Effect of aqueous extracts from vermicomposts on attacks by cucumber beetles (Acalymna vittatum) (Fabr.) on cucumbers and tobacco hornworm (Manduca sexta) (L.) on tomatoes

Vermicomposts are produced through interactions between earthworms and microorganisms in the breakdown of organic wastes. Aqueous extracts were prepared in commercial brewing equipment from vermicomposts produced from super-market food wastes. The ratio of vermicompost to water was one to five v:v, to produce a 20% aqueous solution which could be diluted to 5% and 10% concentrations. The effects of soil drenches applied at dilutions of 20%, 10%, and 5% vermicompost aqueous extracts, were compared with those of deionized water, in the suppression of cucumber beetles (Acalymna vittatum) attacking cucumbers and tobacco hornworms (Manduca sexta) attacking tomatoes, in greenhouse cage experiments. Tomatoes and cucumber seedlings were germinated and grown for 4 weeks in 25 cm diameter pots containing a soil-less growth medium - Metro-Mix 360 - and thinned to four plants per pot. They were placed under 0.2 mm mesh cages (40 cm×40 cm×40 cm), with one pot containing four plants in each treatment cage. At germination, plants were treated with soil drenches of 5%, 10%, or 20% vermicompost extract or a deionized water control to field capacity and thereafter at weekly intervals. A complete nutrient solution was applied weekly to all plants. In each experiment, eight cucumber beetles or eight tobacco hornworms were released onto the leaves of the appropriate plant species in each cage (four pests per test plant). All treatments were replicated four times per pest experiment, in a randomized complete block design. Numbers of pests were counted and damage rated (0-none to 5-total) on days 1, 3, 5, 7, 9, 11, 13 and 14 after the release of pests into the cages.All of the concentrations of vermicompost extracts significantly suppressed the establishment of and the damage caused by the two pests on the plants. The higher the rate of aqueous extract application the greater was the suppression of the pests. We concluded that the most likely cause for the unpalatability of the plants to pests was the uptake of soluble phenolic compounds from the vermicompost aqueous extracts into the plant tissues. These compounds are known to make plants unattractive to pests and to affect pest reproduction and survival rates.     

黄瓜地上部水浸液对番茄的化感抑制效应

采用培养试验研究了黄瓜地上部水浸液对番茄的化感作用及其生理生化机理,并用试管法对其水浸液的主要化学成分进行定性分析.结果表明,黄瓜地上部水浸液含有生物碱、酚类、有机酸、皂甙、甾体、多糖、蛋白质和油脂,不含鞣质.黄瓜地上部水浸液处理显著抑制番茄种子萌发过程中的呼吸速率和α-淀粉酶活性,使种子萌发率和萌发指数降低,其抑制作用随处理浓度提高而增强.在番茄幼苗生长过程中浇灌黄瓜地上部水浸液提高了番茄叶片中超氧阴离子(O2)、H2O2和丙二醛(MDA)的含量及质膜透性;降低了过氧化氢酶(CAT)和过氧化物酶(POD)活性,还原型谷胱甘肽(GSH)和抗坏血酸(ASA)含量提高,而超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)活性随处理浓度增加先升后降;叶绿素含量、净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)降低,胞间CO2浓度(Ci升高,幼苗干重下降.叶绿素荧光动力学资料显示,番茄叶片的初始荧光(Fo)随着处理浓度提高而增大,最大荧光(Fm)、PSⅡ潜在光化学效率(Fv/Fo)、PSⅡ原初光能转换效率(Fv/Fm)、PSⅡ光合电子传递量子效率(ΦPSⅡ)、光化学猝灭系数(qP)、表观光合电子传递速率(ETR)和光化学速率(PCR)下降,非光化学猝灭系数(NPQ)先升后降,表明叶片光合机构受到伤害.     

