Oxygenation of unsaturated fatty acids in seeds during storage

Seeds of Cichorium intybus L., Crepis thomsonii Babc, and Crepis vesicaria L, were stored from 4 to 8 years at 5°C and then for 18 months under a variety of conditions. Oxygenated acids in Cichorium intybus oil increased from approximately 1% initially to 3% in the first storage period and to 17% while stored at room temperature during the second period. The corresponding levels at these three stages for Crepis thomsonii were 2, 6 and 18%. By gas chromatography (GC) and GC-mass spectrometry, the major oxygenated acids formed during storage were identified as hydroxy acids with conjugated unsaturation and 9,10-epoxy acids. In Crepis vesicaria seed, oil of which contained 53% vernolic (12,13-epoxy-9-octadecenoic) acid originally, approximately 2% of 9,10-epoxides were formed during the storage at room temperature. Levels of hydroxy acids with conjugated unsaturation in this species were 0.3% initially, 2% after 5 years at 5°C, and 9% after 18 months at room temperature. Primary substrates from which oxygenated acids were formed in the three species were crepenynic and linoleic acids, and the almost exclusive formation of 9,10-epoxide from linoleic acid indicated enzymatic involvement.     

Larval survival,host plant preferences and developmental responses of the diamondback moth Plutella xylostella (Lepidoptera: Plutellidae) on wild brassicaceous species

The diamondback moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) is an important pest of cultivated brassicaceous crops worldwide. The host plant preferences, developmental biology and survival and longevity of P. xylostella are relatively well understood on commercial crop species; however, its relationship with brassicaceous weeds is poorly known. Sinapis arvensis L., Erysimum cheiranthoides L. and Capsella bursa‐pastoris (L.) Medicus are among the most common brassicaceous weeds worldwide and can serve as important bridge hosts of P. xylostella. In this study, preference and performance of P. xylostella were compared on these weed species. In free‐choice situations, females deposited 5.5 and 18.8 times more eggs on S. arvensis than on E. cheiranthoides and C. bursa‐pastoris, respectively. Survival from neonate to pupa and from pupa to adult was highest on S. arvensis and E. cheiranthoides and lowest on C. bursa‐pastoris. Development was fastest, foliage consumption was greatest, pupae and silk cocoons were heaviest, adult body masses and longevities were highest and forewings were largest for both females and males when reared as larvae on S. arvensis. Realized fecundity of new generation adults was highest for individuals reared on S. arvensis compared to those reared on E. cheiranthoides or C. bursa‐pastoris. Relative growth rates of pupae and adults were highest on S. arvensis, suggesting that this plant species is a high‐quality host for P. xylostella compared with other species tested. Potential impacts of these wild brassicaceous species on P. xylostella populations are discussed.     

Phylloquinone (Vitamin K1) Levels in Leaves of Plant Species Differing in Susceptibility to 2,4-Dichlorophenoxyacetic Acid

Plant species differing in susceptibility to 2,4-dichlorophenoxyacetic acid (2,4-D) were examined as to the level of phylloquinone (K) in the leaves. The K level was found to be considerably higher in several plants resistant or moderately resistant to 2,4-D (Aegopodium podagraria L., Galium mollugo L., Lamium album L., Matricaria chamomilla L., Oxalis acetosella L., Stellaria media (L.) Vill., Viola arvensis Murr.) than in Chenopodium album L. and Sinapsis arvensis L. which are susceptible to 2,4-D. Capsella bursa-pastoris (L.) Med. and Plantago major L. (both moderately susceptible) and a few resistant or moderately resistant species (Agropyron repens (L.) PB., Anthriscus silvestris (L.) Hoffm., Triticum aestivum L.) had intermediate K levels. Cirsium arvense (L.) Scop. (susceptible) had a relatively high level of K. It is possible that a high K level in the plant can be of importance in the resistance to 2,4-D.     

