Effect of calcium concentration in nutrient solution before and after inoculation with Ralstonia solanacearum on resistance of tomato seedlings to bacterial wilt

We previously reported that calcium (Ca) nutrition in tomato (Lycopersicon esculentum Mill.) significantly affected the resistance to bacterial wilt caused by Ralstonia solanacearum Smith. To elucidate the mechanisms underlying the Ca-dependent resistance, the effect of the Ca concentration in the nutrient solution applied before and after inoculation with the pathogen on the resistance of tomato seedlings to bacterial wilt was studied. One week before inoculation, seedlings were transferred to nutrient solutions containing Ca at concentrations of 0.4, 4.4, or 20.4 mM. Soon after inoculation, the seedlings that were treated with each concentration of Ca before inoculation were transferred to solutions containing the same three concentrations of Ca. Although the disease development was not affected by the concentration of Ca in the solution before inoculation, a higher concentration of Ca after inoculation reduced the disease severity. This result suggests that the concentration of Ca in the host, especially in the cell walls, before infection may not be directly involved in the Ca-dependent resistance of tomato seedlings to bacterial wilt.     

Calcium uptake and resistance to bacterial wilt of mutually grafted tomato seedlings

Bacterial wilt of tomato (Lycopersicon esculentum Mill.) caused by Ralstonia solanacearum Smith is a serious disease in Japan. We previously reported that calcium (Ca) nutrition in tomato significantly affected the resistance to the disease, and that highly resistant cultivars were characterized by a high Ca uptake. We examined the relationship between the Ca uptake and resistance using mutually grafted seedlings of tomato cultivars differing in their resistance. A susceptible (‘Ponderosa’) or moderately resistant (‘Zuiei’) cultivar (scion) was grafted on the rootstock of a susceptible, moderately resistant, or highly resistant cultivar (‘Hawaii 7998’). Roots or petioles of the grafted seedlings were inoculated with the pathogen, and the development of bacterial wilt was observed. Although Ca uptake by shoot increased by grafting on the rootstock of a highly resistant cultivar, the development of the disease was not influenced by the difference in Ca uptake, and depended on the resistance of the cultivar to which the inoculated part of the graft belonged. It was concluded that the differences in Ca uptake of the shoot of the grafted tomato seedlings might not be related to the expression of the resistance to bacterial wilt.     

Relationship between resistance to bacterial wilt and nutrient uptake in tomato seedlings

Abstract

Varietal differences in the resistance to bacterial wilt and nutrient uptake of tomato (Lycopersicon esculentum Mill.) seedlings were examined in pot experiments. Twenty-three tomato cultivars were classified into three groups based on the degree of resistance to the disease. Differences in nutrient uptake among cultivars were observed for all the elements tested, and highly resistant cultivars were characterized by a high calcium uptake.     

Suppression of Ralstonia solanacearum in soil following colonization by other strains of R. solanacearum

The effect of prior colonization of a sterile loam soil and a sterile clay loam soil by individual soil bacteria on the subsequent growth of a bacterial wilt pathogen Ralstonia solanacearum YU1Rif43 (tRNA type III: Seal et al. 1992: Appl. Environ. Microbiol., 58, 3759–3761) was investigated. Various strains, belonging to the same type, the same species, the same genus, Gram-negative, Grampositive, or fungi, were used. The degree of suppression of the growth of R. solanacearum YU1Rif43 was markedly different depending on the species that had previously colonized the soil, hereafter referred to as priorcolonists. All the strains belonging to R. solanacearum type III suppressed the growth of R. solanacearum YU1Rif43 markedly, while strains of R. solanacearum type I and type II showed a moderate suppressive effect on R. solanacearum YU1Rif43. The suppressive effect of the strains belonging to species other than R. solanacearum, including fungal strains, was relatively limited, or some strains did not show any suppressive effect. The production of bacteriocin did not appear to be related to the strong suppressive effect of the R. solanacearum type III strains. Possible mechanisms for the suppressive effect of priorcolonists on R. solanacearum YU1Rif43 are discussed in relation to nutrients and physical sites in soil available for growth.     

