Emergence, Growth and Nutrient Composition of Sugarcane Sprouts Under NaCl Salinity

The changes induced by 80 and 120 mM NaCl during emergence and growth of sprouts in salt-tolerant (CPF-213) and sensitive (L-116) genotypes of sugarcane were determined. The rate and percentage of emergence of sprouts, length and dry mass of shoot and root, and number of nodal roots decreased under salinity. Concentrations of Na and Cl increased and those of K, Ca, N and P decreased with a rise in substrate salinity. A greater salinity tolerance ability of CPF-213 than L-116 was attributable to greater root mass and higher nutrient concentrations in the sprouts of the former genotype.     

Effects of low and high levels of magnesium on the response of sunflower plants grown with ammonium and nitrate

The effect of the nitrogen source (ammonium and nitrate) and its interaction with magnesium on various physiological processes was studied in sunflower plants (Helianthus annuusL.). Plants were grown in hydroponic culture with nitrate (5 mM) or ammonium (5 mM) and four concentrations of magnesium (0.1, 0.8, 5 and 10 mM). After 2 weeks, growth, gas exchange and fluorescence parameters, soluble carbohydrates, free amino acids, soluble protein and mineral elements were determined. Ammonium nutrition resulted in a reduction of dry matter accumulation, as well as in a decrease in the CO₂ assimilation. Moreover, ammonium-fed plants showed a greater content of free amino acids, soluble protein, Rubisco and anions, and a lower cation content, mostly Mg²⁺. The presence of high levels of Mg²⁺ in the nutrient solution containing NH₄ ⁺ resulted in a stimulation of growth and CO₂ assimilation to the levels observed in nitrate-fed plants. The lower photosynthetic rate of ammonium-fed plants grown with low level of magnesium does not seem to be due to a lower photosynthetic pigment content, or a deficiency in Photosystem II activity, or to lower Rubisco content. Hence, Rubisco activity or other enzymes involved in CO₂ fixation could have been affected in ammonium-fed plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Boron Increases Synthesis of Glutathione in Sunflower Plants Subjected to Aluminum Stress

Ionic stress caused by high aluminum (Al) concentrations is one of the most widespread phytotoxicity problems globally in agricultural regions, greatly limiting crop yield in affected areas. The objective of this work was to examine a possible involvement of boron (B) in the detoxification of Al by stimulating glutathione (GSH) metabolism, a mechanism essential for the resistance of plants under stress conditions. Our results clearly demonstrate that increased application of B in the presence of high Al concentrations in the growth medium stimulates GSH biosynthesis, suggesting it could be an effective strategy to combat stress associated with the formation of active-oxygen species (AOS). In the specific case of Al toxicity, B reduces phytotoxicity by stimulating leaf biosynthesis of GSH and an increase in its concentration in the roots. Therefore, in this work, we also identify GSH metabolism as one of the key processes in Al detoxification. Finally, our results imply that greater B application leads to a greater resistance to Al toxicity, a fact that might be significant for higher productivity of agricultural plants grown in acid soils.     

Changes in polyamines,proline and ethylene in sunflower calluses treated with NaCl

Responses of sunflower tissues to NaCl stress were studied in control (C), salt-stressed (S) and salt-adapted (T) calluses in terms of proline, polyamines and ethylene content for a period of 21 days. Salt-adapted calluses showed their adaptation to salinity by growing in the medium with 175 mM NaCl, at a similar rate than C calluses on medium without salt. Proline concentration was 27 times higher in salt-adapted calluses compared to control calluses at time 0, but salt stressed calluses (S calluses) were able to increase proline by day 21, demonstrating that proline was not just an osmoregulator but might be involved in other responses in sunflower salt-stressed calluses. Putrescine (Put) was the most abundant polyamine in C calluses at time 0, while spermidine (Spd) was the main polyamine in salt tolerant (T) calluses. Ethylene increased in C calluses until day 14, decreasing thereafter. In salt-adapted calluses, ethylene increased significantly over the concentration in C and S calluses by the end of the experiment. In control calluses, the highest level of total polyamines and the lowest of ethylene was found on day 21, while T calluses synthesized the highest ethylene level and had the lower polyamines level by this time. It seems that in salt-adapted calluses ethylene was related to stress tolerance and in salt sensitive tissues (S calluses), ethylene formation was related to senescence. The present data suggests a close relationship between proline, polyamines, ethylene and salt-stress tolerance in sunflower dedifferentiated tissues.     