Intergeneric hybridization of marguerite (Argyranthemum frutescens (L.) Sch. Bip.) and Roman chamomile (Chamaemelum nobile (L.) All.) using ovule culture and confirmation of hybridity

To introduce useful characteristics such as fragrance into Argyranthemum frutescens (L.) and to expand the variation, we conducted crosses using A. frutescens as the seed parent and Chamaemelum nobile (L.) All. as the pollen parent. All the tested cross combinations between the three strains of A. frutescens and one strain of C. nobile produced embryos, and healthy plants were obtained by ovule culture. The obtained plantlets had a white ray floret, and the leaf shape was intermediate to those of the parents. The individuals obtained from this cross were subjected to two methods to determine hybridity: flow cytometry analyses and cleaved amplified polymorphic sequence (CAPS) markers. For the CAPS marker, we selected the internal transcribed spacer (ITS) region, which is highly variable among the genera, as the region to be amplified. We selected restriction enzymes BmgT120 I and Afl II, which selectively cut common sequences in the genus Argyranthemum, based on the sequence analysis of one parent strain each of A. frutescens and C. nobile and alignment with known sequences of related species. Flow cytometry analyses and CAPS markers revealed that the individuals obtained from the cross between A. frutescens and C. nobile are intergeneric hybrids. In addition, these established methods were capable of quickly and reliably identifying hybrids between A. frutescens and C. nobile. This report shows for the first time that crossbreeding between A. frutescens (seed parent) and C. nobile (pollen parent) is possible, and further development of Argyranthemum breeding, such as the expansion of variation by intergeneric crosses, is expected.     

Host specificity and biology ofcystiphora sonchi [Dip.: Cecidomyiidae], a candidate for the biological control ofSonchus species

The host specificity ofCystiphora sonchi (Bremi), a promising biocontrol agent of the sow-thistles,Sonchus arvensis L.,S. oleraceus L., andS. asper (L.)Hill, was investigated. These are widespread, serious weeds in Canada and the United States. In the laboratory, 6 females produced up to 721 galls on 1 plant ofS. arvensis, and up to 245 galls on 1 leaf. A total of 59 plant species in 49 genera of the familyCompositae were tested.C. sonchi produced viable galls onSonchus species only, thus confirming European field records.C. sonchi was approved for release in Canada.     

CYTOTAXONOMY OF THREE SONCHUS SPECIES

All hybrid plants from interspecific crosses among the three species, Sonchus asper (L.) Hill, S. oleraceus L., and S. arvensis L., were male-sterile, but the progeny of the cross S. arvensis X S. oleraceus and reciprocal cross produced seed after backcrossing to the male parent. Hybrid plants from crosses between S. oleraceus and S. asper lacked vigor. Cytological data indicated that S. arvensis has one genome in common with S. asper and that S. oleraceus is an autotetraploid (2n = 36) with no genomes in common with S. arvensis or S. asper.     

Content of water soluble carbohydrates under oxygen deprivation in plants with different flooding tolerance

We investigated the carbohydrate concentration of plant species naturally growing in habitats with a high risk of oxygen shortage (Senecio aquaticus Hill,Myosotis palustris (L.) L. em.Rchb) and congeneric species from drier sites (Senecio jacobaea L.,Myosotis arvensis (L.)Hill) Plants from the four species were cultivated in either nitrogen-flushed or aerated nutrient solution. Following oxygen shortage in the root environment a two—fourfold increase of carbohydrate content was found in the roots as well as in the shoots of the species examined. Although, the tendency in the response of both genera to the hypoxic conditions in the nutrient solution was the same, there were differences in concentration and composition of the water soluble carbohydrates. The flooding tolerantSenecio aquaticus accumulated the highest amounts of carbohydrates, in particular fructans (nearly 60% of the soluble carbohydrates, compared with 30% under aerated conditions). The increasing amount of sugars found under hypoxia-inducing conditions proved that substrate availability was not the limiting factor for survival under wetland conditions.     

