<Emphasis Type="Italic">N</Emphasis>-Acyl derivatives of Asn,new bacterial <Emphasis Type="Italic">N</Emphasis>-acyl <Emphasis Type="Italic">D</Emphasis>-amino acids with surfactant activity

Summary. New N-acyl D-amino acids were isolated from Bacillus pumilus IM 1801. Their structures were determined by chemical analysis and mass spectrometry. The lipid part was identified as a mixture of fatty acids with 11, 12, 13, 15, and 16 carbon atoms in the iso, anteiso or n configuration linked by an amide bond with a D-asparagine. They exhibited surfactant properties.     

Compensatory function for water transport by adventitious roots of <Emphasis Type="Italic">Ipomoea pes-caprae</Emphasis>

To determine the role of adventitious roots in supplying water to Ipomoea pes-caprae (L.) Sweet (Convolvulaceae), we examined the effects of water deficit on water uptake and the growth patterns of leaves and shoots. After stopping the water supply from the primary root or adventitious roots, the water-uptake rate of the other root system increased steeply within 90–100 min to a level of 90% of the pretreatment water-uptake rate of the whole plant. Thus, the primary and adventitious roots can compensate for a decrease in the water-uptake rate of the whole plant caused by dehydration. The continuous growth of leaves and shoots after dehydration suggests that an increase in the water-uptake rate by either root system can support plant growth, although the growth rates of immature leaves in plants with no water supply from the primary or adventitious roots were lower than in controls. We conclude that the water supply from adventitious roots contributes to the survival and growth of plants, and will be important for vegetative propagation.     

Differences in swimming and diving abilities between two sympatric species of water shrews: <Emphasis Type="Italic">Neomys anomalus</Emphasis> and <Emphasis Type="Italic">Neomys</Emphasis><Emphasis Type="Italic">fodiens</Emphasis> (Soricidae)

Swimming and diving abilities of two syntopic species of water shrews, Neomys anomalus and Neomys fodiens, were tested in aquaria using video recordings taken from three views (lateral distant, lateral close and dorsal). The frequency and total duration of diving, as well as the mean duration of diving and floating bouts, were significantly higher in N. fodiens than in N. anomalus. Frequency of paddling during surface swimming was lower in N. fodiens than in N. anomalus. N. fodiens dived mainly for long distances at the bottom of the aquarium and performed a wider range of dive profiles than N. anomalus, which preferred rather short and shallow dives. The two species differed also significantly in their fineness ratios (describing how streamlined their bodies are) when diving. When swimming, N. fodiens had a relatively wider body and performed narrower movements with its tail than N. anomalus. These results show quantitatively and qualitatively for the first time that N. fodiens is more proficient at swimming and diving than N. anomalus. The results also help to explain the inter-specific differences in efficiency of underwater foraging, and support the idea of segregation of ecological niches of these species based on their different foraging modes (diving vs. wading).     

Photosynthetic responses to short-term and long-term light variation in <Emphasis Type="Italic">Pinus sylvestris</Emphasis> and <Emphasis Type="Italic">Salix dasyclados</Emphasis>

Pinus sylvestris and Salix dasyclados, which differ in leaf longevity, were compared with respect to four aspects of photosynthetic light use and response: high light acclimation, photoinhibition resistance and recovery, lightfleck exposure and use and chloroplast acclimation across leaves. The first two aspects were examined using seedlings under controlled conditions and the other two were tested using trees in the field. When exposed to high light, shade leaves of Pinus acclimated completely, achieving the same photosynthetic capacities as sun leaves, whereas shade leaves of Salix did not reach sun leaf capacities although the absolute magnitude of their acclimation was larger. Shade leaves of Pinus were also more resistant to photoinhibition than those of Salix. Much of the direct light supplied within the canopy was in the form of rapid fluctuations, lightflecks, for Pinus and Salix alike. They exploited short lightflecks with similar efficiency. The greater proportion of diffuse light in the canopy for Pinus than Salix seems to lead to a lesser degree of differential intra-leaf acclimation of chloroplasts, in turn leading to lower efficiency of photosynthesis under unilateral light as reflected by a lower convexity, rate of bending, of the light–response curve. The differences in light use and responses are discussed in relation to possible differences in characteristics of the long and short-lived leaf.     