Genetic studies on the acidification capacity of sunflower roots induced under iron stress

Under stress of iron deficiency roots of sunflower (Helianthus annuus L.) increase proton efflux which acidifies the root medium, increase the ferric reducing capacity and the exudation of phenolic compounds. Differences have been found previously among sunflower inbred lines in the capacity of their roots to lower pH and it was also found that this character is under genetic control.This work presents the results of an inheritance study made by crossing two genotypes, one (CMS HA 89) without acidification capacity and another (RHA 271) with it. Plants were grown individually in 75 mL vessels with an aerated solution low in iron. After 4 days, solutions were changed to one without iron and the pH of the medium was measured during the following days. Results from F₁, F₂, and backcross generations can be explained with two pairs of alleles controlling the character, being the relation between alleles of complete dominance at both gene pairs, but either gene, when dominant is epistatic to the other.     

向日葵AGO和DCL基因家族的鉴定和表达分析

为了解向日葵(Helianthus annuus)的Argonaute (AGO)和Dicer-like (DCL)的功能,利用拟南芥(Arabidopsis thaliana)的AGO和DCL基因序列在向日葵基因组数据库中进行同源比对,对向日葵AGO和DCL家族成员进行生物信息学分析。结果表明,从向日葵中鉴定到15个Ha AGOs和5个HaDCLs家族成员;这2类基因在染色体上的分布均不均匀。系统发育分析表明,与拟南芥相似,HaAGO家族成员可分为3个分支,HaDCL可分为4个分支;所有的HaAGO都具有保守的N domain、DUF1785、PAZ和PIWI结构域,Ha DCL家族成员都含有PAZ和RIBOc结构域。表达分析表明,Ha DCL3a和Ha DCL3b在茎和花序中高度表达;亚细胞定位表明Ha AGO多定位于细胞核。这表明向日葵中可能存在典型的RNAi干扰机制,并可能参与了协调向日葵的生长发育过程。     

Factors affecting nitrate reductase activity in some monocot and dicot species

Activity of nitrate reductase (NR), the first enzyme in the nitrate-assimilation pathway, was estimated in the cotyledons of the sunflower( Helianthus annuus) using a standardized in-vivo method. Seedlings were grown in the light on a nitrate medium. Various factors that affect NR activity were optimized, including the molarity and pH of the reaction buffer, nitrate concentration, and use of a surfactant. We also determined whether NADH was required for nitrate reduction. The surfactant propanol (2%) gave the best results, and no NADH supplement was necessary: In a separate study, we compared the effect of various culturing components on in-vivo NR activity among monocot and dicot species, and found that Triton X-100 was the best surfactant for monocots whereas dicots performed better with n-propanol. Monocot species also required additional NADH as an external energy source. Moreover, specific purification procedures were needed to enhance NR activity in dicotyledons. Finally, we also assessed the efficacy of in-vivo versus in-vitro procedures for assaying monocots versus dicots.     

Tissue culture and plant regeneration from sunflower (Helianthus annuus) and interspecific hybrids (H. tuberosus x H. annuus)

A method is described for the culture and regeneration of plants from callus of sunflower (Helianthus annuus) andH. annuus x H. tuberosus hybrids. Immature embryos proved to be the only explant which consistently gave regenerable cultures in all genotypes. The most responsive embryos were approximately 12 mm² in area. Genotype had a significant effect on the capacity of cultures to regenerate. Some regeneration was also obtained from cultures of tuber tissue but only from one genotype,H. tuberosus x H. annuus cross 200. None of theH. annuus accessions gave regenerable callus from root tissue. Difficulties included the premature initiation of flowering of regenerating shoots and the frequent occurence of "vitreous" plantlets which could not be transplanted successfully to soil. Some amelioration of both these problems was achieved by replacing inorganic nitrogen partially with amino acids. More effective reduction of these difficulties was accomplished by the addition of 10, 30 and 100 M phloridzin, esculin or naringin.Abbreviations BAP 6-benzylaminopurine; zeatin, trans-6-(4-hydroxy-3-methyl-but-2-enyl) aminopurine; kinetin, 6-furfurylaminopurine - IAA indole-acetic acid - NAA naphthyl acetic acid     

