Form follows function: morphological diversification and alternative trapping strategies in carnivorous Nepenthes pitcher plants

Carnivorous plants of the genus Nepenthes have evolved a striking diversity of pitcher traps that rely on specialized slippery surfaces for prey capture. With a comparative study of trap morphology, we show that Nepenthes pitcher plants have evolved specific adaptations for the use of either one of two distinct trapping mechanisms: slippery wax crystals on the inner pitcher wall and 'insect aquaplaning' on the wet upper rim (peristome). Species without wax crystals had wider peristomes with a longer inward slope. Ancestral state reconstructions identified wax crystal layers and narrow, symmetrical peristomes as ancestral, indicating that wax crystals have been reduced or lost multiple times independently. Our results complement recent reports of nutrient source specializations in Nepenthes and suggest that these specializations may have driven speciation and rapid diversification in this genus.     

Life on a deadly trap: Buckleria paludum,a specialist herbivore of carnivorous sundew plants,licks mucilage from glands for defense

Caterpillars of Buckleria spp. (Lepidoptera: Pterophoridae) have a unique feeding habit of eating trap leaves of carnivorous sundew plants (Drosera spp.). We observed the foraging behavior of Buckleria paludum on trap leaves of Drosera spp. and discussed how the moth species avoided being caught by trap leaves. In 81.5% (66/81) of encounters with glandular hairs on adaxial surfaces of Drosera trap leaves, B. paludum larvae licked mucilage and crawled on the processed hairs. The frequency of licking mucilage was significantly higher than the frequency of other behaviors such as eating glandular hairs, chewing bases of them without eating and ignoring when encountering secreted mucilage. Licking mucilage enables the caterpillars to move safely on trap leaves and prevents bending of glandular hairs.     

Specificity of extrafloral nectar induction by herbivores differs among native and invasive populations of tallow tree

Background and Aims

Invasive plants can be released from specialist herbivores and encounter novel generalists in their introduced ranges, leading to variation in defence among native and invasive populations. However, few studies have examined how constitutive and induced indirect defences change during plant invasion, especially during the juvenile stage.

Methods

Constitutive extrafloral nectar (EFN) production of native and invasive populations of juvenile tallow tree (Triadica sebifera) were compared, and leaf clipping, and damage by a native specialist (Noctuid) and two native generalist caterpillars (Noctuid and Limacodid) were used to examine inducible EFN production.

Key results

Plants from introduced populations had more leaves producing constitutive EFN than did native populations, but the content of soluble solids of EFN did not differ. Herbivores induced EFN production more than simulated herbivory. The specialist (Noctuid) induced more EFN than either generalist for native populations. The content of soluble solids in EFN was higher (2·1 times), with the specialist vs. the generalists causing the stronger response for native populations, but the specialist response was always comparable with the generalist responses for invasive populations.

Conclusions

These results suggest that constitutive and induced indirect defences are retained in juvenile plants of invasive populations even during plant establishment, perhaps due to generalist herbivory in the introduced range. However, responses specific to a specialist herbivore may be reduced in the introduced range where specialists are absent. This decreased defence may benefit specialist insects that are introduced for classical biological control of invasive plants.     

Differential effects of type and quantity of leaf damage on growth,reproduction and defence of lima bean (Phaseolus lunatus L.)

Folivores are major plant antagonists in most terrestrial ecosystems. However, the quantitative effects of leaf area loss on multiple interacting plant traits are still little understood. We sought to contribute to filling this lack of understanding by applying different types of leaf area removal (complete leaflets versus leaflet parts) and degrees of leaf damage (0, 33 and 66%) to lima bean (Phaseolus lunatus) plants. We quantified various growth and fitness parameters including above‐ and belowground biomass as well as the production of reproductive structures (fruits, seeds). In addition, we measured plant cyanogenic potential (HCNp; direct chemical defence) and production of extrafloral nectar (EFN; indirect defence). Leaf damage reduced above‐ and belowground biomass production in general, but neither variation in quantity nor type of damage resulted in different biomass. Similarly, the number of fruits and seeds was significantly reduced in all damaged plants without significant differences between treatment groups. Seed mass, however, was affected by both type and quantity of leaf damage. Leaf area loss had no impact on HCNp, whereas production of EFN decreased with increasing damage. While EFN production was quantitatively affected by leaf area removal, the type of damage had no effect. Our study provides a thorough analysis of the quantitative and qualitative effects of defoliation on multiple productivity‐related and defensive plant traits and shows strong differences in plant response depending on trait. Quantifying such plant responses is vital to our understanding of the impact of herbivory on plant fitness and productivity in natural and agricultural ecosystems.     

