Functions of canopy-stored seeds in the dune ecosystem: conclusions from Agriophyllum squarrosum and Artemisia wudanica

Delay in seed release is found in the dune ecosystem. However, its functions have been rarely reported. We studied delayed seed release in the Agrio-phyllum squarrosum (Chenopodiaceae), an annual psam-mophyte, and the Artemisia wudanica (Asteraceae), a psammophilous subshrub in an active sand dune field in Inner Mongolia, China, to get insights into its functions in dealing with sand movement. We concluded that delay in seed release in the dune ecosystem are as follows: (1) postponing dispersal of a portion of seeds until the end of windy season and the start of growing season; (2) regulating the spatiotemporal pattern of seed bank; (3) helping psammophytes adapt to wind erosion on the active sand dune; and (4) helping psammophytes realize long-distance dispersal.     

Advances in research of induced resistance to insects in cotton

Any change in a plant that occurs following herbivory or environmental factors is an induced response. These changes include phytochemical induction, increases in physical defenses, emission of volatiles that attract predators and parasitoids of herbivores, and reduction in plant nutritional quality for herbivores, which is termed induced resistance. Induced resistance has been demon-strated ubiquitously in plants. It is one of our goals to review what is known about the induced resistance to herbivorous insects in cotton, including three resistance secondary metabolites (terpenoid, tannin, and flavonoids) that are contained at any significant levels of resistance to herbivorous insects in cotton cultivates. In many cases, the quantities or quality of secondary metabolites in plant are changed after attacked by insects. This review focuses on induced plant resistance as quantitative or qualitative enhancement of defense mechanism against insect pests, especially on the abiotic-elicitors-induced resistance in cotton plants. The abiotic-elicitor of cupric chloride, an exogenous inorganic compound, may induce the second-ary metabolites accumulation and is referred to as a copper-inducible elicitor (CIE). Finally, we discuss how copper-inducible elicitor may be used in the Integrated Pest Management (IPM) system for cotton resistance control.     

Distinguishing range expansions from previously undocumented populations using background data from museum records

Aim Knowledge of the distribution of a species is fundamental to understanding the species’ biology, and changes in known distribution may reflect response to environmental change. However, in many cases, purported range expansions are not adequately justified and extra‐limital records may simply reflect previously undocumented populations. Thus, it is critical to distinguish between these hypotheses. This study aimed to provide a simple, conceptual framework for evaluating these hypotheses that depends on the use of museum background data to assess the adequacy of historical sampling. Location American Southwest and worldwide. Methods Background data are records of species other than the taxon of interest that are likely to be documented using the same sampling methods. If evaluation of the background group determines that the taxon of interest would have been documented if present, then the extra‐limital record can be considered a range expansion. Conversely, if evaluation of the background group indicates that historical sampling was inadequate to have documented the taxon of interest, then the most parsimonious explanation for the extra‐limital record is an undocumented population, which should be presented as a range extension. As an example, I applied the methods to a purported range expansion of the yellow‐nosed cotton rat (Sigmodon ochrognathus) in the Rincon Mountains in south‐eastern Arizona. Results Evaluation of the background group revealed that sampling was inadequate to have documented S. ochrognathus in the Rincon Mountains if present. Thus, the record of S. ochrognathus in the Rincon Mountains was interpreted as a previously undocumented population rather than a range expansion. Main conclusion Range expansions can reflect factors that are of important conservation concern, such as climate change or habitat modification. Thus, it is essential that the cause of extra‐limital records be accurately interpreted. The method provides a simple means for testing between hypotheses of range extension and range expansion.     

Conflicting selection on diaspore traits limits the evolutionary potential of seed dispersal by ants

Conflicts of selection on diaspore traits throughout the dispersal cycle can limit the evolutionary consequences of seed dispersal. However, these conflicts have never been investigated in directed dispersal systems. We explored conflicts of selection through life stages of dispersal in the myrmecochorous herb Helleborus foetidus. Seeds are subject to two contrasting partial selective scenarios. Undispersed seeds are subject to positive directional selection on seed size characters, whereas seeds dispersed are subject to stabilizing selection for size. In both scenarios, seedling establishment determined the magnitude and direction of selection. This does not reflect ant preferences for seed size. However, total selection still depends largely on ant activity, as ants control the relative importance of each selective scenario. We advocate the use of analytical approaches combining multiplicative fitness and microenvironment‐specific selection to more realistically estimate the realized selection on traits functional during several life stages. This approach may be extended to any organism dispersing offspring to different environments.     

