Dead Leaves Research Articles

Ammonium overaccumulation in senescent leaves as a novel exclusion mechanism to avoid toxicity in photosynthetically active rice leaves

High ammonium concentration is toxic for most plant species, but some rice cultivars are tolerant by mechanisms not understood yet. We tested the hypothesis that NH4+-tolerance could be associated with an exclusion mechanism involving ammonium deposition on the oldest leaves after triggering localized senescence. An ammonium-tolerant cultivar was exposed to increasing ammonium (NH4+) concentrations for two weeks and afterward subjected to 15 mM throughout 4 weeks, to evaluate toxicity and resistance mechanisms. Plants exposed to similar nitrate (NO3−) concentrations were taken as control. In presence of high NH4+ rice displayed similar nitrogen (N) root influx compared to nitrate-supplied roots. In parallel, these plants exhibited a strong impairment in root growth even after exposure to mild NH4+ concentration (3.75 mM). This response was related to increased activity of type III peroxidases, but no evidence for oxidative stress and tissue damages on roots were apparent. Intriguingly, high NH4+-supplied plants displayed a prominent increase in dry mass of senescent oldest leaves, which were 5-fold higher than that observed in nitrate-supplied ones. Ammonium-treatment induced strong NH4+ accumulation on the dead leaf tissues (by 2.8 mmol g-1 DW) representing 75 % of the total-N in this part. This high deposition rate of potentially toxic NH4+ associated with a “self-destruction” strategy should indicate an exclusion mechanism. In contrast, mature leaves presented low NH4+ content, which was associated with no alterations in both CO2 assimilation and photosystem II activity. Our data suggest that rice displays an unusual NH4+ exclusion mechanism by triggering fast and intense senescence on its older leaves. Afterwards, this process is followed by the death of these leaves and deposition of extremely high amounts of this toxic component but preserving younger photosynthetically active tissues.

Trophic ecology of macrofauna inhabiting seagrass litter accumulations is related to the pulses of dead leaves

Accumulation of exported macrophytodetritus (AEM) represent unique habitats formed by the dead material originating from macrophyte ecosystems (e.g., seagrass, kelp, other seaweeds). AEM can be found everywhere, from the littoral zone to the deepest canyons, and from high to low latitudes. Seagrass AEMs are among the most common detrital accumulations found in marine environments, and sometimes include macroalgae wrack that has been ripped from the substrate. In the Mediterranean Sea, Posidonia oceanica (L.) Delile litter accumulations undergo pulses of new necromass all year, particularly in autumn, when dead leaves are shed. Here, macrofauna inhabiting AEM of Calvi Bay (Corsica, France) was sampled troughout an annual cycle (four seasons). By combining gut content examination and stable isotope analysis, we aimed to assess the effect of seasonal litter pulses on the trophic ecology of the dominant macrofauna species. Litter composition showed drastic variations throughout the sampling period, with the highest leaf litter quantity and contribution to AEMs in November. Dominant detritivores, herbivores, and omnivores responded positively to this increase by ingesting more seagrass material. A Bayesian stable isotope mixing model showed that the assimilation of carbon originating from seagrasses also increased. Additionally, isotopic niche modelling showed that consumer niches shifted towards seagrass isotopic composition in November. Predators did not shift their diet, but their isotopic composition was affected by the isotopic shift of their prey, demonstrating the transfer of seagrass carbon to higher trophic levels and the shift towards dead leaf material in the entire community. This response was, therefore, a rapid (days to weeks) parallel to that of the slow (months to years) decomposition of detrital material via physical alteration and microbial decomposition. This seemingly underestimated transfer route should be better characterised to understand the role of these seagrass beds in carbon sequestration in the marine environment.

Mimicking Nature's Butterflies: Electrochromic Devices with Dual-Sided Differential Colorations.

