Two new species of Phyllonema (Rivulariaceae,Cyanobacteria) with an emendation of the genus

Two untapered, heterocytous species were observed and collected from the intertidal and supratidal zones of the Mexican coastline of the Pacific Ocean near Oaxaca and from the Gulf of Mexico. These populations were highly similar in morphology to the freshwater taxon Petalonema incrustans in the Scytonemataceae. However, 16S rRNA sequence data and phylogenetic analysis indicated that they were sister taxa to the epiphyllic, Brazilian species Phyllonema aveceniicola in the Rivulariaceae, described from culture material. While genetic identity between the two new species was high, they differed significantly in morphology, 16S rRNA gene sequence identity, and sequence and structure of the 16S–23S ITS region. Their morphology differed markedly from the generitype of the previously monotypic Phyllonema, which has tapered, heteropolar, single‐false branched trichomes with very thin or absent sheath. The two new species, Phyllonema ansata and Phyllonema tangolundensis, described from both culture and environmental material, have untapered, isopolar, geminately false branched trichomes with thick, lamellated sheaths, differences so significant that the species would not be placed in Phyllonema without molecular corroboration. The morphological differences are so significant that a formal emendation of the genus is required. These taxa provide a challenge to algal taxonomy because the morphological differences are such that one would logically conclude that they represent different genera, but the phylogenetic evidence for including them all in the same genus is conclusive. This conclusion is counter to the current trend in algal taxonomy in which taxa with minor morphological differences have been repeatedly placed in separate genera based primarily upon DNA sequence evidence.     

Variable responses of tuber moth to the leaf trichomes of wild potatoes

This study examines the response of tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), during the initial stages of attack, to variability in trichome density and composition on foliage of Solanum berthaultii (Hawkes) and Solanum tarijense (Hawkes) (Solanaceae). Solanum berthaultii bears two types of glandular trichome (type A and type B) that together reduced oviposition by the moth. Females were often completely deterred from ovipositing on foliage with >300 trichomes per cm². In contrast, neonate establishment on S. berthaultii was generally positively related to trichome densities, indicating that trichomes may be a poor defense against P. operculella when the moth oviposits in soil and neonate larvae select the host plant. Solanum tarijense has only one type of glandular trichome (type A) and eglandular hairs. Most eggs were deposited on the adaxial leaf surfaces that had lower trichome densities. Although the density of type A trichomes was negatively related to oviposition, high densities of hairs on the abaxial and adaxial leaf surfaces appeared to stimulate oviposition, leading to stronger positive relations between hair densities and oviposition. Larvae generally established on the abaxial surface where hair densities were greatest. Relationships between the abaxial densities of leaf hairs and neonate establishment on S. tarijense were positive. The results indicate that the responses by P. operculella to the types and density of trichomes are complex. Whereas type A and type B trichomes may act synergistically to reduce oviposition by the moth, leaf hairs do not defend against oviposition and neither leaf hairs nor type A and B trichomes reduce neonate establishment by this herbivore species.     

TOMATO TRICHOMES AND MUTATIONS AFFECTING THEIR DEVELOPMENT

A new trichome type for the genus Lycopersicon is described in L. esculentum Mill. It is a short (0.03–0.08 mm), pendant, glandular hair with a club-shaped head consisting of 8–12 cells. Two previously described “hairless” mutations were examined microscopically. One, hl, does not affect the frequency of hairs nor the number of cells per hair, but causes abnormal enlargement of the stalk cells of all hair types, and thus produces shortened, extremely bent and twisted hairs. Observations on the time of action of this gene indicate that in trichome development two to four cell divisions occur prior to any appreciable cell enlargement. The second mutation, h, affects only the large type of trichome. This mutation effects a developmental shift from trichome to stomatal apparatus at the apex of the multicellular base normally supporting the large trichomes.     