盐胁迫对黄瓜幼苗根系脯氨酸和多胺代谢的影响

以2个黄瓜品种‘长春密刺’(抗盐性较强)和‘津春2号’(抗盐性较弱)为材料,采用营养液栽培,研究了盐胁迫对幼苗根系脯氨酸(Pro)和多胺(PAs)代谢的影响。结果表明,盐胁迫能提高黄瓜幼苗根系吡咯啉-5-羧酸合成酶(P5CS)活性,抑制脯氨酸脱氢酶(ProDH)活性,从而显著增加Pro含量,且‘长春密刺’变化幅度显著大于‘津春2号’;盐胁迫下,‘长春密刺’根系精氨酸脱羧酶(ADC)、鸟氨酸脱羧酶(ODC)和S-腺苷蛋氨酸脱羧酶(SAMDC)活性升高幅度显著大于‘津春2号’,而多胺氧化酶(PAO)活性升高幅度显著低于‘津春2号’,引起其根系内亚精胺(Spd)和精胺(Spm)含量显著增加;盐胁迫下,2品种根系腐胺(Put)含量呈先上升后下降的变化趋势,随着Put积累降低,Pro含量显著增加。可见,盐胁迫诱导根系较高的Pro、Spd和Spm积累有利于提高黄瓜幼苗对盐胁迫逆境的适应能力,盐胁迫下PAs代谢和Pro代谢密切相关,Put的积累一定程度上促进了Pro含量的增加。     

棉花两品种耐盐性与抗氧化能力的相关性

对‘新陆早17’和‘中棉49’两个棉花（Gossypium hirsutumL.）品种在氧化剂甲基紫精（MV）和NaCl胁迫下的生理应答进行了研究,以期阐明棉花抗氧化能力与耐盐性的关系。研究结果表明,在40μmol·L-1MV胁迫3d,‘新陆早17’的丙二醛（MDA）和活性氧含量比‘中棉49’低,而抗坏血酸（AsA）、超氧化物岐化酶（SOD）、过氧化氢酶（CAT）和抗坏血酸过氧化物酶（APX）活性则高于‘中棉49’,表明‘新陆早17’抗氧化能力更强。在200mmol·L-1NaCl胁迫25d,‘新陆早17’的株高和叶绿素降低量、根部Na＋含量、相对电导率都低于‘中棉49’,说明‘新陆早17’耐盐更强。盐胁迫下‘新陆早17’的抗氧化酶活性上升而‘中棉49’却降低,表明‘新陆早17’通过上调SOD、CAT和APX活性来提高其耐盐性。结合棉花两品种的抗氧化和耐盐性差异,说明棉花抗氧化能力的高低能够影响品种的耐盐性。     

Classification of Rotylenchulus reniformis Numbers in Cotton Using Remotely Sensed Hyperspectral Data on Self-Organizing Maps

Rotylenchulus reniformis is one of the major nematode pests capable of reducing cotton yields by more than 60%, causing estimated losses that may exceed millions of dollars U.S. Therefore, early detection of nematode numbers is necessary to reduce these losses. This study investigates the feasibility of using remotely sensed hyperspectral data (reflectances) of cotton plants affected with different nematode population numbers with self-organizing maps (SOM) in correlating and classifying nematode population numbers extant in a plant's rhizosphere. The hyperspectral reflectances were classified into three classes based on R. renifomis population numbers present in plant's rhizosphere. Hyperspectral data (350-2500 nm) were also sub-divided into Visible, Red Edge + Near Infrared (NIR) and Mid-IR region to determine the sub-region most effective in spectrally classifying the nematode population numbers. Various combinations of different feature extraction and dimensionality reduction methods were applied in different regions to extract reduced sets of features. These features were then classified using a supervised-SOM classification method. Our results suggest that the overall classification accuracies, in general, for most methods in most regions (except visible region) varied from 60% to 80%, thereby, indicating a positive correlation between the nematode numbers present in plant's rhizosphere and the corresponding plant's hyperspectral signatures. Results showed that classification accuracies in the Mid-IR region were comparable to the accuracies obtained in other sub-regions. Finally, based on our findings, the use of remotely-sensed hyperspectral data with SOM could prove to be extremely time efficient in detecting nematode numbers present in the soil.     

夏块菌与青刚栎形成外生菌根形态变化的研究

夏块菌（Tuber aestivum）是一种具有较高经济价值的菌根食用菌。对夏块菌与青刚栎（Cycloba-lanopsis glauca）在形成菌根过程中不同阶段的菌根形态变化进行了研究,结果显示：用夏块菌孢子液接种青刚栎苗后,第14天起开始形成淡乳色的外生菌根,外延菌丝刚毛状;第一至第二个月可形成黄褐色、褐色外生菌根,外延菌丝刚毛或羊毛状。外生菌根为单根,长1～4mm,直径150～250μm。菌套厚12～20μm,平坦或自菌根延伸出刚毛状菌丝,外延菌丝束黄绿色;哈替氏网菌丝直径1～1.5μm。菌根老化后变暗褐或萎缩。外延菌丝束呈黄绿色是夏块菌菌根区别于其它块菌菌根最重要的形态特征。