Some butterfly species such as the orange oakleaf (Kallima inachus) have strikingly different colors on the dorsal (front) sides of their wings compared to those on the ventral (back) sides of their wings, which helps camouflage the butterflies from predators and attract potential mates. However, few human-made materials, devices, and technologies can mimic such differential coloring for a long time. Here, a new type of Janus-structured two-sided electrochromic device is developed that, upon application of different voltages, exhibits a coloration state on one side that is distinctly different from that on the other side. This is achieved by inserting an optically thin (4-8 nm) metallic layer with a complex refractive index, such as a layer composed of tungsten, titanium, copper or silver, into typical electrochromic structures.

First Report of Alternaria tenuissima Causing Leaf Blight on Sugarcane in China.

Sugarcane (Saccharum officinarum L.) is the main sugar crop in China. Yunnan is the second largest sugarcane production province in China. In December 2018, leaf blight was first observed on almost every leaf of sugarcane on 'Huanan 54-11', 'Baimei' and 'Chongan' in Kaiyuan (103°27' E, 23°72' N), Yunnan. In October 2019, during our survey in the field in Lingcang (100°08' E, 23°88' N), Yunnan, this disease was also observed on 'ROC 25'. Symptoms of the disease initially appeared as wilted, which seemed to be cause by water stress. As the disease progressed, irregular straw-yellow and blighted lesion ran throughout the leaf lamina from leaf tip to entire leaf sheath, many small black conidia formed in the dead leaf tissue under humid conditions. Symptomatic leaf tissues were surface-sterilized with 70% ethanol for 30 s, 0.1% HgCl2 for 1 min, and rinsed with sterilized water three times, air dried on sterile filter paper, and plated on potato dextrose agar (PDA). Six isolates were obtained from six symptomatic leaf samples and were transferred onto potato carrot agar (PCA). Colonies on PDA were white with loose aerial hyphae at first, then turned to dark olive or dark. Colonies on PCA were grayish with sparse hyphae, then turned to dark gray. Conidiophores were brown, simple or branched, and produced numerous conidia in short chains. Conidia (n = 50) were obclavate to obpyriform or ellipsoid, brown to dark brown, with a cylindrical short beak at the tip (2.3 to 17.3 µm in length), and 15.3 to 46.6 μm × 4.2 to 17.9 μm, 2 to 7 transverse septa and 0 to 3 longitudinal septa. Morphologically, the isolates were identified as Alternaria tenuissima (Simmons 2007). Two representative isolates C4 and C5 were selected for molecular identification. The internal transcribed spacers (ITS), Histone 3 genes and plasma membrane ATPase were amplified with primer pairs ITS1/ITS4, H3-1a/H3-1b and ATPDF1/ATPDR1, respectively (Glass et al. 1995; Lawrence et al. 2013). The sequences were deposited in GenBank (ITS, MT679707-MT679708; Histone 3, MT710929-MT710930; ATPase, MT833928-MT833929). BLAST searches showed ≥99% nucleotide identity to the sequence of A. tenuissima (ITS, 100% to MN822571; Histone 3, 100% to MN481955; ATPase, 99% to JQ671875, 100% to MH492703, respectively). Thus, the fungus was identified as A. tenuissima based on morphological and molecular characteristics. For pathogenicity tests, five healthy 2-month-old potted sugarcane leaves were wounded with one sterile needle and inoculated with 20 μl of suspension of 106 conidia/ mL, and five plants were inoculated with distilled water as the controls. Plants were placed in a greenhouse at 25 to 35°C. After two months, the leaf wound inoculated with the putative pathogen displayed blighted as those observed in the field whereas the controls remained symptomless. The fungus was reisolated from symptomatic leaves with the same morphological and molecular traits as the original isolates. The fungus was not isolated from the control plants. Pathogenicity tests were repeated two times. A. tenuissima causing leaf blight on barley in China was reported in 2008 (Luo et al. 2008). Leaf spot disease of sugarcane caused by A. tenuis has been recorded in Maharashtra (Patil et al. 1974). To our knowledge, this is the first report on A. tenuissima affecting leaf blight on sugarcane in Yunnan Province, China. Identification of the causes of the disease is important to develop effective disease management strategies. The author(s) declare no conflict of interest. Funding: This research was supported by Sugar Crop Research System (CARS-170303), the Yunling Industry and Technology Leading Talent Training Program "Prevention and Control of Sugarcane Pests" (2018LJRC56), and the Yunnan Province Agriculture Research System.