Trichome morphology provides phylogenetically informative characters for Tremandra, Platytheca and Tetratheca (former Tremandraceae)

Summary Trichomes of Tremandra R.Br. ex DC., Platytheca Steetz and Tetratheca Sm. (Elaeocarpaceae, former Tremandraceae), together with two outgroup species of Elaeocarpus L., are illustrated using scanning electron microscopy, and their distribution on various plant organs is documented. Various trichomes types were identified that relate taxa: simple hairs, stellate hairs, short glandular trichomes, long glandular trichomes, and three forms of tubercules. Both outgroup and ingroup taxa have simple hairs. Stellate hairs are confirmed as unique to Tremandra. Prominent and sculptured multicelled tubercules, some bearing a stout hair, are characteristic of Platytheca. Smaller multicelled tubercules occur in both Platytheca and Tetratheca, except for the Western Australian taxon Te. filiformis Benth. (possibly plesiomorphic). Unicellular tubercules (papilla) characterise two species of Tetratheca. Short glandular trichomes, usually found on the ovary, also occur in both of these genera but not in all species (possibly secondary losses), while long glandular trichomes, usually on stems and leaves, occur only in some groups of Tetratheca. Within Tetratheca, Western Australian taxa that have five-merous flowers fall into three ‘groups’: seven species (together with one from South Australia) that have short glandular trichomes but no long glandular trichomes; six species that have long glandular trichomes but no short glandular trichomes; and four species that have both trichome types. All other species of Tetratheca have four-merous flowers and form two ‘groups’: 12 eastern species (including one from South Australia) that have both short glandular trichomes and long glandular trichomes; 4 western species and six eastern species that lack short glandular trichomes. On the basis of these characters, a phylogenetic hypothesis for the three genera is presented.     

黑龙江悬钩子属植物叶表皮形态结构的研究

利用扫描电子显微镜对黑龙江悬钩子属植物的叶表皮形态结构进行比较研究。结果显示:(1)悬钩子属植物叶的上表皮细胞呈多边形,垂周壁平直,或无规则形,垂周壁浅波纹;下表皮细胞无规则形,垂周壁浅波纹或深波纹。(2)表皮毛类型有单细胞直立不分支、卷曲不分支,头状腺毛和盾状腺毛四种类型。(3)气孔器均分布于下表皮,且气孔器类型为无规则形;气孔外拱盖单层、内缘平滑或不规则波状。研究表明,黑龙江悬钩子属植物的叶表皮微形态学特征表现出一定差异性,对种间的划分和鉴定具有一定的分类学意义。     

Ultrastructural ontogeny of leaf cavity trichomes inAzolla implies a functional role in metabolite exchange

Summary Anabaena azollae is associated with two types of multicellular epidermal trichomes inAzolla leaf cavities, the simple and branched hairs. The observation of transfer cell ultrastructure in some hair cells led to speculation that the cavity hairs might participate in metabolite exchange between the symbionts. The developmental ontogeny of cavity trichomes is described here, using transmission electron microscopy, with a goal of improving our understanding of possible functions of these structures in the symbiosis. The observations have established that all cells of simple and branched hairs develop the structural characteristics of transfer cells, but not simultaneously. Rather, there is an acropetal succession of transfer cell ultrastructure beginning in terminal cells, moving to body cells where present, and ending in stalk cells. The transfer cell stage is followed immediately by senescence in all hair cells. The timing of transfer cell differentiation, considered together with information from other studies, suggests that branched hairs may be involved in exchange of fixed nitrogen between the symbionts, while simple hairs may participate in exchange of fixed carbon fromAzolla toAnabaena. Contribution no. 869 from the Battelle-C. F. Kettering Research Laboratory.     

