Reproductive traits in the tropical moss Octoblepharum albidum Hedw. differ between rainforest and coastal sites

Abstract

Octoblepharum albidum Hedw. is an autoicous moss commonly occurring in tropical savannas, dry forests, rainforests and coastal habitats. It frequently reproduces by spores and asexual structures (gemmae and protonemata or buds at leaf tips), making it a good model for understanding how reproductive traits change with respect to habitat type. Our aims were to characterize the different life-history traits in O. albidum relative to sexual and asexual cycles and to detect variations in reproductive performance among the different habitats, trade-offs among these traits, and relationships among reproductive traits and plant length. We studied colonies from two Atlantic rainforests and two coastal sites in north-eastern Brazil. Shoots in the coastal sites, compared to those of the forest sites, had higher numbers of sporophytes, male and female branches per shoot, male gametangia per sexual branch, and longer setae. Numbers of female gametangia per sexual branch did not differ between forest and coastal sites. A male-biased sex ratio of branches and gametangia occurred in all sites. Compared to gemmae, sporophytes and protonemata or buds were more likely to be found on longer shoots than on shorter ones, but this relationship was only applicable to forest sites. The abundant production of gemmae and protonemata or buds at leaf tips, and sporophytes (spores) in O. albidum are important components in explaining colonization success and maintenance in this tropical moss. Longer sporophytic setae in addition to a higher reproductive performance (especially for number of male gametangia and sporophytes per shoot) may favour spore dispersal and colonization in plants of coastal sites.     

An Outline of the Bryophytes of County Laois (Queen's County)

Abstract

Scapania lingulata is reported from five vice-counties in Scotland and from one in Ireland, two gatherings bearing ♂ shoots and one with perianths. It differs from S. scandica in its larger gemmae, from S. praetervisa in its broadly rounded postical leaf lobes, and from both species in its larger leaf cells, more numerous oil bodies and polyploid chromosome complement. Usually it grows on base-deficient earthy banks but also on base-rich rock ledges.     

Protonemal gemmae on Amblystegium serpens (Hedw.) B., S. & G. from Macquarie Island

Abstract

Amblystegium serpens, collected on Macquarie Island, formed protonemal gemmae in laboratory culture. The gemmae germinated to form leafy shoots. They are presumed to be vegetative reproductive structures.     

Occurrence of Colletotrichum graminicola on wheat in Pakistan

Abstract

During a survey of foliar spot of wheat in different agro-ecological wheat production zones, conducted in 2005, Collectotrichum graminicola was found to cause anthracnose in wheat with other foliar diseases like leaf blotch. Pathogenicity has been carried out to fulfill Koch's postulates.     

Two new species of Cololejeunea from Peninsular India

Abstract

Two new species of Cololejeunea (sub-genus Lep tocolea), C. pandei sp. nov. and C. dentifolia sp. nov. are described from fudia. Both species are epiphyllous with ascending leaves. The former is characterized by uniseriate stylus, serrated margin of leaf, discoid gemmae on ventral surface of leaf-lobe with 2-3 mamillose cells and inflated perianthwith lateral winged plicae. The latter is characterized by dentate margin of leaf, leaf-cells with distinct trigones and intermediate nodular, thickenings, bidentate leaf-lobule and discoid gemmae with 4 mamillose cells.     

Reproductive modes in the epixylic hepatic Anastrophyllum hellerianum

The frequency and dynamics of sexual and asexual reproduction were investigated in a dioecious epixylic hepatic, Anastrophyllum hellerianum, which has declined in recent decades in Finland as a consequence of forestry practices. In our investigation asexual reproduction by gemmae was the dominant mode of reproduction and specialised gemmiparous shoots were present in all colonies studied. The proportions of dead shoots were considerably higher among sex-expressing than among non-sexexpressing shoots. Our results suggest that lower reproductive investment is required for asexual than for sexual reproduction. For instance, no trade-off is detected between asexual reproduction and survival of the gemmiparous shoots in A. hellerianum. Sexual reproduction occurred only in 12% of the colonies and it was promoted by the following factors: medium shoot density, high proportion of sex-expressing shoots, an even sex ratio and very short distances between individuals representing opposite sexes. The ratio of dead males to dead females was significantly female-biased, which suggests higher mortality among female shoots. At the level of individual shoots, more spores than gemmae were produced. However, as a consequence of the low frequency of sporophyte-bearing shoots, gemma production highly exceeded spore production at the colony level. Furthermore, cultivation tests of the propagules showed that gemmae germinate faster than spores.     