三种堆肥对番茄生长及青枯病防治效果的影响

合理施用堆肥能够有效地改善植物的生长条件和土壤的生态环境,从而提高植物对病害的抗性。通过盆栽试验,研究了药渣、 污泥和猪粪三种堆肥以不同比例与泥炭混合对番茄植株生长和番茄青枯病防治的影响。结果表明: 三种不同堆肥均能促进番茄植株生长,其中猪粪堆肥对番茄生长的促进效果最显著,当泥炭与猪粪的混合比例为3∶1时效果最好,当收获番茄植株时,其鲜重和干重较泥炭基础基质处理分别提高了29.8%和41.2%,污泥堆肥次之,药渣堆肥最差; 三种不同堆肥都能抑制青枯病的发生,药渣堆肥对番茄青枯病的抑制效果最明显,当泥炭与药渣的混合比例为4∶1时效果最好,在番茄植株移栽33d 时,其病情指数较泥炭基础基质降低了66.7%,污泥堆肥次之,猪粪堆肥最差。添加不同堆肥使得盆栽基质的理化性质、 酶活性和可培养微生物的数量发生了不同的变化,推测可能是上述因素的变化使其对番茄的生长和青枯病的防治效果产生了明显的差异。     

Control of tomato bacterial wilt and root-knot diseases by Bacillus thuringiensis CR-371 and Streptomyces avermectinius NBRC14893

Ralstonia solanacearum and Meloidogyne incognita are two soilborne pathogens that cause serious damage and great losses in the production of tomato. For this purpose, a bacterial isolate, Bacillus thuringiensis CR-371, and an actinomyces isolate, Streptomyces avermectinius NBRC14893, were examined for their ability to protect tomato from root-knot nematode and bacterial wilt diseases under glasshouse conditions. Treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 followed by challenge inoculation with R. solanacearum and M. incognita significantly decreased disease severity of bacterial wilt alone, root-knot nematode alone, or mixed infection by both pathogens compared to the control. Furthermore, pretreatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 significantly reduced bacterial proliferation of R. solanacearum both in pathogen alone inoculated plants and in plants co-inoculated with R. solanacearum and M. incognita. In conclusion, our results suggest that the treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 simultaneously suppresses bacterial wilt and root-knot nematode diseases. Therefore, B. thuringiensis CR-371 and S. avermectinius NBRC14893 could provide new options for integrated pest management strategies against plant diseases, especially against bacterial-nematode disease complexes that cause synergistic yield losses.     

番茄青枯病拮抗菌X10的鉴定和田间应用

对番茄青枯病拮抗菌X10进行了形态学特征、生理生化特征测定,结果表明它与侧孢短芽孢杆菌种的特征一致。测定了菌株的16S rDNA序列并根据其构建了系统发育树,在系统发育树中,X10与侧孢短芽孢杆菌形成一个类群,序列同源性为99%。因此将X10鉴定为侧孢短芽孢杆菌。制备了侧孢短芽孢杆菌X10的固体菌剂,在山东肥城科技示范园的蔬菜大棚里进行了小区试验,对田间应用效果进行了测定。结果表明,固体菌剂的两种接种量对番茄青枯病的防治效果分别达到了58.42%和68.68%,同时还能够促进番茄植株生长和增加产量。     

基于BOX-PCR和REP-PCR技术青枯雷尔氏菌遗传多样性分析

青枯雷尔氏菌(Ralstonias olanace arum)能够对许多重要作物引起致命性萎蔫病害,广泛分布在热带、亚热带以及温带地区.研究青枯雷尔氏菌的遗传多样性对于了解青枯病的发生和流行具有十分重要的意义.本研究利用青枯雷尔氏菌特异性引物鉴定84株来自福建地区不同寄主的青枯雷尔氏菌,结果表明,这些菌株均在504 bp位置出现特异性条带.同时采用BOX插入因子PCR(BOX-PCR)和重复基因外回文序列PCR(REP-PCR)对这些菌株进行基因多样性研究,基于它们所扩增出的基因指纹图谱表明,BOX-PCR扩增出19条特异性条带,REP-PCR扩增出20条特异性条带.系统聚类结果表明,青枯雷尔氏菌的遗传分化与寄主作物和地理来源都存在相关性,其中,寄主植物是在遗传差异中起主导作用.进一步分析可知,地域性的差异主要由BOX-PCR提供,寄主间的差异主要由REP-PCR提供.不同地理来源的青枯雷尔氏菌在BOX-PCR中可扩增出各自特异性条带,在REP-PCR中同样具有与各个寄主相对应的特异性条带,利用这些特异性条带可以很容易区分不同寄主以及来源的青枯雷尔氏菌.BOX-PCR和REP-PCR多态性分析技术可为我国青枯雷尔氏菌基因多样性的研究提供另一条途径.     