Growth,trichome size and akinete production of Cylindrospermopsis raciborskii (cyanobacteria) under different temperatures: Comparison of two strains isolated from the same pond

Coiled morphotype Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju that forms a water bloom in a shallow pond in northern Taiwan exhibits a negative correlation between trichome size and temperature. To investigate how temperature influences the growth and trichome size of C. raciborskii, two C. raciborskii strains isolated from the pond in August and February were grown at three temperatures (18, 24 and 30°C). Both strains exhibited the lowest and highest specific growth rates at 18°C and 24°C, respectively, and the trichomes became the largest at 18°C. However, specific growth rates of the strain isolated in August exceeded those of the strain isolated in February, and the trichomes of the strain isolated in February were larger than those of the strain isolated in August regardless of temperature. Moreover, although both strains produced larger numbers of akinetes at higher temperatures, the strain isolated in August produced many more akinetes than did the other. These findings suggest that the two strains are not identical, leading to the conclusion that the C. raciborskii population in the pond consists of at least two ecotypes. Large trichome formation and akinete production are thought to be different types of countermeasure against cold of C. raciborskii, and the patterns of investment in developing these functions seemed to vary between the strains.     

The defensive role of trichomes in black medick (Medicago lupulina,Fabaceae)

Simple and gland-tipped trichomes occur in varying proportions in the cosmopolitan weed black medick (Medicago lupulina L.). Densities of both simple and glandtipped trichomes were separately negatively correlated with the amount of damage to leaves in herbarium collections from throughout the world. This indicates that both types of trichomes are protective against herbivores, but suggests that the two types of hair differ in effectiveness against different species. Since an average of less than 1% herbivore consumption of the foliage of black medick was observed, it is remarkable that adaptive value of the trichomes was demonstrable. In a greenhouse experiment, both gland-tipped and simple hairs provided considerable resistance against whitefly oviposition. For both herbarium collections and the greenhouse experiment, conspicuously fewer gland-tipped hairs than simple hairs were required to achieve a given level of resistance to insects. Low trichome density considerably reduced damage in comparison to the absence of trichomes, while increasing density was progressively less efficient, suggesting that moderate pubescence is the most desirable strategy.     

EOCENE ALGAE AND PLANT HAIRS FROM THE GREEN RIVER FORMATION OF WYOMING

Four new species of algae and two kinds of fossil plant hairs are described from a rich oil shale bed of the mid-Eocene Green River Formation of Wyoming. Two of the algae belong to the Cyanophyceae and two to the Chlorophyceae. On the basis of their morphology alone, they are assigned to four new species among four genera, as follows: Symploca hedraia, sp. n.; Stigonema anchistina, sp. n.; Schizochlamys haywellensis, sp. n.; and Spirogyra wyomingia, sp. n. One kind of fossil plant hair is similar to those observed in organic sediments of an existing lake and identified with trichomes on the under surface of live oak leaves (Quercus virginiana). Assignment of the fossil trichomes to a taxon is not warranted at present.     

Morphological synergism in root hair length,density, initiation and geometry for phosphorus acquisition in Arabidopsis thaliana: A modeling approach

Low phosphorus availability regulates root hair growth in Arabidopsis by (1) increasing root hair length, (2) increasing root hair density, (3) decreasing the distance between the root tip and the point at which root hairs begin to emerge, and (4) increasing the number of epidermal cell files that bear hairs (trichoblasts). The coordinated regulation of these traits by phosphorus availability prompted us to speculate that they are synergistic, that is, that they have greater adaptive value in combination than they do in isolation. In this study, we explored this concept using a geometric model to evaluate the effect of varying root hair length (short, medium, and long), density (0, 24, 48, 72, 96, and 120 root hairs per mm of root length), tip to first root hair distance (0.5, 1, 2, and 4 mm), and number of trichoblast files (8 vs. 12) on phosphorus acquisition efficiency (PAE) in Arabidopsis. SimRoot, a dynamic three-dimensional geometric model of root growth and architecture, was used to simulate the growth of Arabidopsis roots with contrasting root hair parameters at three values of phosphorus diffusion coefficient (D _e=1×10^–7, 1×10^–8, and 1×10^–9 cm² s^–1) over time (20, 40, and 60 h). Depzone, a program that dynamically models nutrient diffusion to roots, was employed to estimate PAE and competition among root hairs. As D _e decreased from 1×10^–7 to 1×10^–9 cm² s^–1, roots with longer root hairs and higher root hair densities had greater PAE than those with shorter and less dense root hairs. At D _e=1×10^–9 cm² s^–1, the PAE of root hairs at any given density was in the order of long hairs > medium length hairs > short hairs, and the maximum PAE occurred at density = 96 hairs mm^–1 for both long and medium length hairs. This was due to greater competition among root hairs when they were short and dense. Competition over time decreased differences in PAE due to density, but the effect of length was maintained, as there was less competition among long hairs than short hairs. At high D _e(1×10^–7 cm² s^–1), competition among root hairs was greatest among long hairs and lowest among short hairs, and competition increased with increasing root hair densities. This led to a decrease in PAE as root hair length and density increased. PAE was also affected by the tip to first root hair distance. At low D _e values, decreasing tip to first root hair distance increased PAE of long hairs more than that of short hairs, whereas at high D _e values, decreasing tip to first root hair distance increased PAE of root hairs at low density but decreased PAE of long hairs at very high density. Our models confirmed the benefits of increasing root hair density by increasing the number of trichoblast files rather than decreasing the trichoblast length. The combined effects of all four root hair traits on phosphorus acquisition was 371% greater than their additive effects, demonstrating substantial morphological synergy. In conclusion, our data support the hypothesis that the responses of root hairs to low phosphorus availability are synergistic, which may account for their coordinated regulation.     