Overexpression of <Emphasis Type="Italic">SsDGAT2</Emphasis> from <Emphasis Type="Italic">Sapium sebiferum</Emphasis> (L.) Roxb Increases Seed Oleic Acid Level in <Emphasis Type="Italic">Arabidopsis</Emphasis>

Sapium sebiferum (L.) Roxb is one of the most important oil trees in China. Diacylglycerol acyltransferases (DGATs) esterify sn-1, 2-diacylglycerol with a long-chain fatty acyl-CoA, the last step and the rate-limiting step of triacylglycerol (TAG) biosynthesis in prokaryotic and eukaryotic organisms. At least 74 DGAT2 sequences from 61 organisms have been identified, but the SsDGAT2 gene had not been reported to date. To clarify the function of SsDGAT2, we cloned the CDS (rapid amplification of cDNA end) of SsDGAT2 by RACE technology. The full-length CDS of SsDGAT2 contains 1011 bp and encodes a protein of 336 amino acids. Recombinant SsDGAT2 restored TAG biosynthesis to the yeast strain Saccharomyces cerevisiae H1246 TAG-deficient mutant and preferentially incorporated unsaturated C18 fatty acids into lipids. To investigate the biotechnological potential of SsDGAT2, it was expressed under the control of the 35S promoter in Arabidopsis Col-4. The oleic acid content increased by 50 % in transgenic plants relative to the control. The results indicated that most of the oleic acid increase was at the expense of linolenic acid (18:3) content, which suggests that high-oleic-acid-content seeds can be created by the overexpression of SsDGAT2 in S. sebiferum (L.) Roxb.     

<Emphasis Type="Italic">In vitro</Emphasis> propagation of the genus <Emphasis Type="Italic">Clivia</Emphasis>

We have developed a protocol for the in vitro propagation of the genus Clivia. Shoots were regenerated when fragments of the peduncle-pedicel junction (PP junction) from young inflorescences were used as explants. The optimal media for PP junction were Murashige and Skoog (MS)-based medium containing 10 M of 6-benzyladenine (BA) and 10 M of 2,4-dichlorophenoxyacetic acid (2,4-D) or MS supplemented with 5 M BA, 10 M -naphthaleneacetic acid (NAA), 250 mg l^-1 glutamine and 500 mg l^–1 casein hydrolysate and their usage depended on the breeding lines. Multiplication from initiations and in vitro seedlings was the best when the explants were cut longitudinally through the meristem and placed on MS plus 44 M BA. Plantlets were transferred on to hormone -free MS medium with charcoal for rooting.     

Foliar nutrition of <Emphasis Type="Italic">in vitro</Emphasis>-cultured <Emphasis Type="Italic">Prosopis chilensis</Emphasis> (Molina) Stuntz shoots

Summary Foliar nutrition has been conceived as a possible means of overcoming the recalcitrance of Prosopis chilensis (Molina) Stuntz explants to standard in vitro culture. The foliar uptake of cations (K from 20 gl⁻¹ KNO₃ and Ca from 50 gl⁻¹ CaCl₂), anions (NO₃ from 50 gl⁻¹ KNO₃ and PO₄ from 50 gl⁻¹ NaH₂PO₄), and glucose from a 100 mg l⁻¹ solution studied. All of the nutrients examined were absorbed. The efficacy of foliar nutrition in prolonging the vigor of micropropagated P. chilensis shoot tips was compared with nutrients supplied as a liquid to the base of the stem (liquid) or as an agar-solidified medium (agar). A foliar-feeding apparatus was constructed that employed pressurization of the medium reservoir to drive the medium into the culture vessel with a passive return by a siphoning effect. The medium used was Murashige and Skoog with 30 gl⁻¹ sucrose, 0.1 mgl⁻¹ benzylaminopurine, and 1 mgl⁻¹ indole-3-butyric acid. Over a 9-wk test period it was found that explants cultured by foliar nutrition performed significantly better than those grown on agar for shoot length, nodal production, and leaf retention; and better than liquid MS for node production. There was no significant difference among the three treatments in percentage survival, percentage rooting, or the mean number of roots.     

