Recruitment potential of a green alga Ulva flexuosa Wulfen dark preserved zoospore and its development

The recruitment potential and the ability of Ulva flexuosa Wulfen zoospores to survive darkness were tested under different conditions in the present study. The dark preserved zoospore was cultured under a two-factor experimental design to test the effect of salinity and nitrate, effect of salinity and phosphate, effect of light and salinity, and effect of light and phosphate. The recruitment (germination and growth) of zoospores was significantly affected by light and salinity. The nitrate concentration of 20 μmol.l(-1) was found to initiate the process of germination and its subsequent growth and, its effect appeared greatest under 25 psu condition. While nitrate enhances the growth of biomass more than phosphate, both show a positive interactive effect on biomass increase when crossed with salinity. The combined effect of 25 psu salinity and 8 μmol.l(-1) phosphate exhibited higher biomass growth. There was a significant effect of light and salinity on the biomass of zoospore, though there was no significant interaction between the two factors. There was an increase in biomass of growing zoospores to increase in light intensity and 80 μmol.m(-2).s(-1) of light intensity was considered optimal. Similarly, high light intensity condition favored higher biomass growth and there was significant interaction between light (80 μmol. m(-2). s(-1)) and phosphate (4 μmol. l(-1)) in high salinity (35 psu) condition. The result of this study showed that dark preserved zoospores of U. flexuosa have the potential for recruitment and it gives us an understanding how different factors play a role in the process of recruitment.     

Carbon source dependent somatic embryogenesis and plant regeneration in cotton, Gossypium hirsutum L. cv. SVPR2 through suspension cultures

Highly reproducible and simple protocol for cotton somatic embryogenesis is described here by using different concentrations of maltose, glucose, sucrose and fructose. Maltose (30 g/l) is the best carbon source for embryogenic callus induction and glucose (30 g/l) was suitable for induction, maturation of embryoids and plant regeneration. Creamy white embryogenic calli of hypocotyl explants were formed on medium containing MS basal salts, myo-inositol (100 mg/l), thiamine HCI (0.3 mg/l), picloram (0.3 mg/l), Kin (0.1 mg/l) and maltose (30 g/l). During embryo induction and maturation, accelerated growth was observed in liquid medium containing NH3NO4 (1 g/l), picloram (2.0 mg/l), 2 ip (0.2 mg/l), Kin (0.1 mg/l) and glucose (30 g/l). Before embryoid induction, large clumps of embryogenic tissue were formed. These tissues only produced viable embryoids. Completely matured somatic embryos were germinated successfully on the medium fortified with MS salts, myo-inositol (50 mg/l), thiamine HCl (0.2 mg/l), GA3 (0.2 mg/l), BA (1.0 mg/l) and glucose (30 g/l). Compared with earlier reports, 65% of somatic embryo germination was observed. The abnormal embryo formation was highly reduced by using glucose (30 g/l) compared to other carbon sources. The regenerated plantlets were fertile but smaller in height than the seed derived control plants.     

Effect of alar and CCC on induction and germination of bulbils in <Emphasis Type="Italic">Curculigo orchioides</Emphasis> grown in shake flask cultures

Bulbil formation in Curculigo orchioides is followed by asynchronous germination. The effect of alar and CCC incorporated in Murashige and Skoog (MS) medium has been studied on bulbil induction from leaf explants and subsequent germination of bulbils. MS medium contained 1 mg/l BA and 0.1 mg/l morphactin for bulbil induction while germination medium contained 1 mg/l gibberrelic acid and both the media contained alar or CCC (0.5–5.0 mg/l). Growth retardants markedly reduces the bulbil formation, yield and fresh weight of bulbils. Incorporation of retardants resulted in 60% germination inhibition, thereby prolonging the storage conditions.     

