大型海藻龙须菜浸出组分对中肋骨条藻的化感抑制作用

研究了龙须菜乙醇浸出组分对中肋骨条藻的化感抑制作用。结果显示,浸出组分对中肋骨条藻产生明显抑制作用,且微藻的生物量迅速减少。当龙须菜浸出成分浓度为42mgL-1时,相对抑制率为50%,即半效应浓度(EC50)。龙须菜对赤潮藻产生明显的化感抑制作用,延缓了富营养化水体中赤潮藻的爆发,从而使龙须菜具有控制中肋骨条藻赤潮发生的潜在价值。     

The effect of costs associated with toxin production in a competitive system

In this paper, we study a two-species competitive system where both the species produce toxin against each other at some cost to their growth rates. A much wider set of outcomes is possible for our system. These outcomes are important contrasts to competitive exclusion or bistable attractors that are often the outcomes for competitive systems. We show that toxin helps to gain an advantage in competition for toxic species whenever the cost of toxin production remains within some moderate value; otherwise it may result in the extinction of the species itself.     

外来入侵植物银胶菊水提物对三叶鬼针草和茶条木种子萌发的化感作用

以伴生草本植物三叶鬼针草和能源木本植物茶条木为受试植物,初步研究了外来入侵植物银胶菊根、茎、花水浸提液对二者种子萌发的化感效应。根据发芽率、化感效应敏感指数、发芽速率可以看出,银胶菊不同部位的浸提液在不同浓度下对三叶鬼针草的种子萌发的影响力不同;而对茶条木种子萌发无明显的作用。为选择适宜植物,生物替代防治银胶菊提供依据。     

苗期紫花苜蓿株体对不同地区垂穗披碱草种子萌发生长的化感作用

以发芽率、苗长、根长、苗干重、根干重变化为种子萌发和幼苗生长参数,研究苗期紫花苜蓿(Medicago sativa)植株浸提液对不同地区垂穗披碱草(Elymus nutans)种子萌发生长的化感作用。结果表明:地上部浸提液对LS、DX垂穗披碱草种子发芽率具有明显的促进作用,而对GS、KMX、LKZ、LZ地区垂穗披碱草种子发芽率均表现为抑制作用,其中对GS垂穗披碱草种子发芽率的抑制作用最强,在14.5%和5.5%浓度处理时抑制率分别为57.89%、55.26%;苗长方面,浸提液5.5%浓度对垂穗披碱草苗长的抑制率顺序为:LZNQDXLSKMXQHGSLKZ,14.5%处理时抑制率顺序为:LZKMXLKZNQGSQHDXLS,其中抑制率最高的为LZ垂穗披碱草,在14.5%和5.5%浓度处理时抑制率分别为33.03%、28.97%;根长方面,5.5%处理对垂穗披碱草根长的抑制率顺序为:QHNQLZKMX、GSLKZDX、LS,14.5%处理时抑制率顺序为:GSQH、NQLZLSKMXDXLKZ,其中在高浓度下抑制率最高的为GS垂穗披碱草,抑制率为57.69%;地上部浸提液对LKZ、LZ垂穗披碱草苗干重均具有促进作用,高浓度浸提液对NQ垂穗披碱草苗干重产生促进作用(RI0),而对KMX、DX垂穗披碱草苗干重均表现为抑制作用;根干重方面,浸提液对LS、QH、GS、NQ、LKZ垂穗披碱草根干重均有明显的抑制作用,而对KMX、DX垂穗披碱草根干重产生促进作用,高浓度浸提液对LZ垂穗披碱草的根干重产生促进作用。从根浸提液的作用来看,根浸提液除对LS、DX垂穗披碱草种子发芽率和根干重、GS垂穗披碱草种子发芽率和苗干重及NQ垂穗披碱草根干重具有促进作用外(P 0.05),对其余地区垂穗披碱草的各项指标均有明显的抑制作用(RI0)。所有以上结果表明,紫花苜蓿植株浸提液对垂穗披碱草种子萌发生长的作用具有一定的浓度效应。不同地区垂穗披碱草对紫花苜蓿地上部浸提液的敏感性趋势总体为:GSQHLSKMXNQLKZLZ,最不敏感或有促进作用的是DX垂穗披碱草;对根浸提液的敏感性趋势总体为:QHNQLZKMX,根浸提液对LS、GS、LKZ、DX垂穗披碱草种子萌发生长具有促进作用。紫花苜蓿植株不同部位浸提液对垂穗披碱草种子萌发生长的化感效应顺序为:地上部根。     

Allelopathic effects of volatile organic compounds released from Pinus halepensis needles and roots