根结线虫接种对黄瓜植株根际土壤pH和微生物的影响

通过人工接种不同数量的根结线虫卵,测定了黄瓜植株根际土壤的pH和微生物数量。结果表明,随接种数量的增加,根际土壤好气性细菌数量、厌气性细菌数量、细菌总数及细菌/真菌(B/F)逐渐降低;真菌数量却逐渐升高;放线菌数量在接种量为2000个·株-1时显著升高,之后随着接种量的增加逐渐降低;放线菌/真菌(A/F)在接种量为2000个·株-1时略有升高,之后随着接种量的增加逐渐降低。接种根结线虫后,黄瓜植株根际土壤中好气性细菌数量和B/F值与pH呈显著正相关,厌气性细菌数量、细菌总数、放线菌数量以及A/F值与pH呈极显著正相关,真菌数量与pH呈显著负相关。根结线虫侵染黄瓜植株导致根际土壤发生"真菌化",显示土壤质量下降。     

锰硼营养对黄瓜产量及抗氧化酶活性的影响

采用田间试验、植株生理生化测定方法,研究了Mn、B营养对黄瓜产量与抗氧化酶活性的影响。结果表明,Mn、B营养具有明显的互作效应,适宜的Mn、B配施可提高黄瓜产量和叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(cAT)、硝酸还原酶(NR)活性以及叶绿素、抗坏血酸(ASA)含量,降低丙二醛(MDA)含量。黄瓜生产能力与超氧化物歧化酶、过氧化物酶、过氧化氢酶、硝酸还原酶活性显著正相关,与丙二醛含量呈显著负相关。     

Suppression of damping-off of cucumber caused by Pythium ultimum with live cells and extracts of Serratia marcescens N4-5

Environmentally friendly control measures are needed for the soil-borne pathogen, Pythium ultimum. This pathogen can cause severe losses to field- and greenhouse-grown cucumber and other cucurbits. Live cells and ethanol extracts of cultures of the bacterium Serratia marcescens N4-5 provided significant suppression of damping-off of cucumber caused by P. ultimum when applied as a seed treatment. Live cells of this bacterium also suppressed damping-off caused by P. ultimum on cantaloupe, muskmelon, and pumpkin. Culture filtrates from strain N4-5 contained chitinase and protease activities while ethanol extracts contained the antibiotic prodigiosin, the surfactant serrawettin W1, and possibly other unidentified surfactants. Production of prodigiosin and serrawettin W1 was temperature-dependent, both compounds being detected in extracts from N4-5 grown at 28 °C but not in extracts from N4-5 grown at 37 °C. Ethanol extracts from strain N4-5 grown at 28 °C inhibited germination of sporangia and mycelial growth by P. ultimum in in vitro experiments. There was no in vitro inhibition of P. ultimum associated with ethanol extracts of strain N4-5 grown at 37 °C. Prodigiosin, purified from two consecutive thin-layer chromatography runs using different solvent systems, inhibited germination of sporangia and mycelial growth of P. ultimum. Another unidentified compound(s) also inhibited germination of sporangia but did not inhibit mycelial growth. There was no in vitro inhibition associated with serrawettin W1. These results demonstrate that live cells and cell-free extracts of S. marcescens N4-5 are effective for suppression of damping-off of cucumber caused by P. ultimum possibly due in part to the production of the antibiotic prodigiosin.     

Responses of co-occurring populations of Dendrobaena octaedra (Lumbricidae) and Cognettia sphagnetorum (Enchytraeidae) to soil pH, moisture and resource addition