Resistance in apple to shoot infection by Venturia inaequalis

Eight apple genotypes, including cultivars and breeding selections resistant and susceptible to Venturia inaequalis on foliage, were screened for shoot infection and the development of wood pustules following inoculation of shoot tips of 1–year maiden trees in the greenhouse. Where genotypes were highly resistant in terms of foliar symptoms (cvs Prima and Gavin), no shoot infection was observed. Where genotypes were highly susceptible in terms of foliar symptoms, then shoot tissue was either resistant (cv. Shinko) or susceptible (cv. Starking). In one experiment, shoot tips were inoculated sequentially as shoots extended. No pustules developed where inoculations were made later than May. In a further experiment, two leaf internode positions were inoculated on one occasion. Pustules were only observed where inoculations were made above the youngest unrolled leaf. The results suggested that shoot tips were more susceptible during early extension growth of the shoot. Pustules were noted in abundance on petioles of susceptible cultivars, and these probably contributed to early leaf abscission.     

Cryopreservation for eradication of Jujube witches' broom phytoplasma from Chinese jujube (Ziziphus jujuba)

Here, we report efficient eradication of Jujube witches' broom phytoplasma (Candidatus Phytoplasma ziziphi) from Chinese jujube (Ziziphus jujuba) by cryopreservation. Shoot tips (1.0 mm in size) with 5–6 leaf primordia (LPs) excised from diseased in vitro stock shoots were subject to droplet‐vitrification cryopreservation. Shoot tips following cryopreservation were post‐cultured on a recovery medium for survival. Plantlet regeneration was obtained by micrografting of surviving shoot tips upon in vitro rootstocks. With this protocol, 85% of shoot tips survived following cryopreservation, among which 75% regenerated into whole plantlets and all of them were free of phytoplasma, regardless of the sizes used for cryopreservation. Ultrastructural studies demonstrated that phytoplasma was absent in the apical dome, and leaf primordia (LPs) 1 and 2, while abundance of phytoplasma was present in the lower parts of shoot tips, leaf primordium 3 and older tissues. Histological observations showed that much more damage was found in cells located in the lower part of apical dome, leaf primordium 3 and older tissues than in those at the upper part of apical dome and in the LPs 1 and 2. These cells were most likely to survive and regenerate into phytoplasma‐free plantlets following cryopreservation and micrografting. Ploidy levels analyzed by flow cytometry (FCM) were maintained in plantlets regenerated from cryopreservation followed by micrografting. Results reported here would provide technical support for production of phytoplasma‐free plants and for long‐term storage of germplasm of Chinese jujube.     

Scapania praetervisa Meyl., not S. mucronata Buch in Britain

Abstract

The protonema of Orthotrichum obtusifolium, regenerated from leafy shoots, comprises a dense mass of largely unbranched exclusively upright filaments. All the cells have transverse cross-walls and contain numerous chloroplasts which become larger and discoidal in older filaments. Differentiation into chloro- and caulonema is absent. When upright filaments are transplanted onto an agar surface, they act as the main axes for a further set of upright branches. Buds and side branches are produced symmetrically at right angles to the mother cells. Protonemal morphogenesis hardly changes on nutrientfree medium and spherical brood cells are not produced after prolonged culture or in the presence of abscisic acid. Rhizoids with oblique septa and pigmented walls arise from the base of gametophores. These revert to protonemata when in contact with nutrient agar.

The upright filaments produce terminal and intercalary filamentous gemmae with well defined abscission cells. The latter swell and lose their contents prior to liberation. Cells immediately below the abscission cells produce side branches in acropetal succession. Secondary gemmae arise by percurrent proliferation and gemmae frequently germinate in situ.     