Plant regeneration,origin, and development of shoot buds from root segments of <Emphasis Type="Italic">Melia azedarach</Emphasis> L. (<Emphasis Type="Italic">Meliaceae</Emphasis>) seedlings

Summary In vitro regeneration of plants from root culture of Melia azedarach seedlings was obtained. The origin and mode of development of the regenerated shoot buds were studied by means of histological analysis and scanning electron microscopy (SEM). Maximum shoot bud regeneration was achieved when root segments were cultured on Murashige and Skoog (MS) medium at quarter strength with 3% sucrose and 0.44 μM benzyladenine (BA) and kept under light (116 μmol m⁻² s⁻¹). Shoot bud elongation was achieved on MS with 0.44 μM BA, 0.46 μM kinetin (KIN), and 3.26 μM adenine sulphate (AD). Regenerated shoots were rooted on MS with 12.26 μM indole-3-butyric acid (IBA) for 4 d and subsequently in MS lacking plant growth regulators for 26 d. Plants were established in a potting substrate. Histological analysis of roots from intact seedlings (without treatment) demonstrated that during the early life of the roots, M. azedarach lacks preformed buds. In contrast, when the roots were excised and cultured in vitro, the histology and SEM observations revealed that buds originated from meristematic groups of cells, which had been formed from the pericycle and several layers beneath. These meristematic groups of cells grew towards the periphery of the cortex by crushing the outer layer of cortical cells. Further develoment led to the differentiation of leaf primordia and a shoot apical meristem.     

Antisense suppression of thioredoxin<Emphasis Type="Italic">h</Emphasis>mRNA in <Emphasis Type="Italic">Brassica napus cv.</Emphasis>

In Brassica, the thioredoxinhproteins, THL1 and THL2, were previously found to be potential inhibitors of the S receptor kinase (SRK) in the Brassica self-incompatibilty response. To investigate the biological roles of THL1 and THL2 in pollen–pistil interactions, the stigma-specific SLR1 promoter was used to drive antisense THL1/2 expression in Brassica napus cv. Westar. This cultivar is normally compatible, but antisense suppression of THL1/2 led to a low level constitutive rejection of all Brassica napus pollen tested. Fluorescence microscopy revealed that the pollen rejection was a typical Brassica self-incompatibility rejection response with reduced pollen adhesion, germination and pollen tube growth. In addition, Westar was found to express the SLG₁₅ and SRK₁₅ proteins which may be the target of regulation by THL1 and THL2. Thus, these results indicate that the THL1 and THL2 are required for full pollen acceptance in B. napus cv. Westar.     

Micropropagation of <Emphasis Type="Italic">Ailanthus altissima</Emphasis> and <Emphasis Type="Italic">in vitro</Emphasis> heavy metal tolerance

Ailanthus altissima, a fast-growing and contamination-resistant species is investigated for its use in areas contaminated by heavy metals. A micropropagation protocol for A. altissima was developed, cultured shoots were tested for in vitro heavy metals tolerance. Proliferation rate and shoot length were affected by 6-benzylaminopurine (BAP) and Murashige and Skoog’s (MS) salt concentrations, best results were obtained in full strength MS medium supplemented with 1.32 or 2.64 μM BAP. Rooting percentage was strongly influenced by indole-3-butyric acid. Cultures of A. altissima exposed to heavy metals demonstrated a tolerance comparable to species already utilized in phytoremediation.     