Symbiotic properties of sinorhizobia isolated from Acacia and Prosopis nodules in Sudan and Senegal

The host specificity, infection process and effectiveness of nodules produced by several African sinorhizobial strains on different Acacia and Prosopis species (Leguminosae, Mimosoideae) were studied. Sinorhizobium arboris strain HAMBI 1552^T, S. kostiense strains HAMBI 1489^T and HAMBI 1493, S. saheli strain HAMBI 1496 and S. terangae bv. acaciae strain ORS 1058 induced nitrogen fixing nodules on seedlings of the following African or Latin American species (marked with ^*): A. angustissima ^* , A. mellifera, A. nilotica, A. oerfota (synonym A. nubica), A. senegal, A. seyal, A. sieberiana, A. tortilis subsp. raddiana, P. chilensis ^* , P. cineraria, P. juliflora and P. pallida ^* . All strains increased plant yield significantly compared with uninoculated seedlings watered with nitrogen-free medium, but none appeared to be superior. The sinorhizobial strains were unable to effectively nodulate Sesbania rostrata (Papilionoideae).All roots had hairs, but particularly in the case of Acacia spp. they were often sparse. After inoculation root hairs were deformed and, in general, infection in Acacia spp. occurred through short root hairs and in Prosopis spp. through longer ones. After entry, the rhizobia filled infection pockets in the root hair, which later expanded into sac-like structures. When infection threads occurred, they usually started from sac-like structures. Elongation and ramification of the nodules indicated that Acacia spp. and Prosopis spp. have indeterminate nodules. A persistent apical meristem, which is the characteristic feature of the indeterminate nodule type, was much clearer in Prosopis spp. than in Acacia spp. Sinorhizobial strains formed tumour-like structures with undifferentiated cell tissue on the Australian acacia A. holosericea and ineffective, nodule-like structures on the African P. africana.     

The shape of wind-receptor hairs of cricket and cockroach

We examined the exact shapes of the thread-like wind-receptor hairs in the cricket and cockroach. The diameters of hairs at various distances from the hair tip as measured by scanning electron microscopy revealed unexpected hair shapes. We had expected, a priori, that the shape of the hair would be a slender linearly tapered cone, but the measurements revealed hairs in the form of extremely elongated paraboloids. The diameter of the wind-receptor hairs varies with the square root of the distance from the hair tip, i.e., the diameter rapidly increases with the distance from the tip and is asymptotic to the base diameter. Both the cricket, Gryllus bimaculatus, and the cockroach, Periplaneta americana, showed the same hair shape. In both insects, the formation of the wind-receptor hair during metamorphosis seems to be controlled by a common cytological program. The shape of the hair constrains the mobility of the wind-receptor hair, because both the drag force caused by moving air and the moment of inertia of motion dynamics are functions of shaft diameter. The shape of the hair is a biological trait which affects the sensory information transmitted to the central nervous system. Accepted: 24 February 1998     

Structure and distribution of floral trichomes in Lycaste and Sudamerlycaste (Orchidaceae: Maxillariinae s.l.)

