Epidermal structures and stomatal parameters of Chinese endemic Glyptostrobus pensilis (Taxodiaceae)

Glyptostrobus pensilis K. Koch, the only living species, is endemic to southern China. Epidermal structures of G .  pensilis have been studied on leaves collected from Guangzhou, southern China, the native locality of the species, and from Hangzhou, eastern China, the cultivated locality. Leaves are linear, linear-subulate and scale-like. Epidermal cells are rectangular and elongate parallel to the mid-vein on areas lacking stomata, and short, with rounded corners, on intrastomatal areas. Stomatal bands lie parallel to the mid-vein on both surfaces of leaves. Commonly the stomata have five or six subsidiary cells. Stomatal parameters (density and index) of the same surfaces of linear leaves from Guangzhou and Hangzhou show no statistically significant differences ( P  > 0.05). Considering the stomatal parameters of the same surfaces of linear-subulate leaves between the two localities, the stomatal index of the abaxial surfaces reveals no significant differences ( P  > 0.05), while the stomatal index of the adaxial surfaces and the stomatal density of both surfaces exhibit significant differences ( P  < 0.05). Intra-individual variation in stomatal index is smaller than that in stomatal density based on the coefficient of variability of stomatal parameters of the same areas of leaves. When studying the correlation between stomatal parameters of G. pensilis and atmospheric CO₂ concentrations, the stomatal parameters of linear leaves are mostly significant, and stomatal index is more useful than stomatal density.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 153–162.     

Influence of atmospheric oxygen on leaf structure and starch deposition in Arabidopsis thaliana

Plant culture in oxygen concentrations below ambient is known to stimulate vegetative growth, but apart from reports on increased leaf number and weight, little is known about development at subambient oxygen concentrations. Arabidopsis thaliana (L.) Heynh. (cv. Columbia) plants were grown full term in pre-mixed atmospheres with oxygen partial pressures of 2·5, 5·1, 10·1, 16·2, and 21·3 kPa O₂, 0·035 kPa CO₂ and the balance nitrogen under continuous light. Fully expanded leaves were harvested and processed for light and transmission electron microscopy or for starch quantification. Growth in subambient oxygen concentrations caused changes in leaf anatomy (increased thickness, stomatal density and starch content) that have also been described for plants grown under carbon dioxide enrichment. However, at the lowest oxygen treatment (2·5 kPa), developmental changes occurred that could not be explained by changes in carbon budget caused by suppressed photorespiration, resulting in very thick leaves and a dwarf morphology. This study establishes the leaf parameters that change during growth under low O₂, and identifies the lower concentration at which O₂ limitation on transport and biosynthetic pathways detrimentally affects leaf development.     

Larval performance in relation to oviposition site preference in olive kernel moth (Prays oleae Bern., Yponomeutidae,Praydina)

1 The tri‐voltine moth Prays oleae Bern. spends its larval stages on the native olive tree (Olea europaea L. var. sylvestris Brot. and five cultivars, Oleaceae) mining the leaves, the flowers and the fruits in each generation; it seldom switches to other native or introduced confamilial plant species. 2 In this study the pattern of oviposition of the olive moth was examined in olive fields and natural vegetation, in relation to in situ recruitment as an outcome of processes such as density dependence or risk spreading. 3 Larval body size (width of epicranial sclerites) was also examined and compared between host substrates, years and morphological, physiological, ecological and nutritional attributes of the host. 4 The factors influencing the oviposition pattern of the olive moth such as the carbon/nitrogen ratio, number of flowers, branch length and previous leaf damage were ranked differently in different cultivars. 5 ‘Hot spots’, i.e. olive trees or parts of trees receiving a high egg load, were found to be the result of in situ recruitment. 6 Physiological mortality among first instar larvae was significantly negatively correlated with the number of oviposited upon leaves; suggesting that the adult selects for oviposition the best available substrate. 7 As adult moths selected leaves with minimal probability of abscission for oviposition, leaf abscission was not a major mortality factor, although first instar larvae reduced leaf longevity. 8 Host quality did not affect all larval stages in the same way. 9 The more nutritionally poor the substrate, the longer the duration of the larval stage feeding on it. The phenological timing of the insect life stages very closely tracks the phenological phases of its host plant, primarily focusing on the most nutritious host stage in terms of larval performance.     