OCCURRENCE,TYPE, AND LOCATION OF CALCIUM OXALATE CRYSTALS IN LEAVES AND STEMS OF 16 SPECIES OF POISONOUS PLANTS

Crystals in 16 species of poisonous plants growing naturally in Saudi Arabia were studied with light microscopy. Three types of crystals were observed: druses, prismatics, and crystal sand. Raphides and styloids were not observed in any of the species studied. Druses occur more frequently in the leaf midrib and in the cortex and pith of the stem. In contrast, crystal sand and prismatic crystals are rare and occur in the leaf, intercostal lamina, and in the vascular tissues. The preliminary results show the absence of the three types of calcium oxalate crystals in the stem and leaf of seven species: Ammi majus L., Anagallis arvensis L., Calotropis procera Ait., Citrullus colocynthis (L.) Schard, Euphorbia peplis L., Hyoscyamus muticus L., and Solarium nigrum L., and the presence of druses, prismatic crystals, and crystal sand either in the leaf and stem or in the leaves or stems of nine species: Anabasis articulata (Forssk.) Moq. in DC., Chenopodium album L., Convolvulus arvensis L., Datura stramonium L., Nerium oleander L., Ricinus communis L., Rumex nervosus Vahl., Pergularia tomentosa L., and Withania somnifera (L.) Dun. in DC. These observations indicate that there is no apparent relationship between the distribution of calcium oxalate crystals and the toxic organs of the plants, and supports the view that the presence of calcium oxalate crystals may not be related to plant toxicity.     

C(4) Pathway Photosynthesis at Low Temperature in Cold-tolerant Atriplex Species

Two species of Atriplex were grown under low temperature (8 C day/6 C night) and high temperature (28 C day/20 C night) regimes. The photosynthetic capacity of these plants was studied as a function of temperature in a leaf gas exchange cuvette. Both species showed substantial photosynthetic capacity between 4 and 10 C and this was not enhanced by growth at low temperatures but rather, was somewhat greater in plants grown at higher temperature. Photosynthetic capacity of low temperature-grown plants at high temperature was greater in Atriplex confertifolia (Torr. and Frem.) S. Watts., a native of cool deserts, than in Atriplex vesicaria (Hew. ex. Benth.) from warmer desert areas. Leaves of both species were also subjected to ¹⁴CO₂ pulse-chase and steady-state feeding experiments under controlled temperature conditions. These experiments revealed that the kinetics of carbon assimilation through the intermediates of the C₄ pathway is not substantially disrupted at low temperature in either species. There was, however, a substantial interchange of label between aspartate and malate at low temperature which was not evident at high temperature. There was also an increase in the pool sizes of the C₄ acids involved in photosynthesis of A. confertifolia. Speculation as to the explanation of these changes and their possible significance in promoting low temperature C₄ photosynthesis in these plants is presented.     

Estimates of root system topology of five plant species grown at steady-state nutrition

Results from a controlled growth-analysis experiment were used to illustrate some methods for measuring and describing root system topology. The experiment was performed in a nutrient solution system with an exponential nutrient supply and steady-state growth, to achieve well-defined levels of whole-plant nutrient status. Five naturally coexisting grassland species were included: The slow-growing forbs Polygala vulgaris L. and Crepis praemorsa (L.) F. L. Walth., and the grass Danthonia decumbens (L.) DC. were compared with the more common, fast-growing grasses Agrostis capillaris L. and Dactylis glomerata L. The most marked difference in morphological indices was a much higher specific root length in the grasses than in the forbs, which implies thinner roots. In contrast to the conclusions of previous studies, an index of the topology for the grasses was very similar to that for the forbs. The specific root lenght and link length apparently vary more between species and nutrient levels than topology does, and may therefore be more ecologically important. The only clear plastic response to growth-limiting nitrogen supply was a markedly increased link length in P. vulgaris. There were also indications that nitrogen limitation led to more herringbone-like root systems in P. vulgaris and C. praemorsa. In general, there was a clear tendency for the estimates of topology to change with plant size, which may make many topological indices, especially those based on regression slopes, very difficult to interpret. Until interactions with plant size, other morphological parameters and among-plant competition can be properly understood, the relevance of root topology for plant performance remains unclear. This revised version was published online in June 2006 with corrections to the Cover Date.     