Lipid turnover during morphogenesis in the water mold Blastocladiella emersonii

The lipid content of $\text{Blastocladiella emersonii}$ zoospores is 5 pg/cell or about 13% of dry weight. Within the first few minutes of germination 60–70% of total zoospore lipid is lost, with neutral lipid, glycolipid and phospholipid fractions decreasing to about the same extent. These changes in lipid content precede the breakdown during germination of the complex and extensive membrane system of zoospores. During growth, which immediately follows germination, net phospholipid synthesis resumes so that total lipid is maintained at 6% of dry weight, but net synthesis of neutral and glycolipid does not begin until induction of sporulation. During sporulation the phospholipid level decreases so that the distribution of lipid among the three fractions approaches that found in zoospores. These changes in lipid content suggest that zoospore membranes containing neutral and glycolipids are synthesized $\text{de novo}$ during spore formation.     

大花斑叶兰种子无菌萌发及快繁技术研究

对大花斑叶兰（Goodyera biflora）成熟种子无菌萌发、原球茎分化及根诱导进行了研究。结果表明：黑暗或弱光照培养有利于大花斑叶兰种子萌发,而较强的光照对形成健壮的原球茎有利;1/2MS＋NAA0.2mg/L培养基较为适合大花斑叶兰种子的萌发;MS＋KT1.0mg/L＋NAA0.5mg/L＋活性炭2.0g/L对原球茎增殖形成类原球茎有较好效果;1/2MS＋6-BA2.0mg/L＋NAA0.5mg/L＋2.0g/L活性炭对根诱导效果较为理想。     

Hg浸种对玉米种子萌发过程中几种酶活性的影响

1　引　　言Hg是环境污染的重要因素,有关Hg对植物生长发育的影响及危害机制已有报导[1,3],但Hg对玉米种子萌发作用尚未见报道.种子萌发依靠自身储存的淀粉、脂肪和蛋白质的分解来提供物质和能量,合成新的生命物质.因此环境对种子萌发的影响首先表现在对这些大物质分解代谢的影     

野生毛葡萄远缘杂交后代离体培养研究

以MS、1/2MS、GS三种培养基为基本培养基,以及在1/2MS培养基上分别附加6-BA 1.0mg/L+IAA 0.1mg/L和6-BA 1.0mg/L+NAA 0.1mg/L两组植物生长调节剂,对野生毛葡萄及其远缘杂交种后代213、741、196、296、B₂等6个品种(种类)进行茎段腋芽萌发离体培养试验。结果表明:1/2MS培养基为基本培养基最适宜茎段腋芽的诱导萌发;NAA对毛葡萄及其杂交种后代的萌芽生长影响明显,若单独使用,对绝大多数品种的茎段腋芽萌发有明显的抑制作用,与IAA交替使用,则对茎段腋芽萌发有促进作用。     

阔鳞鳞毛蕨孢子的无菌繁殖

以阔鳞鳞毛蕨（Dryopteris championii）成熟孢子为外植体,研究了不同植物生长调节剂及浓度对其孢子萌发、愈伤组织诱导、丛生芽分化及生根的影响。结果表明：1/2MS＋2%蔗糖为孢子萌发最适培养基,20 d后萌发率达65%;诱导愈伤组织的最适培养基为MS＋KT 0.5 mg.L-1＋2,4-D 1 mg.L-1,诱导率达39.8%,愈伤组织为绿色颗粒状;颗粒状愈伤组织在MS＋KT0.2 mg.L-1的培养基中生长出大量丛生芽,转化率可达66.3%;MS＋IAA 0.2 mg.L-1＋NAA 0.2 mg.L-1培养基可有效促进幼孢子体苗生根。     

仙鹤藓的孢子萌发及愈伤组织诱导

通过对采自河北雾灵山海拔1500m的仙鹤藓（Atrichum undulatum）的孢子萌发以及原丝体发育的观察,发现仙鹤藓孢子无休眠现象,孢子接种3天左右萌发：其原丝体发育分为绿丝体和轴丝体两个阶段。扩大培养实验结果表明。仙鹤藓茎叶体在添加2％葡萄糖的MS培养基上,置于25℃／20℃、14小时光照/10小时黑暗、36μmol·m^-2·s^-1条件下培养．产生新生茎叶体最多,且茎叶体长势最好,可以获得大量无菌材料。仙鹤藓愈伤组织诱导实验显示,形成愈伤组织的最佳培养基为添加2％葡萄糖和1．0mg·L^-16-BA的MS培养基。     