Effect of NaCl and Proline on Bean Seedlings Cultured in vitro

Effects of NaCl (150 mM), proline (10 mM) and their combination on growth and contents of chlorophyll, proline and protein of bean (Phaseolus vulgaris cv. Kizilhaç) seedlings in vitro were investigated. NaCl decreased seedling growth. Proline added to control seedlings did not change seedling growth but decreased chlorophyll and increased protein contents. When proline added to NaCl-treated seedlings growth was increased in comparison with NaCl-treated only. Thus, proline alleviated salinity stress in bean seedlings.     

Influence of genotype and gelling agents on in vitro regeneration by organogenesis in sunflower

Fourteen recombinant inbred lines of sunflower (Helianthus annuus L.) and their parents (PAC-2 and RHA-266) were tested for their organogenesis ability. Seeds were surface sterilized and germinated on hormone free half strength MS basal medium containing 10 g l^-1 sucrose solidified with five different gelling agents: Phytagar (Gibco laboratoires) 3 g l^-1, Phytagel (Sigma) 3 g l^-1, Agarose (Sigma) 5 g l^-1, Arcagel (Sigma) 4 g l^-1 and Agar-Agar (Fisher France) 7 g l^-1. Cotyledons from 2-day-old seedlings were split in half and the four explants of each seed were cultived in 55 mm diameter petri dishes containing 10 ml of MS medium supplemented with 50 μM KNO₃, 1 μM myo-inositol, 5 μM casein hydrolysate, 4.4 μM of BA and 5.4 μM of NAA solidified with the same gelling agents. The experimental design was a randomized complete block with 3 replications. A replicate for each genotype consisted of ten petri dishes containing four explants. The statistical analysis showed significant differences among genotypes and gelling agents. Of the fourteen recombinant inbred lines tested `C93' presented the highest values for all regeneration traits in the five different media and it was better than the best parent. Agarose and Agar-Agar were more better than other gelling agents for shoot induction. This revised version was published online in June 2006 with corrections to the Cover Date.     

Bacterial antagonists of Sunflower (Helianthus annuus L.) fungal pathogens

Bacteria isolated on nutrient agar and King's medium B from sunflower leaves, crown and roots inhibited in vitro growth of the leaf spot and wilt pathogens Alternaria helianthi, and Sclerotium rolfsii, respectively, and also the root rot pathogensRhizoctonia solani and Macrophomina phaseolina. Antagonistic bacteria from leaves were mainly actinomycetes and pigmented Gram-positive bacteria, while those from roots and crowns were identified asPseudomonas fluorescens-putida, P. maltophilia, P. cepacia, Flavobacterium odoratum andBacillus sp. In soil bioassays, when used as seed inoculum in the presence ofS. rolfsii, P. cepacia strain N24 increased significantly the percentage of seedling emergence. Bacterial strains which exhibited broad spectrum in vitro antagonistic activity were tested for colonisation of sunflower roots, when used as a seed inoculum. Good colonisers (10⁴ to 10⁶ bacteria/g root) were consistent in their ability to reduce disease and fungal wilt. A seedling having a primary root length < 5 cm with fewer lateral roots, necrosed cotyledons or crown and a wilted shoot indicated its diseased status. On an average, only 30% of seedlings were diseased when treated with the antagonistic strains, in the presence of the pathogen, while 60% of the seedlings were diseased in the presence of the pathogen alone. In microplots treated with strain N24, only 1 to 3% of the seedlings were wilted, while 14% of the seedlings were wilted in the presence of the pathogen alone. The results obtained show that bacterial antagonists of sclerotial fungi can be used as seed inocula to improve plant growth through disease suppression     

Effects of leaf position and nitrogen supply on the expansion of leaves of field grown sunflower (Helianthus annuus L.)

