Floral micromorphology and nectar composition of the early evolutionary lineage Utricularia (subgenus Polypompholyx, Lentibulariaceae)

Utricularia (Lentibulariaceae) is a genus comprising around 240 species of herbaceous, carnivorous plants. Utricularia is usually viewed as an insect-pollinated genus, with the exception of a few bird-pollinated species. The bladderworts Utricularia multifida and U. tenella are interesting species because they represent an early evolutionary Utricularia branch and have some unusual morphological characters in their traps and calyx. Thus, our aims were to (i) determine whether the nectar sugar concentrations and composition in U. multifida and U. tenella are similar to those of other Utricularia species from the subgenera Polypompholyx and Utricularia, (ii) compare the nectary structure of U. multifida and U. tenella with those of other Utricularia species, and (iii) determine whether U. multifida and U. tenella use some of their floral trichomes as an alternative food reward for pollinators. We used light microscopy, histochemistry, and scanning and transmission electron microscopy to address those aims. The concentration and composition of nectar sugars were analysed using high-performance liquid chromatography. In all of the examined species, the floral nectary consisted of a spur bearing glandular trichomes. The spur produced and stored the nectar. We detected hexose-dominated (fructose + glucose) nectar in U. multifida and U. tenella as well as in U. violacea. In both U. multifida and U. tenella, there were trichomes that blocked the entrance into the throat and spur. Because these trichomes were rich in chromoplasts and contained lipid droplets, they may form an additional visual attractant. Bearing in mind the phylogenetic hypothesis for the genus, we suggest that an early ancestor of Utricularia had a nectariferous spur flower with a lower lip that formed a wide landing platform for bee pollinators

Floral micromorphology of the bird-pollinated carnivorous plant species Utricularia menziesii R.Br. (Lentibulariaceae)

Made available in DSpace on 2019-10-06T16:15:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01• Background and Aims Bird pollination is rare among species in the genus Utricularia, and has evolved independently in two lineages of this genus. In Western Australia, the Western Spinebill, Acanthorhynchus superciliosus, visits flowers of Utricularia menziesii (section Pleiochasia: subgenus Polypompholyx). This study aimed to examine the micromorphology of U. menziesii flowers to assess traits that might be linked to its pollination strategy. • Methods Light microscopy, histochemistry and scanning electron microscopy were used. Nectar sugar composition was analysed using high-performance liquid chromatography. • Key Results The flowers of U. menziesii fulfil many criteria that characterize bird-pollinated flowers: red colour, a large, tough nectary spur that can withstand contact with a hard beak, lack of visual nectar guides and fragrance. Trichomes at the palate and throat may act as tactile signals. Spur nectary trichomes did not form clearly visible patches, but were more frequently distributed along vascular bundles, and were small and sessile. Each trichome comprised a single basal cell, a unicellular short pedestal cell (barrier cell) and a multicelled head. These trichomes were much smaller than those of the U. vulgaris allies. Hexose-dominated nectar was detected in flower spurs. Fructose and glucose were present in equal quantities (43 ± 3.6 and 42 ± 3.6 g L-1). Sucrose was only detected in one sample, essentially at the limit of detection for the method used. This type of nectar is common in flowers pollinated by passerine perching birds. • Conclusions The architecture of nectary trichomes in U. menziesii was similar to that of capitate trichomes of insect-pollinated species in this genus; thus, the most important specializations to bird pollination were flower colour (red), and both spur shape and size modification. Bird pollination is probably a recent innovation in the genus Utricularia, subgenus Polypompholyx, and is likely to have evolved from bee-pollinated ancestors.Department of Plant Cytology and Embryology Jagiellonian University in Kraków, 9 Gronostajowa St.Faculty of Biology University of Warsaw Botanic Garden, Al. Ujazdowskie 4Department of Animal Histology and Embryology University of Silesia in Katowice, 9 Bankowa St.School of Biological Sciences University of Western Australia (M084), 35 Stirling HighwayDepartamento de Biologia Aplicada à Agropecuária Faculdade de Ciências Agrárias E Veterinárias Universidade Estadual Paulista (Unesp)Faculty of Science School of Biological Sciences University of AdelaideUnit of Botany and Plant Physiology Institute of Plant Biology and Biotechnology University of Agriculture in Kraków, 29 Listopada 54 StreetDepartamento de Biologia Aplicada à Agropecuária Faculdade de Ciências Agrárias E Veterinárias Universidade Estadual Paulista (Unesp

Herbicide resistance endowed by enhanced rates of herbicide metabolism in wild oat (Avena spp.)

