Patch colonization by Trirhabda canadensis (Coleoptera: Chrysomelidae): effects of plant species composition and wind

Summary The goldenrod leaf beetle, Trirhabda canadensis, is known to respond to odors of host and non-host species in the laboratory. Here we report movements of T. canadensis in the field in response to volatile odors from monocultures and polycultures of host plants. Overall, beetles preferentially colonized plots with a higher density of host plants and lower diversity of allelochemicals, but under some wind conditions there were marked exceptions. At high windspeeds, they colonized whichever plot(s) was upwind. At low windspeeds, beetles colonized preferred plots even when they were not upwind. The data suggest that odor dispersion varies in a complex way with windspeed: at low windspeeds beetles received information from a wide are of vegetation and made choices while at high windspeeds information was available only from upwind plot(s).     

Flight behaviour of the cabbage seedpod weevil

The influence of host odour, windspeed, position of the sun, and temperature on flight behaviour of the cabbage seedpod weevil (Ceutorhynchus assimilis Paykull) were studied. This weevil showed a positive anemotaxis (upwind flight) inside the odour plume of a host crop (Brassica napus L.). Outside the odour plume the weevil showed a pronounced phototaxis at windspeeds below 1.5 m/s. At higher windspeeds, the seedpod weevils flew downwind. The cabbage seedpod weevil flies most readily at low windspeeds (less than 0.5 m/s) and at temperatures above 22 °C.     

Effects of windspeed on the growth and biomass allocation of white mustard Sinapis alba L.

Summary We examined how different wind speeds and interactions between plant age and wind affect growth and biomass allocation of Sinapis alba L. (white mustard). Physiological and growth measurements were made on individuals of white mustard grown in controlled-environment wind tunnels at windspeeds of 0.3, 2.2 and 6.0 ms^–1 for 42 days. Plants were harvested at four different dates. Increasing wind speed slightly increased transpiration and stomatal conductance. We did not observe a significant decline in the photosynthetic rate per unit of leaf area. Number of leaves, stem length, leaf area and dry weights of total biomass and plant parts were significantly lower in plants exposed at high wind speed conditions. There were no significant differences in the unit leaf rate nor relative growth rates, although these were always lower in plants grown at high wind speed. Allocation and architectural parameters were also examined. After 42 days of exposure to wind, plants showed higher leaf area ratio, root and leaf weight ratios and root/shoot ratio than those grown at control treatment. Only specific leaf area declined significantly with wind speed, but stem and reproductive parts also decreased. The responses of plants to each wind speed treatment depended on the age of the plant for most of the variables. It is suggested that wind operates in logarithmic manner, with relatively small or no effect at lower wind speeds and a much greater effect at higher speeds. Since there is no evidence of a significant reduction in photosynthetic rate of Sinapis with increasing wind speed it is suggested that the effect of wind on plant growth was due to mechanical effects leading to changes in allocation and developmental patterns.     

Induction of systemic resistance against Fusarium crown and root rot disease by blast processing

The effect of fan-forced wind on the severity and growth of Fusarium oxysporum f. sp. radicis-lycopersici (FORL) was examined in this study. The discoloration severity of the total root system was significantly reduced in plants treated with air blasting for 30?min at a wind speed of 4?m/s compared with the control. In addition, the number of colony-forming units of FORL per gram of fresh root weight was significantly reduced (p?≤?0.05) in plants treated with air blasting at a wind speed of 4?m/s for 30?min, and the root extracts of these plants had a significantly lower production of FORL budding cells. Booster wind treatments significantly reduced the severity and growth of FORL compared with single and control treatments. Furthermore, RT-PCR analysis indicated that the expression of defense-related genes was induced in the leaves of seedlings treated with air blasting at a wind speed of 4?m/s.     

Post-illumination stimulation of respiration rate in the coral Porites porites

The respiration rate of the Caribbean reef coral Porites porites was shown to increase by a mean of 39% above the pre-illumination respiration rate when exposed for 3 h to light equivalent to that at 10 m depth on the reef. When exposed to a subsaturating irradiance of 140 E m^-2 s^-1, the respiration rate increased successively in a curvilinear form to 58% greater than the preillumination respiration rate after 80 min. It is suggested that this increase may be analogous to the elevation in respiration rate observed in cnidarians and other animals after feeding on particulate food and may represent energy expenditure in growth. If this elevated respiration rate is maintained over the whole of the daytime period, the current methodologies used for determining carbon and energy budgets in symbiotic cnidarians result in an underestimation of the 24 h energy expenditure.     