Evidence for mutualism between a flower-piercing carpenter bee and ocotillo: use of pollen and nectar by nesting bees

Abstract.

• 1 Carpenter bees (Xylocopa californica arizonensis) in west Texas, U.S.A., gather pollen and ‘rob’ nectar from flowers of ocotillo (Fouquieria splendens). When common, carpenter bees are an effective pollen vector for ocotillo. We examined ocotillo's importance as a food source for carpenter bees.
• 2 The visitation rate of carpenter bees to ocotillo flowers in 1988 averaged 0.51 visits/flower/h and was 4 times greater than that of queen bumble bees (Bombus pennsylvanicus sonorus), the next most common visitor. Nectar was harvested thoroughly and pollen was removed from the majority of flowers. Hummingbird visits were rare.
• 3 Pollen grains from larval food provisions were identified from sixteen carpenter bee nests. On average, 53% of pollen grains sampled were ocotillo, 39% were mesquite (Prosopis glandulosa), and 8% were Zygophyllaceae (Larrea tridentata or Guaiacum angustifolium). Carpenter bee brood size averaged 5.8 per nest.
• 4 We measured the number of flowers, and production of pollen and nectar per flower by mature ocotillo plants, as well as the quantity of pollen and sugar in larval provisions. An average plant produced enough pollen and nectar sugar to support the growth of eight to thirteen bee larvae. Ocotillo thus has the potential to contribute significantly to population growth of one of its key pollinators.
• 5 Although this carpenter bee species, like others, is a nectar parasite of many plant species, it appears to be engaged in a strong mutualism with a plant that serves as both a pollen and as a nectar source during carpenter bee breeding periods.

     

PDGF AA homodimers are potent chemoattractants for fibroblasts and neutrophils, and for monocytes activated by lymphocytes or cytokines.

The A-chain homodimers of the platelet-derived growth factor (PDGF AA) are widely expressed in normal and transformed cells. The mitogenic properties of PDGF AA are well established; however, the chemotactic potential of PDGF AA remains controversial. We now show that PDGF AA is a strong chemoattractant for human monocytes, granulocytes, and fetal bovine ligament fibroblasts. However, highly purified (greater than 98%) monocytes require the addition of lymphocytes or IL-1 for chemotactic responsiveness to PDGF AA but not for full chemotactic activity with formyl-methionyl-leucyl-phenylalanine (fMLP) or C5a. These results indicate that PDGF AA is a potent chemoattractant. These results also indicate that monocytes require activation either by lymphocytes or exogenous cytokines in order to respond chemotactically to PDGF AA but not to fMLP or C5a and suggest roles of the lymphocyte and cytokine in the chemotactic response of the monocyte to PDGF AA in vivo.     

Resistance in sorghum to the shoot fly, Atherigona soccata: epicuticular wax and wetness of the central whorl leaf of young seedlings

Sorghum genotypes known to be resistant or susceptible to shoot fly, Atherigona soccata Rondani were examined by scanning electron microscopy for differences in epicuticular wax structure and wetness of the central leaf whorl. Two major types of wax structures were observed: shoot fly resistant and moderately resistant genotypes were characterised by a smooth amorphous wax layer and sparse wax crystals while susceptible genotypes possessed a dense meshwork of crystalline epicuticular wax. The density of wax crystals decreased from the third leaf to the seventh leaf stage and was related to both seedling age and leaf position. Water droplets on susceptible genotypes with dense wax crystals showed spreading at the edges indicating a tendency to wet easily. In resistant genotypes with less dense wax crystals the droplets remained intact and did not spread.     

Rapid responses of mesophyll conductance to changes of CO2 concentration,temperature and irradiance are affected by N supplements in rice

Photosynthesis in C₃ plants is significantly limited by mesophyll conductance (g_m), which can vary with leaf anatomical traits and nitrogen (N) supplements. Several studies have investigated the response of g_m to N supplements; however, none examined the implications of N supplements on the response of g_m to rapid environmental changes. Here we investigated the effect of N supplement on g_m and the response of g_m to change of CO₂, temperature and irradiance in rice. High N supplement (HN) increased mesophyll cell wall surface area and chloroplast surface area exposed to intercellular airspace per leaf area, and reduced cell wall thickness. These changes resulted in increased g_m. The g_m of leaves with HN was more sensitive to changes in CO₂ concentration, temperature and irradiance. The difference in leaf structural features between low N supplement and HN indicates that a rapid change in g_m is related to the regulation of diffusion through biological membranes rather than leaf structural features. These results will contribute to an understanding of the determinants of g_m response to rapid changes in environmental factors.     

