas as seguintes variáveis em porcentagem: estacas enraizadas; estacas com calos; estacas vivas e estacas mortas. Foi possível concluir que estacas de kiwizeiro cv. Bruno apresentaram heterogeneidade de resposta com relação ao enraizamento nas quatro estações do ano; a maior porcentagem de enraizamento foi obtida com 5000 mg.Kg-1 NAA em talco no inverno.

ENRAIZAMENTO DE ESTACAS DE KIWIZEIRO COM FITORREGULADORES NAS QUATRO ESTAÇÕES DO ANO

A propagação de kiwizeiro (Actinidia deliciosa A. Chevallier (C. F. Lang et A. R. Ferguson)) normalmente ocorre pela enxertia das copas sobre porta-enxertos originados de sementes. Tendo em vista o tempo de formação dos porta-enxertos e posterior enxertia, este trabalho surge como uma alternativa para a propagação da espécie, utilizando a estaquia direta das copas como técnica de maior rapidez e eficiência. Diferentes concentrações das auxinas exógenas ácido indol butírico (IBA) e ácido naftaleno acético (NAA) foram aplicadas em solução e em talco, na base de estacas caulinares de kiwizeiro das cultivares Bruno, Abbott e Monty, oriundas de plantas comerciais pertencentes à Fazenda Boutin, localizada em Porto Amazonas-PR, coletadas nas quatro estações do ano (outono/2001, inverno/2001, primavera/2001 e verão/2002). As estacas foram preparadas com comprimento de aproximadamente 12 cm e diâmetro médio de 0,65 cm e tiveram suas bases imersas por 10 segundos em soluções concentradas contendo fitorreguladores e nos tratamentos em talco, conforme segue: T1: água destilada; T2: 2500 mg.L-1 IBA (solução); T3: 5000 mg.L-1 IBA (solução); T4: 2500 mg.L-1 NAA (solução); T5: 5000 mg.L-1 NAA (solução); T6: talco inerte; T7: 2500 mg.Kg-1 IBA (talco); T8: 5000 mg.Kg-1 IBA (talco); T9: 2500 mg.Kg-1 NAA (talco); T10: 5000 mg.Kg-1 NAA (talco). Os dados foram analisados dentro de cada estação separadamente segundo um delineamento inteiramente casualizado com arranjo fatorial de 10 tratamentos e 3 cultivares, com 4 repetições por combinação, sendo as unidades experimentais formadas por 10 estacas. As estacas foram mantidas em tubetes utilizando vermiculita como substrato, permanecendo em casa-de-vegetação com nebulização intermitente. As avaliações foram realizadas aos 70 dias da instalação do experimento, sendo observadas as seguintes variáveis: porcentagem de estacas enraizadas; número de raízes por estaca; comprimento das três maiores raízes por estaca; porcentagem de estacas com calos; porcentagem de estacas vivas e porcentagem de estacas mortas. Pelo trabalho foi possível concluir que estacas de kiwizeiro das cultivares Bruno, Abbott e Monty apresentaram heterogeneidade de resposta com relação ao enraizamento nas quatro estações do ano; as estações da primavera e verão apresentaram elevada mortalidade das estacas; as maiores porcentagens de enraizamento foram obtidas com 5000 mg.Kg-1 NAA em talco para as cultivares Bruno (70,0%) e Monty (40,0%) no inverno e 5000 mg.L-1 NAA em solução para a cultivar Abbott (37,5%) no verão.

The yield and composition of switchgrass and coastal panic grass grown as a biofuel in Southern England

Switchgrass ( Panicum virgatum L.) and coastal panic grass ( Panicum amarum A.S. Hitchc. & Chase) are perennial grasses indigenous to North America. Switchgrass has been shown to have good potential as a biofuel crop in both the US and Canada. In the study reported here, seven varieties of switchgrass and one panic grass were evaluated for 5 years under the temperate maritime conditions in Southern England. Both species had 0 or 60 kg N ha −1 applied annually in spring as treatment. Yield was measured after flowering and when stems were dead in the winter. Yield increased annually for 4–5 years except for the variety Dacotah, and in the fifth year dead stem yields ranged from 8.82 to13.97 t dm ha −1 . There was no response to N except for one variety in one year. Mineral concentration in biomass was higher at flowering than at dead stem harvest and delaying harvesting further provided more time for P, K and Cl to be leached but yield also declined.