Host-plant resistance to Pseudomonas solanacearum in tomato germplasm

Seedlings of two hundred and thirty-three accessions of the tomato collection maintained at the Centro Agronómico Tropical de Investigación y Enseñanza, Turrialba, Costa Rica (CATIE) and 7 cultivars used as controls were evaluated for host-plant resistance to 4 virulent strains of Pseudomonas solanacearum representing race 1 biovars 1 and 3. In general, biovar 3 strains wilted seedlings faster than biovar 1 strains but, after 20 days post-inoculation, no significant differences were noted in susceptible control ratings. Significant differences for disease index were noted, but no line with complete resistance was found. For the USA biovar 1 strain UW-25, only 5 accessions, CATIE 17331, 17334, 17349, 17739, 17740, and 2 of the control cultivars, Hawaii 7998 and UC-82B showed some degree of resistance. Conversely, both the frequency and the degree of resistance were high for Costa Rican biovar 1 strain UW-256. For biovar 3, the Costa Rican strain UW-255 was more virulent than the Peruvian strain UW-130. Eight CATIE accessions, 5539, 17331, 17333, 17334, 17345, 17349, 17742, and MIP-CH1, were as resistant as the resistant control Hawaii 7998 to 3 strains and accession 17740 was as resistant as Hawaii 7998 to all 4 strains.Journal Paper No. J-16011 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project 3123.     

Changes in the nitrogen localized in the lamellae systems and stroma of rice chloroplast accompanying the stages of growth

The change in the nitrogen localized in the lamellae systems and stroma region of the rice chloroplast was pursued throughout the stages of growth and, further, the relationship between the composition of the chloroplast and leaf N content was examined. A common trend accompanying the stages of growth is recognized: that in the early stages of growth the amount of nitrogen existing as a form of stroma N is larger than that of lamellae N. Thereafter, stroma N tends to decrease in relation to lamellae N and finally, lamellae N becomes a dominant nitrogenous fraction in the chloroplast. The change in the composition of the chloroplast seems to be brought about by a change in the nitrogen metabolism of the chloroplast by which the distribution of absorbed nitrogen among the nitrogenous fractions of the chloroplast differs.     

Effect of Ralstonia solanacearum on Mineral Nutrients and Infrared Temperatures in Two Tomato Cultivars

ABSTRACT

The objective of this study was to determine how the responses of two tomato cultivars to Ralstonia solanacearum relate to their leaf infrared temperature and acquiring of nutrients from soil. Tomato (Solanum lycopersicum L.) cultivars of disease susceptible-‘FL 47’ and resistant-‘H 7998’ were grown in soil inoculated with R. solanacearum. Bacterial wilt incidence, leaf infrared temperatures, and uptake of nutrients were measured for 28 d. In bacterial wilt-resistant cultivar ‘H 7998’, concentration of sulfur (S; +77%), calcium (Ca; +66%), boron (B; +60%) were found higher and nitrogen (N; ?26%) were found lower, compared with susceptible ‘FL 47’. Infrared temperatures were correlated with wilt percentage at 14 d, but not at 7 d. These results provide evidence that there is a correlation between bacterial wilt resistance and translocation of some nutrients in the shoots. Additionally, data indicates that the infrared thermometer could only detect wilting after obvious symptoms were visibly incited by R. solanacearum in tomato.     