Phylogenetic analysis of the nocturnal avian family Nyctibiidae (Caprimulgiformes) inferred from osteological characters

The family Nyctibiidae (potoos) comprises seven extant species currently included in the genera Nyctibius and Phyllaemulor, endemic to the Neotropical region, and the extinct genus Paraprefica from the Eocene of Europe. The living species are secretive nocturnal birds, characterized by spend most of the daylight time in a freezing, upright posture, resembling the top of a stump or a dead leaf. Here we present the first phylogenetic analysis of the family based on morphological characters, inferred from 37 cranial and post-cranial characters of all but one representatives of Nyctibiidae, including the extinct genus Paraprefica. TNT analysis resulted in a single most parsimonious tree with a length of 47 steps, and the ingroup topology was (Paraprefica (Phyllaemulor bracteatus (Nyctibius leucopterus (Nyctibius griseus, Nyctibius jamaicensis (Nyctibius aethereus, Nyctibius grandis))))). These results partially corroborate previous phylogenetic hypotheses based on molecular data, mainly concerning the position of P. bracteatus, but the relationships among Nyctibius species remain controversial. The osteology of this family is remarkably distinct from close related groups, especially regarding the cranial and mandibular structures, mainly due to their noteworthy habits and large eyes and mouth. The distinction between Paraprefica and Phyllaemulor + Nyctibius, allied to the geographical and temporal disjunction of these two groups, seems to be enough for their separation at the subfamily level. A notable osteological variation exists also among the Nyctibius species, albeit included in a single genus, following the high levels of genetic divergence presented in the literature, suggesting that the currently accepted systematics of the family must be reviewed.

A new approach for biogas slurry disposal by adopting CO2-rich biogas slurry as the flower fertilizer of Spathiphyllum: Feasibility, cost and environmental pollution potential

A new approach for biogas slurry disposal was put forward in this study through converting biogas slurry to the organic fertilizer of Spathiphyllum. The biogas slurry was firstly concentrated by vacuum distillation to reduce its volume by 80% who is called 5CBS, and then CO2 saturated to reduce its pH to about 6.50 ± 0.20. With or without adding the exogenetic Ca, Mg and P nutrients, CO2-rich 5CBS (i.e., CR-5CBS) was adopted as the root or foliar fertilizer to cultivate Spathiphyllum. Additionally, the commercial Spathiphyllum fertilizer was also experimented as a control. Results showed that the cases adopting CR-5CBS as the root or foliar fertilizer can obtain the agronomic traits and ornamental values of Spathiphyllum better those irrigated by the commercial fertilizer. Exogenetic nutrients added into CR-5CBS can lead to a decreased dead leaf number of Spathiphyllum, an enhanced N assimilation performance, however only a slightly improved assimilation performance of Ca, Mg and P. In terms of the fertilizer economy, CR-5CBS without exogenetic nutrient addition may be a promising for replacing the commercial Spathiphyllum fertilizer in the future. Economic and environmental pollution potential (EPP) analyses indicated that treating biogas slurry as the organic flower fertilizer can achieve a high net profit with about $ 28.89/m3-biogas slurry and a negative EPP value (−3.9), showing its profitability and environmental friendliness.

Diversity and Composition of Microbial Communities in an Eelgrass (Zostera marina) Bed in Tokyo Bay, Japan.

Zostera marina (eelgrass) is a widespread seagrass species that forms diverse and productive habitats along coast lines throughout much of the northern hemisphere. The present study investigated the microbial consortia of Z. marina growing at Futtsu clam-digging beach, Chiba prefecture, Japan. The following environmental samples were collected: sediment, seawater, plant leaves, and the root-rhizome. Sediment and seawater samples were obtained from three sampling points: inside, outside, and at the marginal point of the eelgrass bed. The microbial composition of each sample was analyzed using 16S ribosomal gene amplicon sequencing. Microbial communities on the dead (withered) leaf surface markedly differed from those in sediment, but were similar to those in seawater. Eelgrass leaves and surrounding seawater were dominated by the bacterial taxa Rhodobacterales (Alphaproteobacteria), whereas Rhodobacterales were a minor group in eelgrass sediment. Additionally, we speculated that the order Sphingomonadales (Alphaproteobacteria) acts as a major degrader during the decomposition process and constantly degrades eelgrass leaves, which then spread into the surrounding seawater. Withered eelgrass leaves did not accumulate on the surface sediment because they were transported out of the eelgrass bed by wind and residual currents unique to the central part of Tokyo Bay.