Some effects of differently-acting nematicides on the cereal cyst-nematode (Heterodera avenae) and on the appearance of ''scorch'' in spring wheat on light loamy sand

In fungitoxicity tests against Phytophthora cinnamomi on Chamaecyparis lawsoniana cv. Ellwoodii, a drench of furalaxyl (1000 mg a.i./l) applied to the compost in which 1-yr-old plants were growing, 1 wk before they were inoculated with 650 000 zoospores, controlled disease for at least 12 months. With an inoculum dose of 650 zoospores/plant, furalaxyl at 500 mg a.i./l controlled disease even when inoculation was 12 wk after fungicide treatment. Aluminium tris (ethyl phosphonate) (2000 mg a.i./l) applied as a drench 1 wk before inoculation with 650 000 zoospores/plant did not prevent root infection but delayed foliar symptoms for 9 months: the same treatment, using etridiazole (500 mg a.i./l) only slightly reduced disease incidence. When applied as a single drench 2 days before inoculation, prothiocarb (2000 mg a.i./l) and cuprammonium compounds (200 mg a.i./l) were much less effective than furalaxyl (1200 mg a.i./l), sodium ethyl phosphonate (1500 mg a.i./l), aluminium tris (ethyl phosphonate) (1500 mg a.i./l) or etridiazole (500 mg a.i./l). However, a drench of furalaxyl at 1000 mg a.i./l, aluminium tris (ethyl phosphonate) at 2000 mg a.i./l or etridiazole at 500 mg'a.i./l did not eradicate P. cinnamomi from compost containing infected root debris. Pre-planting drenching of the compost was ineffective. All fungicide treatments were non-phototoxic to 1-yr-old C. lawsoniana cv. Ellwoodii. These results are of special relevance to the control of P. cinnamomi on container-grown woody ornamentals.     

Optimization of germination,callus induction,and cell suspension culture of African locust beans Parkia biglobosa (Jacq.) Benth

The present study was carried out to determine the best pre-sowing treatments that can enhance the germination and seedling growth of Parkia biglobosa (Jacq.) Also, to establish and long-term maintenance of calli and cell suspension cultures . The result of various pre-sowing treatments showed that seeds soaked in concentrated H₂SO₄ treatment appeared the highest germination percentage, higher value of plant height, number of leaves, number of branches and stem girth. The MS medium containing 1mg/l 2, 4-D was the best for callus induction of stem explants. The addition of 50 mg /l citric acid to the MS medium was effective for reducing browning of callus than other treatments. However, the viability percent recorded the maximum (87.76%) on the 9^th day while the concentration of viable cells per ml reached the higher record (137.5 viable cell/ml) at the 12^th and cell viability remains (≈ 68.39%) throughout 18 days of culture     

Host-specific plant signal and G-protein activator, mastoparan, trigger differentiation of zoospores of the phytopathogenic oomycete Aphanomyces cochlioides

We found that the gradient of a host-specific attractant, cochliophilin A (5-hydroxy-6,7-methylenedioxyflavone) isolated from the roots of spinach triggered encystment followed by germination of zoospores of Aphanomyces cochlioidesat a concentration less than micromolar order. This compound did not affect the growth and reproduction of this phytopathogen up to 10^–6 M concentration in the culture medium. We also observed that mastoparan, an activator of heterotrimeric G-protein could inhibit the motility of zoospores and then strikingly effect encystment followed by 60–80% germination of cysts. Concomitant application of cochliophilin A and mastoparan showed stronger encystment followed by 100% germination of cysts. In addition, we have observed that chemicals interfering with phospholipase C activity (neomycin) and Ca²⁺ influx/release (EGTA and loperamide) suppress cochliophilin A or mastoparan induced encystment and germination. These results suggest that G-protein mediated signal transduction mechanism may be involved in the differentiation of the A. cochlioides zoospores. This is the first report on the differentiation of oomycete zoospores initiated by a host-specific plant signal or a G-protein activator.     