插入序列ISRso21在青枯雷尔氏菌中的分布以及插入位点多态性分析

插入序列(insertion sequence,IS)元件可以插入到基因或DNA序列,其可能在生物体进化中起着重要的作用。ISRso21是在青枯雷尔氏菌(Ralstonia solanacearum)FJAT-1458菌株中发现的一个新的插入序列。根据序列分析可知,该插入序列是属于ISL3家族中的一个成员。本研究发现,福建闽北地区菌株ISRso21的阳性率高于其他地区的趋势,不同地区的青枯雷尔氏菌ISRso21的分布有显著性差异,ISRso21的分布可能与菌株分离个体的地理来源有关。不仅如此,由于ISRso21在青枯雷尔氏菌插入位点的不同,从而导致青枯雷尔氏菌致病性的差异。研究表明,由于ISRso21的插入导致表现型转换系统转录调控因子A(phc A)的重排可能在青枯雷尔氏菌的致病性起着极其重要的作用。在所有菌株中,ISRso21在phc A基因上游中插入的检出率达到4.71%,其中无致病力菌株和强致病力菌株中的检出率分别为28.57%和0.00%。而ISRso21在二氨基庚二酸脱羧酶基因中的插入可能是为了更好地适应环境。ISRso21在不同致病性青枯雷尔氏菌中的插入位点的研究,可能为揭示青枯雷尔氏菌致病性机制提供新的研究途径。     

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。     

高浓度营养液对黄瓜和番茄下胚轴徒长的抑制作用

【目的】黄瓜和番茄是我国主栽蔬菜种类,育苗过程中容易遭遇高温、高湿、弱光等不良环境,导致幼苗下胚轴徒长,严重影响后期丰产性。在控制幼苗徒长的实际操作中,利用植物生长调节剂、机械刺激、补光、温度调节、水分控制等调控方法容易受到多种因素影响而效果不佳。本文研究高浓度营养液浓度对黄瓜和番茄幼苗下胚轴徒长的抑制作用,以期提出一种有效制御幼苗徒长的方法。【方法】试验以Hoagland标准营养液配方为基础浓度（设为1.0C）,通过成比例增减大量元素组分用量而不改变微量元素组分用量,组成0.5C、2.5C、5.0C、7.5C、10.0C和12.5C 6个浓度。以0.5C为对照,在日光温室条件下分别对黄瓜和番茄幼苗进行灌施处理。待幼苗生长至子叶平展期时,测定黄瓜和番茄幼苗形态及生长指标,研究营养液浓度对幼苗下胚轴细胞长度、生长速率及内源激素含量的影响;随后对幼苗进行0.5C低浓度营养液的恢复生长处理,待幼苗生长至第一真叶平展期时,再次进行幼苗形态及生长指标的测定,从而确定高浓度营养液对黄瓜和番茄下胚轴徒长的抑制效果及机制,并确定最适合制御幼苗徒长的营养液浓度。【结果】6种浓度营养液对黄瓜和番茄幼苗下胚轴徒长的影响结果为: 1）高浓度营养液显著提高了基质EC值（r=0.99）,黄瓜和番茄幼苗在子叶平展期其下胚轴生长受到明显抑制,下胚轴长度、绝对生长速率和含水量均呈下降趋势,下胚轴皮层薄壁细胞轴/径向生长也受到影响。与对照相比,10.0C营养液处理下黄瓜和番茄幼苗下胚轴皮层薄壁细胞缩短为49%和48%。2）随着营养液浓度的增加,黄瓜和番茄下胚轴内源激素含量发生显著变化,其中赤霉酸（GA3）、玉米素核苷（ZR）含量呈降低趋势,而脱落酸（ABA）含量呈升高趋势,且ABA含量与下胚轴长度呈极显著负相关关系（P＜0.01）。生长素（IAA）含量在不同浓度营养液处理下呈现区位性变化特征。3）在幼苗子叶平展期重新灌施0.5C浓度的营养液,对5.0C和7.5C处理下生长的幼苗均有恢复生长的作用,且幼苗株高/茎粗比明显优于对照和其它处理,该浓度可望有效避免幼苗徒长。【结论】高营浓度养液通过改变幼苗内源激素的动态平衡,特别是促进ABA的合成和积累,从而抑制幼苗下胚轴皮层细胞伸长生长,有效制御幼苗徒长。灌施高浓度营养液对黄瓜、番茄幼苗下胚轴伸长的抑制作用可以通过降低营养液浓度而得到解除,这种防治幼苗徒长的操作方法简便易行,具有潜在的应用前景,但在不同品种蔬菜幼苗生长过程中,最优化的营养液施用浓度及其影响机制尚需进一步研究分析。     