Ecophysiological adaptations of black spruce (<Emphasis Type="Italic"> Picea mariana</Emphasis>) and tamarack (<Emphasis Type="Italic"> Larix laricina</Emphasis>) seedlings to flooding

Black spruce [ Picea mariana (Mill.) B.S.P.] and tamarack [ Larix laricina (Du Roi) K. Koch] are the predominant tree species in boreal peatlands. The effects of 34 days of flooding on morphological and physiological responses were investigated in the greenhouse for black spruce and tamarack seedlings in their second growing season (18 months old). Flooding resulted in reduced root hydraulic conductance, net assimilation rate and stomatal conductance and increased needle electrolyte leakage in both species. Flooded tamarack seedlings maintained a higher net assimilation rate and stomatal conductance compared to flooded black spruce. Flooded tamarack seedlings were also able to maintain higher root hydraulic conductance compared to flooded black spruce seedlings at a comparable time period of flooding. Root respiration declined in both species under flooding. Sugar concentration increased in shoots while decreasing in roots in both species under flooding. Needles of flooded black spruce appeared necrotic and electrolyte leakage increased over time with flooding and remained significantly higher than in flooded tamarack seedlings. No visible damage symptoms were observed in flooded tamarack seedlings. Flooded tamarack seedlings developed adventitious roots beginning 16 days after the start of flooding treatment. Adventitious roots exhibited significantly higher root hydraulic conductivity than similarly sized flooded tamarack roots. Flooded black spruce lacked any such morphological adaptation. These results suggest that tamarack is better able to adjust both morphologically and physiologically to prolonged soil flooding than black spruce seedlings.     

Multiple defence strategies of <Emphasis Type="Italic">Daphnia</Emphasis><Emphasis Type="Italic">galeata</Emphasis> against predation in a weakly stratified reservoir

In the presence of size-selective fish daphnids were shown to exhibit two alternative inducible defence strategies: They may either escape predation by active migration or adopt a life history strategy, e.g., reproduce earlier and at a smaller size. Depending on the type of habitat, migration may either be vertically (in deep stratified lakes) or horizontally (in shallow lakes with macrophytes) oriented. Concerning behavioural defence strategies, daphnids living in medium-deep, weakly stratified water bodies with a poorly developed littoral face a dilemma, since the littoral provides no shelter and the availability of a deep-water refuge is unpredictable. We studied the population dynamics, life history changes (size at maturity) and daytime vertical distribution of Daphnia galeata in a weakly stratified reservoir in relation to predation by juvenile fish during 6 years. While temperature gradients were usually small, oxygen concentrations suggest that a low-oxygen refuge for daphnids was available in every year to some extent. Our results indicate that, depending on predation intensity and stratification patterns, daphnids exhibit both, behavioural and life history defences. In years with a high biomass of young-of-the-year (YOY) perch Daphnia abundance declined rapidly at the end of the clear water stage while at the same time the vertical distribution at daytime shifted to deep strata providing a low-oxygen refuge and the size at maturity decreased. However, while the life history response in some years lasted throughout most of the summer period, a shift in daytime vertical distribution was exhibited for much shorter periods. Both traits were much less expressed in years with low YOY fish densities and no negative correlation between them could be verified. We suggest that under high predation pressure in this relatively shallow reservoir no strictly alternative (either behavioural or life history) strategies exist, but that daphnids make use of the full range of possible anti-predator defences available, at least during short periods when predation is most intense. Guest editor: Piet Spaak Cladocera: Proceedings of the 7th International Symposium on Cladocera     

No diapause prolongation response of <Emphasis Type="Italic">Daphnia</Emphasis> in the presence of planktivorous mosquitofish (<Emphasis Type="Italic">Gambusia holbrooki</Emphasis>)

Recent research suggests that planktonic organisms in resting stages can perceive predators chemically and delay hatching to evade predation. Using a co-occurring predator–prey pair (Gambusia holbrooki Girard and Daphnia curvirostris Eylmann) from a Mediterranean floodplain wetland, this study tested for such predator-avoidance behaviour of Daphnia. Results show that hatching patterns of Daphnia were not reduced by the presence of different biomass levels of Gambusia. This could be due to the fact that the density of Gambusia in the wetland is high from late spring to late autumn, suggesting that delayed hatchlings would face increased mortality through consumptive predation.     