Effect of organic pollutant treatment on the growth of pea and maize seedlings

This study confirmed the considerable effect of polycyclic aromatic hydrocarbon fluoranthene (FLT; 0.01, 0.1, 1, 4 and 7 mg/l) exposure on the germination of seeds, growth and root morphology of seedlings in Zea mays and Pisum sativum. Seed germination was significantly inhibited at FLT≥0.01 mg/l in maize and at ≥1 mg/l in pea. The amount of released ethylene after 3 days of germination was significantly increased in both species at FLT≥0.1 mg/l. After 7 days of seedling cultivation a significant decrease in the dry weight of roots and shoots occurred in maize at FLT≥0.1 mg/l while in pea similar effect was observed at ≥1 mg/l. The total length of primary and lateral roots was significantly reduced by FLT≥1 mg/l in maize and by 4 and 7 mg/l in pea. The length of the non-branched part of the primary root was significantly reduced by FLT≥0.1 mg/l in maize and ≥0.01 mg/l in pea. In both species the number of lateral roots was significantly increased at FLT≤1 mg/l and inhibited at concentrations of 4 and 7 mg/l. Fluoranthene content in roots and shoots of both species positively correlated with the FLT treatment.     

Isolation and identification of N-mercapto-4-formylcarbostyril, an antibiotic produced by Pseudomonas fluorescens.

Pseudomonas fluorescens strain G308 isolated from barley leaves produces a novel antibiotic substance that was purified by preparative TLC and HPLC and identified as N-mercapto-4-formylcarbostyril (Cbs) by LC/DAD, IR, LC-ES(+)/MS, LC-ES(-)/MS, GC-EI/MS, LC-HRES(+)/MS, mass isotope ratios analysis, 1H NMR and 13C NMR analysis. The purified new antibiotic compound is effective against many phytopathogenic fungi in vitro. The compound inhibited at 25 ppm spore germination and germ tube growth of the following fungi; Fusarium oxysporum f. sp. lycopersici, Fusarium culmorum, Cladosporium cucumerinum and Colletotrichum lagenarium. At concentrations up to 125 ppm, the compound did not interfere with release of zoospores from sporangia and germination of encysted zoospores of Phytophthora infestans.     

Influence of genotype, growth regulators, sucrose level and preconditioning of donor plants on flax (Linum usitatissimum L.) anther culture

The effect of genotype, growth regulators and preconditioning of donor plants on callus induction in anther culture of flax was investigated. Anthers were cultured on modified MS medium supplemented with five different combinations of plant growth regulators. The results suggested that specific combinations of growth regulators must be designed for each genotype. Major differences between the present results and previous reports are discussed. The influence of sucrose concentration was also investigated. For flax cultivar, 'Mikael', callus induction was higher in medium supplemented with 1 mg l(-1) BAP and 2 mg l(-1) 2,4D containing 6% sucrose, while this combination of growth regulators significantly increased callogenesis in cultivars 'Lirina', 'Barbara' and 'Szaphir' when supplemented with 9% or 12% sucrose. The preconditioning of donor plants influenced callogenesis in subsequently isolated anthers. Anthers from donor plants grown at a lower temperature (18/14 degrees C) significantly increased callus induction over those from plants grown at a higher temperature (22/18 degrees C), although each genotype still required optimization of growth regulator combinations in the induction medium. Only 'Mikael' regenerated shoots when the callus was from induction medium supplemented with 2 mg I(-1) BAP and 1 mg l(-1) NAA.     