Selection of aquatic plants for phytoremediation of heavy metal in electroplate wastewater

The remediation of heavy metal-contaminated sites using plants is a promising alternative to current methodologies. In this study, small-scale wetlands were constructed to search for new plant species that are suitable and hold potential for phytoremediation of heavy metal-contaminated wastewater originating from an electroplating plant. Ten macrophyte species [Phragmites australis (Cav.) Trin., Typha orientalis Presl, Lythrum salicaria Linn., Arundo donax Linn. var. versicolor Stokes, Typha minima Funk, Juncus effusus L., Pontederia cordata L., Cyperus alternifolius Linn. subsp. flabelliformis (Rottb.) Kükenth., Acorus calamus Linn., and Iris pseudacorus Linn.] were investigated and compared for their shapes, biomass, roots, and ability to accumulate heavy metals. Acorus calamus Linn., T. orientalis Presl, P. australis (Cav.) Trin., T. minima Funk, and L. salicaria Linn. exhibited the highest levels of metal tolerance, whereas P. cordata L., I. pseudacorus Linn., and C. alternifolius Linn. subsp. flabelliformis (Rottb.) Kükenth. had the lowest. Some plants accumulated higher concentrations of metals in the tissues compared with other species such as T. minima Funk, P. australis (Cav.) Trin., L. salicaria Linn., A. donax Linn. var. versicolor Stokes, P. cordata L., and A. calamus Linn., whereas T. orientalis Presl and C. alternifolius Linn. subsp. flabelliformis (Rottb.) Kükenth. had poor capacity to accumulate heavy metals. The results showed that, of the 10 species, P. australis (Cav.) Trin., A. calamus Linn., T. minima Funk, and L. salicaria Linn. are the most suitable and promising plant materials for phytoremediation of heavy metal-contaminated wastewater.     

Photorespiratory properties of protoplasts from C3-C4 intermediate species of moricandia

Protoplasts were isolated from leaves of the C₃-C₄ intermediate species, Moricandia arvensis (L.) DC. and Moricandia spinosa Pomel. Analysis by light and transmission electron microscopy indicated that these purified preparations contained both mesophyll protoplasts (MP) and bundle-sheath protoplasts (BSP). Conventional density gradient centrifugation procedures failed to yield separations of pure protoplasts from each cell-type. With these heterogeneous suspensions of MP and BSP, values measured for (i) the percentage inhibition of photosynthetic CO₂ fixation by O₂, (ii) the apparent K_m(CO)2 of photosynthesis, and (iii) dark/light ratios of the rate of ¹⁴CO₂ evolution during decarboxylation of exogenous [1-¹⁴C] glycine were not significantly different from those determined for protoplast preparations from related or representative C₃ plants, including M. foetida, Nicotiana tabacum, and Triticum aestivum. In contrast, previous comparisons with C₃ species, using intact leaf tissue from M. arvensis, have shown a reduced sensitivity of net photosynthesis to inhibition by O₂ [Holaday et al., Plant Sci. Lett., 27 (1982) 181] and an enhanced capacity for the photosynthetic refixation of CO₂ evolved during decarboxylation of exogenous photorespiratory substrates [Holbrook et al., Plant Physiol., 77 (1985) 578]. We conclude that these photosynthetic properties, associated with reduced photorespiration by M. arvensis and M. spinosa, are dependent upon the integrity of the anatomical and ultrastructural arrangement of bundle-sheath and mesophyll cells in these C₃-C₄ intermediate species.     