作物轮作对土壤中烟草青枯菌数量及发病的影响

为查明春烟换茬后青枯菌在土壤中的消长规律, 采用接种耐药性青枯菌的盆土种植烟草, 烟草枯死后种植不同轮作作物的方法, 研究不同作物对土壤中青枯菌数量及其越冬状况的影响。设茄子、大豆、花生、甘薯、大蒜、玉米、晚稻和双季稻8 个轮作物处理, 后作生长期间定期取样, 用含利福平的选择性培养基检测样品中的青枯菌数量。结果表明, 栽后第4 周起秋茄子和秋大豆根中皆测出青枯菌, 秋茄子根达10⁶ cfu·g^-1;晚稻和秋花生根只第2 周和第8 周测出带菌。秋茄子、秋大豆、秋花生和晚甘薯生长期间土壤皆测出青枯菌,数量先降后升至10⁴~10⁶ cfu·g^-1; 晚稻和秋玉米土壤中青枯菌数量持续下降; 大蒜处理先测出带菌后未测到。冬季对水稻残桩青枯菌数量监测显示, 稻桩根和土壤中青枯菌数量先后出现峰值, 分别达1.00×10⁵ cfu·g^-1 和5.17×10⁴ cfu·g^-1; 发现病菌能在稻根变黑腐烂时增殖。翌年春季从茄子、大豆、花生和甘薯茬口土壤中测出遗留青枯菌数量皆达10⁴ cfu·g^-1, 玉米为10³ cfu·g^-1。烟草移栽后青枯病调查表明, 不同处理发病迟早取决于茬口土壤中菌源数量, 两者相关系数r 为0.908 9。不同茬口土壤发病轻重有显著差异, 茄子茬土发病最重,病情指数100, 大豆和大蒜茬土发病略重于花生、甘薯和玉米茬土; 晚稻茬土发病最轻, 病情指数16.7, 与茄子茬土相比发病期推迟20 d, 病情指数下降83.3%; 双季稻茬土未见发病, 证明烟稻轮作对青枯病有较好的控制效果。     

Suppression of rice blast,cabbage black leaf spot,and tomato bacterial wilt diseases by Meyerozyma guilliermondii TA-2 and the nature of protection

This study was conducted to evaluate the efficacy of yeast strain TA-2 for controlling rice blast, cabbage black leaf spot, and tomato bacterial wilt diseases. Microscopic and phylogenetic analyses based on rDNA-internal transcribed region (ITS) and rDNA-D1/D2 sequences indicated that yeast strain TA-2 is Meyerozyma guilliermondii. Pretreatment with TA-2 by soil drenching significantly reduced the severity of black leaf spot disease caused by Alternaria brassicicola and leaf blast disease caused by Magnaporthe oryzae. Symptom development of tomato bacterial wilt caused by Ralstonia solanacearum in both soil drench and needle inoculation tests was significantly reduced in TA-2-pretreated plants under soil drenching. Disease severity and R. solanacearum growth were significantly reduced in tomato plants pretreated with yeast culture, cell suspension, or culture filtrate of TA-2 under soil drenching. TA-2 does not produce antibiotics. The present study indicates that disease suppression is systemic, as the roots were treated with TA-2 and the pathogens were inoculated onto leaves or stems, thereby separating the two spatially. M. guilliermondii TA-2 could become a promising natural antimicrobial agent against rice blast, cabbage black leaf spot, and tomato bacterial wilt diseases and might be useful as an eco-friendly control measure, contributing to sustainable agriculture.     

Acute and chronic effect of copper on levels of reduced and oxidized glutathione and nutrient uptake of tomato plants

Phytotoxicity due to copper (Cu) is generally associated with visible symptoms such as a decrease in plant shoot and root growth and chlorosis. The application of low levels of Cu or plant exposure to the metal for short periods can affect several cell processes, involving changes in the levels of metabolites related to the plant antioxidative response. The purpose of this study was to compare the response of the reduced and oxidized glutathione system and Cu uptake in tomato plants exposed to phytotoxic levels of Cu in hydroponic culture. Attention was centered on establishing whether determination of the levels of both peptides in plants exposed for a short period of time (acute treatment) compared with exposure for an extended period (chronic treatment) could be used as an early indicator of Cu stress in tomato plants. For the acute treatment, the plants were exposed to 0.4, 9, and 36 μM Cu for 48 h, and for the chronic treatment to 0.4, 3, and 12 μM Cu for 28 d. Results indicate that plants subjected to the chronic treatment showed toxicity symptoms, among them chlorosis and a drastic decrease of the aerial part and root biomass, an effect that was not observed in the plants subjected to the acute treatment. Moreover, Cu applied to the plant, either in the acute or in the chronic treatment, modified the levels of reduced and oxidized glutathione in shoots and roots. The most noticeable effect was observed on the concentration of reduced glutathione in roots, where the concentration of this peptide decreased as the Cu concentration increased, and this effect was independent of the morphological changes undergone by the root and of the time of Cu application. The similarity of the responses to the acute and the chronic treatments indicates that assessment of the redox state of glutathione in the roots of plants exposed to copper, especially the change in levels of reduced glutathione, may represent a good indicator of the early plant response to stress due to excessive Cu supply.     