Dendrobaena octaedra (Lumbricidae) and Cognettia sphagnetorum (Enchytraeidae) are the two most dominating soil invertebrates in terms of biomass in boreal coniferous forest soils. A microcosm experiment was set up in order to study the influence of pH, moisture and resource addition on D. octaedra and C. sphagnetorum when both species are simultaneously present. Two kinds of coniferous forest humus were used as substrate, pine stand humus (pH 4.2), and spruce stand humus (pH 4.6); in the third treatment the pine stand humus was adjusted with slaked lime (CaOH₂) to the same initial pH as the spruce stand humus. Each substrate was adjusted to water contents of 25%, 42.5% and 60% of WHC (referred to as ‘dry’, ‘moist’ and ‘wet’). In the second part of the experiment, spruce needle litter and birch leaf litter were separately added into the pine stand humus (‘moist’, unlimed) and compared with a control without litter. The microcosms were plastic jars with 75 g (d.m.) of humus, into which 4 specimens of D. octaedra and 70 specimens of C. sphagnetorum were added. D. octaedra showed the highest biomass and C. sphagnetorum the lowest biomass in the spruce stand humus with higher pH. Moisture did not affect earthworms, while C. sphagnetorum thrived best at the highest moisture. Addition of both kinds of litter increased the numbers and biomass of D. octaedra, while on C. sphagnetorum resource addition had little effect. The results help to explain the abundance of these two species in coniferous forests differing in soil acidity, moisture and fertility.     

土壤厌氧消毒对青枯病的控制及土壤细菌群落结构的影响

近年来,土壤厌氧消毒(Anaerobic soil disinfestation,ASD)作为一种非化学、环境友好型土壤消毒方法,在缓解连作障碍和防治土传病害方面具有显著效果,但其作用机理尚不完全清楚。本研究设置6个处理,即对照、添加米糠(DRB)、麦麸(DWB)、茶麸(DTB)、秸秆(DRS)和不添加物料(D)5种土壤厌氧消毒处理,分析不同处理对青枯病防控效果、土壤理化性质及土壤细菌群落结构组成及多样性的影响。结果表明,与CK相比,添加4种物料厌氧消毒处理对青枯病的防效均达100%,单纯厌氧处理防效为83.3%,且除了DRB外各厌氧处理均能大幅度促进番茄生长。各ASD能显著提高土壤温度、p H和电导率,降低Eh和土壤青枯菌数量。田间试验表明,与CK相比,ASD的番茄青枯病发病率降低29.4%~42.7%,产量增加2.5倍~4.7倍。利用16S r DNA对土壤测序表明,ASD降低了土壤细菌α多样性指数,不同处理间土壤细菌物种种类、丰富度及多样性均存在显著差异。添加不同有机物料的ASD厚壁菌门(Firmicutes)相对丰度大幅度提高,成为优势群落;该门中的厌氧型细菌梭菌科(Clostridiaceae)、瘤胃菌科(Ruminococcaceae)和耐受性细菌芽孢杆菌科(Bacillaceae)等相对丰度也大幅度提高。本研究表明,土壤厌氧消毒处理显著改变了土壤细菌群落结构组成及多样性,厌氧和耐受型细菌丰度大幅度增加,这可能是ASD防控土传病害青枯病的作用机理之一。     

Impacts of red wood ants Formica polyctena on the spatial distribution and behavioural patterns of ground beetles (Carabidae)

The aim of this study was to examine the effect of red wood ants Formica polyctena s.l. Foerst. on the spatial distribution of carabids and describe mechanisms of the ant–beetle interactions at the individual level. Fifteen carabid species were found in the foraging territory of an ant colony. The difference in the numbers of carabids in ant-controlled and ant-free territories was maximal in July, when the ants were most active. Measurements of running speed, duration of stops, and individual trajectories showed significant alterations in the behaviour of beetles in the ant-controlled territory. Experiments with a binary Y-shaped labyrinth showed that different carabid species used species-specific sets of behavioural tactics for avoiding conflict with ants. Pterostichus magus and P. oblongopunctatus, which are comparable with red wood ants in body length and speed of movement, possess the most effective stereotyped tactics in combination with a flexible behaviour. Such properties allow these species to penetrate ant foraging territory and partly avoid interference competition.     