Stomatal conductance, photosynthesis and respiration of temperate deciduous tree seedlings grown outdoors at an elevated concentration of carbon dioxide

Seedlings of temperate deciduous tree species were grown outdoors at ambient and at an elevated concentration of carbon dioxide to examine how aspects of their gas exchange would be altered by growth at elevated carbon dioxide concentration. Leaf conductances to water vapour and net carbon dioxide exchange rates were determined periodically near midday. Whole-plant carbon dioxide efflux rates in darkness were also determined. The stomatal conductance of leaves of plants grown and measured at 700 cm³ m^?3 carbon dioxide did not differ from that of plants grown and measured at 350 cm³ m^?3 in Malus domestica, Quercus prinus and Quercus robur at any measurement time. In Acer saccharinum, lower conductances occurred for plants grown and measured at elevated carbon dioxide concentration only at measurement temperatures above 33°C. Photo-synthetic adjustment to elevated carbon dioxide concentration was evident only in Q. robur. All species examined had lower rates of dark respiration per unit of mass when grown and measured at elevated carbon dioxide concentration.     

Magnolia (Magnoliaceae) in Mexico and Central America: a synopsis

As a result of a recent alpha-taxonomic study of the genusMagnolia s. str. in Mexico and Central America, four new species and four new subspecies ofMagnolia sect.Theorhodon are proposed, includingM. iltisiana, M. panamensis, M. tamaulipana, M. sororum subsp.lutea, andM. pacifica, consisting of three subspecies:pacifica, pugana, andtarahumara. Additionally, a new combination,M. guatemalensis subsp.hondurensis, is made, and a new section,M. sect.Splendentes, is erected for the Caribbean species. The results have implications for understandingMagnolia biogeography, andM. tamaulipana has potential for horticulture in temperate zones. Keys to genera, sections, and species, and maps of species distributions are presented.Magnolia grandiflora L. andM. schiedeana Schltdl. are lectotypified. Como resultado de un estudio alfa-taxonómico reciente del géneroMagnolia s.str. en México y Centro América, se proponen cuatro especies nuevas y cuatro subespecies nuevas deMagnolia sect.Theorhodon, incluyendoM. iltisiana, M. panamensis, M. tamaulipana, M. sororum subsp.lutea y.M. pacifica, la última consiste de tres subespecies:pacifica, pugana ytarahumara. Adicionalmente, se hace la combinaciónM. guatemalensis subsp.hondurensis y se erigeM. sect.Splendentes para las especies del Caribe. Los hallazgos tienen implicaciones en el entendimiento de la biogeografia deMagnolia y.M. tamaulipana tiene potencial en la horticultura de zonas templadas. Se presentan claves para géneros, secciones y especies, y mapas de distribución para las especies.Magnolia grandiflora L. yM. schiedeana Schltdl. son lectotipificadas.     

Dispersal of Septoria nodorum Pycnidiospores by Simulated Rain and Wind

The influence of wind on the splash dispersal of Septoria nodorum pycnidiospores was studied in a raintower/wind tunnel complex with single drops or simulated rain falling on spore suspensions or infected stubble with windspeeds of 1.5 to 4 m/sec. When single drops fell on spore suspensions (depth 0.5 mm, concentration 7.8 × 10⁵ spores/ml) most of the spore-carrying droplets collected on fixed photographic film between 0–4 m downwind (windspeed 3 m/sec) were >200 μm in diameter. However, most spores were carried in droplets with diameter > 1000 μm, 70 % of which carried more than 100 spores. When simulated rain fell on infected stubble most of the spore-carrying droplets collected beyond 1 m downwind (windspeeds 1.4 and 4 m/sec) were <200 μm in diameter and none were >600 μm; most of these droplets carried only one spore. The distribution of splash droplets (with diameter >100 μm) deposited on chromatography paper showed a maximum at 40–50 cm upwind of the target but many more droplets were deposited 20–30 cm downwind, when single drops fell on a spore suspension (concentration 1.2 × 10⁵ spores/ ml) containing fluorescein dye with a windspeed of 2 m/sec; droplets were collected up to 3 m downwind but not more than 70 cm upwind. With a windspeed of 3 m/sec, numbers of sporecarrying droplets and spores collected on film decreased with increasing distance downwind; most were collected within 2 m of the target but some were found up to 4 m. When simulated rain fell on infected stubble, increasing the windspeed from 1.5 to 4 m/sec greatly increased the number of spores deposited more than 1 m downwind. At 1.5 m/sec none were collected beyond 2 m downwind, whereas at 4 m/sec some were collected at 4 m. A few air-borne S. nodorum spores were collected by suction samplers at a height of 40 cm at distances up to 10 m downwind of a target spore suspension on which simulated rain fell.     