A global prognostic scheme of leaf onset using satellite data

Leaf phenology describes the seasonal cycle of leaf functioning. Although it is essential for understanding the interactions between the biosphere, the climate, and biogeochemical cycles, it has received little attention in the modelling community at global scale. This article focuses on the prediction of spatial patterns of the climatological onset date of leaf growth for the decade 1983–93. It examines the possibility of extrapolating existing local models of leaf onset date to the global scale. Climate is the main variable that controls leaf phenology for a given biome at this scale, and satellite observations provide a unique means to study the seasonal cycle of canopies. We combine leaf onset dates retrieved from NOAA/AVHRR satellite NDVI with climate data and the DISCover land‐cover map to identify appropriate models, and determine their new parameters at a 0.5° spatial resolution. We define two main regions: at temperate and high latitudes leaf onset models are mainly dependent on temperature; at low latitudes they are controlled by water availability. Some local leaf onset models are no longer relevant at the global scale making their calibration impossible. Nevertheless, we define our unified model by retaining the model that best reproduced the spatial distribution of leaf onset dates for each biome. The main spatial patterns of leaf onset date are well simulated, such as the Sahelian gradient due to aridity and the high latitude gradient due to frost. At temperate and high latitudes, simulated onset dates are in good agreement with climatological observations; 62% of treated grid‐cells have a simulated leaf onset date within 10 days of the satellite observed onset date (which is also the temporal resolution of the NDVI data). In tropical areas, the subgrid heterogeneity of the phenology is larger and our model's predictive power is diminished. The difficulties encountered in the tropics are due to the ambiguity of the satellite signal interpretation and the low reliability of rainfall and soil moisture fields.     

Stem hydraulic supply is linked to leaf photosynthetic capacity: evidence from New Caledonian and Tasmanian rainforests

A strong relationship between hydraulic supply of water to leaves and maximum photosynthetic capacity was found in a group of seven conifers and 16 angiosperm species, including two vessel‐less taxa, from similar rainforest communities in New Caledonia and Tasmania (Australia). Stem hydraulic supply was expressed as the hydraulic conductivity of branches in terms of leaf area supplied (K_L) and leaf photosynthetic capacity was measured as the mean quantum yield of PSII (Ø_PSII) in leaves exposed to full sun, as determined by chlorophyll fluorescence analysis. A single, highly significant linear regression (r² = 0·74) described the relationship between hydraulic conductivity and quantum yield in all species. This suggests that the maximum photosynthetic rate of leaves is constrained by their vascular supply. In both rainforest locations, the K_L of conifer wood overlapped broadly with that of associated vessel‐bearing and vessel‐less angiosperms indicating a degree of hydraulic convergence in these forests.     

First phylogenetic analysis of the subfamily Pachydeminae (Coleoptera,Scarabaeoidea, Melolonthidae): the Palearctic Pachydeminae*

This paper presents the first phylogenetic analysis of Pachydeminae Reitter, 1902 ; one of the least known subfamilies of Melolonthidae, `leaf‐chafers' (Scarabaeoidea, Coleoptera). Some species of Pachydeminae have recently become agricultural pests in southern Spain. We analysed the phylogenetic relationships among 49 species belonging to 16 genera in the Palearctic region, based on a set of 63 morphological characters from the adult external morphology, wing anatomy, mouthparts and male and female genitalia. The last three sets of characters are described here for the first time. The phylogeny shows that the Palearctic Pachydeminae are monophyletic within the subfamily. Mouthparts and male and female genitalia provide the best synapomorphies for intergeneric relationships. In contrast, most of the external morphological characters used in the taxonomy of Pachydeminae are highly homoplastic. The phylogeny shows a basal split between the genera Hemictenius Reitter, 1897; Pachydema Castelnau, 1832, and the monospecific Peritryssus Reitter, 1918; and a second clade including the rest of genera. The remarkable Peritryssus is confirmed as a Pachydeminae, being the sister group to the monophyletic Hemictenius . Except for the position of P. rubripennis (Lucas, 1848) and P. zhora Normand, 1951, the phylogeny supports the monophyly of Pachydema but rejects the traditional division into species groups and the monophyly of the endemic Canarian species. In contrast, Tanyproctus Faldermann, 1835, must be rejected as polyphyletic. Otoclinius Brenske, 1896, is also probably polyphyletic (two new species synonymies), whereas Leptochristina Baraud and Branco, 1991 , is either mono‐ or paraphyletic. The two Mediterranean genera Ceramida Baraud, 1897, and Elaphocera Gené, 1836, form a monophyletic group, this clade being the best supported by the data set. Ceramida is clearly monophyletic, whereas Elaphocera is probably monophyletic except for E. barbara Rambur, 1843, which shares with Ceramida the character state for numerous mouthpart and genitalic characters. The phylogeny questions the generic status of the small and monospecific genera of Pachydeminae. The monotypic Alaia Petrovitz, 1980 , and Brenskiella Berg, 1898, are merged with Europtron Marseul, 1867, into one clade, whereas Atanyproctus Petrovitz, 1954, is grouped with some species of Tanyproctus , and the monotypic Pachydemocera Reitter, 1902 , is proposed as a junior synonym of Elaphocera .     