土壤施肥对烟粉虱生长发育、寄主选择及繁殖的影响

为探讨土壤施肥对烟粉虱种群的影响,在室内采用盆栽方法测定了11种氮、磷、钾施肥组合处理和对照处理的黄瓜苗上烟粉虱的发育历期、存活率、若虫大小、寄主选择、繁殖力及寿命等生命参数。结果表明,烟粉虱的发育历期受施肥影响显著;施肥对卵和低龄若虫存活率无显著影响,但对高龄若虫存活率及各龄若虫大小影响显著;成虫较喜欢在氮肥施用量适中且不施用钾肥和磷肥的黄瓜植株上取食和产卵,而不喜好氮肥施用量大且施用钾肥和磷肥的植株;烟粉虱的寿命及繁殖力在单独施用磷肥的黄瓜植株上低于对照处理的植株,在其他施肥处理上均高于对照。在氮肥施用量大且施用钾肥和磷肥的植株上,一个世代后烟粉虱种群增殖最大,达74．4倍;在单独施用磷肥时增殖最小,仅17．2倍。     

Sex and seasonal differences in the spatial terrestrial distribution of gray treefrog (Hyla versicolor) populations

Fragmentation of terrestrial landscapes has exacerbated the need to understand the spatial requirements of organisms, especially those that undergo seasonal migrations, such as pond-breeding amphibians. Pond-breeding amphibians spend much of their lives in terrestrial habitat at some distance from aquatic breeding sites. The terrestrial habitat required by a particular individual encompasses the area adjacent to a breeding pond that is used for activities such as foraging or overwintering, as well as the expanses of habitat through which it moves. To elucidate amphibian spatial habitat requirements, we monitored gray treefrog (Hyla versicolor) movements through terrestrial habitat adjacent to breeding ponds using radiotelemetry and mark–recapture along transects of artificial refugia. Results indicate that gray treefrogs frequently make migrations between foraging grounds, overwintering sites, and breeding ponds of 200 m or more, with a maximum-recorded movement distance of 330 m. Additionally, females travel farther than males for reasons independent of body size, and the distribution of males during the breeding season is biased towards breeding ponds relative to the non-breeding season. The data illustrate the importance of habitat directly adjacent to breeding sites for males, and indicate that habitat loss resulting in small patches may have a greater negative impact on females than males, and consequently may have disproportionately large effects on population persistence. These results emphasize that effective management of amphibian breeding locations via protection of both aquatic and adjacent upland terrestrial resources likely requires detailed information regarding variation in movements between the sexes and among seasonal activity periods.     

High levels of genetic differentiation between Wolbachia-infected and non-infected populations of Folsomia candida (Collembola, Isotomidae)

The Gram-negative -Proteobacterium Wolbachia pipientis has been described as an obligate endosymbiont in many arthropod species, where it induces a variety of reproductive alterations, including parthenogenesis. Recently, this microorganism has also been detected in the parthenogenetic collembolan Folsomia candida. Here, we confirm the occurrence of the endosymbiont also in two Italian parthenogenetic populations of F. candida using ultrastructural (electron microscopy) and molecular (PCR screening on two bacterial genes) evidence. The strain isolated in the Italian populations has almost-identical gene sequences compared to that previously isolated in other populations of F. candida. In addition, we discovered a population of Folsomia cf. candida, which showed the presence of both males and females. This population is not infected by Wolbachia. A screening of two mitochondrial genes (COI and COII) showed that the bisexual population has high levels of genetic divergence in comparison with the parthenogenetic ones, even suggesting the possibility that it belongs to a different species. Furthermore, the remarkably high levels of genetic divergence between the two parthenogenetic populations suggests a possible influence of Wolbachia on inducing such differentiation, and, in the long term, speciation.     

