Biological Control and Use of Adjuvants against Multiple Seeded Cocklebur (Xanthium strumarium) in Comparison with Several Other Cocklebur Types

Common cocklebur has several biotypes including multiple seeded cocklebur (MSC), NCC-TX, and NCC-MS. Alternaria helianthi applied at 2.5×10⁴ conidia mL^-1 in a 50% micro-emulsion of unrefined corn oil (MESUCO) or 0.2% Silwet L 77 caused 60-75% mortality on NCC-TX and MSC. Increasing the conidial concentration to 5×10⁴ mL^-1 increased mortality to 100% on MSC and NCC-TX, and 75% on NCC-MS. At 10×10⁴ conidia mL^-1, A. helianthi caused 100% mortality in all three biotypes. No mortality occurred in any biotype at inoculation rates of 2.5 and 5×10⁴ conidia mL^-1 when applied in water. Increasing the dew period from 0 to 12 h increased mortality from 0 to 100% on all three biotypes at a rate of 2.5×10⁴ conidia mL^-1 in Silwet and MESUCO. MSC appears to be the most sensitive biotype.     

Accumulation of 6-Azauridine by Mutants of Brevibacterium ammoniagenes

From the inosine producing mutants of Brevibacterium ammoniagenes, KY 13761 was selected as a strain which produced 6-azauridine from 6-azauracil.

The conditions for the conversion were examined and the intermitent feeding of 6-azauracil was found effective for the accumulation.

In order to increase the accumulation, prototrophic revertants were induced from KY 13761 and KY 13021 was selected. By intermitent feeding of 6-azauracil of a final concentration of 6 mg per ml, a maximal accumulation, 12.4 mg/ml, of 6-azauridine was obtained with KY 13021.     

Evaluation of common cocklebur Xanthium strumarium leaf extract as post‐harvest grain protectant of black gram against pulse beetle Callosobruchus chinensis (Coleoptera: Bruchidae) and isolation of crude compound

The pulse beetle Callosobruchus chinensis L. is considered the most important stored grain pest of black gram Vigna mungo Hepper in Bangladesh and other tropical and subtropical countries. Bioactive compounds derived from plants can be used to control of the pulse beetle as a potential alternative to synthetic insecticides. Therefore, aqueous extracts of common cocklebur Xanthium strumarium L. leaf was examined for insecticidal properties against C. chinensis. The extracts showed toxicity, repellent properties, inhibited fecundity and adult emergence of the insects, and protected grains. Insect mortality was accounted highest (72.6%) with 4% extract at 4 days after treatment. The beetles showed highest repellency rate (58.0%) with 4% concentration at 1 hour exposure; however insect repellency decreased with time. The beetles exerted the lowest fecundity and grain damage and produced the lowest number of offspring when they were reared on grains treated with 4% extract. The insecticidal compounds present in common cocklebur leaf were extracted in chloroform and ethanol, and isolated by thin layer chromatography (TLC) and spectral studies (¹H‐NMR and IR), which identified the presence of aromatic ester, n‐hexyl salicylate or o‐hydroxy‐n‐hexyl‐benzoate and a long‐chain ketone. Therefore, naturally occurring X. strumarium and its derivatives may be potential components for integrated management of C. chinensis.     

Two Phytotoxins Isolated from the Pathogenic Fungus of the Invasive Weed Xanthium italicum

Alternariol and altenuisol were isolated as the major phytotoxins produced by an Alternaria sp. pathogenic fungus of the invasive weed Xanthium italicum. Altenuisol exhibited stronger phytotoxic effect compared with alternariol. At 10 μg/mL, alternariol and altenuisol promoted root growth of the monocot plant Pennisetum alopecuroides by 11.1 % and 75.2 %, respectively, however, inhibitory activity was triggered by the increase of concentration, with root elongation being suppressed by 35.5 % and 52.0 % with alternariol and altenuisol at 1000 μg/mL, respectively. Alternariol slightly inhibited root length of the dicot plant Medicago sativa at 10–1000 μg/mL, whereas altenuisol stimulated root growth by 51.0 % at 10 μg/mL and inhibited root length by 43.4 % at 200 μg/mL. Alternariol and altenuisol did not exert strong regulatory activity on another dicot plant, Amaranthus retroflexus, when tested concentration was low, however, when the concentration reached 1000 μg/mL, they reduced root length by 68.1 % and 51.0 %, respectively. Alternariol and altenuisol exerted similar effect on shoot growth of three tested plants but to a lesser extent. It is noteworthy to mention that this is the first report on the phytotoxicity of altenuisol.     

入侵植物刺苍耳在新疆的分布及其群落特征

刺苍耳是原产于南美洲的菊科植物,2009年首次在新疆的伊宁县发现。于2010～2011年对新疆南北疆近40个县(市)中刺苍耳可能出现的区域进行调查,并采用样方法,对不同生境中刺苍耳分布相对集中的23个样地所有物种的多度、频度和重要值进行了观测和分析,以明确刺苍耳在新疆的分布区及其群落特征,为有效防治其扩散提供依据。结果显示:(1)刺苍耳分布于新疆的昌吉市、伊宁市、伊宁县、巩留县、特克斯县、新源县、察布查尔县、霍城县和尼勒克县,分布区海拔597～1 834m,生境类型包括荒漠草原和绿洲。(2)刺苍耳在荒漠草原和绿洲生境中的相对多度均处于首位,且在绿洲中达到最大值,为入侵区域最重要的物种;刺苍耳在2种生境中的相对盖度均为第一,且绿洲(46.83%)大于荒漠草原(43.00%)。(3)刺苍耳在2种生境中的综合适应力均最强,在绿洲中尤为突出,是其最易入侵的区域。研究表明,刺苍耳在新疆荒漠草原生境中尚处于局部危害阶段,但在绿洲中已处于蔓延期。     