Type of shelter and first description of the echolocation call of disk-winged bat (Thyroptera devivoi)

Abstract: Thyropteridae is a family of bats endemic to the Neotropical region, and Thyroptera devivoi is the only species in the family that occurs exclusively in forest patches within savannas of northern South America and north of the Brazilian Cerrado. Primary data on the species are still scarce. Therefore, in this study our objective was to fill knowledge gaps on geographical distribution, roost-use, and echolocation for the species. We observed a T. devivoi colony of 15 individuals living under a dead palm leaf. The bats used the leaf as a roost for at least four days. After capturing one individual, we confirmed the species identification via skull size and the oblong shape of the adhesive disk. The new record reinforces the association of this species with non-forested formations, and its occurrence mainly in savannas. Echolocation calls of T. devivoi are consistent with those known for the genus, with multiharmonic, low intensity and high frequency pulses. Despite these new data, more studies are certainly needed to enhance distribution data for the species, as well as to clarify the biological and ecological requirements of the species.

Patterns of Dispersion, Movement and Feeding of the Sea Urchin Lytechinus variegatus, and the Potential Implications for Grazing Impact on Live Seagrass

The sea urchin Lytechinus variegatus is a known grazer of both living and dead tissue of turtlegrass, Thalassia testudinum, occasionally denuding large areas of seagrass. Field studies have attempted to assess effects of herbivory on seagrass by enclosing urchins at various densities. However, it is unclear how unrestricted urchins affect seagrass at lower densities more typically observed in the field. This study describes movement, feeding, and distribution of L. variegatus within beds of T. testudinum in St. Joseph Bay, Florida (USA) to quantify this urchin’s impact as a seagrass grazer. Urchins were absent from portions of seagrass beds closest to shore, present at low densities midway across the bed, and at highest densities (up to ~5 individuals/m2) at the offshore edge of the bed. Urchins tended not to aggregate, moved twice as rapidly where seagrass cover was reduced, and moved > 20X faster when placed in areas of open sand. Dead seagrass tissue occurred 4—30X more frequently on oral surfaces than living seagrass tissue. Fecal pellets with dead seagrass tissue were > 3X more common than pellets with live seagrass tissue. Injury to seagrass leaves was more common along dead leaf sections than live sections (> 2—10X). Overall, spatial distributions, movement, and diet indicate that L. variegatus at densities observed in this study would tend to have minimal effects on living seagrass. Episodic periods of denuding grassbeds reported in the literature suggest L. variegatus switches to live seagrass tissue as dead tissue becomes scarce during times of high urchin density.

Meiofauna in stream habitats: temporal dynamics of abundance, biomass and secondary production in different substrate microhabitats in a first-order stream

Meiofaunal abundance, biomass and secondary production were investigated over 13 months in an unpolluted first-order stream. Four microhabitats were considered: sediment and the biofilms on dead wood, macrophytes and leaf litter. The relative contribution of the microhabitats to secondary production and the influence of environmental factors on meiofaunal density distribution were estimated. We expected (1) meiofaunal abundance and biomass to exhibit seasonal patterns, with more pronounced seasonal fluctuations on macrophytes and leaf litter than in the other microhabitats, (2) annual secondary production to be highest in sediment; however, the relative contribution of the microhabitats to monthly secondary production would change during the year, and (3) a bottom-up driven influence on meiofaunal density distribution in the microhabitats. Meiofaunal annual mean abundance, biomass and secondary production were 7–14 times higher in sediment and on dead wood than on macrophytes and leaf litter. Significant seasonal patterns described the meiofaunal abundance in sediment and on leaf litter as well as the biomass in sediment, on macrophytes and leaf litter. Organisms in sediment and on dead wood contributed 48 and 43%, respectively, to secondary production m−2, but in regard to the stream area covered by the microhabitats, sediment had the highest share (80%). Significant determinants of the density distribution were AFDM, protozoans, bacteria and Chl-a, which influenced all meiofaunal groups. Our study clearly indicates that meiofaunal organisms in sediment and on dead wood have a remarkable share on total secondary production of lotic systems which is especially relevant for forested low-order streams.