Phylogenetic analysis indicates that Lycastinae should be incorporated into a more broadly defined Maxillariinae. This is supported by several anatomical features, including the presence of sunken, glandular trichomes in both Lycastinae and Maxillariinae s.s. Until recently, these were known only from vegetative organs, but have since been reported from flowers of Maxillaria dichroma. One character currently used to distinguish between Lycaste and Sudamerlycaste is the distribution of floral trichomes. In this article, we test the reliability of this character, describe the floral micromorphology of Lycaste and Sudamerlycaste and investigate whether their flowers bear sunken hairs. Their floral micromorphology is compared with that of other genera currently assigned to Maxillariinae s.l. Flowers of Lycaste and Sudamerlycaste bear conical or obpyriform papillae and unbranched and unequally branched multicellular trichomes. Contrary to previous reports that trichomes are confined to the column in Sudamerlycaste, they also occur in the tepal axils. Labellar trichomes, although often present in Lycaste, are lacking in Sudamerlycaste. In Lycaste sections Lycaste and Aromaticae, floral trichomes tend to be unbranched, whereas section Intermediae has both unbranched and branched hairs. Branched hairs are more common in Sudamerlycaste. Some hairs are tracheoidal, pitted and lignified. These mainly occur in section Lycaste and, to a degree, in section Intermediae, but are absent from section Aromaticae and most species of Sudamerlycaste. Branched column hairs, present in Sudamerlycaste, are absent from all sections of Lycaste, and tracheoidal column hairs occur only in Sudamerlycaste. Sunken floral hairs are absent from both genera. Trichome structure and distribution may prove useful in distinguishing between these taxa and in elucidating the intergeneric relationships of Maxillariinae s.l.© 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 409–421.     

Early interactions between Alnus glutinosa and Frankia strain ArI3. Production and specificity of root hair deformation factor(s)

Actinomycetes from the genus Frankia are able to form symbiotic associations with more than 200 different species of woody angiosperms, so called actinorhizal plants. Many actinorhizal plants are infected via deformed root hairs. Factor(s) eliciting root hair deformation in actinorhizal symbioses have been found to be released into the culture medium, but the factor(s) has (have) not yet been characterized. In the present work, we describe the constitutive production of factor(s) by Frankia strain ArI3 causing root hair deformation on Alnus glutinosa . Deformation was detected after 4–5 h of incubation with both Frankia cultures and their cell-free culture filtrates. When culture filtrate was used, deformation was concentration dependent. A contact time of 2 min between culture filtrate and host roots was sufficient to induce subsequent root hair deformation. No root hair deformation on A. glutinosa could be detected with purified Nod factors from Rhizobium meliloti or R. leguminosarum biovar viciae . No correlation was found between Frankia strains belonging to different host specificity groups and their ability to deform root hairs on A. glutinosa. However, strains not able to deform root hairs on A. glutinosa were also unable to nodulate.     

Pectinase production by a Brazilian thermophilic fungus <Emphasis Type="Italic">Thermomucor indicae-seudaticae</Emphasis> N31 in solid-state and submerged fermentation

Thermophilic organisms produce thermostable enzymes, which have a number of applications, justifying the interest in the isolation of new thermophilic strains and study of their enzymes. Thirty-four thermophilic and thermotolerant fungal strains were isolated from soil, organic compost, and an industrial waste pile based on their ability to grow at 45°C and in a liquid medium containing pectin as the only carbon source. Among these fungi, 50% were identified at the genus level as Thermomyces, Aspergillus, Monascus, Chaetomium, Neosartoria, Scopulariopsis, and Thermomucor. All isolated strains produced pectinase during solid-state fermentation (SSF). The highest polygalacturonase (PG) activity was obtained in the culture medium of thermophilic strain N31 identified as Thermomucor indicae-seudaticae. Under SSF conditions on media containing a mixture of wheat bran and orange bagasse (1 : 1) at 70% of initial moisture, this fungus produced the maximum of 120 U/ml of exo-PG, while in submerged fermentation (SmF) it produced 13.6 U/ml. The crude PG from SmF was more thermostable than that from SSF and exhibited higher stability in acidic pH.     

