Phenology of the red mangrove, Rhizophora mangle L., in the Caeté Estuary,Pará, equatorial Brazil

The current study presents phenology data for Rhizophora mangle from two equatorial mangrove stands with different salinity regimes in Brazil. Observations based on litter fall and individual shoot development were compared and related to environmental factors. Patterns observed in litter fall were consistent with results of direct monitoring. While both reproductive organs and leaves were produced throughout the year, rates of formation followed seasonal trends. Distinct differences in propagule production between low and high salinity sites and between years of observation were detected; main propagule release was, however, restricted to the wet season which offers enhanced conditions for propagule establishment. Emergence of flowers was linked to leaf production. While there was no obvious single peak in leaf production, it was reduced towards the end of the dry season at both high and low salinity sites. Time series analysis revealed an independent pattern of leaf development superimposed on this annual seasonal trend, indicating slower development of leaf primordia during periods of low light availability in the wet season. No significant difference in age structure was detected between sun and shade leaves; maximum leaf life-time was approximately 1 year.     

Vegetation dynamics in the fens of Chautagne (Savoie,France) after the cessation of mowing

The mechanisms controlling secondary succession on eutrophic peat are analyzed on an area of 500 ha marsh near the Lac du Bourget in the Rhône floodplain between Geneva and Lyon. After describing the succession, the authors compare the succession with that described for fens in England.During succession, three categories of phenomena occur:-Predictable phenomena based on the occurrence of well-established relationships between species with a high cover density. When mowing ceases, populations with increasingly higher biomasses reach dominance one by one.-Phenomena which were to be expected although the manner in which they occurred were more difficult to predict, such as the conditions in which woody plants take over.-Phenomena hidden in the framework of a synchronic analysis. The lowering of the water table, for example, can modify the entire community of species occurring in the sequence as well as the competition between species. The pecularities of each type of ecological situation made it difficult to develop general models.     

Leaf structure and histochemistry of Ecballium elaterium (L.) A. Rich. (squirting cucumber)

Light, scanning and transmission electron microscopy as well as histochemical reactions were employed to study the leaf structure and secretory activity of Ecballium elaterium, a hairy pharmaceutical perennial common in the Mediterranean region. The amphistomatic leaf has a peculiar structure due to special cells supporting the conductive bundles, a remarkable shortage of mechanical tissue, and the existence of pectin strands between mesophyll cells. The secreting activity is limited mostly to secretary hairs. These attributes of the Ecballium leaf fine structures do not resemble the common structure of leaves from Mediterranean plants and point to a peculiar strategy of this species coping with stress conditions of its habitat.     

Polar extracts of the brown alga Fucus vesiculosus (L.) reduce assimilation efficiency but do not deter the herbivorous isopod Idotea baltica (Pallas)

Plant secondary metabolites provide resistance against herbivory if they are capable of decreasing herbivore performance or deterring feeding. Here we test the effects of phlorotannin-containing polar extracts from the brown alga Fucus vesiculosus on the assimilation efficiency and feeding preferences of the herbivorous isopod Idotea baltica. We test the effects separately for each sex of the isopod to test the hypothesis that the digestive efficiencies of the sexes may have diverged. Phlorotannin-containing polar extracts were incorporated into an agar-based artificial food in varying amounts. We also varied the quality of the food, using high-quality food containing animal proteins and low-quality food containing only algal material. The total assimilation efficiency as well as the assimilation efficiencies of carbon and nitrogen decreased with an increasing concentration of phlorotannin-containing extracts. The negative effects on carbon and nitrogen assimilation were higher when extracts were incorporated in the high-quality food. Females were consistently more efficient than males in all assimilation measures; there were no interactions between sex and food quality or phlorotannin concentration, suggesting that the digestive efficiency of the sexes had diverged but that the two sexes responded similarly to phlorotannin enriched artificial food. Although phlorotannin-containing extracts were harmful to performance, they did not deter feeding in preference tests. On the contrary: the isopods preferred the food containing more phlorotannins, suggesting that phlorotannins may act as cues in host recognition. Thus phlorotannins were inefficient deterrents, and I. baltica seems to be adapted to utilizing phlorotannin-containing foods despite their detrimental effects on assimilation. We suggest that F. vesiculosus provides a predation refuge and temporal constancy in availability for I. baltica, both of which select for the ability to utilize it as a food. Phlorotannin-containing polar extracts from F. vesiculosus are still harmful digestibility reducers, and may thereby prevent complete specialization and generate selection for utilization of a wider host range.     

