Feeding performance of <Emphasis Type="Italic">Clostera fulgurita</Emphasis> on three clones of <Emphasis Type="Italic">Populus deltoides</Emphasis>

Poplar leaf defoliator, Clostera fulgurita (Walker) larvae were reared on three Populus deltoides clones (PL1, PL5 and PL7) in the laboratory. The nutritional indices were computed for working out the relationship between food consumption and growth rate of 3rd, 4th and 5th instar larvae on three clones. The result showed that the consumption index (CI), approximate digestibility (AD), growth rate (GR), relative growth rate (RGR) and efficiency of conversion of ingested food (ECI) decreased with the increase in the age of the larvae. Efficiency of conversion of digested food (ECD) increased with increase in age of the larvae. GR and RGR varied significantly, indicating that larval development was enhanced on PL1 as compared to PL5 & PL7. The values of AD, ECI and ECD were not affected by the different clones. Feeding and growth indices could be useful to define a defoliation prediction model.     

Tracking leaf area index and coefficient of light extinction over the harvesting cycle of black wattle

The amount of photosynthetic radiation intercepted by a crop is a function of the incident solar radiation on the plants, the leaf area index (L _AI), and the light extinction coefficient (k). We quantified L _AI and k in stands of black wattle (Acacia mearnsii De Wild.) over a 7-year growth cycle at two locations in the state of Rio Grande do Sul, Brazil. Our study was conducted in commercial stands in agroecological regions with high densities of black wattle plantations. L _AI was calculated as the ratio between the leaf area of a tree and its planting space, and k was derived from Beer’s law. L _AI depends on the planting site and stand age. Between the two sites, the L _AI was similar over time, the amount of variation differed. Values of k depended only on stand age, with the highest average observed for stands up to 5 years old. The trend of k during the plantation cycle was inversely proportional to L _AI and was correlated with L _AI, leaf area, leaf dry mass, canopy volume, height, branches dry mass, total dry mass, and crown diameter.     

Periodicity of different phenophases in selected trees from Himalayan Terai of India

The temporal phenology of leaf bud bursting, leaf initiation, leaf maturation, leaf fall, flower initiation, fruit initiation and fruit fall was recorded for eight tree species (Ficus hispida, F. squamosa, Mallotus nudiflorus, M. philippensis, Shorea robusta, Schleichera oleosa, Pongamia pinnata and Terminalia arjuna) in the tropical moist deciduous forest of Himalayan Terai region from November 2009 to October 2012. The study revealed that a short low temperature dry period, sufficient winter rain and temperature rise are the triggering factors for summer leaf flushing and, the increased soil water availability for second leaf flushing in rains. Initiation of flowering with leaf emergence in the dry period supports higher rate of fruit setting due to maximum availability and activities of pollinators. The dispersal and post dispersal success of fruits increased by their ripening before and/or in the rainy season. In T. arjuna, no correlation has been found between the fruiting and rains. M. nudiflorus and M. philippensis initiate leaves and flowers with the first significant increase in temperature and photoperiod and are thus suggested as the potential tree species for climate change studies in tropics.     

Susceptibility of selected stored product insects to a combination treatment of pyriproxyfen and novaluron

There are many published studies of either insect growth regulators (IGR) or chitinase inhibitors applied directly to larvae of stored product insects or incorporated into their diets, but few studies evaluating efficacy of IGRs or chitinase inhibitors applied alone or in combination with a surface for residual control. Tests were conducted to evaluate susceptibility of Tribolium castaneum (Herbst), the red flour beetle, Trogoderma variabile (Ballion), the warehouse beetle, and Dermestes maculatus (DeGeer), the hide beetle, to Tekko^® Pro which contained the IGR pyriproxyfen and the chitinase inhibitor novaluron as active ingredients. Efficacy was assessed by adult emergence of exposed immatures, an index based on development of those exposed immatures, and progeny production of exposed adults. Concrete arenas were treated with the label rate of the insecticide applied to a surface, and bioassays were conducted at 0–16 weeks post-treatment. No exposed T. castaneum eggs or larvae reached the adult stage and index values for exposed eggs and larvae remained near the minimum. Adult emergence of T. variable from eggs or larvae did not exceed 25% for the first 8 weeks of the test, but at the end of the test at 16 weeks adult emergence was 44 and 71%, respectively, for eggs and larvae. No eggs or larvae of D. maculatus emerged as adults, but excessive cannibalization in untreated controls occurred throughout the test. Results show that Tekko^® Pro will give residual control of T. castaneum and T. variabile, and could replace older conventional neurotoxic insecticides for management of stored product insects.     