Leaf growth responses to N supply and leaf position were studied using widely-spaced sunflower plants growing under field conditions. Both N supply (range 0.25 to 11.25 g added N per plant) and leaf position significantly (p=0.001) affected maximum leaf area (LA_max) of target leaves through variations in leaf expansion rate (LER); effects on duration of expansion were small. Specific leaf nitrogen (SLN, g N m^-2) fell quite rapidly during the initial leaf expansion phase (LA < 35% LA_max) but leveled off during the final 65% increase of leaf area. This pattern held across leaf positions and N supply levels. Leaf nitrogen accumulation after 35% LA_max continued up to achievement of LA_max; reductions in the higher SLN characteristic of the initial phase were insufficient to cover the nitrogen requirements for expansion during the final phase. LER in the quasi-linear expansion phase (35 to 100% of LA_max) was strongly associated with SLN above a threshold that varied with leaf position (mean 1.79±0.225 g N m^-2). This contrasts with the response of photosynthesis at high irradiance to SLN, which has previously been shown to have a threshold of 0.3 g N m^-2; in the present work saturation of photosynthetic rate was evident when SLN reached 1.97 g N m^-2. Thus, once the area of a leaf exceeds 35% of LA_max, expansion proceeds provided SLN values are close to the levels required for maximum photosynthesis. However, growth of leaves during the initial expansion phase ensures a minimum production of leaf area even at low N supply levels.     

氮素营养对苗期菘蓝叶中硝酸还原酶活性与矿质元素吸收的影响

采用正交试验设计,研究铵态氮、硝态氮和酰胺态氮3种氮素形态及其不同浓度配比对苗期菘蓝的单株干重、叶内的硝酸还原酶活性及矿质元素吸收的影响。结果显示:(1)影响苗期菘蓝单株干重的氮素形态依次为酰胺态氮>铵态氮>硝态氮。(2)不同氮素形态对叶片硝酸还原酶活性影响有差异,铵态氮影响最大,其次是硝态氮和酰胺态氮。(3)不同形态氮素配合施用后均能促进P、K、Ca、Mg、Cd、Mn、Cr、Sr 8种元素的吸收,但不利于Ni和Fe的吸收;元素吸收受铵态氮影响最大的矿质元素有K、Ba、Se、Ni、B、Si、Fe 7种元素,受硝态氮影响最大的元素有P、Cd、Ti、Al、Cu 5种元素,受酰胺态氮影响最大的元素有Na、Ca、Mg、Zn、Mo、Mn、Cr、Sr 8种元素。研究表明,不同形态氮素对苗期菘蓝吸收矿质元素的影响存在很大的差异,应注重酰胺态氮与无机的铵态氮、硝态氮的配合施用;适宜氮素形态及其配比能提高叶中硝酸还原酶的活性并促进矿质元素的吸收,从而有效地促进菘蓝的生长。     

Isolation of HMW DNA from sunflower (Helianthus annuus L.) for BAC cloning

The cultivated sunflower (Helianthus annuus L.) is one of the most important oil crops in the world. The importance of sunflower oil in human nutrition and in the chemical industry makes the sunflower a major research interest. An essential element for genomic libraries is the preparation of high molecular weight (HMW) DNA. We developed 2 methods for isolating HMW sunflower DNA. We prepared the DNA from nuclei and from protoplasts isolated from mesophyll tissue with the enzymes cellulase RS and pectolyase Y23. The HMW DNA was digested with restriction endonucleases. The ethidium bromide-stained gel suggested the DNA to be completely digested. These results were confirmed by Southern analysis using a radiolabeled RFLP marker. Both methods made it possible to generate sufficient quantities of megabase-size sunflower DNA suitable for bacterial artificial chromosome (BAC) cloning.     