苍耳Xanthium strumarium L. 染色体数目和核型的观察

苍耳Xanthium strumarium L.(X. sibiricum Patr. ex Widder, X. iaponicum Widder)为菊科苍耳属的一年生草本,广布于欧亚大陆和北美洲;我国各地也均有分布。苍耳为常用中药,其果实入药,能发汗通窍、祛风湿,解表镇痛,用于治风湿性关节痛及鼻炎等症。     

Thigmomorphogenesis: XXIII. Promotion of foliar senescence by mechanical perturbation of Avena sativa and four other species

Mechanical perturbation (MP, gentle tubbing) promoted the senescence of detached oat ( Avena sativa L. cv. Victory) leaf segments in the dark. The promotion of senescence increased with increase in the number of rubbings and could be seen after 24 h of dark incubation; the maximum effect was reached on day 3. The effect (% of control) of MP on the loss of protein was greater than the effect on chlorophyll (Chl) loss on day 1. However, on day 3 the effect of MP on the loss of Chl became greater than the effect on the loss of protein. Ethephon and 1-aminocyclopropane-1-carboxylic acid (ACC) marginally promoted the loss of Chl by both control and rubbed oat leaf segments, and the effect was additive with MP. Chloramphenicol (CAP), spermine, aminoethoxyvinylglycine (AVG) and Ca²⁺ marginally delayed the loss of Chl and protein in both control and rubbed segments. Kinetin greatly retarded the senescence of all segments. Even in the presence of these substances, the amounts of Chl and protein in the rubbed segments were always less than in their respective controls, thus retaining the effect of the MP. However, abscisic acid (ABA) and cycloheximide (CHI) caused the rubbed oat leaf segments to retain more Chl and protein than their respective control segments. The effect of CHI was actually enhanced by MP. Rubbing promoted the senescence of attached leaves of oats ( Avena sativa L. cv. Victory), maize ( Zea mays L. cv. Early Belle) and pumpkin ( Cucurbita pepo L. cv. Jack-o-lantern) cotyledons in the dark. Rubbing promoted the senescence of oat leaf segments even in light, although to a lesser extent compared to the effect in the dark. The senescence of leaves of pumpkin and cocklebur ( Xanthium strumarium Wallr. var. Pennsylvanicum ) in situ was also enhanced by MP.     

Spectrophotometric characterization of phytochromes in dimorphic cocklebur seeds in relation to capacity for germination

Phytochrome was measured spectrophotometrically in different tissues of the upper (positively photoblastic) and lower (negatively photoblastic) seeds of the cocklebur (Xanthium pennsylvanicum Wallr.). Axial parts of the seeds, in particular parts of the radicle, contained high levels of phytochrome, while cotyledonary parts contained only low levels. These results were consistent with the distribution of the light-sensitive areas of the seeds that were associated with germination. Phytochrome levels in both types of dimorphic seeds increased gradually with increasing duration of dark imbibition for 4–8 h, then the rates of increase in levels of phytochrome accelerated. In both types of seed, some phytochrome was measurable even before imbibition. In the lower seeds, up to 20% of the phytochrome was occasionally observed as P_fr in samples imbibed in darkness for a short time (up to 12 h). A slight blue shift of the peak of P_T in the difference spectrum of phytochrome was observed in the case of lower seeds imbibed for 0–2 h. These results suggest that, to some extent, the lower axes contain dehydrated P_fr or intermediate(s) in the photoconversion of phytochrome. The dark reactions of P_fr were also examined in excised axes of both types of dimorphic seed after they had been pre-imbibed for 16 h in darkness. Dark destruction of P_fr was observed in both types of seed. In addition, net increases in levels of P_r were observed in the dark controls and in the samples irradiated with red light after the level of P_fr diminished. No ‘inverse’ dark reversion from P_r to P_fr was detected. Thus, after 16 h of imbibition, there were no differences in terms of properties of phytochrome between the two types of seed, and the different responses to light of upper and lower seeds might depend mainly on a difference in the physiological state of the two types of seed rather than the properties of phytochrome.     

Endogenous evolution of HCN during pre-germination periods in many seed species

Both cyanogenic ( Malus pumila Mill) and acyanogenic ( Oryza sativa L., Hordeum vulgare L., Zea mays L., Glycine max Merr., Lactuca sativa L., and Xanthium pennsylvanicum Wallr. etc.) seeds evolve HCN gas during the early periods of water imbibition. All tested seeds contained reserve cyanogens which liberated HCN upon hydrolysis with H₂SO₄ and with β-glucosidase and/or lipase. The amounts of liberated HCN were roughly comparable to those of unidentified cyanogens. It is thus conceivable that the cyanogens within seeds are available as precursors for free HCN evolved in the pre-germination period. The amounts of HCN evolved in the acyanogenic seeds were only 0.002 to 1% of that in apple, but the contents of the cyanogenic compounds in rice and cocklebur increased temporarily during the pre-germination period, then decreased and, finally, disappeared completely with the start of germination.