Responses of root-feeding nematodes (Helicotylenchus spp.) to local and non-local populations of the host plant Ammophila arenaria

The root-feeding nematode community of wild plants may vary throughout their natural range. Little is known about how the variation of wild plants along their range affects their relationship with root-feeding nematodes. In the present study, we examined local and non-local combinations of host plants and root-feeding nematodes to test the hypothesis that nematode reproduction is favoured by local hosts. In two indoor experiments, we exposed populations of the wild dune grass Ammophila arenaria from northern and southern European coastal sand dunes to plant parasitic nematode species (Helicotylenchus spp.) from those same geographical origins. First, we used the southern nematode species to determine whether the effect of a local versus a non-local host may depend on nematode density. Then, in a cross-inoculation experiment we investigated how both nematode species performed with their local, as compared to the non-local hosts.

In both experiments, plant biomass and ontogenetic characteristics were not significantly different between the northern and southern populations. The applied nematode densities did not have a negative impact on plant performance. This allowed us to consider the response of the two different nematode species and their host plants without co-varying differences in plant responses. Reproduction of the nematode species differed according to host origin, but contrary to what we expected, nematode species did not perform better on their local hosts. Helicotylenchus n. sp., the southern species originating from Portugal, performed better on the non-local than on the local host. Male to female ratios were significantly different between the two nematode populations and were lowest in Helicotylenchus pseudorobustus from The Netherlands. Female and juveniles percentages were also quite distinct, with more females in the nematode species from The Netherlands and more juveniles in the nematode species from Portugal.

We concluded that ectoparasitic root-feeding nematodes Helicotylenchus spp. do not necessarily perform best on their local host population of the foredune grass A. arenaria. Our results imply that the natural distribution of Helicotylenchus spp. along the European coast is determined by other factors than host populations. These other factors that could be abiotic, e.g. water availability, or biotic, e.g. local natural enemies adapted to Helicotylenchus spp. Introducing plant genotypes from other parts of the natural range will, therefore, not necessarily lead to reduced abundance of semi-endo or ectoparasitic root-feeding nematodes.     

低氮胁迫下小麦抑草作用的化感效应与资源竞争分析

化感效应和资源竞争在作物抑草中起重要作用。为区分低氮胁迫下小麦抑草作用的化感效应与资源竞争,以强化感小麦品种‘115/青海麦’、‘92L89’和弱化感小麦‘抗10103’为材料,设置氮水平为25 mg·L-1、50mg·L-1、100 mg·L-1和200 mg·L-1的水培试验,通过小麦与看麦娘共培、应用含小麦根系分泌物的小麦-看麦娘共培液处理看麦娘,分别测定了小麦对看麦娘的生物干扰作用、化感效应及资源竞争效应。结果表明,不同化感潜力的小麦对看麦娘的抑制能力存在显著差异,抑制率大小为‘115/青海麦’(55.1%~73.9%)‘92L89’(48.9%~65.9%)‘抗10103’(15.4%~45.5%),且抑制率随氮水平的降低而增大。在小麦的抑草作用中,化感效应与资源竞争并存。低氮胁迫条件下,强化感小麦抑草能力增强主要通过提高化感效应实现;弱化感小麦抑草能力增强主要通过提高资源竞争实现。不同化感潜力小麦的抑草作用在低氮胁迫下表现出不同的生态策略。小麦抑草作用的化感效应均随氮水平降低而增大,其抑制率随氮水平的变化可用一元二次方程加以拟合。     

Extreme neutral genetic and morphological divergence supports classification of Adriatic three-spined stickleback (Gasterosteus aculeatus) populations as distinct conservation units