Production of selected short-rotation wood crop species and quality of obtained biomass

Short-rotation coppice (SRC) represents an important source of wood biomass. Many uncertainties create barriers to farmers establishing SRC plantations, especially under Mediterranean climate conditions. In this study, five species and respective genotypes were analyzed. The five species were Fraxinus angustifolia, Robinia pseudoacacia, Salix alba, Populus nigra (Limatola), and Populus × euroamericana, with the genotypes of the latter being Grimminge, Vesten, Hoogvorst, Muur. For the plantations studied, two different harvesting systems were replicated: the single machine pass, or cut-and-chip (CC); and the double machine pass, for which the tree are cut first, then chipped later (chip of stored trees CS). In the CC, fresh trees were harvested and chipped by Claas Jaguar 880. In the CS, dry trees were chipped by Farmi Forest CH 260. Within the same site, in climatic conditions and low-input management, the best result in terms of biomass yield was obtained from the black poplar Limatola. Both wood typologies and harvesting systems affected the chip quality. The disk chipper, when working on dried biomass, produced lower quality chips than the other chipping device in terms of particle size. In the chips obtained, there was an increase in the number of chips classified as being “larger size” and “oversized”, and a decrease in the percentage of those classified as “accept” (45–3 mm fraction). The chips obtained from dried trees were of better energy quality compared with the same biomass obtained from the fresh trees in terms of heating value and ash content.     

Altägyptische Fliegen- und Käferrelikte in einem Priestersarg der achtzehnten Dynastie

Ancient Egyptian insect relics were accidentally enclosed in embalming resin which leaked from a priest's mummy and solidified on the floor of a wooden coffin from the end of the XVIII^th Dynasty (presumably 1323?–?1295 BC). The preserved insect relics were blowflies (Calliphoridae) recognized as Chrysomya marginalis or Chrysomya megacephala whose larvae had developed by feeding on the deceased's body prior to mummification as well as furniture beetles (Anobiidae) being either Oligomerus ptilinoides or Priobium carpini whose larvae had ingested the coniferous wood of the coffin. It is most likely that the human corpse and coffin were first attacked by the blowflies and furniture beetles prior to embalming, while infestation of the insect remains and textiles by Anthrenus sp. (Dermestidae) occurred in our time.     

Heterotrophic components of biofilms on wood artefacts

Heterotrophic components of biofilms on wood artefacts were studied at the Conservation Laboratory for Wood Artefacts of the University Suor Orsola Benincasa of Naples, Italy. The aim of the study was to add new information on the micro-habitats represented by biofilms formed by wood-dwelling organisms. Light and electron microscopy of histological features of woods used to make the artefacts showed that the woods belonged to species of lime (Tilia sp.), poplar (Populus sp.) and pear (Pyrus sp.). A Denaturing Gradient Gel Electrophoresis analysis performed on heterotrophic microorganisms colonizing the artefacts led to identify four species of bacteria, namely Bacillus cereus, B. mycoides, B. subtilis and Microbacterium oleivorans, and seven species of fungi, namely Alternaria alternata, Aspergillus fumigans, A. versicolor, Cladosporium cladosporioides, C. oxysporum, Fusarium oxysporum and Penicillium chrysogenum. Based on its morphological features, an insect found on some artefacts was identified as the xylophagous beetle Nicobium castaneum (Anobiidae). The influence of wood type and environmental conditions on the diversity of microorganisms was discussed.     