Differences in egg parasitism of Chrysophtharta agricola (Chapuis) (Coleoptera: Chrysomelidae) by Enoggera nassaui Girault (Hymenoptera: Pteromalidae) in relation to host and parasitoid origin

Abstract The first instances of egg parasitism of Chrysophtharta agricola , a pest of eucalypt plantations, are recorded. Enoggera nassaui was found parasitising C. agricola egg batches in Tasmania, the Australian Capital Territory (ACT), New South Wales and Victoria: this is the first record of this parasitoid species from Victoria. One instance of Neopolycystus sp. parasitising C. agricola eggs in Victoria was also recorded. Parasitism of egg batches by E. nassaui ranged from 0 to 55% between five geographical populations collected in mainland Australia ( n  = 45), and from 0 to 2% between two populations collected in Tasmania ( n  = 300). For mainland sites at which parasitism was recorded, parasitism rates within sites differed significantly from either population in Tasmania. Reciprocal exposure experiments using one Tasmanian (Florentine Valley) and one parasitised mainland (Picadilly Circus, ACT) population were conducted in the laboratory to examine whether these different parasitism rates were attributable to egg or parasitoid origin. Parasitoids from the ACT parasitised C. agricola eggs of both origins more successfully than parasitoids from Tasmania, with up to 65% wasp emergence compared with 33% from Tasmania. Parasitoid origin significantly affected the number of wasps that emerged from exposed batches, but not the total loss from parasitism.     

Interactive effects of elevated CO2 and temperature on the leaf-miner Dialectica scalariella Zeller (Lepidoptera: Gracillariidae) in Paterson's Curse, Echium plantagineum (Boraginaceae)

Doubling of the current atmospheric CO₂ concentration, and an increase in global mean annual temperatures of 1.5–6 °C, have been predicted to occur by the end of this century. Whilst the separate effects of CO₂ and temperature on plant–insect interactions have been examined in a number of studies, few have investigated their combined impact. We carried out a factorial experiment to explore the effect of a doubling of CO₂ concentration and a 3 °C temperature increase on the development of a complete generation of the leaf‐miner, Dialectica scalariella, in the host plant Paterson's Curse, Echium plantagineum. Elevated CO₂ increased biomass, reduced leaf N and increased C:N ratios in the host plants. Leaf thickness also increased under elevated CO₂, but only in the high‐temperature treatment. Female D. scalariella did not discriminate between plants grown at the different CO₂ levels when ovipositing, despite the reduction in foliage quality under elevated CO₂. Overall, the negative response of D. scalariella to elevated CO₂ was greater than for many species of free‐living insects, presumably because of the limited mobility imposed by the leaf‐mining habit. Development was accelerated at the high temperature and slowed under elevated CO₂. The net result was a reduction in development time of ～14 days in the elevated CO₂/high temperature treatment, compared to the ambient CO₂/low temperature treatment. Larval survivorship and adult moth weight were both affected by a significant interaction between CO₂ and temperature. At the low temperature, CO₂ had little effect on survivorship, but at the high temperature, survivorship was significantly reduced under elevated CO₂. Similarly, elevated CO₂ had a stronger negative effect on adult moth weight when combined with the high‐temperature treatment. A possible explanation for these results is that the high temperature accelerated insect development to such an extent that the larvae did not have sufficient feeding time to compensate for the poorer quality of the foliage. The frequency with which interactions between CO₂ and temperature affected both plant and insect performance in this study highlights the need for caution when predicting the effects of future climate change on plant–insect interactions from single‐factor experiments.