Mowing and lowering the marandu palisadegrass sward height at late winter improve the sward structure

The structure of the sward is important because it influences the responses of plants and animals in grazing conditions. The objective with this work was to evaluate the structural characteristics of the Marandu palisade grass pasture (Brachiaria brizantha syn. Urochloa brizantha) during spring and summer, depending on the condition of the sward at the end of winter. Four grazing conditions at the end of winter were evaluated: short (24.1 cm), short (25.2 cm)/mown (8 cm), tall (49.0 cm) and tall (50.0 cm)/mown (8 cm). The foliar area index was lower in the tall pasture than in the tall/mown pasture. The mass and the volumetric density of dead stem were higher in the tall pasture, intermediate in the short pasture, and lower in mowed pastures. At the beginning of the grazing period, the live stem mass was higher in the tall pasture. At the beginning and middle of the grazing period, the volumetric density of dead leaf lamina was lower in mowed pastures. At the beginning of the pasture period, the short pasture had a higher tiller number (TN). In the middle of the grazing period, the short and short/mown pastures had higher TN. At the end of the pasture period, the lowest TN value occurred in the tall pasture. The tall pasture at the end of winter presents an unfavorable structure to the animal in grazing, while the mowing and reduction in the height of the marandu palisade grass improves the structure of the sward in spring and summer.

Converting dead leaf biomass into activated carbon as a potential replacement for carbon black filler in rubber composites

In this work, the feasibility of converting dead leaf biomass into green activated carbon for use as a reinforcement filler in natural rubber composites was assessed. The dead leaf activated carbon (DLAC) was prepared by pyrolysis at 550, 700, 900, and 1000 °C at a heating rate of 10 °C min−1 under nitrogen gas flow of 100 cm3 min−1 and was activated by CO2 gas at the same flow rate when the pyrolysis temperature was reached. The properties of DLACs were characterized by particle size analysis, density, scanning electron microscopy, elemental energy-dispersive X-ray spectroscopy and Raman spectroscopy. The results revealed that the DLAC obtained by pyrolysis at 1000 °C had a small particle size of 28.86 μm; a highly porous structure; high carbon purity, at 82.58%; and a low density, at 1.588 g cm−3. The effect of different DLAC contents (5, 10, and 15 phr) on the curing properties and the physical and mechanical performance of the rubber composites was investigated and compared with rubber composites containing carbon black (CB). The results showed that the addition of DLAC increased the maximum torque and reduced the scorch and cure times. The tensile strength for rubber composites containing 15 phr of DLAC increased by 8%, the M100 and M300 improved 40%, and the elongation at break and crosslink density decreased by approximately 5% and 24%, respectively. The studied DLAC is a promising, cost-effective alternative to commercial carbon black for improving the performance of rubber composites.

Predicting litter decomposition rate for temperate forest tree species by the relative contribution of green leaf and litter traits in the Indian Himalayas region

We examined eight green leaf traits (leaf area, specific leaf area, leaf dry matter, leaf water content, leaf carbon, nitrogen, phosphorous, and chlorophyll) and eight litter traits (cellulose, lignin, litter carbon, nitrogen, phosphorous, lignin: nitrogen, carbon: nitrogen and ash content) and the litter decomposition rates of 10 tree species from a temperate forest ecosystem. Amongst all green leaf and litter traits tested, cellulose content, lignin content and specific leaf area were identified as the best predictors of litter decomposition, with percentage contributions to litter decomposition of 40%, 36% and 8%, respectively. The results indicated that litter decomposition in the temperate forest ecosystem studied was not dependent solely on litter traits, as green leaf traits also contributed to nutrient cycling. Individual green leaf traits of living species and dead leaf characteristics both influenced the fate of leaves, affecting decomposition and nutrient and carbon cycling in the forest ecosystem. For a better overall understanding of the decomposition mechanisms operating in a temperate forest, both green leaf traits and litter traits thus need to be considered.