Effect of Short-Term Salinity on Lipid Metabolism and Ion Accumulation in Tomato Roots

To examine the ion accumulation and membrane lipid metabolism in response to salinity we compared two tomato cvs. Pera and Hellfrucht Fruhstamm (HF), considered to be salt-tolerant and sensitive respectively. Na⁺ and K⁺ accumulation was significantly higher in roots of cv. Pera after 24 h and 72 h of 100 mM NaCl. While in cv. HF, a temporary increase in K⁺ accumulation at 24 h was accompanied by a sustained increase in Na⁺ content. Both cultivars enhanced incorporation of [³²P]orthophosphate into phosphatidylinositol 4,5-bisphosphate at 24 h and 72 h of NaCl. In parallel to the increase of phosphatidylinositol 4,5-bisphosphate a decrease in phosphorylation of phosphatidic acid and phosphatidylcholine were observed in the sensitive cv. HF. Structural and signal lipid changes in response to salinity were more evident in the sensitive cv. HF. Salt tolerant cv. Pera accumulated Na⁺ ions in the roots without considerable modifications in lipid metabolism. This revised version was published online in July 2006 with corrections to the Cover Date.     

盐碱协同胁迫对向日葵抗氧化酶系统的影响

根据中国东北盐碱土壤特点,将4种盐NaCl、NaHCO3、Na2SO4和Na2CO3按不同比例混合,模拟出25种盐度和pH值各不相同的复杂盐碱条件(盐浓度为50～250 mmol/L,pH值为712～1046),并对向日葵苗进行盐碱混合胁迫处理,研究了向日葵超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)酶等抗氧化酶系统和丙二醛(MDA)的盐碱协同胁迫效应．结果表明, 向日葵抗氧化物酶活性强弱同时与盐度和碱度密切相关,3种抗氧化物酶活性对于盐浓度的反应相似,均为其含量随着盐浓度的升高开始逐渐升高然后下降,而对于pH的影响,不同酶反应结果不同．即随着pH值升高,SOD酶活性和CAT酶活性降低,而POD酶活性反应则是随着pH值升高活性也升高．双向方差分析(ANOVA)结果表明：盐碱效应对于3种酶活力的影响是显著的．其中,盐效应对POD和SOD活性的影响比pH值的影响大,而pH值对CAT活性的影响效应比盐效应大．除SOD外,盐碱效应的交互作用显著 (P<0001)．抗氧化酶系统和MDA含量两者间相关性和逐步回归分析表明,3种酶对MDA的影响效应随其强度不同呈现显著不同．其中SOD是1个主导因子,CAT 处于次位, 而POD的影响不大,甚至可以忽略．     

Changes in Activities of Antioxidant Enzymes in Sunflower Leaves of Different Ages

Role of superoxide dismutase isozymes and other antioxidant enzymes was studied in relation to leaf age in sunflower (Helianthus annuus L. cv. ACC 1508) at pre-flowering and grain filling stages. Relative water content (RWC) did not change much in leaves of different age and at the two stages. Protein content declined continuously from the youngest to the oldest leaf, while chlorophyll (Chl) and carotenoids (Car) contents increased down to 7^th/9^th leaf and declined in subsequent older leaves. Protein, Chl and Car contents were higher at pre-flowering than at seed filling stage. Superoxide dismutase (SOD), its isozymes, and ascorbate peroxidase (APO) and catalase (CAT) activities were highest in the 9^th leaf and declined in subsequent older leaves. SOD and APO activities were higher at seed filling, except in oldest senescent (13^th, 15^th) leaves. Among SOD isozymes, Cu/Zn-SOD and Mn-SOD activities accounted for most of the total SOD, and only marginal activity was observed for Fe-SOD. Peroxidase activity increased from youngest to the oldest leaf at pre-flowering stage and down to 13^th leaf at seed filling stage. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of denaturants on the oligomeric structure of the 11 S protein of sunflower (Helianthus annum)

The effect of sodium dodecyl sulphate, urea, guanidinium hydrochloride and heat on the oligomeric structure of the 11 S protein of sunflower has been determined. Sodium dodecyl sulphate directly dissociates the protein to 2 S subunits, whereas urea and guanidinium hydrochloride dissociate it through an intermediate 7 S protein. Heating the protein at 90‡C for 20 min caused dissociation of the 11 S protein, without any precipitation.