The Amoeba-to-Flagellate Transformation Test is not Reliable for the Diagnosis of the Genus Naegleria. Description of three new Naegleria spp.

Trophozoites of several isolates from one location in Australia have failed consistently to transform into flagellates, although they display all other characteristics of the genus Naegleria. When changing the standard transformation test, flagellates were produced. In phylogenetic trees derived from partial small subunit ribosomal DNA (SSUrDNA) sequences, one of these strains branches close to a cluster comprising N. clarki, N. australiensis, N. italica and N. jadini. It is proposed that these Australian isolates represent a new species, named N. fultoni (strain NG885). Failing to form flagellates since their isolation, even when different transformation procedures are used, are two Naegleria strains from Chile and Indonesia. In SSUrDNA-based phylogenetic trees the Chilean strain clusters with N. pussardi and the Indonesian strain clusters with N. galeacystis, but the degree of sequence difference from these described species (3.5% and 2.2%, respectively) is sufficient to propose that both of the strains represent new species, named N. chilensis (strain NG946) and N. indonesiensis (strain NG945), respectively. The close relationships between each of the new species and the Naegleria species with which they cluster in SSUrDNA-based trees were confirmed by ribosomal internal transcribed spacer region (ITS) sequence comparisxdons. In France, several non-flagellating N. fowleri strains were isolated from one location. ITS rDNA sequence comparisons indicated that they correspond to a ‘type’ of N. fowleri found in both Europe and the USA. A redefinition of the genus Naegleria is proposed as a consequence of these and previous findings.     

中国特有属藤山柳属(猕猴桃科)植物的叶表皮形态及其分类学意义

由于形态特征变异和地理分布区域存在重叠,中国特有属藤山柳属(猕猴桃科)的物种划分问题长期以来存在争议,曾被分为20种或修订为含1种4个亚种的单型属。该研究选取了在形态和地理分布上有代表性的29个居群的184份标本,利用光学显微镜和扫描电镜观察了叶表皮形态和微形态特征,以探讨它们的分类学意义。结果表明:(1)藤山柳属植物叶表皮毛被的形态和微形态特征有3类,即光滑-短柱状毛、刚毛-长柱状毛/长刺毛、绒毛-单列多细胞毛,且这些特征在居群间差异明显,并各具明显的地理分布格局,支持把藤山柳属分为3类,即光滑类、刚毛类和绒毛类。(2)3类藤山柳植物在个别居群表现出部分同域分布现象,在峨眉山不同海拔高度的3个居群存在垂直地带性分布特点。(3)藤山柳属植物叶表皮的其他形态特征,如不规则型表皮细胞、6类气孔器、叶表皮初级蜡质纹饰以网状隆起为主,伴随着2～4类次级纹饰,在居群间变化多样等均没有明显的分类学意义。(4)由于具有相同的叶表皮形态特征和地理分布,建议把繁花藤山柳合并到绒毛藤山柳,故支持藤山柳属是1个正处于分化进程中的单型属,包括1个种3个亚种。     

Studies on Mold Dextranases

Nine strains capable of producing dextranase were isolated from soil. Among them, a strain belonging to the genus Aspergillus was chosen as the best producer of the enzyme. The mold produced greater amounts of dextranase than those found in some strains in the genus Penicillium, when grown aerobically at 28°C for 5 to 6 days in medium containing 1% dextran, 1% NaNO₃ or polypeptone, 0.2% yeast extracts, 0.4% K₂HPO₄ and small amounts of inorganic salts, pH 8.5. From the comparative taxonomic experiments, the mold used here was identified to be a strain belonging to Aspergillus carneus.     