Detrital stocks and dynamics of the seagrass Posidonia oceanica (L.) Delile in the Spanish Mediterranean

Previous studies have shown that most leaf production (>90%) of the seagrass Posidonia oceanica is shed after senescence and that a substantial percentage (up to 80%) may thereafter be exported off the seagrass meadows by waves and currents. It has also been reported that P. oceanica meadows can accumulate large stocks of belowground detritus due to slow decomposition rates. However, the generality of these results across broad spatial scales is poorly known. In this report, we examine the fate of leaf production and the magnitude and dynamics of belowground detritus in 16 P. oceanica meadows distributed along the Spanish Mediterranean. Herbivores removed a small percentage of leaf production in all the meadows (≤13%), with most leaf production (>85%) being shed after senescence. Most shed leaves (>90%) were exported off the meadows by physical agents, such as waves and currents. The amount of belowground detritus stored within 10–15 cm from the sediment surface varied from ca. 70 to 7500 g DW m⁻² among the meadows examined, and they accumulated at rates ranging from ca. 65 to 650 g DW m⁻² per year. These values are large when compared to other communities of aquatic and terrestrial macrophytes. Our results show that P. oceanica meadows in the Spanish Mediterranean support high values of secondary production in other systems by exporting large amounts of leaf detritus as well as acting as substantial carbon sinks by accumulating large reservoirs of belowground detritus. Therefore, the increasing anthropogenic threats on P. oceanica could entail an important loss of secondary production and carbon storage in Mediterranean coastal ecosystems.     

Assessing within habitat variability in plant demography, faunal density, and secondary production in an eelgrass (Zostera marina L.) bed

This investigation addressed faunal relationships with habitat structure within a Zostera marina community targeting differences between seagrass bed edge and interior. Z. marina biomass was significantly higher from the interior portions of the bed compared to the edge, but shoot density did not vary. Additionally, leaf width and length were significantly greater in the interior of the bed, suggesting greater total leaf area. Densities of larger organisms (> 0.85 mm) were significantly greater in vegetated samples (Z. marina edge and interior) compared to unvegetated, but an analysis of similarities demonstrated significant faunal community differences among each of the identified habitats. Densities of small organisms (0.25-0.85 mm), however, were significantly greater at Z. marina edge compared to unvegetated samples and Z. marina interior. Additionally, secondary production (μg AFDW day^− 1) was estimated based on the size distribution of taxa and showed significantly greater production from samples gathered in Z. marina compared to unvegetated samples. The relative size distribution of taxa was assessed using regression analysis and results showed that the size distribution was similar for samples collected at edge and interior Z. marina, but these distributions differed significantly when compared to unvegetated samples. The results of this study suggest that although similarities exist between edge and interior portions of Z. marina beds, especially compared to unvegetated habitats, noteworthy differences in faunal density, species composition, size distribution, and secondary production exist between edge and interior Z. marina.     