虎尾兰水提取物对黄瓜霜霉病的防治研究

明确虎尾兰水提取物对黄瓜霜霉病菌无性阶段的抑制作用及对黄瓜霜霉病的防治效果。采用凹玻片法和离体叶五点接种法分别测定该提取物对游动孢子的释放和游动、休止孢的萌发和芽管伸长以及菌丝生长和孢子囊产生的抑制作用,采用离体叶五点接种法测定该提取物的保护作用、治疗作用和持效期,并采用盆栽试验测定该提取物的保护作用和治疗作用。一系列试验结果显示,虎尾兰水提取物对黄瓜霜霉病菌游动孢子的释放和游动,休止孢的萌发和芽管伸长以及菌丝生长和孢子囊产生的EC₅₀值分别为1.19、0.77、0.70、2.13、9.09和13.15 mg/mL。在离体叶片条件下,虎尾兰水提取物对黄瓜霜霉病的保护和治疗作用的EC₅₀值分别为3.69 和14.57 mg/mL,持效期达14 d以上。盆栽条件下,该提取物对黄瓜霜霉病保护作用和治疗作用的防效分别为68.38%和21.33%。虎尾兰水提取物对黄瓜霜霉病具有很好的保护作用和较长的持效期。     

球子蕨孢子的无菌繁殖

以球子蕨成熟孢子为外植体,研究了不同激素及浓度对其孢子萌发、愈伤组织诱导、丛生芽分化及生根的影响。结果表明：孢子萌发最适培养基为1／2MS＋2％蔗糖,20d后萌发率达55．7％;诱导愈伤组织的最适培养基为MS＋0．5mg·L-1 KT＋0．5mg·L～2,4-D,诱导率达36％,愈伤组织为绿色颗粒状;颗粒状愈伤组织在不添加激素的MS培养基中即可生长出大量丛生芽,转化率可达49．3％;低浓度（0．2mg·L-1）的IAA可有效促进幼孢子体苗生根。     

Nicotinamide and structurally related compounds show halting activity against zoospores of the phytopathogenic fungus Aphanomyces cochlioides

In a survey of plant secondary metabolites regulating the behavior of phytopathogenic Aphanomyces cochlioides zoospores, we found that leaf extracts of Amaranthus gangeticus and cotyledon extracts of pea (Pisum sativum) remarkably halted the motility of zoospores. Bioassay-directed fractionation of A. gangeticus and pea constituents revealed that the halting activity was dependent on a single chemical factor (halting factor). The active principle was identified as nicotinamide (1) by comparing its biological activity and spectroscopic properties with those of the authentic compound. Nicotinamide (1) showed potent halting activity toward the zoospores of A. cochlioides and A. euteiches, but it exhibited very less activity against other Oomycetes, Pythium aphanidermatum and Phytophthora infestans zoospores. Interestingly, the zoospores halted by nicotinamide (1) encysted within 10-15 min and then the resulting cystospores regenerated zoospores instead of germination. Nicotinamide (1) and related compounds were subjected to the halting activity bioassay to elucidate the structure-activity relationships. These bioassays revealed that part structures of (A) the aromatic ring containing at least one nitrogen atom, (B) carbonyl-like group adjacent to the aromatic ring and (C) hydrogen atoms on the amide group are responsible for the strong activity. So far, this is the first report of halting activity of nicotinamide (1) against fungal zoospores.     

Protein degradation and protease activity during the late cycle of Blastocladiella emersonii

Analysis of protein degradation during the life cycle of Blastocladiella emersonii showed that (i) protein degradation is especially high during two phases of differentiation (sporulation, 12%/h and germination, 5%/h) in contrast with a much smaller degradation rate in the other phases (growth and zoospores, less than 1%/hr); (ii) protein degradation during germination in growth medium, as well as most of the germination process, is quantitatively unaffected by cycloheximide; (iii) a caseinolytic protease (pH optimum 5.5, apparent molecular weight 55,000 to 60,000) is present in extracts of zoospores and germinating cells; (iv) this protease activity is very low (perhaps absent) in extracts of late growth phase cells, but reappears during induced sporulation; (v) a different class of caseinolytic protease activity (pH optima 7 and 10; apparent molecular weight 25,000 to 30,000) is found in cellular extracts of late growth phase and early phases of sporulation; (vi) the latter class of enzyme activity is released into the medium during later phases of sporulation and is replaced in the cells by the former class. Speculations as to the roles of protein degradation in cell differentiation are discussed.