Soil microorganisms alleviate the allelopathic effect of <Emphasis Type="Italic">Eucalyptus grandis</Emphasis> × <Emphasis Type="Italic">E</Emphasis>. <Emphasis Type="Italic">urophylla</Emphasis> leachates on <Emphasis Type="Italic">Brassica chinensis</Emphasis>

Soil microbes may be critical players in determining the allelopathic potential of some plants. Low levels of plant community biodiversity in Eucalyptus plantations have been attributed to the allelopathic potential of these tree species. The role of soil microbes in the allelopathic effect of leaf leachates of the hybrid tree Eucalyptus grandis × E. urophylla, was tested in Petri dish assays with Brassica chinensis as a receiver plant. Soils were collected from either a local garden (soil A) or a Eucalyptus plantation (soil B) and half of each soil was sterilized to remove microbes. These soils were then treated with E. grandis × E. urophylla leachates for 0–72 h. Seed germination of B. chinensis was significantly inhibited in soils treated with leaf leachates relative to untreated soils. The inhibitory effect of the leaf leachates was more pronounced in sterilized soils. Total phenolic content was obvious lower in nonsterile leachate-treated soils than in sterile soils. Biomass of B. chinensis was negatively correlated with the total phenolic content in soils. Our findings suggest that soil microbes can alleviate the allelopathic potential of Eucalyptus and thereby its negative impact on plant growth.     

Genetic variation in heartwood properties and growth traits of <Emphasis Type="Italic">Eucalyptus bosistoana</Emphasis>

Forty-one E. bosistoana families were evaluated for the production of heartwood quantity and quality in two sites. High estimated heritabilities of heartwood diameter (HWD) were found in both sites (0.66 and 0.71). The estimated heritabilities of extractives content (EC) were lower with 0.16 and 0.25. Weak genetic correlations between HWD and EC were found in one site, but highly negative (??0.86) genetic correlations were observed in the other. The G?×?E interaction had no significant influence on growth traits but a small-level influence on the EC. Five families were selected for tree breeding as they produced both large HWD and high EC in both sites. It was suggested that genetic breeding selection could improve the heartwood quantity and quality of E. bosistoana plantations.     

From lethality to mortality: exploring the “grey area” of knockdown as an efficacy indicator of different insecticides against major storage insects using a lethality index

In the present work, a lethality index was applied for the evaluation of three insecticides with different modes of action, i.e., thiamethoxam, chlorfenapyr and lambda-cyhalothrin, as surface treatment against adults of Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.) and Tribolium confusum Jacquelin du Val, in laboratory bioassays. The insecticides were applied at their highest label dose, while insect knockdown and mortality were evaluated after 1, 3, 5 and 7 days of exposure to the treated surfaces according to the Standardized Lethality Index, by ranking each insect from “0” to “4,” with “0” corresponding to insects moving normally and “4” corresponding to dead individuals. After the end of the exposure, the surviving insects were transferred to clean, untreated dishes and delayed mortality was assessed after an additional period of 1, 3, 5 and 7 days. Based on the results, initial knockdown was high for S. oryzae after exposure to thiamethoxam and lambda-cyhalothrin even after 1 day of exposure, whereas for longer exposures high mortality levels were recorded. In contrast, in the case of chlorfenapyr knockdown was low after 1 day of exposure; however, high mortality levels were noted after 3 and 5 days of exposure. Similar results were noted for O. surinamensis, which was highly susceptible to all three insecticides tested. The most tolerant insect species to the tested insecticides was T. confusum, since a noticeable number of T. confusum adults were still active at the end of the exposure (7 days). Our results indicate that knockdown is most likely to lead to mortality than to recovery, but there were important differences among the three insecticides tested.     

