Storage and recall of environmental signals in a plant: modelling by use of a differential (continuous) formulation

The breaking of the symmetry of bud growth in Bidens seedlings involves a sort of plant 'memory'. An asymmetrical stimulus (e.g., the pricking of one of the seedling cotyledons) stores a 'symmetry-breaking' signal within the plants (function STO). Depending on other stimuli received by the seedlings, the stored signal may remain silent or be recalled (RCL function) and take effect in the seedling morphogenesis (asymmetry of the growth of the cotyledonary buds, with a statistical advantage to the bud at the axil of the non-stimulated cotyledon). We show that this memory mechanism can be interpreted by a model taking into account a genetic control exerted on a non-linear enzymatic system that is able to choose trajectories going to different attractors, depending on the stimulation intensity.     

Reduction of Pear Psylla Damage by the Predatory Bug Anthocoris nemoralis (Heteroptera: Anthocoridae): The Importance of Orchard Colonization Time and Neighboring Vegetation

This 5-year field study was aimed at assessing the importance of predatory arthropods in suppressing pear psylla, Cacopsylla bidens (Sulc), and reducing damage caused by psylla in pear orchards in northern Israel. Correlative data suggest that Anthocoris nemoralis (Fabricius) is the only naturally occurring predator in the system that may reduce pear psylla damage; densities of other predacious taxa in the system (Araneidae, Orius spp., Chrysopidae and Coccinellidae) were not correlated significantly with psylla numbers in the orchards. However, A. nemoralis entered pear orchards at least a month after the beginning of pear psylla activity, apparently too late to prevent fruit damage. Data suggest that A. nemoralis reproduction is lower on both wild and cultivated pears than on Rhamnus, Laurus and Pistacia trees in nearby woods. Furthermore, A. nemoralis populations build up on the wild trees in March, but appear in orchards only in late May. We propose that planting R. alaternus trees near pear orchards could enhance the level of biological control of pear psylla by A. nemoralis. Preliminary results indeed show that pear psylla densities were lower on pear trees grown near Rhamnus alaternus trees than on distant trees.     

Flow cytometry reveals that the rust fungus,Uromyces bidentis (Pucciniales), possesses the largest fungal genome reported—2489 Mbp

Among the Eukaryotes, Fungi have relatively small genomes (average of 44.2 Mbp across 1850 species). The order Pucciniales (Basidiomycota) has the largest average genome size among fungi (305 Mbp), and includes the two largest fungal genomes reported so far (Puccinia chrysanthemi and Gymnosporangium confusum, with 806.5 and 893.2 Mbp, respectively). In this work, flow cytometry was employed to determine the genome size of the Bidens pilosa rust pathogen, Uromyces bidentis. The results obtained revealed that U. bidentis presents a surprisingly large haploid genome size of 2489 Mbp. This value is almost three times larger than the previous largest fungal genome reported and over 50 times larger than the average fungal genome size. Microscopic examination of U. bidentis nuclei also showed that they are not as different in size from the B. pilosa nuclei when compared with the differences between other rusts and their host plants. This result further reinforces the position of the Pucciniales as the fungal group with the largest genomes, prompting studies addressing the role of repetitive elements and polyploidy in the evolution, pathological specialization and diversity of fungal species.     