Colonization of biofilms by bacteria capable of biodegrading sodium dodecyl sulphate (SDS) at clean and polluted riverine sites

Fifty cyanobacterial strains (10 genera) were tested in batch culture for their ability to use organic phosphorus compounds (1 mg liter⁻¹ P) as their sole P source. Two monoesters, Na₂-β-glycerophosphate and π-nitrophenyl phosphate (πNPP), supported growth of all strains, and the diester bis-π-nitrophenyl phosphate (bis-π-NPP) and herring sperm DNA supported almost all strains. ATP was either a very favorable or poor P source and failed to support growth of nine strains, seven of which were Rivulariaceae with trichomes ending in a hair or long tapered region. Phytic acid was in general the least favorable P source. P-limited cultures grown initially with inorganic phosphate to conditions of P limitation were also tested for cell-bound and extracellular phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activities at two pH values (7.6, 10.3) using πNPP and bis-πNPP as substrates. Cell-bound PMEase was inducible in all strains and cell-bound PDEase in most strains. Most showed extracellular PMEase, but not extracellular PDEase. The highest values (μM πNPP or bis-πNPP hydrolyzed mg dry weight⁻¹ hour⁻¹) all occurred in strains ofGloeotrichia as follows: cell-bound PMEase at pH 7.6, 2.7 μM in strain D602; cell-bound PMEase at pH 10.3, 5.2 μM in D602; extracellular PMEase at pH 7.6, 0.73 μM in D281; extracellular PMEase at pH 10.3, 6.6 μM in D281; cell-bound PDEase at 7.6, 0.40 μM in D613; cell-bound PDEase at pH 10.3, 1.0 μM in D613. The results were compared to see if they indicated possible relationships between phosphatase activity and taxonomic or ecological grouping. The following differences were significant (P<0.05). Rivulariaceae produced higher yields than filamentous non-Rivulariaceae with β-glycerophosphate, πNPP, and DNA. Rivulariaceae with the ability to form hairs in culture showed poorer growth in ATP than non-hair-forming Rivulariaceae, but were more effective at utilizing phytic acid. Strains from calcareous environments had higher PMEase activity at pH 10.3 than strains from noncalcareous environments (P<0.01).     

Influence of Hairiness ofGerbera jamesoniiLeaves on the Searching Efficiency of the ParasitoidEncarsia formosa

To characterize the relationship between the leaf surface ofGerbera jamesoniiHooker cultivars and the searching behavior of the parasitoidEncarsia formosaGahan on a leaf, the trichome density and shape were described, and the walking behavior was quantified. Leaf hair density varied from 80 to more than 1000 trichomes/cm²and the hair shape varied from single erect trichomes to tapestries of entangled trichomes above the leaf surface. The walking activity, speed, and pattern of the parasitoid were tested on leaves with different hair density and shape. In spite of the large differences in leaf surface structure, the walking activity was similar and around 75% on most cultivars. The walking speed was between 0.2 and 0.3 mm/s on all cultivars and was not significantly different from the speed on tomato. On hairless sweet pepper leaves the walking speed is much higher (0.73 mm/s), so the hairs onGerberaleaves do hamper parasitoid females and result in a strong reduction of the walking speed, but the variation in hair density and shape onGerberadoes not lead to differences in walking activity, pattern, and speed. It appears that the hairs ofGerberaare less of an obstacle forE. formosathan the stiff, large hairs occurring in a high density on cucumber, where the walking speed of the parasitoid is less than 0.2 mm/s. A rise of temperature of 5°C gave a significantly higher walking speed (0.39 mm/s) ofE. formosafemales on all cultivars tested. The relative straightness of the walking track was high and the same on all cultivars. Consequences of the results of the searching behavior ofE. formosaonG. jamesoniicultivars are discussed with respect to other host plants. As parasitoid walking speeds are the same onGerberaand tomato, and whitefly reproduction is also similar on these two host plants, we conclude that biological control of whiteflies onGerberais a realistic option. This conclusion is confirmed by the strong increase of commercial biological control onGerberawhich occurred during the past 5 years.