<Emphasis Type="Italic">In vitro</Emphasis> regeneration of <Emphasis Type="Italic">Leucaena leucocephala</Emphasis> by organogenesis and somatic embryogenesis

In the present study, in vitro regeneration system for a recalcitrant woody tree legume, Leucaena leucocephala (cvs. K-8, K-29, K-68 and K-850) from mature tree derived nodal explants as well as seedling derived cotyledonary node explants was developed. Best shoot initiation and elongation was found on full-strength Murashige and Skoog (MS) medium supplemented with 3 % (m/v) sucrose, 100 mg dm⁻³ myoinositol, 100 mg dm⁻³ glutamine, 20.9 μM N ⁶-benzylamino-purine (BAP) and 5.37 μM 1-naphthalene acetic acid (NAA). Rooting was induced in half-strength MS medium containing 2 % (m/v) sucrose, 100 mg dm⁻³ myoinositol, 14.76 μM indole-3-butyric acid (IBA) and 0.23 μM kinetin. The cultivar K-29 gave the best response under in vitro conditions. Rooted plantlets were subjected to hardening and successfully transferred to greenhouse. Further, somatic embryogenesis from nodal explants of cv. K-29 via an intermittent callus phase was also established. Pronounced callusing was observed on full-strength MS medium containing 3 % (m/v) sucrose, 100 mg dm⁻³ myoinositol, 40.28 μM NAA and 12.24 μM BAP. These calli were transferred to induction medium and maximum number of globular shaped somatic embryos was achieved in full-strength MS medium fortified with 3 % (m/v) sucrose, 100 mg dm⁻³ myoinositol, 15.0 μM 2,4-dichlorophenoxyacetic acid (2,4-D), 5.0 μM BAP and 1.0 mM proline. Moreover, an increase in endogenous proline content up to 28^th day of culture in induction medium was observed. These globular shaped somatic embryos matured in full-strength MS medium with 3 % (m/v) sucrose, 100 mg dm⁻³ myoinositol, 10.0 μM BAP, 2.5 to 5.0 μM IBA and 0.5 mM spermidine.     

Seedling growth variation in response to sand burial in four <Emphasis Type="Italic">Artemisia</Emphasis> species from different habitats in the semi-arid dune field

We compared seedling growth of four Artemisia species dominated at different habitats to determine whether interspecific seedling growth variation of a same genus in tolerance to burial can be used to explain plant distribution in the sand dune field. Interdune lowland species, Artemisia gmelinii, stabilized dune species, A. frigida, semi-stabilized dune species, A. halodendron, and active dune species, A. wudanica were selected. Seedlings grown for 3 weeks were treated at five burial depths for three burial times in pot experiments. Species from the habitats with little burial had smaller survival rate, dry weight and stem elongation speed than those from the habitats with intensive burial when buried. Furthermore, when buried, the former tended to adjust biomass allocation between shoot and root and produce adventitious buds, while the latter tended to maintain a constant root:shoot ratio and produce adventitious roots. We conclude that (1) seedlings of species with a long evolutionary history of exposure to sand burial (from the active sand dune), show quicker stem growth when buried than do seedlings of species from the habitats with little or no sand burial; (2) seedlings of species which do not change root:shoot ratio might be more tolerant of sand burial than those do; (3) seedlings of species from the habitats with intensive sand burial is prone to produce adventitious roots and seedlings of species from the habitats with little or no sand burial tend to produce adventitious buds when buried.     