The complete mitochondrial genome of the black dead leaf butterfly Doleschallia melana (Insecta: Lepidoptera: Nymphalidae)

The black dead leaf butterfly Doleschallia melana (Staudinger, 1886) (Nymphalidae) is a leaf mimic endemic to Indonesia. Genome skimming by Illumina sequencing enabled the assembly of a complete 15,269 bp circular mitogenome from D. melana consisting of 80.0% AT nucleotides, 22 tRNAs, 13 protein-coding genes, 2 rRNAs and a control region in the typical butterfly gene order. Doleschallia melana COX1 features an atypical CGA start codon while ATP6, COX1, COX2, ND1, ND2, ND4, and ND5 exhibit incomplete stop codons. Phylogenetic reconstruction places D. melana as the sister taxon to the clade containing the tribes Kallimini, Nymphalini and Junoniini.

Chromosome-level reference genome assembly and gene editing of the dead-leaf butterfly Kallima inachus.

The leaf resemblance of Kallima (Nymphalidae) butterflies is an important ecological adaptive mechanism that increases their survival. However, the genetic mechanism underlying ecological adaptation remains unclear owing to a dearth of genomic information. Here, we determined the karyotype (n=31) of the dead-leaf butterfly Kallima inachus, and generated a high-quality, chromosome-level assembly (568.92Mb; contig N50: 19.20Mb). We also identified candidate Z and W chromosomes. To our knowledge, this is the first study to report on these aspects of this species. In the assembled genome, 15,309 protein-coding genes and 49.86% repeat elements were annotated. Phylogenetic analysis showed that K. inachus diverged from Melitaea cinxia (no leaf resemblance), both of which are in Nymphalinae, around 40 million years ago. Demographic analysis indicated that the effective population size of K. inachus decreased during the last interglacial period in the Pleistocene. The wings of adults with the pigmentary gene ebony knocked out using CRISPR/Cas9 showed phenotypes in which the orange dorsal region and entire ventral surface darkened, suggesting its vital role in the ecological adaption of dead-leaf butterflies. Our results provide important genome resources for investigating the genetic mechanism underlying protective resemblance in dead-leaf butterflies and insights into the molecular basis of protective coloration.

Simulation of Maize Lethal Necrosis (MLN) Damage Using the CERES-Maize Model

Maize lethal necrosis (MLN), maize streak virus (MSV), grey leaf spot (GLS) and turcicum leaf blight (TLB) are among the major diseases affecting maize grain yields in sub-Saharan Africa. Crop models allow researchers to estimate the impact of pest damage on yield under different management and environments. The CERES-Maize model distributed with DSSAT v4.7 has the capability to simulate the impact of major diseases on maize crop growth and yield. The purpose of this study was to develop and test a method to simulate the impact of MLN on maize growth and yield. A field experiment consisting of 17 maize hybrids with different levels of MLN tolerance was planted under MLN virus-inoculated and non-inoculated conditions in 2016 and 2018 at the MLN Screening Facility in Naivasha, Kenya. Time series disease progress scores were recorded and translated into daily damage, including leaf necrosis and death, as inputs in the crop model. The model genetic coefficients were calibrated for each hybrid using the 2016 non-inoculated treatment and evaluated using the 2016 and 2018 inoculated treatments. Overall, the model performed well in simulating the impact of MLN damage on maize grain yield. The model gave an R2 of 0.97 for simulated vs. observed yield for the calibration dataset and an R2 of 0.92 for the evaluation dataset. The simulation techniques developed in this study can be potentially used for other major diseases of maize. The key to simulating other diseases is to develop the appropriate relationship between disease severity scores, percent leaf chlorosis and dead leaf area.