Acclimation of respiration to temperature and CO2 in seedlings of boreal tree species in relation to plant size and relative growth rate

The role of acclimation of dark respiration to temperature and CO₂ concentration and its relationship to growth are critical in determining plant response to predicted global change. We explored temperature acclimation of respiration in seedlings of tree species of the North American boreal forest. Populus tremuloides, Betula papyrifera, Larix laricina, Pinus banksiana, and Picea mariana plants were grown from seed in controlled-environments at current and elevated concentrations of CO₂ (370 and 580 μmol mol^–1) in combination with three temperature treatments of 18/12, 24/18, and 30/24 °C (light/dark period). Specific respiration rates of roots and shoots acclimated to temperature, damping increases in rates across growth-temperature environments compared to short-term temperature responses. Compared at a standard temperature, root and shoot respiration rates were, on average, 40% lower in plants grown at the highest compared to lowest growth temperature. Broad-leaved species had a lower degree of temperature acclimation of respiration than did the conifers. Among species and treatment combinations, rates of respiration were linearly related to size and relative growth rate, and relationships were comparable among growth environments. Specific respiration rates and whole-plant respiratory CO₂ efflux as a proportion of daily net CO₂ uptake increased at higher growth temperatures, but were minimally affected by CO₂ concentration. Whole-plant specific respiration rates were two to three times higher in broad-leaved than coniferous species. However, compared to faster-growing broad-leaved species, slower-growing conifers lost a larger proportion of net daily CO₂ uptake as respiratory CO₂ efflux, especially in roots. Interspecific variation in acclimation responses of dark respiration to temperature is more important than acclimation of respiration to CO₂ enrichment in modifying tree seedling growth responses to projected increases in CO₂ concentration and temperature.     

Effects of enhanced atmospheric CO2 and nutrient supply on the quality and subsequent decomposition of fine roots of Betula pendula Roth. and Picea sitchensis (Bong.) Carr.

Fine root litter derived from birch (Betula pendula Roth.) and Sitka spruce (Picea sitchensis (Bong.) Carr.) plants grown under two CO₂ atmospheric concentrations (350 ppm and 600 ppm) and two nutrient regimes was used for decomposition studies in laboratory microcosms. Although there were interactions between litter type, CO₂/fertiliser treatments and decomposition rates, in general, an increase in the C/N ratio of the root tissue was observed for roots of both species grown under elevated CO₂ in unfertilized soil. Both weight loss and respiration of decomposing birch roots were significantly reduced in materials derived from enriched CO₂, whilst the decomposition of spruce roots showed no such effect. A parallel experiment was performed using Betula pendula root litter grown under different N regimes, in order to test the relationship between C/N ratio of litter and root decomposition rate. A highly significant (p<0.001) negative correlation between C/N ratio and root litter respiration was found, with an r²=0.97. The results suggest that the increased C/N ratio of plant tissues induced by elevated CO₂ can result in a reduction of decomposition rate, with a resulting increase in forest soil C stores.     

High capacity of plant regeneration from callus of interspecific hybrids with cultivated barley (Hordeum vulgare L.)

Callus was induced from hybrids between cultivated barley (Hordeum vulgare L. ssp. vulgare) and ten species of wild barley (Hordeum L.) as well as from one backcross line ((H. lechleri x H. vulgare) x H. vulgare). Successful callus induction and regeneration of plants were achieved from explants of young spikes on the barley medium J 25–8. The capacity for plant regeneration was dependent on the wild parental species. In particular, combinations with four related wild species, viz. H. jubatum, H. roshevitzii, H. lechleri, and H. procerum, regenerated high numbers of plants from calli.     

Respiratory CO2 Fluxes in Photosynthesizing Leaves of C3 Species Varying in Rates of Starch Synthesis1

The rates of CO₂ fixation and respiratory CO₂ fluxes in six C₃ species, namely Solanum tuberosum, Nicotiana tabacum, Arabidopsis thaliana, Hordeum vulgare, Triticum aestivum, and Secale cereale, were determined under steady-state photosynthesis. The plants may be divided into two groups: (a) cereals with a low rate of starch synthesis (7–5% of true photosynthesis); (b) plants with a high rate of starch synthesis (45–35% of true photosynthesis). In the light, primary and stored photosynthates are consumed as substrates for both respiratory and photorespiratory pathways. In leaves of cereals, the total rate of respiratory and photorespiratory decarboxylations of stored photosynthates was higher in the light than in the dark, while, in starch-synthesizing species, stored photosynthates were consumed at a higher rate in the dark. Under normal environmental conditions, respiratory decarboxylation of stored photosynthates was suppressed by light in all species studied. The total rate of respiration as the sum of decarboxylation of stored and primary photosynthates was not affected by light in cereals, but suppressed in starch-accumulating plants. This suppression was not compensated for by the additional supply of respiratory substrates from primary photosynthates in the light.     