Sociality in <Emphasis Type="Italic">Euglossa</Emphasis> (<Emphasis Type="Italic">Euglossa</Emphasis>) <Emphasis Type="Italic">viridissima</Emphasis> Friese (Hymenoptera,Apidae, Euglossini)

Euglossa viridissima is an orchid bee that forms both solitary and multiple female nests, making it a suitable species for the study of factors leading to diverse degrees of sociality in Euglossines. We conducted observations in eight reused nests (where a first generation of bees had been produced) kept in artificial boxes from the Yucatan Peninsula, Mexico. Five nests were reused (reactivated) by a single female (SFN), two nests reused by a mother and one daughter (MFN1) and one nest reused by the mother and two daughters (MFN2). No single nest was reactivated by unrelated females. The number of foraging trips, their duration and the duration of cell provisioning was not different between SFN and MFN. The overall production of cells per female was not different either between both types of nest. However, in MFN although all females did lay eggs, there was a reproductive skew in favor of the mother (95 and 45% of the brood produced in MFN1 and MFN2 respectively). She showed reproductive control of her daughters through oophagy and displaying threatening behavior when the daughters tried to open a cell where she had laid an egg. Brood losses to parasites (Anthrax sp. (Bom-byliidae) and Hoplostelis bivittata (Megachilidae)) were only found in SFN which possibly reflects and advantage of MFN in this respect. Our results coupled with other studies in Euglossa, reveal that a wide range of social behaviors occur in this genus, from solitary and communal to primitive reproductive division of labor. Multiple factors involving different levels of pressure imposed by food availability and parasites may favor such a diverse range of nesting behaviors. Interestingly, female associations in E. viridissima seem a result of kin selection that is enforced by coercion from mother females on their daughters. More studies are needed to shed light upon the social organization of Euglossa and other Euglossines and on their phylogenetic relationships in order to trace the origins of eusociality in Apidae. Received 12 February 2008; revised 25 June 2008; accepted 17 July 2008.     

New combinations and typifications in <Emphasis Type="Italic">Bistorta</Emphasis>, <Emphasis Type="Italic">Persicaria</Emphasis>, <Emphasis Type="Italic">Polygonum,</Emphasis> and <Emphasis Type="Italic">Rumex</Emphasis> (Polygonaceae)

New combinations are proposed in anticipation of the Polygonaceae treatment in the forthcoming volume of Intermountain Flora: Polygonum kelloggii var. esotericum, P. kelloggii var. watsonii , Rumex densiflorus var. pycnanthus , R. salicifolius var. utahensis, and R. occidentalis var. tomentellus. Typifications are proposed to facilitate ongoing studies in Polygonaceae and to maintain current usage.     

Increased competitive ability and herbivory tolerance in the invasive plant <Emphasis Type="Italic">Sapium sebiferum</Emphasis>

The evolution of increased competitive ability (EICA) hypothesis predicts that release from natural enemies in the introduced range favors exotic plants evolving to have greater competitive ability and lower herbivore resistance than conspecifics from the native range. We tested the EICA hypothesis in a common garden experiment with Sapium sebiferum in which seedlings from native (China) and invasive (USA) populations were grown in all pairwise combinations in the native range (China) in the presence of herbivores. When paired seedlings were from the same continent, shoot mass and leaf damage per seedling were significantly greater for plants from invasive populations than those from native populations. Despite more damage from herbivores, plants from invasive populations still outperformed those from native populations when they were grown together. Increased competitive ability and higher herbivory damage of invasive populations relative to native populations of S. sebiferum support the EICA hypothesis. Regression of biomass against percent leaf damage showed that plants from invasive populations tolerated herbivory more effectively than those from native populations. The results of this study suggest that S. sebiferum has become a faster-growing, less herbivore-resistant, and more herbivore-tolerant plant in the introduced range. This implies that increased competitive ability of exotic plants may be associated with evolutionary changes in both resistance and tolerance to herbivory in the introduced range. Understanding these evolutionary changes has important implications for biological control strategies targeted at problematic invaders.