Demystifying SP cell purification: viability, yield, and phenotype are defined by isolation parameters

Side population (SP) cells isolated from bone marrow, skeletal muscle, and skin have been shown to engraft in dystrophic muscle. However, there have been questions on the phenotypical heterogeneity, tissue of origin, and relationships among SP cell populations extracted from different tissues. Studies on bone marrow SP cells have followed a consistent protocol for their isolation and results obtained are concordant. In contrast, protocols for the isolation of muscle SP cells vary greatly, and consequently reports on their phenotype, differentiation potential and origin have been inconsistent. To address this controversy, we demonstrate that isolation parameters, such as tissue dissociation, cell counting, Hoechst concentration, and stringency in the selection of SP cells, have an effect on the yield, viability, and homogeneity of SP cells derived from bone marrow, skeletal muscle, and skin. In this paper, we demonstrate that SP cells isolated from the bone marrow are distinct from SP cells extracted from skeletal muscle and skin tissues. This study offers an explanation for the controversy surrounding muscle SP cells, provides a detailed standardized protocol for their isolation, and highlights basic guidelines for reproducible and reliable isolation of SP cells from any tissue.     

Manipulation of the hypocotyl sink activity by reciprocal grafting of two Raphanus sativus varieties: its effects on morphological and physiological traits of source leaves and whole‐plant growth

To reveal whether hypocotyl sink activities are regulated by the aboveground parts, and whether physiology and morphology of source leaves are affected by the hypocotyl sink activities, we conducted grafting experiments using two Raphanus sativus varieties with different hypocotyl sink activities. Comet (C) and Leafy (L) varieties with high and low hypocotyl sink activities were reciprocally grafted and resultant plants were called by their scion and stock such as CC, LC, CL and LL. Growth, leaf mass per area (LMA), total non‐structural carbohydrates (TNCs) and photosynthetic characteristics were compared among them. Comet hypocotyls in CC and LC grew well regardless of the scions, whereas Leafy hypocotyls in CL and LL did not. Relative growth rate was highest in LL and lowest in CC. Photosynthetic capacity was correlated with Rubisco (ribulose 1·5‐bisphosphate carboxylase/oxygenase) content but unaffected by TNC. High C/N ratio and accumulation of TNC led to high LMA and structural LMA. These results showed that the hypocotyl sink activity was autonomously regulated by hypocotyl and that the down‐regulation of photosynthesis was not induced by TNC. We conclude that the change in the sink activity alters whole‐plant growth through the changes in both biomass allocation and leaf morphological characteristics in R. sativus.     

Manipulation of the onset of ectomycorrhiza formation by indole-3-acetic acid, activated charcoal or relative humidity in the association between oak microcuttings and Piloderma croceum: influence on plant development and photosynthesis

A Petri dish system in which development of oak (Quercus robur L.) microcuttings is stimulated by the late stage ectomycorrhizal (EM) fungus Piloderma croceum J. Erikss. & Hjortst. in a long pre-symbiotic stage was optimised to allow synchronous, rhythmic plant growth. Addition of indole-3-acetic acid or activated charcoal to the medium caused an early and more intensive EM formation coupled with suppression of most developmental effects of P. croceum. Leaf area, chlorophyll fluorescence, and content were compared in inoculated and uninoculated plants grown at two relative humidity levels (45 and 95%) and under consideration of three possible answers to inoculation, that is, no or EM formation after the 1st or the 2nd shoot flush. The culture conditions for uninoculated plants were suboptimal, leading toward photochemical stress reflected by a non photochemical quenching (qE) increase and a reduced Chl content at the end of the assay. Prior to EM formation, inoculation itself enhanced the optimal (Fv/Fm) and effective (phiPSII) quantum yield in leaves of the 1st shoot flush under reduced relative humidity. It also fully protected the plants against stress during the complete assays. The results indicate that inoculated plants only form EM once they have acquired a sufficient development level and C-providing capacity. However, the fungus actively improves the development and photosynthesis of plants up to the pre-mycorrhizal stage, helping them to reach this capacity.     