Effect of salt stress on tomato plant and the role of calcium

Abstract

Salinity is one of the serious abiotic stresses that has adverse effects on plant growth. The aim of this study was to investigate the effect of sodium chloride (NaCl) on germination and growth parameters of tomato plant as well as the role of Ca²⁺as an ameliorating agent. 100?mM NaCl and two concentrations of calcium (5 and 10?mM) were applied to tomato seeds and seedlings. This study was carried out in a Completely Randomized Design (CRD) with a total of six treatments each comprising of three replicates. The application of 100?mM of NaCl delayed the germination time by 27.6%, reduced the seedling length and seedling vigor by 24.33% and germination stress tolerance by 27.6% as compared to control. Salinity also reduced the plant growth (root and shoot length, root fresh and dry weight, shoot fresh and dry weight, membrane stability, relative water content and leaf area), whereas the application of calcium mitigated the negative effects of salinity on germination and growth to a greater extent. With increased calcium concentration, growth and germination increased significantly both alone and in the salt-affected plant. 10?mM calcium showed best results and enhanced the promptness index by 20.7%, seedling length and vigor by 15.1% and GSI by 20.7%. It also improved root fresh and dry weight, shoot fresh and dry weight, relative water content and leaf area. Similarly, 5?mM calcium also increased plant height and membrane stability index. The present study suggests that application of Ca²⁺ enhanced the growth of tomato plant under saline conditions.     

二氧化碳施肥对番茄幼苗生长与养分吸收利用的影响

Exposing tomato seedlings to elevated CO2 concentrations may have potentially profound impacts on the tomato yield and quality. A growth chamber experiment was designed to estimate how different nutrient concentrations influenced the effect of elevated CO2 on the growth and nutrient uptake of tomato seedlings. Tomato (Hezuo 906) was grown in pots placed in controlled growth chambers and was subjected to ambient or elevated CO2 (360 or 720 μL L-1), and four nutrient solutions of different strengths (1/2-, 1/4-, 1/8-, and 1/16-strength Japan Yamazaki nutrient solutions) in a completely randomized design. The results indicated that some agricultural characteristics of the tomato seedlings such as the plant height, stem thickness, total dry and fresh weights of the leaves, stems and roots, the G value (G value = total plant dry weight/seedling age),and the seedling vigor index (seedling vigor index = stem thickness/(plant height × total plant dry weight) increased with the elevated CO2, and the increases were strongly dependent on the nutrient solution concentrations, being greater with higher nutrient solution concentrations. The elevated CO2 did not alter the ratio of root to shoot. The total N, P, K, and C absorbed from all the solutions except P in the 1/8- and 1/16-strength nutrient solutions increased in the elevated CO2 treatment. These results demonstrate that the nutrient demands of the tomato seedlings increased at elevated CO2 concentrations.     

土壤中钙、氮含量对番茄枯萎病抗性的影响

采用土培的方法,研究土壤中钙、氮含量对番茄接种枯萎病病原菌后其体内有效钙含量、干物质重及番茄抗病指标变化的影响。结果表明,接种病原菌后各处理番茄病情指数、叶片组织苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)、过氧化物酶(POD)和过氧化氢酶(CAT)活性、丙二醛(MDA)和细胞膜透性均显著提高,以土壤有效钙为241.36 mg·kg-1、碱解氮为553.63 mg·kg-1条件下番茄有效钙含量及干物质重较高,病情指数较低、4种防御酶活性增加幅度较大且峰值较高,丙二醛和细胞膜透性较低,氮含量随土壤碱解氮的增加而增加。因此,在土壤碱解氮过多处理中施入适量钙肥可以缓解其对番茄抗枯萎病的抑制作用,提高钙素有效性,使番茄具有较高抗枯萎病能力。