The fact that the intraspecific genetic differentiation in neutral genetic markers and genes coding for adaptive traits are not typically correlated has caused a great deal of conceptual and practical trouble in delimitation of conservation units. Although the importance of combining information on adaptive genetic divergence with information on historical and recent gene flow in the delimitation of conservation units has been recognized, integrated empirical studies to this end are still rare. We explored the evidence for the specific conservation status of two freshwater three-spined stickleback (Gasterosteus aculeatus) populations on the Adriatic side of the Balkan Peninsula by comparing their phenotypic and genetic characteristics to those of other representative European populations. Apart from focusing on the neutral genetic divergence in mitochondrial DNA sequences and microsatellite markers, we also compared the patterns of morphological differentiation (i.e. bony armour development) resulting from adaptation to freshwater environments. The Balkanic populations formed two distinct groups with regard to neutral genetic variation and had the least developed bony armour of all the examined populations. All morphometric analyses identified the two Balkanic populations as phenotypically – and hence most likely also ecologically – clearly distinct from other European three-spined stickleback populations. These results suggest that the two Balkanic populations (River Neretva and River Zeta) fulfil the most stringent criteria (i.e. lack of genetic and ecological exchangeability) to be classified as conservation units distinct from other European three-spined stickleback populations.     

Selective consumption and digestion of litter microbes by Porcellio scaber (Isopoda: Oniscidea)

In feeding preference tests with artificial diets consisting of food sources inoculated with different types of litter microbes, Porcellio scaber was capable of discriminating between different microbe species. Generally, microbial colonisation increased the attractiveness of a given food source, in particular, when the food source was of low quality (cellulose) and when food sources were inoculated with single species of actinomycetes (Streptomyces celluloflavus or Pseudonocardia autotrophica). In most cases, actinomycetes (Gram-positive bacteria) were preferred over both Gram-negative bacteria and fungi, whether or not these microbes exhibited cellulolytic activity. Enzymatic in vitro digestion of both the Gram-positive S. celluloflavus and P. autotrophica was significantly greater than that of Gram-negative bacteria (Pseudomonas fluorescens and Myxococcus xanthus) or fungi (Chaetomium globosum and Fusarium ventricosum). S. celluloflavus biomass was more effectively incorporated into isopod biomass than that of fungi and Gram-negative bacteria; P. autotrophica was more effectively incorporated into isopod biomass than that of Gram-negative bacteria. Based on these results, we hypothesise that P. scaber preferentially feeds on those microbes that it can readily digest. Whether this holds true for other Gram-positive bacteria or for other detritivores awaits investigation.     

Ovaries of Petrobius brevistylis (Archaeognatha, Machilidae) and Tricholepidion gertschi (Zygentoma, Lepidotrichidae): Morphology, ultrastructure and phylogenetic implications

The ovaries of Petrobius brevistylis (Archaeognatha) and Tricholepidion gertschi (Zygentoma) are composed of seven metamerically arranged panoistic ovarioles that are covered with the external epithelial sheath (=tunica externa) and the basal lamina (=tunica propria). The germaria are small and enclose oogonial cells and somatic prefollicular cells. The vitellaria contain 10–15 linearly arranged oocytes that are surrounded by a one-layered follicular epithelium. Oocyte nuclei (=germinal vesicles) are large and possess giant, compact (P. brevistylis) or lobate (T. gertschi) nucleoli. In both studied species the majority of yolk is incorporated to the oocyte via endocytosis; however, appearance of numerous Golgi complexes and rough endoplasmic reticulum cisternae at the onset of vitellogenesis suggests the involvement of these organelles in synthesis of yolk precursors. The obtained results are discussed in the phylogenetic context and support the idea that Lepidotrichidae are the most basal zygentoman clade.     