Different mechanisms are involved in intracellular calcium increase by insulin-like growth factors 1 and 2 in articular chondrocytes: Voltage-gated calcium channels,and/or phospholipase C coupled to a pertussis-sensitive G-protein

This study describes the mechanisms involved in the IGF-1 and IGF-2-induced increases in intracellular calcium concentration [Ca²⁺]i in cultured chondrocytes and the involvement of type 1 IGF receptors. It shows that IGF-1, IGF-2, and insulin increased the cytosolic free calcium concentration [Ca²⁺]i in a dose-dependent manner, with a plateau from 25 to 100 ng/ml for both IGF-1 and IGF-2 and from 1 to 2 μg/ml for insulin. The effect of IGF-1 was twice as great as the one of IGF-2, and the effect of insulin was 40% lower than IGF-1 effect. Two different mechanisms are involved in the intracellular [Ca²⁺]i increase. 1) IGF-1 and insulin but not IGF-2 involved a Ca²⁺ influx through voltage-gated calcium channels: pretreatment of the cells by EGTA and verapamil diminished the IGF-1 or insulin-induced[Ca²⁺]i but did not block the effect of IGF-2.2)IGF-1, IGF-2, and insulin also induced a Ca²⁺ mobilization from the endoplasmic reticulum: phospholipase C (PLC) inhihitors, neomycin, or U-73122 partially blocked the intracellular [Ca²⁺]i increase induced by IGF-1 and insulin and totally inhibited the effect of IGF-2. This Ca²⁺ mobilization was pertussis toxin (PTX) dependent, suggesting an activation of a PLC coupled to a PTX-sensitive G-protein. Lastly, preincubation of the cells with IGF₁ receptor antibodies diminished the IGF-1-induced Ca²⁺ spike and totally abolished the Ca²⁺ influx, but did not modify the effect of IGF-2. These results suggest that IGF-1 action on Ca²⁺ influx involves the IGF₁ receptor, while part of IGF-1 and all of IGF-2 Ca²⁺ mobilization do not implicate this receptor. J. Cell. Biochem. 64:414–422. © 1997 Wiley-Liss, Inc.     

Mycosphaerella chaenomelis sp. nov.: The teleomorph ofCercosporella sp., the causal fungus of frosty mildew inChaenomeles sinensis, and its role as the primary infection source

A leaf spot disease called frosty mildew was observed onChaenomeles sinensis throughout Japan. Small brown spots with white tufts occurred followed by successive defoliation. On the fallen leaves, minute black dots are formed. The causal fungus was regarded as a new species ofMycosphaerella, M. chaenomelis, andCercosporella chaenomelis in anamorph. Pathogenicity of the fungus was confirmed only inC. sinensis by inoculation experiments. Colonies of the fungus grew well on potato sucrose agar, and grew at 10–30°C with an optimum temperature of 25°C. The fungus overwintered on the fallen diseased leaves in the form of pseudothecia, and ascospores served as the primary infection source from April to June.     

The fate of nitrogen from winter-frozen rapeseed leaves: mineralization,fluxes to the environment and uptake by rapeseed crop in spring

For environmental purposes, very early sowing of winter rapeseed may reduce winter nitrate leaching thanks to the high N uptake capacities of rapeseed in autumn. However, freezing could lead to high losses of leaf nitrogen, amounting to more than 100 kg N ha^-1 (Dejoux et al., 1999). Here we investigated the agronomic and environmental consequences of the decomposition of fallen leaves, based on field and laboratory studies with ¹⁵N labeled leaves (C:N=9). The potential kinetics of decomposition of leaves were measured by incubation in the laboratory. In the field, all leaves were removed at beginning of winter and replaced by labeled leaves, artificially frozen at −15°C , which were laid on the soil surface. Compared on a thermal time basis, decomposition proceeded as quickly in the field as in the incubations and was complete after 116 normalized days at 15 °C. The proportion of ¹⁵N derived from labeled leaves, absorbed again by the rape plants, was 28% at flowering and 24% at harvest. This high N recovery is assumed to result from the synchronization of leaves decomposition and active N absorption by rape in spring. Leaf N mineralization did not increase soil N mineral content at flowering or at harvest, but we observed a 40% loss of ¹⁵N. As no leaching was simulated, this loss was supposed to be gaseous. Such a high percentage could be explained by the fact that the decomposing leaves lay on the soil surface, and by climatic conditions conducive to such emissions. For environmental purposes, the quantity and nature of these gaseous N emissions have to be studied for other climatic conditions and types of leaves. As a proportion of N is reabsorbed, N fertilizer application rates could be reduced accordingly. This revised version was published online in August 2006 with corrections to the Cover Date.     