Comparison of leaf stomatal conductance models for typical desert riparian phreatophytes in northwestern China

Stomatal regulation plays a vital role related to plant functioning, especially with a limited water supply. Estimating the leaf stomatal conductance (g _s) is pivotal for further estimation of transpiration as well as energy and mass balances between air and plant in arid regions. Based on successive measurements of leaf gas exchange of two typical desert riparian phreatophytes, Tamarix ramosissima Ledeb., and Populus euphratica Oliv., we estimated g _s using the empirical, optimal, and mechanistic models. Measurements were conducted on T. ramosissima during the growing seasons in 2011 and 2012 and P. euphratica in 2013 and 2014. Estimated values were compared with those measured by the portable open-path gas exchange measurement system. Results indicated that Ye’s mechanistic model always performed best among all the g _s models tested here with R ² values of 0.878 and 0.723 for T. ramosissima in 2011 and 2012, and 0.625 and 0.867 for P. euphratica in 2013 and 2014, respectively. Meanwhile, Medlyn’s optimal model exhibited the least reliable performance with R ² at values of 0.514 and 0.398 for T. ramosissima in 2011 and 2012, and 0.385 and 0.101 for P. euphratica in 2013 and 2014, respectively. Empirical models may not be suitable for application in novel situations because they have been developed from experimental observations rather than from any mechanistic understanding or theory of stomatal behavior. Consequently, the application of Ye’s mechanistic model will be of great significance for the modeling and up-scaling of g _s in extremely arid regions in the future.     

When host-plant resistance to a pest leads to higher plant damage

The effects of the association between grasses and fungal endophytes on orthopterans are very poorly studied although they are important grassland pests. Here, the endemic New Zealand weta, Hemiandrus sp. ‘promontorius’, and Festulolium loliaceum infected with Epichloë uncinata, were used to study the effect of endophyte-mediated resistance in grasses on this large orthopteran insect in the laboratory, and the effects of this interaction on the grass. The insect was presented with F. loliaceum with and without E. uncinata infection in no-choice and paired choice experiments. Other controls were Epichloë festucae-infected Festuca rubra and endophyte-free Lolium perenne. In no-choice experiments, persistent attempts by the insect to graze the endophyte-infected grasses (but promptly abandoning them) resulted in a significantly higher number of plants lost due to excision at their stems after the first bite (P = 0.004). The inability of affected grasses to compensate for the lost biomass resulted in a lack of significant difference between the dry biomass of endophyte-infected and endophyte-free controls (P = 0.206). However, in choice experiments, there was a preference for the endophyte-free controls when they were paired with the endophyte-infected grasses (P < 0.05). The current work shows that endophyte-infected grasses can sustain high plant losses when attacked by an orthopteran insect in the absence of an alternative food source. This contrasts other endophyte/herbivory experiments in which high herbivory occurs because chemical plant defences are at a low concentration or the endophytes have other non-toxin roles in the plant.     

The effects of phenolic acid on nitrogen metabolism in <Emphasis Type="Italic">Populus</Emphasis> × <Emphasis Type="Italic">euramericana</Emphasis> ‘Neva’

The declines in soil fertility and productivity in continuously cropped poplar plantations are related to phenolic acid accumulation in the soil. Nitrogen is a vital life element for poplar and whether the accumulation of phenolic acid could influence nitrogen metabolism in poplar and thereby hinder continuous cropping is not clear. In this study, poplar cuttings of Populus × euramericana ‘Neva’ were potted in vermiculite, and phenolic acids at three concentrations (0X, 0.5X and 1.0X) were added according to the actual content (1.0X) in the soil of a second-generation poplar plantation. Each treatment had eight replicates. We measured gas exchange parameters and the activities of key enzymes related to nitrogen metabolism in the leaves. Leaf photosynthetic parameters varied with the concentration of phenolic acids. The net photosynthetic rate (P_N) significantly decreased with increasing phenolic acid concentration, and non-stomatal factors might have been the primary limitation for P_N. The activities of nitrate reductase (NR), glutamine synthetase (GS) and glutamate synthase (GOGAT), as well as the contents of nitrate nitrogen, ammonium nitrogen, and total nitrogen in the leaves decreased with increasing phenolic acid concentration. This was significantly and positively related to P_N (P < 0.05). The low concentration of phenolic acids mainly affected the transformation process of NO₃^? to NO₂^?, while the high concentration of phenolic acids affected both processes, where NO₃^? was transferred to NO₂^? and NH₄⁺ was transferred to glutamine (Gln). Overall, phenolic acid had significant inhibitory effects on the photosynthetic productivity of Populus × euramericana ‘Neva’. This was probably due to its influence on the activities of nitrogen assimilation enzymes, which reduced the amount of amino acids that were translated into protein and enzymes. Improving the absorption and utilization of nitrogen by plants could help to overcome the problems caused by continuous cropping.     