Effects of linuron and dimethenamid on antioxidant systems in weeds associated with soybean

Changes in antioxidant systems in soybean and associated weeds (Ambrosia artemisiifolia L., Chenopodium album L., Convolvulus arvensis L and Sinapis arvensis L.) were studied in relation to treatment with herbicides linuron and dimethenamid in the field experiment. Differences in the total superoxide dismutase (SOD) and catalase (Cat) activities were observed in plants after application of herbicide formulation. Quantities of superoxide (O₂.-) and hydroxyl (·OH) radicals and malonyldialdehyde (MDA), reduced glutathione (GSH) and total polyphenols content were also determined. In addition to this, potential antioxidant activity of the plant ethanolic extracts were assessed based on the scavenging activity of stable DPPH free radicals. Results obtained suggest that plants investigated 1) expressed different antioxidant systems in response to herbicide treatment; 2) enzymatic and non-enzymatic protective mechanisms were complementary; 3) some weed species showed distinctive and combined activity of several biochemical parameters, such as Ambrosia artemisiifolia.     

Diurnal patterns of abundance of aphidophagous lady beetle species on chili (Capsicum annuum L.)

The influence of temperature on the diurnal activity of five species of aphidophagous lady beetles (Coleoptera: Coccinellidae) was investigated between 0700 and 1900 h in chili (Capsicum annuum L.) agroecosystems and neighboring vegetation (goose grass, Eleusine indica L.). The lady beetle species observed were Menochilus sexmaculatus Fabricius, Coelophora inaequalis F., Coccinella transversalis F., Harmonia octomaculata F. and Coelophora bissellata Mulsant. More lady beetles (of all species) were found during cooler periods (at 0700, 0900, 1100, and 1900 h). The diurnal pattern of lady beetle adult was temperature dependent. On chili plants, numbers were higher at temperatures between 22 to 30 °C (at 0700, 0900, 1100 and 1900 h) and numbers decreased when temperatures were above 30 °C. When temperature was above 30 °C under the chili plant canopy, numbers were higher in neighboring goose grass, where temperatures were cooler (< 30 °C). Numbers of all species were negative correlated between chili plant and goose grass.     

Coordination of the cell-specific distribution of the four subunits of glycine decarboxylase and of serine hydroxymethyltransferase in leaves of C3-C4 intermediate species from different genera

The cell-specific distribution of the four subunit proteins (P, L, T and H) of glycine decarboxylase (GDC) and of serine hydroxymethyltransferase (SHMT) has been studied in the leaves of C₃-C₄ intermediate and C₄ species of three genera (Flaveria, Moricandia and Panicum) using immunogold localization. Antibodies raised against these proteins from pea leaf mitochondria were used to probe Western blots of total leaf proteins of F. linearis Lag., M. arvensis (L.) DC and P. milioides Nees ex Trin. (C₃-C₄), and F. trinervia (Spring.) Mohr and P. miliaceum (L.) (C₄). For all species, each antibody recognised specifically a protein of similar molecular weight to that in pea leaves. In leaves of M. arvensis the P protein was present in the mitochondria of the bundle-sheath cells but was undetectable in those of the mesophyll, whereas the L, T and H proteins and SHMT were present in both cell types. The density of immunogold labelling of SHMT on the mitochondria of mesophyll cells was less than that on those of the bundle-sheath cells, which correlates with the relative activities of SHMT in these cell types. These data reveal that the lack of functional GDC in the mesophyll cells of M. arvensis, which is the principal biochemical reason for reduced photorespiration in this species, is due to the loss of a single subunit protein. This lack of coordinate expression of the subunit proteins of GDC within a photosynthetic cell represents a clear difference between M. arvensis and other C₃ and C₃-C₄ species. None of the GDC proteins was detectable in the mesophyll cells of the C₃-C₄ and C₄ Flaveria and Panicum species but all were present in the bundle-sheath cells. The differences in the distribution of the GDC proteins in leaves of the C₃-C₄ species studied are discussed in relation to the evolution of photosynthetic mechanisms.     