Effect of long photoperiod on the reproductive and bulbing processes in garlic (Allium sativum L.) genotypes

Garlic (Allium sativum L.) genotypes differ considerably in scape length, flowering ability, and seed production. In bolting clones reproductive processes are facilitated by a combination of specific temperature and photoperiod regimes. However, it is yet unclear whether the phase-specific photoperiod effect on florogenesis is universal for all garlic genotypes. We investigated the effect of ambient day length interruption by 10 or 30 days of long photoperiod in ten garlic accessions belonging to four bio-morphological groups. It was evident that garlic genotypes vary significantly in response to long photoperiod, and that in some clones the treatment enhances florogenesis, flower stalk elongation and bulbing. The competition for resources by the simultaneously developing bulb and inflorescence sinks differentially determines the fate of stalk elongation and flower development in the investigated genotypes. It is concluded that florogenesis in garlic can be promoted by exposure to proper environmental stimuli, during pre-planting storage and sprouting to the later growth stages. The genetic variability acquired from sexual reproduction and vegetatively preserved collections can serve in genetic and physiological studies as well as in breeding programs.     

Oxygen consumption and aspects of energetics in a Malaysian population of Natica maculosa Lamarck (Gastropoda) feeding on the trochacean gastropod Umbonium vestiarium (L.)

Oxygen consumption in sea water increased with size and tissue weight of Natica maculosa Lamarck at ambient temperatures (28–29.5 dgC) and salinities (31–32‰) in a fashion comparable with other naticids. When measured in submerged shore sand, oxygen consumption resembled that in sea water among smaller and some larger Natica but was much lower in several larger snails. Even using the higher measurements, respiration accounted for a remarkably low proportion of the energy consumed in Umbonium prey, and this also matches previous findings with Polinices. Limited observations indicate that production of egg collars may account for > 30‰ of the consumption in adult females. Estimation of faeces and mucus were, however, unsuccessful. It is suggested that respiration in nature might be higher than recorded hitherto because of high metabolic costs and very long duration of drilling the shelled prey.     

Effects of moderate and severe iron deficiency chlorosis on fruit yield, appearance and composition in pear (Pyrus communis L.) and peach (Prunus persica (L.) Batsch)

The effects of different levels of Fe-deficiency chlorosis on the fruit yield, appearance and composition of pear and peach trees grown in field orchards have been studied. The major effect of Fe deficiency in both species was a large yield reduction, even when chlorosis was moderate, associated to decreases in fruit tree load. Fruit size increased with moderate chlorosis in both species and decreased with severe chlorosis in peach. In peach, moderate or severe chlorosis affected uniformly all branches, leading to firmer fruits with higher acidity, total phenolics and carboxylates. This indicates a delayed maturity that can be attributed to a low C-availability for fruits. In Fe-deficient pear trees, the majority of fruits (98%) were on non-chlorotic or moderately chlorotic branches, and fruits were less green and firm with an increased sugars/acids ratio. This indicates an advanced fruit maturity that can be attributed to an increased C-availability for fruits. All chlorosis levels increased within-tree variation in fruit appearance.     

Transport of DMAA and MMAA into rice (Oryza sativa L.) roots

Arsenate (As(V)) transport into plant cells has been well studied. A study on rice (Oryza sativa L.) showed that arsenite is transported across the plasma membrane via glycerol transporting channels. Previous studies reported that the dimethylarsinic acid (DMAA) and monomethylarsonic acid (MMAA) uptake in duckweed (Spirodela polyrhiza L.) differed from that of As(V), and was unaffected by phosphate (H₂PO₄). This article reports the transport mechanisms of DMAA and MMAA in rice roots. Linear regression analysis showed that the DMAA and MMAA uptake in rice roots increased significantly (p ≤ 0.0002 and ≤0.0001 for DMAA and MMAA, respectively) with the increase of exposure time. Concentration-dependent influx of DMAA and MMAA showed that the uptake data were well described by Michaelis-Menten kinetics. The MMAA influx was higher than that of DMAA. The DMAA and MMAA uptake in rice roots were decreased significantly (p ≤ 0.0001 and ≤0.0077 for DMAA and MMAA, respectively) with the increase of glycerol concentration indicating that DMAA and MMAA were transported into rice roots using the same mechanisms of glycerol. Glycerol is transported into plant cells by aquaporins, and DMAA and MMAA are transported in a dose-dependent manner of glycerol which reveals that DMAA and MMAA are transported into rice roots through glycerol transporting channels. The DMAA and MMAA concentration in the solution did not affect the inhibition of their uptake rate by glycerol.     

