Growth trades off with habitat specialization

How differences in niche breadth evolve and are maintained remains largely unknown. The 'jack of all trades is master of none' model of resource specialization has been widely considered, but, to our knowledge, never before supported empirically. It invokes performance trade-offs associated with specialization. Specialists should outperform generalists on a subset of resources, but be unable to maintain high performance over a broader range of resources. By contrast, generalists should perform less well, on average, using a greater diversity of resources. We report such trade-offs among four coral goby species in the wild. Habitat specialists grew faster than generalists in one of two habitats. Average growth rates of generalists were less than that of specialists, but more consistent between habitats. Performance trade-offs associated with resource specialization could influence the evolution and maintenance of narrow niche breadth.     

The development of the mucilage gland of two Japanese species ofAlaria

The genusAlaria possesses a structure known as the mucilage gland which appears mainly on the frond. This is also true ofUndaria. The mucilage gland ofUndaria usually originates from some of the epidermal cells. However, observations of plants ofAlaria at various stages indicate that glands originate not only in the surface layer. There are still other glands which are initiated by some cortical cells situated directly beneath the epidermis. In both, a refractive substance is gradually accumulated as these cells enlarge. The mucilage glands starting in the surface (the primary mucilage glands) resemble those ofUndaria in their development, whereas those in the cortex (the secondary mucilage glands) are quite analogous to the secretory cells ofLaminaria, etc., which secrete mucilage into a mucilage canal in the first stage. Thus,Alaria seems to constitute a link betweenUndaria andLaminaria, etc.     

Callus Growth and Plantlet Regeneration in Taro, Colocasia esculenta var. esculenta (L) Schott (Araceae)

Explants of taro cultivars belonging to Colocasia esculentavar. esculenta have been nearly impossible to culture untilrecently. Here, we describe a method which induces callus formationfrom bud explants of Colocasia esculenta var. esculenta cv.Akalomamale, brings about shoot and root production, and leadsto plantlet regeneration. The medium used is half-strength Murashige-Skoog(HMS) solution containing 25 ml taro tuber extract (TE), 2 mg2, 4, 5-trichlorophenoxyacetic acid and 200 mg glutamine 1^–1.TE is an important requirement for bud explants and callus tissues.Root induction on callus-derived shoots (i.e. plantlet formation)occurs on HMS containing only 25 ml TE and 100 ml coconut water1^–1. Taro, Colocasia esculenta var. esculenta (L) Schott (Araceae), coconut water, micropropagation, plantlet regeneration, root formation, taro extract, tissue culture     

Reproduction and fecundity of the musselmytilus edulis at helgoland (North sea)

The reproductive cycle of aMytilus edulis population in the lower tidal zone at the island of Helgoland from Spring 1980 to Summer 1981 is described. In both years the spawning period extended from the end of April until the end of June at water temperatures between 6° and 14°C. The gametes were built up again in autumn and most individuals were mature in February. Sex ratio did not differ significantly from 1:1. Fecundity, egg diameter and gamete weight of this and another population in the subtidal zone were assessed and size frequency distribution of shell lengths was established. Based on data of body weight prior to spawning, the following tendencies could be outlined: animals of the intertidal population had significantly smaller eggs than those from the subtidal area. Although the soft body biomass per unit area of the subtidal population was nearly double that of the tidal, their annual egg output was nearly the same (2.3 × 10⁹ eggs m^?2). This was achieved by a smaller size at the onset of sexual maturation (18 mm instead of 30 mm shell length) and a higher egg output at comparable shell lengths in the intertidal. In both populations, large animals contributed most to gamete production, although they did not necessarily dominate in biomass.     

A Comparison of Two Approaches for Modelling Cassava (Manihot esculenta Crantz.) Crop Growth

Two approaches for modelling the growth and development of cassava,Manihot esculenta Crantz, are described and evaluated. The twomodels differ only in the hypotheses accounting for storageroot growth. In model 1, assimilate allocation to storage rootsis governed by the combined Chanter's (1976: Mathematical modelsin mushroom research and production. PhD Thesis, Universityof Sussex, UK) growth equation; and in model 2 the spill-overhypothesis for assimilate allocation to storage root governsstorage root growth. In both models, canopy photosynthesis generatesthe carbon substrate required for all growth processes. Thegrowth rates of leaves, stems and storage roots are definedby growth equations subject to substrate saturation kinetics.A key feature of both models is that the growth demands of thestem, fibrous roots and storage roots are related to leaf demandrates. Allocation to stems and branches was modelled by meansof a modified logistic growth equation which includes all theparameters and variables (number of nodes, internode lengths,stem density, stem modulus of elasticity and branch tensilestrength) that define the limits of the load bearing capacityof the shoot's supportive structures. The correlation coefficientsfor determination of yield prediction for the models werer =0.898,P =0.0385 (model 1) and r =0.954, P =0.0117 (model 2). For agrowth season of 290 d (after which leaf area index equals zeroand crop growth ceases), both models simulate the sigmoidaltransition from the lag to exponential phase of crop growth.Both models are equally well corroborated by observed data;however, model 1 has greater explanatory power. Copyright 2000Annals of Botany Company Allocation, simulation, model, crop growth, cassava, Manihot esculenta Crantz.     