The biochemical basis of resistance to the acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicide diclofop-methyl was investigated in a resistant wild oat population (R1), which does not exhibit a resistant ACCase. Rates of foliar uptake and translocation of [14C]-diclofop were the same in the R1 vs. susceptible (S) populations. However, the level of phytotoxic diclofop acid was always found to be lower in the R1 vs. S plants, with a concomitant higher level (up to 1.7-fold) of nontoxic polar diclofop metabolites in R1 relative to the S plants. These results indicate that a non–target-site-based mechanism of enhanced rate of diclofop acid metabolism confers resistance in population R1. Moreover, the high-performance liquid chromotography elution profile of the major diclofop metabolites in R1 is similar to that of wheat, suggesting resistance in individuals of population R1 involves a wheat-like detoxification system mediated by cytochrome P450 monooxygenases. In addition, lower level of tissue diclofop acid was also observed using nonradioactive ultra-performance liquid chromatography–mass spectrometry analysis in resistant individuals of three other resistant wild oat populations (R2, R3, and R4) known to posses ACCase gene resistance mutations. These results establish that either one or at least two independent resistance mechanisms (target-site ACCase resistance mutations and non–target-site enhanced rates of herbicide metabolism) can be present in individual wild oat plants

pH regulation in anoxic rice coleoptiles at pH 3.5: biochemical pHstats and net H+ influx in the absence and presence of NO3−

During anoxia, cytoplasmic pH regulation is crucial. Mechanisms of pH regulation were studied in the coleoptile of rice exposed to anoxia and pH 3.5, resulting in H+ influx. Germinating rice seedlings survived a combination of anoxia and exposure to pH 3.5 for at least 4 d, although development was retarded and net K+ efflux was continuous. Further experiments used excised coleoptile tips (7–10 mm) in anoxia at pH 6.5 or 3.5, either without or with 0.2 mM NO3−, which distinguished two processes involved in pH regulation. Net H+ influx (μmol g−1 fresh weight h−1) for coleoptiles with NO3− was ∼1.55 over the first 24 h, being about twice that in the absence of NO3−, but then decreased to 0.5–0.9 as net NO3− uptake declined from ∼1.3 to 0.5, indicating reduced uptake via H+–NO3− symports. NO3− reduction presumably functioned as a biochemical pHstat. A second biochemical pHstat consisted of malate and succinate, and their concentrations decreased substantially with time after exposure to pH 3.5. In anoxic coleoptiles, K+ balancing the organic anions was effluxed to the medium as organic anions declined, and this efflux rate was independent of NO3− supply. Thus, biochemical pHstats and reduced net H+ influx across the plasma membrane are important features contributing to pH regulation in anoxia-tolerant rice coleoptiles at pH 3.5

Cercosporin from Pseudocercosporella capsellae and its critical role in white leaf spot development