Yakushimabryum longissimum (Pylaisiadelphaceae) gen. & sp. nov., from the Yakushima Island,Japan

Abstract

Yakushimabryum longissimum gen. & sp. nov. (Pylaisiadelphaceae, Musci), is described from Yakushima Island, Japan, on the basis of morphology and rbcL data. It is characterized by more or less glossy, yellowish green living plants, naked dormant branch buds, absence of costa in the leaves, smooth and linear leaf lamina cells, alar groups composed of a number of quadrate cells arranged in a scalariform manner, ascending branches that are often elongate into slender tips, and filamentous gemmae consisting of smooth, long-rectangular cells. Molecular phylogenetic analyses suggest an affinity neither to Clastobryopsis nor Gammiella, both of which grow in similar habitats and share alar morphology and shape of propagules, but to Isocladiella and Isopterygium, both of which have filamentous pseudoparaphyllia and different types of propagules. A key to the Japanese genera of Pylaisiadelphaceae is provided.     

Problems associated with the use of foliar analysis for diagnosing boron toxicity in barley

The effects of evapotranspiration conditions on the distribution of B in leaves and critical values for B toxicity measured in shoots were examined in solution culture experiments with barley.Increased water use resulted in increased B accumulation by plants and B was concentrated in the leaf tips. The relationship between shoot DM production and shoot B concentrations was markedly affected by evapotranspiration conditions, but the effect could be removed by not analysing leaf tips. Excluding the leaf tips also decreased the shoot B concentration at which shoot DM production was depressed.Regularly spraying plants with water removed considerable B from leaves without affecting DM production.The present results indicate a number of problems in the establishment of critical values and the use of foliar analysis for diagnosing B toxicity. These problems may account for conflicting reports of critical values and discrepencies between results from glasshouse- and field-cultured plants.     

Targeted destruction of fungal structures of Erysiphe trifoliorum on flat leaf surfaces of Marchantia polymorpha

In this study, we observed the germination behaviour of airborne conidia from powdery mildews that settle on thalloid surfaces. We inoculated thalli (flat, sheet‐like leaf tissues) and gemmae (small, flat, sheet‐like leaf tissues that propagate asexually via bud‐like structures) of the common liverwort (Marchantia polymorpha) with conidia from tomato powdery mildew (Oidium neolycopersici; KTP‐02) and red clover powdery mildew (Erysiphe trifoliorum; KRCP‐4N) and examined their germination and subsequent appressorium formation under a high‐fidelity digital microscope. Conidial bodies and germ tubes of the inoculated KRCP‐4N conidia were destroyed on both the thalli and gemmae. The destruction of these fungal structures was observed only for KRCP‐4N conidia inoculated onto M. polymorpha on both leaf surfaces. No differences in destruction of the KRCP‐4N fungal structures between thalli and gemmae were observed. At 4 h post‐inoculation, destruction of the germ tube tip was observed when it reached the gemmae leaf surface. At 6 h post‐inoculation, the conidial bodies and germ tubes were destroyed. In contrast, KTP‐02 conidia were not destroyed and formed normal, well‐lobed appressoria on the surface of M. polymorpha gemmae.     

中国新记录种——摩拉维采真藓(新拟)

该文首次报道了摩拉维采真藓(新拟)在中国的分布。研究表明:(1)摩拉维采真藓的主要识别特征为:叶常聚集在茎顶成莲座状,叶倒卵状披针形至匙形,具长毛尖,具分化边缘,中肋消失于叶尖下,叶细胞长菱形至六边形,叶腋处着生大量单列细胞构成的分枝或不分枝的丝状芽胞。(2)通过对摩拉维采真藓的命名和系统位置的讨论,确认该种是真藓属细叶真藓组的有效种。(3)摩拉维采真藓与近缘种细叶真藓和幽美真藓有诸多相似特征:莲座状的茎顶、有分化边和菱形至六边形中上部细胞的倒卵形叶,但该种以具有大量叶腋生丝状芽胞和叶中肋不及顶等特征区别于细叶真藓的无腋生芽胞、叶中肋突出叶尖成长芒状,以具有叶湿时平展、干时卷曲和叶腋有芽胞等特征区别于幽美真藓的叶湿时内凹、干时紧贴于茎和无腋生芽胞;拟三列真藓、圆叶真藓和灰黄真藓的部分种群都曾报道有与摩拉维采真藓相似的腋生丝状芽胞,但摩拉维采真藓的假根集生于植株基部、叶有狭分化边、叶缘平直、中肋消失于叶尖下而区别于拟三列真藓的茎中下部密被假根、叶有宽分化边、叶缘背卷、中肋及顶或短出,摩拉维采真藓有分化边和长毛尖的倒卵状披针形区别于圆叶真藓叶有无分化边和圆钝叶尖的卵圆形叶,区别于灰黄真藓有中肋及顶和短尖的卵状披针形叶;柔叶真藓有与摩拉维采真藓相似、中肋不及顶的叶,但无芽胞而易与新记录种区分。(4)该种在北温带有较广泛分布,形成欧洲-北亚-中亚-西亚和北美两个主要分布区;作者在四川和新疆等地的发现可以推测摩拉维采真藓在中国可能有更广泛的分布。     