The Mediterranean region is recognized as a global biodiversity hotspot. However, over the last decades, the cessation of traditional farming in the north part of the Mediterranean basin has given way to strong afforestation leading to occurrence of abandoned agricultural lands colonized by pioneer expansionist species like Pinus halepensis. This pine species is known to synthesize a wide range of secondary metabolites, and previous studies have demonstrated strong allelopathic potentialities of its needle and root leachates. Pinus halepensis is also recognized to release significant amounts of volatile organic compounds (VOC) with potential allelopathic effects that have never been investigated. In this context, the objectives of the present study were to improve our knowledge about the VOC released from P. halepensis needles and roots, determine if these VOC affect the seed germination and root growth of two herbaceous target species (Lactuca sativa and Linum strictum), and evaluate if soil microorganisms modulate the potential allelopathic effects of these VOC. Thirty terpenes were detected from both, needle and root emissions with β‐caryophyllene as the major volatile. Numerous terpenes, such as β‐caryophyllene, δ‐terpinene, or α‐pinene, showed higher headspace concentrations according to the gradient green needles < senescent needles < needle litter. Seed germination and root growth of the two target species were mainly reduced in presence of P. halepensis VOC. In strong contrast with the trend reported with needle leachates in literature, we observed an increasing inhibitory effect of P. halepensis VOC with the progress of needle physiological stages (i.e., green needle < senescent needle < needle litter). Surprisingly, several inhibitory effects observed on filter paper were also found or even amplified when natural soil was used as a substrate, highlighting that soil microorganisms do not necessarily limit the negative effects of VOC released by P. halepensis on herbaceous target species.     

云雾山铁杆蒿茎叶浸提液对封育草地四种优势植物的化感效应

为了揭示铁杆蒿群落在植被演替中的作用,通过研究铁杆蒿茎叶浸提液对铁杆蒿草地4种优势植物(百里香、大针茅、本氏针茅和赖草)的种子萌发及幼苗生长的干扰,结果表明:高浓度的铁杆蒿浸提液(甲醇浸提液和水浸提液)使得百里香、大针茅、本氏针茅和赖草的种子发芽指数降低,发芽率、芽长和根长低于对照,种子平均发芽时间延长达1.13-2.16 d。而低浓度浸提液(0.005 g/mL)使得百里香的发芽要高于对照11.63%(水浸提液)、15.12%(甲醇浸提液)。在幼苗生长期,铁杆蒿浸提液对4种受试植物幼苗芽和根的生长受到不同程度的抑制,不同浓度的浸提液对植物的化感作用强度不同,随浓度的增加,抑制作用越强,0.1 g/mL相对其他浓度有显著性差异;其中0.005 g/mL浸提液对本氏针茅和赖草的幼苗生长有促进作用,幼根生长高出对照19.00%、16.06%,水浸提液对幼芽促进了2.33%、9.06%,在0.1 g/mL浓度下,本氏针茅或大针茅的生长完全受到抑制,芽长和根长抑制率为100%;同一浓度下的不同浸提液对植物的抑制作用也不同,其中百里香对铁杆蒿浸提液的敏感度是最低的;甲醇浸提液的化感作用要强于水浸提液。在封育过程中,百里香群落向铁杆蒿群落的过渡,铁杆蒿的化感作用是该草地演替的一个重要影响因子。     

花生根分泌物的鉴定及其化感作用

采用改进的根系分泌物循环收集系统收集花生根系分泌物,利用气相色谱/质谱联用仪(GC-MS)鉴定其结构,并研究了花生根系分泌物对花生青枯病原菌的化感作用.结果表明,花生根系分泌物中主要含有丙三醇、苯甲酸、3,5-二甲基苯甲醛、苯乙酮、硬脂酸、棕榈酸和乳酸等7种物质.7种根系分泌物中只有苯乙酮在浓度低于0.1g·L-1时,对花生青枯病原菌生长才有明显的促进作用.同时还发现,苯乙酮浓度超过0.1 gL-1后对花生青枯病原菌有显著的抑制作用.这一结论为利用苯乙酮调控花生青枯病害的发生提供了可靠的依据.     

外源酚酸对欧美杨‘I-107’水培幼苗硝态氮吸收利用的影响

连作杨树人工林地力衰退可能与土壤中累积的酚酸存在密切的关系。土壤氮素供应是决定杨树生长发育的重要因素, 而硝态氮是土壤无机氮化合物的主要形式之一。研究酚酸作用下杨树对硝态氮的吸收利用对于揭示酚酸化感机理、明确林地改良的途径和方法具有重要意义。以欧美杨‘I-107’ (Populus × euramericana ‘Neva’)水培苗为试验材料, 采用改良Hoagland营养液培养, 以二代杨树连作人工林土壤酚酸的实际含量为参照浓度(X), 设置5个酚酸浓度水平(0, 0.5X, 1.0X, 1.5X, 2.0X), 分析不同浓度酚酸混合物对杨树硝态氮吸收利用的影响。分别在酚酸处理后第1、5、10、20、30和40天测定分析与硝态氮吸收利用密切相关的生理特性。试验结果表明: 酚酸处理导致根系伤害度明显提高, 根系活力受到酚酸物质的明显抑制, 处理后第40天各处理间表现出显著差异(p < 0.05); 48 h动态测定发现酚酸物质对硝态氮的吸收存在显著的抑制作用(p < 0.05); 处理后第40天, 低浓度酚酸(0.5X, 1.0X)导致硝态氮在植株体内发生积累, 而高浓度酚酸(1.5X, 2.0X)导致植株硝态氮含量下降; 酚酸物质明显抑制植株硝酸还原酶活性, 处理后第40天各处理间表现出显著差异(p < 0.05), 酚酸物质处理后期则引起亚硝态氮含量的升高。酚酸浓度与处理时间对杨树水培苗硝态氮的生理效应关系可以用多元线性模型描述。