Growth of Vibrio cholerae O1 in red tide waters off California

Vibrio cholerae serotype O1 is autochthonous to estuarine and coastal waters. However, its population dynamics in such environments are not well understood. We tested the proliferation of V. cholerae N16961 during a Lingulodinium polyedrum bloom, as well as other seawater conditions. Microcosms containing 100-kDa-filtered seawater were inoculated with V. cholerae or the 0.6- micro m-pore-size filterable fraction of seawater assemblages. These cultures were diluted 10-fold with fresh 100-kDa-filtered seawater every 48 h for four cycles. Growth rates ranged from 0.3 to 14.3 day(-1) (4.2 day(-1) +/- 3.9) for V. cholerae and 0.1 to 9.7 day(-1) (2.2 +/- 2.8 day(-1)) for bacterial assemblage. Our results suggest that dissolved organic matter during intense phytoplankton blooms has the potential to support explosive growth of V. cholerae in seawater. Under the conditions tested, free-living V. cholerae was able to reach concentrations per milliliter that were up to 3 orders of magnitude higher than the known minimum infectious dose (10(4) cell ml(-1)) and remained viable under many conditions. If applicable to the complex conditions in marine ecosystems, our results suggest an important role of the growth of free-living V. cholerae in disease propagation and prevention during phytoplankton blooms.     

Growth of Vibrio cholerae O1 in Red Tide Waters off California

Vibrio cholerae serotype O1 is autochthonous to estuarine and coastal waters. However, its population dynamics in such environments are not well understood. We tested the proliferation of V. cholerae N16961 during a Lingulodinium polyedrum bloom, as well as other seawater conditions. Microcosms containing 100-kDa-filtered seawater were inoculated with V. cholerae or the 0.6-μm-pore-size filterable fraction of seawater assemblages. These cultures were diluted 10-fold with fresh 100-kDa-filtered seawater every 48 h for four cycles. Growth rates ranged from 0.3 to 14.3 day⁻¹ (4.2 day⁻¹ ± 3.9) for V. cholerae and 0.1 to 9.7 day⁻¹ (2.2 ± 2.8 day⁻¹) for bacterial assemblage. Our results suggest that dissolved organic matter during intense phytoplankton blooms has the potential to support explosive growth of V. cholerae in seawater. Under the conditions tested, free-living V. cholerae was able to reach concentrations per milliliter that were up to 3 orders of magnitude higher than the known minimum infectious dose (10⁴ cell ml⁻¹) and remained viable under many conditions. If applicable to the complex conditions in marine ecosystems, our results suggest an important role of the growth of free-living V. cholerae in disease propagation and prevention during phytoplankton blooms.     

Photosynthetic performance of deep-water macroalgae (Phaeophyta,Dictyotales) off Bermuda

Photosynthetic performance and dark respiration rates were determined in situ for abundant macroalgae occurring between 27–49 m depths off Bermuda. Brown algae, particularly members of the order Dictyotales, predominated at all deep-water sites, and Stypopodium zonale was the most abundant species. Species showed net photosynthesis at very low ambient irradiances (<0.01 maximum I_o). Lobophora variegata, a species with a highly decumbent growth form, had low productivity across all irradiances. In contrast, Dictyota spp. (D. bartayresii, D. dichotoma, D. divaricata) and S. zonale had high photosynthetic capacity (ca. 400 µmol O₂ gdw^–1 h^–1), and light saturation was not evidenced at the highest ambient irradiance level (300 µE m^–1 s^–1) for species with thin, flat thalli. Light-harvesting pigment concentrations reflected tissue-nitrogen levels. C:N atom ratios, except for L. variegata and D. divaricata, were within the ratio for balanced growth. The repeated occurrence and photosynthetic efficiency of these Dictyotalean species in subtropical and tropical deep-water habitats emphasize their successful adaptation to low-light, nutrient-poor environments.     

Structure and In Vitro Growth of Zygotic Embryos of Taro (Colocasia esculenta var. antiquorum)

Zygotic embryos of taro, Colocasia esculenta var. antiquorumwere examined using both light and scanning electron microscopyand cultured on Linsmaier-Skoog (LS) medium without the additionof growth regulators. Embryos present within mature seed consistof a hypocotyl-root axis and an undeveloped cotyledon and aresurrounded by two major types of endosperm cells, aleurone andstarchy endosperm. Embryos cultured on LS medium developed intomature plants only in the presence of endosperm tissue. Excisedembryos turned green after 2–4 d in culture and reacheda rapid growth period between days 4 and 6. Culture of taroembryos leading to viable plantlet development depends upon(1) removal of the outer and inner integument, and (2) the presenceof endosperm tissue (including an intact aleurone layer). Colocasia esculenta var. antiquorum, Araceae, taro, embryo culture, integument, endosperm     