Plant phenology-mediated indirect effects: The gall midge opens the phenological window wider for a leaf beetle

We examined whether larvae of the gall midge Rabdophaga rigidae (Diptera: Cecidomyiidae) can modify the seasonal dynamics of the density of a leaf beetle, Plagiodera versicolora (Coleoptera: Chrysomelidae), by modifying the leaf flushing phenology of its host willow species, Salix serissaefolia and Salix eriocarpa (Salicaceae). To test this, we conducted field observations and a laboratory experiment. The field observations demonstrated that the leaf flushing phenology of the willows and the seasonal dynamics of the beetle density differed between shoots with stem galls and shoots without them. On galled shoots of both willow species, secondary shoot growth and secondary leaf production were promoted; consequently, leaf production showed a bimodal pattern and leaf production periods were 1 to 2 months longer than on non‐galled shoots. The adult beetle density on galled shoots was thus enhanced late in the season, and was found to change seasonally, synchronizing with the production of new leaves on the host willow species. From the results of our laboratory experiment, we attributed this synchrony between adult beetle density and willow leaf flush to beetles’ preference to eat new leaves rather than old. Indeed, beetles consumed five times more of the young leaves when they were fed both young and old leaves. These results indicate that stem galls indirectly enhance the adult beetle density by enhancing food quality and quantity late in the beetle‐feeding season. We therefore conclude that midge galls widen the phenological window for leaf beetles by extending the willows’ leaf flush periods.     

Shoot tip culture and cryopreservation for eradication of Apple stem pitting virus (ASPV) and Apple stem grooving virus (ASGV) from apple rootstocks ‘M9’ and ‘M26’

This study attempted to eradicate Apple stem pitting virus (ASPV) and Apple stem grooving virus (ASGV) from virus‐infected in vitro shoots of apple rootstocks ‘M9’ and ‘M26’ using shoot tip culture and cryopreservation. In shoot tip culture, shoot tips (0.2 mm in length) containing two leaf primordia failed to show shoot regrowth. Although shoot regrowth rate was the highest in the largest shoot tips (1.0 mm in length) containing four leaf primordia, none of the regenerated shoots was virus‐free. Shoot tips (0.5 mm in length) containing two and three leaf primordia produced 100% and 10% of ASPV‐free shoots, respectively, while those (1.0 mm) containing four leaf primordia were not able to eradicate ASPV. ASGV could not be eradicated by shoot tip culture, regardless of the size of the shoot tips tested. In cryopreservation, shoot tips (0.5 mm in length) containing two leaf primordia did not resume shoot growth. Although 1.0‐mm and 1.5‐mm shoot tips gave similarly high ASPV‐free frequencies, the latter had much higher shoot regrowth rate than the former. Very similar results of shoot regrowth and virus eradication by shoot tip culture and cryopreservation were observed in both ‘M9’ and ‘M26’. Histological observations showed that only cells in upper part of apical dome and in leaf primordia 1–3 survived, while other cells were damaged or killed, in shoot tips following cryopreservation. Virus immunolocalization found ASPV was not detected in upper part of apical dome and leaf primordia 1 and 2, but was present in lower part of apical dome, and in leaf primordium 4 and more developed tissues in all samples tested. ASPV was also detected in leaf primordium 3 in about 16.7% and 13.3% samples tested in ‘M9’ and ‘M26’. ASGV was observed in apical dome and leaf primordia 1–6, leaving only a few top layers of cells in apical dome free of the virus. Different abilities of ASPV and ASGV to invade leaf petioles and shoot tips were also noted.     