Assessing water use and soil water balance of planted native tree species under strong water limitations in Northern Chile

Some forest plantations with native species are established in semiarid central Chile to compensate for industrial activities such as those of mining. Two of those operational forest plantations were monitored from age 1 to 3 years-old (2014–2016). Some plant attributes and soil volumetric water content (VWC) were monitored for eight native tree species (Acacia caven, Schinus polygamus, Porlieria chilensis, Lithraea caustica, Quillaja saponaria, Cryptocarya alba, Drimys winteri and Maytenus boaria), and a water balance model fitted to assess plant water use. Site preparation comprised planting holes of 40 cm?×?40 cm by 50 cm in depth dug with a backhoe. Substrate was removed and mixed with compost in proportion 70:30 before mixing it in the planting hole. Planting holes acted as water reservoirs over the study period with soil VWC generally increasing with soil depth being also less variable deeper than in the upper soil layers. The ratio of adaxial (upper leaf side) to abaxial (lower leaf side) stomatal conductance approximately followed a species gradient from xeric to mesic. Irrigation represented about 26% and 53% of the total water input for the sclerophyll and the D. winteri plantation, respectively. At the plant level (0.4?×?0.4 m), soil evaporation and transpiration of D. winteri (273 and 232 mm year^?1, equivalent to 43.7 and 37.1 L plant^?1, respectively) were about twofold the values for the sclerophyllous/malacophyllous plantation (138 and 128 mm year^?1, 22.1 and 20.5 L plant^?1, respectively). We suggest the water budget for the sclerophyll/malacophyllous plantation was tight but feasible to be adjusted while for D. winteri irrigation was excessive, could be drastically reduced, and suppressed altogether if planted in gullies. We believe water balance models and soil moisture content sensors could be used to better plan and manage irrigation frequency and amounts in compensation forest plantations in semiarid central Chile.     

Potential of Ethiopian mustard, <Emphasis Type="Italic">Brassica carinata</Emphasis> as a trap crop for large white butterfly, <Emphasis Type="Italic">Pieris brassicae</Emphasis> infesting Indian mustard, <Emphasis Type="Italic">Brassica juncea</Emphasis>

The large white butterfly, Pieris brassicae (L.), is an important pest of Indian mustard, Brassica juncea (L.) Czern., and inflicts heavy damage to all the above ground plant parts with strong yield reducing impacts. Farmers have few practical options other than to spray insecticides to protect their crop. In this study, an attempt was made during 2012–2013 and 2013–2014 crop seasons at Ludhiana, India, to evaluate Ethiopian mustard, Brassica carinata A. Braun as a trap crop to manage this pest as an alternate pest management strategy. B. carinata borders surrounding B. juncea were compared to chemically protected B. juncea and control (without B. carinata borders) plots for their effects on P. brassicae infestation and grain yield. Oviposition preference of adult butterflies was studied in a two-choice test in field cages, while the effect of two host plants on larval performance was studied under laboratory conditions under no choice conditions. B. juncea plots bordered with B. carinata harbored significantly lower larval population compared to control B. juncea plots during both the seasons. The grain yield in the bordered plots was also significantly higher than that from control plots and was statistically non-significant from that obtained in chemically protected plots. Female butterflies showed distinct oviposition preference for B. carinata over B. juncea and the larvae reared on B. carinata completed development in shorter period and grew bigger and heavier than those reared on B. juncea. Results indicated that B. carinata has potential to be used as trap crop to manage P. brassicae.     