恒温和变温培养对羊肚菌菌丝生长及菌核形成影响的比较研究

为了探究恒温和变温培养对羊肚菌菌丝生长和菌核形成的影响,设置-9℃-30℃的7个恒温处理,3个变温处理,通过观察和记录在两种不同培养方式下菌丝的长势、生长速度、菌落干重、产核时间、菌核数量等内容,从而比较出恒温和变温培养对羊肚菌菌丝生长和菌核形成的影响效果。结果表明,在恒温条件下羊肚菌菌丝生长和菌核发育比变温好,20℃最适宜菌丝生长,菌丝生长速度较快,菌落干重最大;25℃最适宜菌核生长发育,产核最早。菌核数量最多。     

Glucosidase inhibitor from Umbilicaria esculenta

Inhibitory activity toward beta-glucosidase was detected in extracts of the lichen, Umbilicaria esculenta. The extract showed strong inhibition of disaccharide hydrolytic enzymes of mold and mammalian origin, but weak or no inhibition of polysaccharide hydrolytic enzymes except glucoamylase and laminarinase. The inhibitor in the extract was very stable, retaining more than 95% of its activity when treated with heat, acid, alkali, and some hydrolytic enzymes. Purified inhibitor was identified as 1-deoxynojirimycin (1,5-dideoxy-1,5-immino-D-glucitol) by NMR spectrometry, which was known to be produced by Streptomyces sp. and the plant Morus sp. Extracts from Parmelia austrosinensis, Parmelia praesorediosa, and an unidentified lichen species, showed glucosidase inhibitory activities similar to U. esculenta.     

Quantitative Growth Relationships of Cassava (Manihot esculenta Crantz): Crop Development in a Savanna Wet Season

Growth characteristics of Manihot esculenta Crantz cv. Cubanawere determined for a crop, cultivated in savanna soil withfive different levels of fertilizer. A population of 25000 plantsha^–1 was studied using conventional growth analysis techniques. The storage root does not act as a sink for large amouns ofassimilates and differences in growth response were mainly aresult of the morphology development and function of leavesin the cassava canopy (source activity). Thus, during tuberization,the cultivar Cubana produces a progressively higher proportionof new leaves, maintaining throughout the season a relativelyhigh net assimilation rate and leaf area index. Manihot esculenta Crantz, Cassava, source-sink relationship, net assimilation rate, leaf area index, growth analysis     

Growth kinetics related to physiological parameters in young Saccorhiza dermatodea and Alaria esculenta sporophytes exposed to UV radiation

Young sporophytes of Saccorhiza dermatodea and Alaria esculenta cultured from Spitsbergen isolates were exposed in the laboratory to either only photosynthetically active radiation (PAR) or to a spectrum including UV-radiation (PAR+UVA+UVB) by use of cutoff glass filters. The plants were grown at 8±2°C and 16:8 h light–dark cycles with 6 h additional UV exposure in the middle of the light period. Growth was measured every 10 min using growth chambers with online video measuring technique for 18–21 days. Tissue morphology and absorption spectra were measured in untreated young sporophytes while tissue chlorophyll-a content and DNA damage were measured from treated thalli at the end of the experiment. Under UVR, growth rates of S. dermatodea were significantly reduced while A. esculenta have a potential to acclimate. Tissue chlorophyll-a contents in both species were not significantly different between treatments suggesting that these algae may acclimate to moderate UVR fluence. Higher DNA damage in S. dermatodea effectively diverted photosynthetic products for repair constraining growth. Tissue optics (opacity and translucence) was correlated to the tissue absorbance in the UVR region characteristics of phlorotannin, an important UV-absorbing compound in brown macroalgae. Growth rates of sporophytes of both species exposed to PAR without UV was similar during day and night. The results showed that both species can recruit and inhabit a similar coastal zone when appropriate strategies are expressed to minimize damage in response to the stress factor.     

Molecular analysis off the phylogeny off 11 genera off the Corvidae

Phylogenetic analysis of 11 genera of Corvidae has been undertaken using a sequence of 925 bp of the cytochrome b gene of the mtDNA. Both maximum-parsimony and maximum-likelihood analyses were performed, and different weighting schemes have been used according to the saturation observed in the data (mostly at the third codon position). The cytochrome b data provide good evidence for the monophyly of the Corvidae, including the Piapiac Ptilostomus afer in spite of its aberrant morphology. In all analyses, the choughs are the first lineage emerging in the family; this result conflicts with the traditional chough-crow group, as well as the hypothesis of the ancestral position of the jays. The monophyly of the American jays is well supported by the molecular data, unlike the Palearctic jays, which are not closely related. The other intergeneric relationships are not strongly supported by bootstrap proportions, and are not congruent in all different weightings and methods, except for groups of species of the same or very closely related genera.