Effects of elevated CO2 on growth,photosynthesis and respiration of sweet chestnut (Castanea sativa Mill.)

Two year old sweet chestnut seedlings (Castanea sativa Mill) were grown in pots at ambient (350 µmol·mol^–1) and double (700 µmol·mol^–1) atmospheric CO₂ concentration in constantly ventilated greenhouses during entire growing seasons. CO₂ enrichment caused either no significant change or a decrease in shoot response, depending on yearly weather conditions. Similarly, leaf area was either reduced or unchanged under elevated CO₂. However, when grown under controlled conditions in a growth chamber, leaf area was enlarged with elevated CO₂.The CO₂ exchanges of whole plants were measured during the growing season. In elevated CO₂, net photosynthetic rate was maximum in May and then decreased, reaching the level of the control at the end of the season. End of night dark respiration of enriched plants was significantly lower than that of control plants; this difference decreased with time and became negligible in the fall. The original CO₂ level acted instantaneously on the respiration rate: a double concentration in CO₂ decreased the respiration of control plants and a reduced concentration enhanced the respiration of enriched plants. The carbon balance of a chestnut seedling may then be modified in elevated CO₂ by increased carbon inputs and decreased carbon outputs.     

Influence of Cd2+ on growth, chlorophyll content, and water relations in young barley plants

Barley (Hordeum vulgare L., cv. Hemus) plants were grown in nutrient solution with or without 54 μM Cd²⁺ for 12 d. A treatment with Cd²⁺ inhibited the growth of young barley plants. The main factor limiting plant growth was net assimilation rate, due to decreased photosynthetic rate and accelerated dark respiration rate. One of the reasons for the reduced photosynthetic rate was the lower chlorophyll and carotenoid content. Cd²⁺ decreased water potential and transpiration rate, but relative water content in leaves of the treated plants was not significantly changed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Scaling of heat production by thermogenic flowers: limits to floral size and maximum rate of respiration

Effect of size of inflorescences, flowers and cones on maximum rate of heat production is analysed allometrically in 23 species of thermogenic plants having diverse structures and ranging between 1.8 and 600 g. Total respiration rate (, µmol s^?1) varies with spadix mass (M, g) according to in 15 species of Araceae. Thermal conductance (C, mW °C^?1) for spadices scales according to C = 18.5M^0.73. Mass does not significantly affect the difference between floral and air temperature. Aroids with exposed appendices with high surface area have high thermal conductance, consistent with the need to vaporize attractive scents. True flowers have significantly lower heat production and thermal conductance, because closed petals retain heat that benefits resident insects. The florets on aroid spadices, either within a floral chamber or spathe, have intermediate thermal conductance, consistent with mixed roles. Mass‐specific rates of respiration are variable between species, but reach 900 nmol s^?1 g^?1 in aroid male florets, exceeding rates of all other plants and even most animals. Maximum mass‐specific respiration appears to be limited by oxygen delivery through individual cells. Reducing mass‐specific respiration may be one selective influence on the evolution of large size of thermogenic flowers.     

Ecophysiological characterization of carnivorous plant roots: Oxygen fluxes,respiration, and water exudation

Various ecophysiological investigations on carnivorous plants in wet soils are presented. Radial oxygen loss from roots of Droseraceae to an anoxic medium was relatively low 0.02 – 0.07 mol(O₂) m^{– 2} s^–1 in the apical zone, while values of about one order of magnitude greater were found in both Sarracenia rubra roots and Genlisea violacea traps. Aerobic respiration rates were in the range of 1.6 – 5.6 mol kg^–1 (f.m.) s^–1 for apical root segments of seven carnivorous plant species and 0.4 – 1.1 mol kg^–1 (f.m.) s^–1 for Genlisea traps. The rate of anaerobic fermentation in roots of two Drosera species was only 5 – 14 % of the aerobic respiration. Neither 0.2 mM NaN₃ nor 0.5 mM KCN influenced respiration rate of roots and traps. In all species, the proportion of cyanide-resistant respiration was high and amounted to 65 – 89 % of the total value. Mean rates of water exudation from excised roots of 12 species ranged between 0.4 – 336 mm 3 kg^–1 (f.m.) s^–1 with the highest values being found in the Droseraceae. Exudation from roots was insensitive to respiration inhibitors. No significant difference was found between exudation rates from roots growing in situ in anoxic soil and those kept in an aerated aquatic medium. Carnivorous plant roots appear to be physiologically very active and well adapted to endure permanent soil anoxia.     