Seasonal distribution of abundance, biomass and secondary production of free-living nematodes and their community composition in different stream micro-habitats

Summary The nematode communities of four different micro-habitats in an unpolluted first-order stream were investigated over a 13-month period in a study of the sediment and the biofilms on dead wood, macrophytes and leaf litter. Nematode abundances, biomass and secondary production were analysed, together with the species composition, proportion of feeding types and diversity of the nematode communities of the micro-habitats. Differences between the investigated micro-habitats in terms of seasonal variations, species composition, proportion of feeding types and diversity were expected. The annual mean values of nematode abundance, biomass and secondary production differed significantly between the micro-habitats. Abundances were highest on dead wood, whereas biomass and secondary production were highest in sediment. In the sediment and on leaf litter, nematode abundance and biomass showed pronounced seasonal patterns. The largest contribution to the total secondary production of the stream was from sediment nematodes. In total, 108 nematode species were detected in the micro-habitats during the 13-month study. Comparisons between them revealed differences in nematode species composition. The annual mean species number was significantly higher in sediment and on leaf litter than on dead wood and macrophytes, whereas the annual mean Shannon-Wiener index was significantly higher in sediment than at all other micro-habitats. All micro-habitats in the studied stream, as well as the stream as a whole, were dominated by nematode species belonging to the deposit feeders. Our study clearly showed that the composition of nematode communities from different micro-habitats within a single stream reach can differ markedly.

Initial height and nitrogen fertilisation on deferred pastures of marandu palisadegrass

In deferred pastures, nitrogen fertilisation and pasture height at the beginning of the deferment period modify the structure and nutritive value of forage. This work was conducted to determine the nitrogen (N) doses and sward heights that were adequate for the deferment of Brachiaria brizantha cv. Marandu syn. Urochloa brizantha cv. Marandu (marandu palisadegrass). Two sward heights (15 and 30 cm) and four N rates (0, 40, 80,120 kg/ha) at the beginning of the deferment period were evaluated in a randomised block design and a factorial scheme with three replications. At the end of the deferment period, the numbers of live and dead tillers, the numbers of tillers with different sizes, the masses of live leaf lamina, dead leaf lamina, live stem and dead stem, the litter mass and the crude protein and neutral detergent fibre contents of the forage were evaluated. With nitrogen fertilisation, there was an increase in the masses of live leaf and live stem in the deferred canopy. With the application of 80 kg/ha of N, the litter mass was higher in the deferred canopy with a height of 30 cm, in relation to that with a height of 15 cm. The highest canopy presented greater stem mass and worse nutritional value when compared to the lowest one. In order to improve forage characteristics, marandu palisadegrass can be deferred by 15 cm and fertilised with 80 kg/ha N. When marandu palisade grass is deferred to 30 cm, nitrogen doses lower than 80 kg/ha can be applied.

Test of hypotheses for dead leaf retention in Protea

Firstly, we show that dead leaf retention occurs in three Cape Protea species and that it is not correlated with a prolonged live leaf retention. Protea amplexicaulis retains dead leaves for up to six years and was used as a focal species. Two hypotheses for the adaptive significance of dead leaf retention in Proteaceae have been previously suggested: that dead leaves increase flammability thus providing open space for seedling establishment by burning neighbouring plants (Flammability hypothesis); and that the retention of dead leaves results in an increase in post-fire nutrients thus providing fertilisation for seedlings (Selfish fertilisation hypothesis). Dead leaves were found to contain significant amounts of calcium but negligible amounts of any other limiting nutrients and below canopy seedlings were neither more numerous nor larger than those in the open. We thus reject the selfish-fertilization hypothesis. We reject the flammability hypothesis as both P. amplexicaulis and its most common near neighbours are fire sensitive reseeders and in any case seeds are likely to disperse outside of the area affected by increased parental flammability.

First sexual morph record of Sarcopodium vanillae

Sarcopodium vanillae was isolated from a dead leaf of Dracaena in Chiang Rai Province, Thailand. Combined analyses of ACT, ITS, LSU, and TUB2 sequence data obtained from the cultures derived from single spore isolates confirm that our collections represent S. vanillae. This is the first record of the sexual morph, and the first record of S. vanillae from Dracaena. A description and illustrations of both sexual and asexual stages of S. vanillae are provided.