Serial Development of Foliar Gemmae in Tortula (Pottiales, Musci), an Ultrastructural Study

The development and liberation mechanism of foliar gemmae havebeen studied by electron microscopy in two mosses, Tortula latifoliaBruch and Tortula papillosa Wils. The gemmae develop on theadaxial surface of mature leaves from single initial cells onboth the lamina and costa in T. latifolia but only on the costain T. papillosa . Elongation of the initial cell is associatedwith the deposition of a highly extensible new wall whilst theold wall and cuticle in the apical dome rupture. The first divisionis transverse and separates a short basal cell embedded in thefoliar tissue and a distal cell, or gemma primordium, protrudingfrom the leaf surface. Subsequent divisions of the gemma primordiumgive rise to a six-to-eight-celled globose gemma with mucilaginousouter walls. During gemma development the basal cell producesa new wall and elongates again whilst the common wall with thegemma splits apart centripetally along the boundary betweenthe old and new wall in the basal cell; plasmodesmal connectionsare gradually severed and eventually the young gemma remainsconnected to the basal cell only by mucilage. After separationof the first-formed gemma, the basal cell may expand and producea second gemma by the same mechanism. The whole process maybe repeated several times resulting in the formation of a chainof gemmae stuck together by mucilage and which are liberatedonly when the leaves are fully hydrated. Accumulation of abundantlipid deposits in the gemmae after symplasmic isolation reflectsconsiderable photosynthetic autonomy. Abscission; bryophytes; cell wall formation; plasmodesmata; vegetative reproduction     

A Bryophyte Flora of Wigtownahire

Abstract

Fissidens macaoensis L. Zhang is described as a new species from Macao, South China. The species can be separated from its congeners by a suite of characters, including (1) minute size; (2) subterraneous tubers, composed of one to several cells, growing laterally from mature rhizoids; (3) abundant rhizoidal gemmae found on the surface of the soil and which are developed from subterraneous rhizoids; and (4) relatively large cells of the leaf lamina. This is the first report of a moss where two types of vegetative diaspores occur simultaneously in a single individual. Their adaptation strategy is briefly addressed.     

Comparison of gemma production among three Lophozia species during the growing season

The extent and seasonal pattern of asexual reproduction and ability to germinate in the rare liverwort Lophozia ascendens and the common liverworts L. ventricosa and L. longiflora were studied in the Boubínský prales National Nature Reserve in Šumava Mts. (Bohemian Forest), South Bohemia, Czech Republic. Asexual reproduction was quantified as the number of gemmae produced per individual shoot. Numbers of gemmae per shoot among sampling months differed significantly; increase of gemma production was delayed in L. ascendens in comparison with gemma production of L. ventricosa and L. longiflora. We suggest that gemma production is influenced by environmental factors, mainly air humidity. Germinability of gemmae was low in early spring, highest in August and September and slightly depressed in October. This pattern suggests that rather mild winters in the Czech Republic cause the lower mortality of shoots during winter and the environmental pressure towards the production of dormant gemmae is not a prominent factor affecting the population dynamics of the species under study.     

The taxonomy of Campylopus pyriformis (Schultz) Bridr and related species

Abstract

Twenty-five species of mosses collected in Costa Rica, mostly in 1965, are recorded. Leptodontium ramosum, remarkable for its peg-like gemmae borne on stout leafless branches, Sematophyllum serrulatum and Trichosteleum sarapiquensis are described as new species.     

Foliar nectar production and ant activity on a neotropical tree,Ochroma pyramidale

Summary In second growth forest in lowland Costa Rica, ants forage at the foliar nectaries of juvenile Ochroma pyramidale. The relationship between leaf development, foliar nectar production and ant visitation indicates that nectar secretion and ant maintenance are greatest following rapid leaf expansion. Nectar measurements in the glasshouse corroborate field measurements showing that nectar production on a sapling is continuous through time and correlated with distribution and abundance of ants within a sapling. The presence of two nectary types, leaf vein and petiolar, on the leaves of O. pyramidale results in the continual maintenance of ants on the leaf undersurface. Nectar production of a sapling increases with increasing leaf area resulting in greater number of ants per sapling. Energetic costs of nectar production and ant maintenance appear low, representing about one per cent of the total energy invested in leaves.Spatial and diurnal patterns of ant activity changed very little over the study period. Removal and exclusion of ants from saplings results in the utilization of foliar nectar by trigonid bees. A significant difference in leaf damage between ant-visited and unvisited saplings, coupled with ant behavioral characteristics, is consistent with the hypothesis that ants act as antiherbivore agents on Ochroma.