鬼针草中一个新的查耳酮甙

从鬼针草BidenspilosaL .地上部分的丙酮提取物中 ,分离鉴定了 1 8个化合物 ,其中包括一个新的查耳酮甙类化合物 (α,3,2′,4′ tetrahydroxy 2′ O β D glucopyranosylchalcone,2 )。其它化合物分别鉴定为butein (1 ) ,okanin 4 methylether 3′ O β glucoside (3) ,sulfuretin (4) ,6 ,7,3′,4′ tetrahydroxyaurone (5) ,海生菊苷 (maritimein ,6) ,(Z ) 6 O (6″ acetyl β D glucopyr anosyl) 6 ,7,3′,4′ tetrahydroxy aurone (7) ,(Z ) 6 O (4″,6″ diacetyl β D glucopyranosyl) 6 ,7,3′,4′ tetrahydroxy aurone (8) ,(Z ) 6 O (3″,4″,6″ triacetyl β D glucopyranosyl) 6 ,7,3′,4′ tetrahydroxy aurone (9) ,木犀草素 (luteolin ,1 0 ) ,槲皮素 (quercetin,1 1 ) ,异槲皮苷 (iso quercitrin,1 2 ) ,芦丁 (rutin,1 3) ,黄芪苷 (astragalin,1 4 ) ,quercetin 3,4′ dimethylether 7 O rutinoside (1 5) ,反式丁烯二酸 (1 6) ,2 β D glucopyranosyloxy 1 hydroxy trideca 3 ,5,7,9,1 1 pentayne (1 7)和 3 β D glucopyranosyloxy 1 hydroxy 6 (E ) tetradecene 8,1 0 ,1 2 triyne (1 8)。     

Potential cytotoxic and mutagenic effect of Pinus wallichiana,Daphne oleiodes and Bidens chinensis

The Pinus wallichiana, Daphne oleiodes and Bidens chinensis have a long history of being used traditionally for treatment of various types of disorders. Most of the uses have been without any scientific evidence and toxicological assessment. We evaluated the mutagenic and cytotoxic capabilities of various parts of P. wallichiana, D. oleoides and B. chinensis. Ames Salmonella mutagenicity assay determined the mutagenicity activity against TA 98 and TA 100 bacterial strains of Salmonella typhimurium without metabolic activator S9 system. The number of mutant colonies in negative control was considered as limit to determine the mutagenicity effects of every extract. Brine shrimps lethality bioassay was used to determine the cytotoxic capabilities of the selected plants. The P. wallichiana, D. oleiodes and B. chinensis did not showed any mutagenic activity both for frameshift mutation (TA98) and base-pair substitution (TA100) without S9 mixture. The crude methanolic extract of P. wallichiana stem showed moderate cytotoxicity (53.33%) at 1000 μg/ml with LD₅₀ value 599.634. The D. oleoides fruit showed a toxicity of 60% at 1000 μg/ml with LD₅₀ value 367.730. The B. chinensis (whole plant) showed lethality of 63.3% at 1000 μg/ml, with LD₅₀ 204.833. The absence of any mutagenic activity of crude extract of the tested plants in both bacteria strains, TA 98 and TA 100 without the S9 mix confirms the safety of these plants to the consumers.     

Reproductive biological characteristics potentially contributed to invasiveness in an alien invasive plant Bidens frondosa

Bidens frondosa L. (Asteraceae) is a widespread invasive weed in China. By experimental observation and bagging treatment, the reproductive biological characteristics of this species, such as phenology of flowering, floral syndrome, breeding system and seed germination characteristics, were studied to assess the association of these reproductive characteristics with invasiveness. Flowers of B. frondosa bloom from September to October every year in Ji'an city, Jiangxi province. The lifespan of a single capitulum is approximately 4 to 5 days, with 30 to 60 florets per capitulum. The capitulum diameter, anthocaulus length, floret length and width, stamen length and pistil length were 6.1, 30.9, 2.2, 0.6, 3.0 and 2.7 mm, respectively. The seed set percentage of 48.5% in the treatment of bagging flowers without emasculation suggests B. frondosa is self‐compatible; meanwhile, the percentage of 63.1% in the treatment of bagging with emasculation and manual xenogamy suggests it also is cross‐compatible. P/O ratio per capitulum of this species was 450.5, which suggests that the breeding system of B. frondosa is facultative xenogamous, and it needs pollinators to some degree. The main floral visitors were insects of Hymenoptera, Diptera and Lepidoptera. The 1000‐achenes weight was 1.97 g. The achenes emerged as a small germination peak from the fourth to fifth day, and had a high accumulated germination rate of up to 84.0% on day 20 after sowing. Our experimental findings suggested that the reproductive biological characteristics, such as the versatile mating system of self‐ and cross‐pollination, high seed production, a special method of achene dispersal and germination peak, accompanied by a high accumulated germination rate, might contribute to the invasive ability of B. frondosa.     