Recent colonization by a coastal plant of inland habitats at an ancient freshwater lake,Lake Biwa: multilocus sequencing and a demographic history of Lathyrus japonicus (Fabaceae)

Ancient lakes have been recognized as “long‐term isolated islands” in terrestrial ecosystems. Lake Biwa, one of the few ancient lakes that formed around 4 million years ago, harbors many coastal species that commonly inhabit seashores. The beach pea, Lathyrus japonicus, is a typical coastal species of this freshwater lake, where morphological, physiological, and genetic differentiations have been reported between Biwa and coastal populations. Whether Biwa populations were isolated for long periods throughout Pleistocene climatic oscillations and subsequent range shifts is unclear. We assessed population genetic structure and demography of beach pea in this ancient freshwater lake using the sequences of eight nuclear loci. The results of STRUCTURE analyses showed evidence of admixture between Biwa and coastal populations, reflecting recent gene flow. The estimated demographic parameters implemented by the isolation with migration model (IM model) revealed a recent divergence (postglacial period) of Biwa populations, with some gene flow from Biwa to coastal populations. In addition, Biwa populations were significantly smaller in size than the ancestral or coastal populations. Our study suggests that a Holocene thermal maximum, when transgression could allow seeds from coastal plants to access Lake Biwa, was involved in the origin of the Biwa populations and their genetic divergence. Thus, coastal populations might have migrated to Lake Biwa relatively recently. Our study concluded that ancestral migrants in Lake Biwa were derived from small founding populations and accelerated genetic isolation of Biwa populations during short‐term isolation.     

Calcium influx into mouse spermatozoa activated by solubilized mouse zona pellucida,monitored with the calcium fluorescent indicator,fluo-3. inhibition of the influx by three inhibitors of the zona pellucida induced acrosome reaction: Tyrphostin A48, pertussis toxin,and 3-quinuclidinyl benzilate

The fluorescent calcium indicator, fluo-3, was loaded as the membrane permeant tetraacetoxymethyl (AM) ester into cauda epididymal mouse sperm at 25°C for 20 min in the absence of bovine serum albumin (BSA) and presence of the dispersant, Pluronic F-127. Excess indicator was removed by two centrifugation washes at 100g for 10 min, a procedure that did not impair sperm motility. Upon resuspension in medium containing 20 mg/ml BSA to promote capacitation, the sperm cells exhibited readily detectable fluorescence uniformly distributed in the cytoplasm. Cell fluorescence was stable over the time of the experiments and was responsive to changes in intracellular calcium concentration, [Ca²⁺]_j. Initial [Ca²⁺]_j was 231 ± 58 nM (±SE, n = 43). Addition of heat-solubilized mouse zonae pellucidae to capacitated sperm increased [Ca²⁺]_j by 106 ± 19 nM (±SE, n = 18), the higher steady-state concentration being reached after 30 min. Subsequent addition of the non-fluorescent calcium ionophore Br-A23187 resulted in a further increase of 114 ± 18 nM (± SE, n = 18), the higher steady-state concentration being reached after 6 min. The increase in [Ca²⁺]_j induced by solubilized zonae pellucidae was largely blocked by 3-quinuclidinyl benzilate (QNB) an antagonist of muscarinic receptors that was earlier shown to block the zona pellucida induced acrosome reaction in mouse sperm (Florman and Storey, 1982: Dev Biol 91:121–130). This [Ca²⁺]_j increase was completely blocked by the tyrosine kinase inhibitor, tyrphostin A48, and by the inactivator of G₁ proteins, pertussis toxin. At the concentrations at which they blocked the zona pellucida-induced increase in [Ca²⁺]_j all three inhibitors also blocked the zona pellucidainduced acrosome reaction. These results indicate that [Ca²⁺]_j increase in is an early, if not the initial, reaction in the sequence leading to zona pellucida induced acrosomal exocytosis in mouse sperm. The observation that the three inhibitors, each having a different mode of action, all block the zona pellucida induced [Ca²⁺]_j suggests that the sperm plasma membrane receptors mediating the zona pellucida induced acrosome reaction may function as a complex, whose formation is activated by zona pellucida ligand binding. © 1994 Wiley-Liss, Inc.