Effects of juvenile hormone on sense organs involved in mating behaviour of Blattella germanica (L.) (Dictyoptera: Blattellidae)

Possible causes of the suppression of mating in juvenile hormone-treated Blattella germanica females, including the roles of the compound eyes and antennal, labial and maxillary palp sensilla in mating, were studied.Either antennectomy or labial palpectomy, but not maxillary palpectomy, leads to complete suppression of mating in females. Vision plays no role in mating. These results show that all the head appendages (antennae and labial and maxillary palps) are important in precopulatory behaviour, individually and collectively. Juvenile hormone treatment of the sixth (last) instar female nymphs leads to retention of nymphal sensillar characteristics on both the antennae and the palps of the resulting adults, with a reduced electroantennogram response. Thus the animal behaves like a nymph and does not mate in spite of its ability to produce pheromone.     

Movements and growth of tagged young-of-the-year Atlantic croaker (Micropogonias undulatus L.) in restored and reference marsh creeks in Delaware Bay, USA

The residence time, movements, and growth of tagged young-of-the-year Atlantic croaker, Micropogonias undulatus L., were studied from July to October 1998 as measures of the success of a marsh restoration project adjacent to Delaware Bay. A total of 8173 croaker (41-121 mm SL) were tagged from each of two creeks in both marshes during July and August with internal sequential coded wire microtags. A prior tag-retention study in the laboratory found a 95% tag retention rate. Of those tagged, 3.6% were recaptured within and nearby the study creeks using seines, otter trawls, and weirs during a 105-day period. Recapture percentages ranged from 1.5% to 6.1% in individual creeks in the restored marsh. There was some movement of tagged fish between creeks in the restored marsh and out into the main creek, but 95% of the recaptures were made in the subtidal and intertidal portions of the same creek in which they were tagged. Fewer fish were recaptured at the reference marsh (1.6% recapture; n=1489 tagged) up to 50 days after tagging, with no evidence of movement between creeks. The average individual growth rates for recaptured croaker was the same in both restored (0.69 mm/day) and reference (0.63 mm/day) marshes before egress from the creeks in September and October. As a result, both created creeks in a restored marsh and natural creeks in a reference marsh appeared to be utilized as young-of-the-year habitat in a similar way during the summer and until egress out of the marshes during the fall, thus this restoration effort has been successful in creating suitable habitat for Atlantic croaker.     

Anti-inflammatory isoflavones and isoflavanones from the roots of Pongamia pinnata (L.) Pierre

A phytochemical study on the roots of Pongamia pinnata afforded five new isoflavone and isoflavanone derivatives (1–5), including two previously undescribed phenylisoflavones possessing an 1,2-oxetane ring, along with 21 known compounds (6–26) among which compound 18 is the first time to be isolated from nature. The structures of the isolated compounds were determined on the basis of 1D, 2D NMR, and HRESIMS. The absolute configurations of the compounds were assigned via analysis of the specific rotations and circular dichroism (CD) spectra, as well as by comparison of the calculated and experimental electronic circular dichroism (ECD) data. All the isolated compounds were evaluated for their inhibitory effects on NO production in LPS-stimulated BV-2 microglial cells. Twelve compounds exhibited different levels of inhibitory effects against NO production, and compound 1 showed the best activity with an IC₅₀ value at 9.0?μM.     