Pseudocercosporella capsellae, the causative agent of white leaf spot disease in Brassicaceae, can produce a purple-pink pigment on artificial media resembling, but not previously confirmed, as the toxin cercosporin. Chemical extraction with ethyl acetate from growing hyphae followed by quantitative [thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC)] and qualitative methods showed an identical absorption spectrum, with similar retardation factor (Rf) values on TLC papers and an identical peak with the same retention time in HPLC as for a standard for cercosporin. We believe this is the first report to confirm that the purple-pink pigment produced by P. capsellae is cercosporin. Confocal microscopy detected green autofluorescence of cercosporin-producing hyphae, confirming the presence of cercosporin inside hyphae. The highly virulent UWA Wlra-7 isolate of P. capsellae produced the greatest quantity of cercosporin (10.69 mg g-1). The phytotoxicity and role of cercosporin in disease initiation across each of three Brassicaceae host species (Brassica juncea, B. napus and Raphanus raphanistrum) was also studied. Culture filtrates containing cercosporin were phytotoxic to all three host plant species, producing large, white lesions on highly sensitive B. juncea, only water-soaked areas on least sensitive R. raphanistrum, and intermediate lesions on B. napus. It is noteworthy that sensitivity to cercosporin of these three host species was analogous to their susceptibility to the pathogen, viz., B. juncea the most susceptible, R. raphanistrum the least susceptible and B. napus intermediate. The presence of cercosporin in the inoculum significantly increased disease severity on the highly cercosporin-sensitive B. juncea. We believe that this is the first study to demonstrate that P. capsellae produces cercosporin in liquid rather than agar media. Finally, this study highlights an important role of cercosporin as a pathogenicity factor in white leaf spot disease on Brassicaceae as evidenced by the ability of the cercosporin-rich culture filtrate to reproduce white leaf spot lesions on host plants and by the enhanced virulence of P. capsellae in the presence of cercosporin

Using activated charcoal to remove substances interfering with the colorimetric assay of inorganic phosphate in plant extracts

Aim Organic substances in leaves of several southwest Australian native species interfere with sensitive colorimetric assays and prevent quantification of inorganic phosphate concentration ([Pi]). We aimed to develop a reproducible routine procedure for treating leaf extracts with activated charcoal (AC) to remove interfering substances, allowing the determination of [Pi] by the malachite green spectrophotometric assay. Methods Leaf extracts of native plants from southwest Australia in 1% (v/v) acetic acid were treated with 10 mg mL−1 acid-washed AC for removal of interfering substances. Standard solutions (0 to 18 μM Pi) with and without AC treatment were compared to quantify Pi loss. A spiking and recovery test was performed to validate the AC treatment. Results Leaf extracts treated with AC exhibited distinguishable absorbance peaks for the malachite green-orthophosphate complex between 630 and 650 nm, as opposed to untreated samples. The Pi-adsorption by AC represented a relatively larger fraction of [Pi] in solutions at 0–4 μM Pi range and stabilised at higher [Pi] when maximum adsorption capacity of AC reached at 11.7 μg Pi g−1AC. The Pi recovery after AC treatment in spiked samples ranged between 100 and 111%. Conclusion The AC treatment successfully removed interfering substances from samples but caused Pi loss. Thus, quantification of [Pi] in AC-treated extracts requires sample [Pi] ≥ 6 μM Pi and the use of AC-treated standards. The error of the AC treatment was minor compared with environmental variability of leaf [Pi]. The AC treatment was a reproducible time- and cost-effective method to remove interfering substances from leaf extracts

Rapid On-Farm Testing of Resistance in Lolium rigidum to Key Pre- and Post-Emergence Herbicides

Overreliance on herbicides for weed control is conducive to the evolution of herbicide resistance. Lolium rigidum (annual ryegrass) is a species that is prone to evolve resistance to a wide range of herbicide modes of action. Rapid detection of herbicide-resistant weed populations in the field can aid farmers to optimize the use of effective herbicides for their control. The feasibility and utility of a rapid 7-d agar-based assay to reliably detect L. rigidum resistant to key pre- and post-emergence herbicides including clethodim, glyphosate, pyroxasulfone and trifluralin were investigated in three phases: correlation with traditional pot-based dose-response assays, effect of seed dormancy, and stability of herbicides in agar. Easy-to-interpret results were obtained using non-dormant seeds from susceptible and resistant populations, and resistance was detected similarly as pot-based assays. However, the test is not suitable for trifluralin because of instability in agar as measured over a 10-d period, as well as freshly-harvested seeds due to primary dormancy. This study demonstrates the utility of a portable and rapid assay that allows for on-farm testing of clethodim, glyphosate, and pyroxasulfone resistance in L. rigidum, thereby aiding the identification and implementation of effective herbicide control options

Summer dormancy and winter growth: root survival strategy in a perennial monocotyledon

Here, we tested the alternation of root summer dormancy and winter growth as a critical survival strategy for a long-lived monocotyledon (Restionaceae) adapted to harsh seasonal extremes of Mediterranean southwest Western Australia. • Measurements of g