田间不同植物上烟粉虱种群密度

对廊坊地区田间81种植物上烟粉虱的发生情况进行了系统调查。结果表明,烟粉虱可为害其中44种植物,且在不同的寄主植物上烟粉虱的种群密度有显著差异;而玉米、高粱和小米等37种植物上无烟粉虱为害。烟粉虱在香水薄荷、荆芥、甘草、薄荷、藿香、益母草、猪屎豆、白晶菊、牛膝、待宵草、蓝蓟、紫花苜蓿、极香罗勒上的虫口密度最高,危害级别达到4级(每100 cm2叶片虫口密度大于50头)。在蜀葵、向日葵和烟草上每100 cm2叶片烟粉虱虫口密度较低,但单株虫口密度较高。鉴于向日葵、玉米、高粱在中国北方棉花产区广泛种植,玉米和高粱的植株高大,且烟粉虱为害对向日葵产量影响极小,可考虑选用向日葵作为田间诱集植物,玉米和高粱作为屏障植物辅助控制棉田烟粉虱。     

The basis for host plant specificity inTephritis dilacerata andT. Formosa [Dipt: Tephritidae]

Strains ofTephritis dilacerata Loew andT. formosa Loew from galls onSonchus arvensis L. andS. asper (L.)Hill, respectively, could be raised reliably in the laboratory only on their host plants. Ovipositing females of both tephritids select a narrow, but different, range of bud sizes. The hatching of the eggs of both flies is synchronized with the onset of rapid but elongation in their respective host plants. Because the growth characteristics of these 2Sonchus species are different, buds of equivalent developmental stages are different average sizes, and ovipositional behavior that brings about synchronization onS. arvensis is not adapted toS. asper and vice versa. Both flies occasionally laid into the flower buds of each others host plant as well asS. oleraceus L. In these cases the buds aborted or the larvae failed to complete normal development. However, both flies appear to be preadapted to the non-host plantSonchus species in this group and host records forT. dilacerata andT. formosa suggest the existence of “host races” attacking theseSonchus species, or alternatively, the frequent occurrence of ovipositional “mistakes” involving these plants.     

Temporal and host-related variation in frequencies of genes that enable Phyllotreta nemorum to utilize a novel host plant, Barbarea vulgaris

The flea beetle, Phyllotreta nemorum L. (Coleoptera: Chrysomelidae), is an intermediate specialist feeding on a small number of plants within the family Brassicaceae. The most commonly used host plant is Sinapis arvensis L., whereas the species is found more rarely on Cardaria draba (L.) Desv., Barbarea vulgaris R.Br., and cultivated radish (Raphanus sativus L.). The interaction between flea beetles and Barbarea vulgaris ssp. arcuata (Opiz.) Simkovics seems to offer a good opportunity for experimental studies of coevolution. The plant is polymorphic, as it contains one type (the P‐type) that is susceptible to all flea beetle genotypes, and another type (the G‐type) that is resistant to some genotypes. At the same time, the flea beetle is also polymorphic, as some genotypes can utilize the G‐type whereas others cannot. The ability to utilize the G‐type of B. vulgaris ssp. arcuata is controlled by major dominant genes (R‐genes). The present investigation measured the frequencies of flea beetles with R‐genes in populations living on different host plants in 2 years (1999 and 2003). Frequencies of beetles with R‐genes were high in populations living on the G‐type of B. vulgaris ssp. arcuata in both years. Frequencies of beetles with R‐genes were lower in populations living on other host plants, and declining frequencies were observed in five out of six populations living on S. arvensis. Selection in favour of R‐genes in populations living on B. vulgaris is the most likely mechanism to account for the observed differences in the relative abundance of R‐genes in flea beetle populations utilizing different host plants. A geographic mosaic with differential levels of interactions between flea beetles and their host plants was demonstrated.