Phylogenetic relationships in Magnoliaceae subfam. Magnolioideae: a morphological cladistic analysis

Relationships within Magnolioideae have been the subject of persistent debate; the main point at issue mostly being the disposition of tribes, genera and sections. A morphological cladistic analysis of the subfamily using Liriodendron as the out-group showed that Magnolioideae consisted of a large basal polytomy, but with five resolved and variously supported clades. Manglietia constituted a clade with sect. Rytidospermum of Magnolia subg. Magnolia. Kmeria and Woonyoungia formed a pair. Pachylarnax, Parakmeria and Manglietiastrum were grouped together, and sect. Splendentes and Dugandiodendron also formed a pair. The largest and best supported clade consisted of Magnolia subg. Magnolia sects. Oyama and Maingola, Magnolia subg. Yulania, Michelia, Aromadendron, Alcimandra, Elmerrillia, Paramichelia and Tsoongiodendron, with sect. Oyama of Magnolia subg. Magnolia is sister to the remainder. Although Magnolia sect. Maingola, Aromadendron, Alcimandra and Elmerrillia constituted a poorly resolved subclade, Aromadendron formed a monophyletic clade with Alcimandra. Within the Michelia/Magnolia subgen. Yulania subclade, Paramichelia was sister to Tsoongiodendron. These results are supported by similar placement of taxa within various molecular analyses of the family, but the low level of resolution indicates that more morphological data are needed to improve phylogenetic signal. Our results support the molecular analyses in suggesting that Magnolia is best considered to be a large and diverse genus, but that the relationships between the taxa within it require more detailed clarification, with more extensive sampling and a combined molecular and morphological approach being needed.     

Major clades and a revised classification of Magnolia and Magnoliaceae based on whole plastid genome sequences via genome skimming

With more than 300 species, the Magnoliaceae family represents a major Magnoliid lineage that is disjunctly distributed in Asia and the New World. The classification of Magnolia s.l. has been highly controversial among taxonomists, varying from one genus with several subgenera, sections, and subsections to several (up to 16) genera. We conducted a comprehensive phylogenetic study of Magnoliaceae on the basis of sequences of the complete chloroplast genomes with a broad taxon sampling of 86 species. The phylogenetic analyses strongly support 15 major clades within Magnolia s.l. due to the non‐monophyly of subgen. Magnolia, the previous subgeneric treatment that recognizes three subgenera, is not supported. Based on the phylogenetic, morphological, and geographic evidence, we recognize two subfamilies in Magnoliaceae: Liriodendroideae and Magnolioideae, each with one genus, Liriodendron and Magnolia, respectively. Magnolia is herein classified into 15 sections: sects. Magnolia, Manglietia, Michelia, Gwillimia, Gynopodium, Kmeria, Maingola, Oyama, Rytidospermum, Splendentes, Talauma, Tuliparia, Macrophylla, Tulipastrum, and Yulania.     

The effects of short term salinity exposure on the sublethal stress response of Vallisneria americana Michx. (Hydrocharitaceae)

Short term exposure of Vallisneria americana to elevated salinity was found to induce a stress response that could be quantified by a series of metabolic assays measuring oxidative stress, photosynthetic efficiency, and dark adapted respiration. Plant specimens exposed to elevated salinity for 24 h displayed signs of oxidative damage represented by the accumulation of reactive oxygen species (ROS) and lipid hydroperoxides in blade tissue (noted at salinities of 10 and 15, respectively). Respiratory demand nearly doubled (140 nanomoles O₂ consumed min⁻¹ g⁻¹) when plants were placed in a salinity of 15 for 24 h versus control specimens maintained at 0. After 1 week of exposure a significant increase in respiration and lipid hydroperoxide content was detected in plants incubated at or above a salinity of 13. In addition, effective quantum yield () dropped significantly compared to plants maintained at a salinity below 13. These results highlight the use of cellular stress assays to monitor salt-induced sublethal responses in V. americana.