Conjugation of δ-endotoxin from <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> with abamectin of <Emphasis Type="Italic">Streptomyces avermitilis</Emphasis> as a new type of biocide,GCSC-BtA,for control of agricultural insect pests

Conjugation of δ-endotoxin from Bacillus thuringiensis with abamectin, a toxin of Streptomyces avermitilis, was carried out to form a new type of biocide, GCSC-BtA based on “Germany-China Scientific Cooperation” research, for the control of agricultural insect pests. The strategy for biochemical linkage was designed by conjugating an amino group in B.t. protoxin with a carboxyl group in carboxylated abamectin under the treatment of conjugator EDC [1-Ethyl-3-(3-dimethylaminopropyl carbodiimide Hydrochloride)]. The formation of B.t. protoxin was processed by solubilizing B.t. crystal in 25?mM dithiothreitol (DTT) at 37?°C for 2?h. The carboxylated abamectin was formed by carboxylating the NaH-activated abamectin with 10?mg/ml butyric anhydride at 111?°C in a water-circumfluent condensation device for 2?h. The conjugating reaction, consisting of 5?mg/ml B.t. protoxin, 10?mg/ml carboxylated abamectin and 19.17?mg/ml EDC, was successfully conducted at room temperature for 24?h. Significant differences were found between pure abamectin, carboxylated abamectin and the conjugated BtA by means of UV-photo absorptions recorded at wavelengths 354, 438, 518, 600?nm (P?<?0.01). LT₅₀ of the conjugated GCSC-BtA to the 3^rd instar larvae of Plutella xylostella (L.) (Lep., Plutellidae) was 35.27 μg a.i./ml, about 62?% and 76?% of that caused by the B.t. protoxin and the caxboxylated abamectin, respectively. The conjugated GCSC-BtA caused 87.14?% mortalities in larvae of P. xylostella, 93.75?% in adult Myzus persicae (Sulzer) (Hom., Aphididae) and 89.33?% in adult Phyllotreta vittata Fabricius (Col., Chrysomelidae) as compared to 48.33?% by the B.t. crystal only in P. xylostella. The symptoms caused by conjugated GCSC-BtA in the 3^rd instar of P. xylostella were black color in the head part and white-yellow in the abdomen of dead larvae, which differed from the black color or the white-yellow all along the body caused by either the B.t. crystal or the abamectin, respectively. It was concluded that the conjugated GCSC-BtA biocide had a broader host spectrum and a faster killing speed than either the B.t. crystal or abamectin alone for the control of agricultural pests.     

Dry mass production,allocation patterns and water use efficiency of two conifers with different water use strategies under elevated [CO<Subscript>2</Subscript>], warming and drought conditions

Knowledge regarding the interactive effects of elevated [CO₂], warming and drought on dry mass production, allocation and water use efficiency (WUE) of tree seedlings is limited, particularly in trees exhibiting different stomatal regulation strategies. Seedlings of Callitris rhomboidea (relatively anisohydric) and Pinus radiata (relatively isohydric) were grown in two [CO₂] (C_a (400 μmol mol^?1) and C_e (640 μmol mol^?1)) and two temperature (T_a (ambient) and T_e (ambient?+?4 °C)) treatments in a sun-lit glasshouse under well-watered conditions prior to imposition of the drought. C_e increased mass production in C. rhomboidea (but not in P. radiata), while drought limited mass production in both species. Mass production was greatest in the combination of C_e, T_e and well-watered conditions. Pinus radiata allocated relatively more dry mass into roots and had higher plant WUE than C. rhomboidea. Noticeably, mass allocation patterns in C. rhomboidea varied as a function of the treatments, but those of P. radiata were constant. C_e enhanced leaf WUE of both species, but to a greater degree under drought stress than well-watered conditions. Moderate drought stress increased both leaf and plant WUE compared to well-watered conditions. C. rhomboidea exhibited plasticity to variable climate conditions through morphological adjustments, while P. radiata exhibited a highly conservative strategy. Collectively, these findings indicate that the two species have different strategies in resource acquisition and utilisation under changing environmental conditions. Future studies on tree response to climate change need to fully consider the integration of species traits, including stomatal behaviour and hydraulic strategies.     