不同土壤养分水平下2种外来鬼针草和近缘本地种的比较研究

【背景】鬼针草属白花鬼针草和三叶鬼针草原产于热带美洲,入侵我国后给生态环境、农业经济等造成严重的危害和影响。目前,关于它们的研究主要针对单个物种。为了更好地理解这2种外来鬼针草的入侵能力和入侵机制,本文开展了这2种入侵种与近缘本地种之间的比较研究。【方法】通过盆栽试验,设置低肥和高肥2个养分水平,测量和计算2种外来鬼针草与近缘本地种金盏银盘在不同土壤养分水平下的形态和生长参数、生物量及其分配、繁殖持续期、单株种子产量以及表型可塑性指数等。【结果】在低肥条件下,除了繁殖持续期和种子产量外,2种外来种和本地种的大多数参数均无显著差异。但在高肥条件下,外来种白花鬼针草的总叶面积、比叶面积、叶面积比、繁殖持续期和种子产量明显高于本地种,而三叶鬼针草总叶面积、比叶面积、总生物量、相对生长速率却显著低于本地种。在对土壤养分的可塑性方面,白花鬼针草在株高、总叶面积、比叶面积、总生物量、叶面积比、相对生长速率、平均叶面积比和种子产量方面的可塑性均高于其他2种植物;三叶鬼针草与金盏银盘相比,大多数参数的可塑性指数较接近。【结论与意义】白花鬼针草是一种入侵能力很强的外来种。长的繁殖持续期和高种子产量是白花鬼针草和三叶鬼针草有别于本地种金盏银盘的重要入侵性状。本研究可为揭示三叶鬼针草和白花鬼针草的入侵机制和影响因素提供依据,并为入侵预测和控制提供基本资料。     

不同生境中鬼针草(Bidens pilosa)碳氮磷化学计量特征及其营养利用策略

该研究通过野外采样和实验室测定的方法,研究了三种生境中鬼针草叶和根碳(C)、氮(N)、磷(P)化学计量特征及其与土壤养分的相关性。结果表明:(1)鬼针草的生境具有不同的资源水平。三种生境的土壤全氮(TN)和速效氮贫乏,有机碳(C)和全磷(TP)较充裕;生境Ⅰ土壤TN含量显著低于其它两个生境,生境II土壤TP含量显著低于其它两个生境,生境III土壤TN、TP含量均大于其它两个生境。(2)不同生境的鬼针草对磷(P)分配策略不同。低N生境的鬼针草叶片P含量根P含量,P较多地分配到植物体地上部分;N、P含量较高的生境中鬼针草根P含量叶P含量,P更多地分配到地下部分。(3)不同生境的鬼针草其地上部分和根的生长速率不同。低N生境的鬼针草叶片N/P和C/P值小,植物体具有较高的相对生长速率,具有地上生长竞争优势;低P生境的植物叶片N/P和C/P值大,植物体具有较慢的相对生长速率;高N、高P生境中根N/P和C/P值小,根具有较高的生长速率,保证了鬼针草的地下生长竞争优势。(4)鬼针草叶片N/P和根N/P之间呈现不显著的负相关关系,植物地上部分和地下部分为异速生长。不同生境的鬼针草具有不同的营养利用和分配策略,保证了植物强大的竞争力和入侵性。     

Growth of three species ofBidens under different levels of soil moisture content

By the assumption that both soil moisture and soil air affect plant growth as linear factor, the relationship between mean plant dry weight and soil moisture content was newly formulated. Its applicability to actual growth data was tested by growing three species ofBidens under different levels of soil moisture content. The growth data ofBidens well satisfied the new formula. The optimum soil moisture content giving a maximum mean plant dry weight was the largest inB. frondosa and the smallest inB. biternata. This result well agreed with field observations. The growth factor represented by the new formula was referred to as “repulsive factor”, and the difference between the repulsive factor and optimum factor was discussed.