Long-term effects on the nitrogen budget of a short-rotation grey alder (Alnus incana (L.) Moench) forest on abandoned agricultural land

Short-rotation energy forestry is one of the potential ways for management of abandoned agricultural areas. It helps sequestrate carbon and mitigate human-induced climate changes. Owing to symbiotic dinitrogen (N₂) fixation by actinomycetes and the soil fertilizing capacity and fast biomass growth of grey alders, the latter can be suitable species for short-rotation forestry. In our study of a young grey alder stand (Alnus incana (L.) Moench) on abandoned arable land in Estonia we tested the following hypotheses: (1) afforestation of abandoned agricultural land by grey alder significantly affects the soil nitrogen (N) status already during the first rotation period; (2) input of symbiotic fixation covers an essential part of the plant annual N demand of the stand; (3) despite a considerable N input into the ecosystem of a young alder stand, there will occur no significant environmental hazards (N leaching or N₂O emissions). The first two hypotheses can be accepted: there was a significant increase in N and C content in the topsoil (from 0.11 to 0.14%, and from 1.4 to 1.7%, respectively), and N fixation (151.5 kg N ha⁻¹ yr⁻¹) covered about 74% of the annual N demand of the stand. The third hypothesis met support as well: N₂O emissions (0.5 kg N ha⁻¹ yr⁻¹) were low, while most of the annual gaseous N losses were in the form of N₂ (73.8 kg N ha⁻¹ yr⁻¹). Annual average NO₃-N leaching was 15 kg N ha⁻¹ yr⁻¹ but the N that leached from topsoil accumulated in deeper soil layers. The soil acidifying effect of alders was clearly evident; during the 14-year period soil acidity increased 1.3 units in the upper 0-10 cm topsoil layer.     

Molecular cloning and functional analysis of two FAD2 genes from American grape (Vitis labrusca L.)

The synthesis of polyunsaturated fatty acids (PUFAs), the most abundant fatty acids in plants, begins with a reaction catalyzed by fatty acid desaturase 2 (FAD2; EC 1.3.1.35), also called microsomal oleate Δ12-desaturase. Since the FAD2 gene was first identified in Arabidopsis thaliana, FAD2 research has gained wide interest as the essential enzyme for synthesizing PUFA. Grapes are one of the most frequently cultivated fruits in the world, with most commercial growers cultivating Vitis vinifera and V. labrusca. Grapeseed oil contains a high proportion, 60–70% of linoleic acid (18:2). We cloned two putative FAD2 genes from V. labrusca cv. Campbell Early based on V. vinifera genome sequences. Deduced amino acid sequences of two putative genes showed that VlFAD2s show high similarity to Arabidopsis FAD2 and commonly contain six transmembrane domain, three histidine boxes and endoplasmic reticulum (ER) retrieval motif representing the characteristics of fatty acid desaturase. Phylogenetic analyses of various plant FAD2s showed that VlFAD2-1 and VlFAD2-2 are separately grouped with constitutive and seed-type FAD2s, respectively. Southern blot showed that one or two bands are found in each lane. Because Campbell Early is a hybrid cultivar, FAD2-1 and FAD2-2 genes may exist as one copy in V. labrusca. Expression analysis in different tissues indicated that VlFAD2-1 is a constitutive gene but VlFAD2-2 is a seed-type gene. Complementation experiments of fad2-1 mutant Arabidopsis with VlFAD2-1 or VlFAD2-2 demonstrated that VlFAD2-1 and VlFAD2-2 can restore low PUFA proportion of fad2 to normal PUFA proportion.     

Spatial dynamics and morphological plasticity of common reed (Phragmites australis) and cattails (Typha sp.) in freshwater marshes and roadside ditches

Over the last decades, the abundance of common reed has significantly increased in freshwater wetlands of eastern North America, and stands of this species are now commonly alternating with stands of cattails. Since these species share many characteristics, the contact zone between common reed and cattail stands may witness strong interspecific interactions. We surveyed stand dynamics in roadside ditches and freshwater marshes at these contact zones over three years, and we examined the morphological plasticity in response to neighbors. Results indicate that common reed is clearly gaining ground over time, while cattails stands are retreating. We also found annual variability in the spatial dynamics, suggesting that other factors, such as the effect of weather conditions on water level, may affect population processes. Interspecific interactions had a detrimental effect on both common reed and cattail biomass. However, common reed showed morphological plasticity in shoot height, number of nodes, and internodes length, while cattails did not. Our observations suggest that common reed has a net competitive advantage over cattails in roadside ditches and freshwater marshes.