Contact,fumigant, and cytotoxic activities of thyme and lemongrass essential oils against larvae and an ovarian cell line of the cabbage looper,Trichoplusia ni

The chemical composition of a plant essential oil can be affected by many environmental and biological factors. Understanding the role of individual constituents as well as their interactions to the overall insecticidal bioactivity is prerequisite to the use of essential oils as an alternative to conventional insecticides. In the present study, the chemical compositions of plant essential oils obtained from Thymus vulgaris (thyme) and Cymbopogon citratus (lemongrass) were analyzed by gas chromatography/mass spectrometry, and the insecticidal and cytotoxic activities of individual constituents were evaluated against third instar larvae and an ovarian cell line of Trichoplusia ni. Thymol was the most abundant compound in thyme oil and the primary active constituent in contact and cytotoxicity tests, whereas p-cymene was the most effective compound for fumigant toxicity. In lemongrass oil, citral was identified as the major active and most abundant constituent. A weak correlation between insecticidal activity and cytotoxicity was observed, indicating limitation of the latter as a screening tool for novel insecticides. Although the evaporation of thymol was enhanced at higher temperatures, its contribution to fumigant activity was limited.     

Root architecture might account for contrasting establishment success of <Emphasis Type="Italic">Pseudotsuga menziesii</Emphasis> var. <Emphasis Type="Italic">menziesii</Emphasis> and <Emphasis Type="Italic">Pinus sylvestris</Emphasis> in Central Europe under dry conditions

Key message

Pinus sylvestris seedlings quickly expand their roots to deeper soil layers while Pseudotsuga menziesii concentrates its root system in the topsoil, thereby running the risk of desiccation during long dry spells, as indicated by lower survival after simulated summer drought.

Context

Pseudotsuga menziesii (Douglas-fir) is regarded as a promising species to maintain the productivity of Central European lowland forests given the projected increase of long dry spells.

Aims

Will the species be able to regenerate from seed and spread outside plantations in a drier temperate Europe?

Methods

We measured the relative growth rate, biomass allocation, root architecture, and phenotypic plasticity of Pseudotsuga menziesii seedlings sown in a common garden and grown under current precipitation and prolonged drought, respectively. The species’ competitive ability with respect to Pinus sylvestris L., the most drought-tolerant native conifer in Central Europe, was assessed during three growing seasons.

Results

Pinus sylvestris seedlings had higher relative growth rates than did Pseudotsuga menziesii seedlings, first in terms of aboveground biomass and later in terms of shoot height. This resulted in heavier and taller seedlings after three growing seasons under both moist and dry conditions. Shorter vertical roots corresponded with lower survival of Pseudotsuga menziesii seedlings under dry conditions.

Conclusion

Fast root proliferation allows Pinus sylvestris seedlings to reach deeper water pools that are less rapidly depleted during transient drought. By contrast, the shallow root system might put Pseudotsuga menziesii seedlings at the risk of desiccation during prolonged dry spells.

     

A novel cold-inducible promoter,P<Emphasis Type="Italic">ThCAP</Emphasis> from <Emphasis Type="Italic">Tamarix hispida</Emphasis>, confers cold tolerance in transgenic <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Our previous studies have revealed that the ThCAP gene plays a vital role in transgenic Populus (P. davidiana × P. bolleana) in response to cold stress. However, the regulatory mechanism of ThCAP gene expression has been unclear. In this study, the 5′ flanking region of the ThCAP promoter (PThCAP) was cloned using a genome-walking method. By analyzing cis-acting regulatory elements of PThCAP, a DRE motif and MYC and MYB elements were found to be located in the promoter. To identify the regulatory elements that control the expression of the ThCAP gene promoter, a series of deletion derivatives of PThCAP, P1–P5, from the translation start code (?1538, ?1190, ?900, ?718 and ?375 bp), were fused to the GUS reporter gene, and then each deletion was stably introduced into Arabidopsis thaliana plants. Deletion analysis of the promoter suggested that only the P2 fragment had strong GUS expression in leaves and roots of A. thaliana exposed to low temperature stress. These results suggest that this 290-bp region (?1190 to ?900 bp), as an important part in PThCAP, was associated with cold tolerance of A. thaliana. Our results provide evidence for the regulatory mechanism of ThCAP gene involved in the response to cold stress, and that the gene is promising candidate gene for genetic improvement of crops.