CO2浓度升高条件下不同程度豌豆蚜危害对紫花苜蓿叶片营养物质和次生代谢物质的影响

由于人类大量开采使用石油、煤炭、天然气等化石燃料,使大气CO₂浓度升高,这不但加速全球变暖,还将影响地球上动植物的生存和分布,从而对整个生态系统产生深远影响。为探明CO₂浓度升高与豌豆蚜（Acyrthosiphon pisum）虫口密度对紫花苜蓿（Medicago sativa）叶片内化学物质的影响,明确CO₂浓度升高和蚜虫密度在紫花苜蓿生理生化中的作用,试验在CO₂光照培养箱内设置380 μL·L^-1（对照）、550 μL·L^-1和750 μL·L^-1 3个CO₂浓度培育苜蓿幼苗并接入10日龄成蚜10头·株^-1、20头·株^-1、30头·株^-1,并以0头·株^-1作为空白对照,1周后测定植物体内营养物质和次生代谢物质含量。结果表明,随CO₂浓度升高,蚜虫密度为30头·株^-1时紫花苜蓿可溶性蛋白、可溶性糖以及淀粉含量均上升,在750 μL·L^-1 CO₂浓度下分别比CK上升11.62倍、0.49倍和0.24倍;黄酮、总酚和简单酚含量也显著上升。随蚜虫危害程度加重,同一CO₂浓度下紫花苜蓿淀粉、简单酚含量先上升后下降,高CO₂浓度蚜虫密度为30头·株^-1时比0头·株^-1时可溶性糖、总酚以及单宁含量上升1.66倍、1.49 mg·g^-1和1.09 mg·g^-1,差异均显著（P<0.05）。说明具有固氮作用的豆科植物更易于适应CO₂浓度升高的变化,从而在受到刺吸胁迫后增强自身诱导抗虫性以抵御害虫为害。     

Fast and efficient discrimination of the Isotoma viridis group (Insecta: Collembola) by PCR-RFLP

Identification of collembolan species is generally based on specific morphological characters, such as chaetotaxy and pigmentation pattern. However, some specimens do not match to described characters because these refer to adult specimens, often of one specific sex, or the characters are highly variable in adults (e.g. pigmentation, setae or furcal teeth). Isozymes have frequently assisted species discrimination, and also these may vary with developmental stage or environmental conditions. For identification of single species of the Isotoma viridis group, we present both direct sequencing of the cytochrome oxidase subunit II (COII) gene and a simple DNA-based molecular method.

Five PCR primers amplifying the COII region (717 bp) of the mitochondrial DNA were used. The sequences clearly separated the species I. viridis, I. riparia and I. anglicana, irrespective of colour varieties within the first species. DNA amplification products of different species can also be distinguished by digestion with restriction endonucleases, followed by gel electrophoresis for separation of fragments. This restriction fragment length polymorphism (RFLP), obtained after digestion with the endonucleases TaqI, VspI, MvaI and Bsp143I, revealed specific fragments that separated the three species from each other. Since restriction enzymes are sensitive to single base mutations, we suggest to use a combination of enzymes with at least two species-specific restriction sites when using the RFLP technique. For the I. viridis complex, VspI and Bsp143I appear to be an appropriate combination.     

短时间亚高温处理及其恢复对番茄光合特性的影响

以“辽园多丽”番茄(Lycopersicon. esculentum Mill.)为试材,在植株第1花序第1花开花时,对其进行2 h＋15 min(光合测定平均时间,下同)、4 h＋15 min、6 h＋15 min、8 h＋15 min的35℃昼间亚高温处理,之后转入25℃条件下分别恢复6 h、4 h、2 h,以25℃处理为对照,研究较短时间亚高温处理及常温恢复对番茄光合作用及叶绿素荧光作用的影响。结果表明：35℃昼间亚高温处理2 h,番茄叶片光合作用即明显降低;而亚高温处理2 h、4 h和6 h的植株在25℃恢复的最初2 h内光合作用持续下降。经35℃亚高温处理2 h,番茄叶片各项叶绿素荧光参数均降低,但亚高温处理6 h内的植株在常温恢复2 h后各项指标即可恢复正常。综合认为,番茄植株经过2 h的35℃昼间亚高温处理,当天的光合作用就难以恢复到对照水平,在持续亚高温条件下,净光合速率的降低主要由非气孔限制因素引起的;而气孔限制因素则是亚高温处理后处于常温恢复初期的植株光合作用下降的一个重要原因。