Oxidation of xenobiotics by plant microsomes, a reconstituted cytochrome P450 system and peroxidase: a comparative study

The microsomal fraction from tulip bulbs (Tulipa fosteriana, L.) contains cytochrome P450 (CYP3, EC 1.14.14.1) and peroxidase (EC 1.11.1.7.) enzymes catalyzing the NADPH--and hydrogen peroxide--dependent oxidation of the xenobiotic substrates, N-nitrosodimethylamine (NDMA), N-nitrosomethylaniline (NMA), aminopyrine and 1-phenylazo 2-hydroxynaphthalene (Sudan I), respectively. Oxidation of these model xenobiotics has also been assessed in a reconstituted electron-transport chain with a partially purified CYP fraction, phospholipid and isolated tulip NADPH:CYP reductase (EC 1.6.2.4.). Peroxidase isolated from tulip bulbs (isoenzyme C) oxidizes these xenobiotics, too. Values of kinetic parameters (Km, Vmax), requirements for cofactors (NADPH, hydrogen peroxide), the effect of inhibitors and identification of products formed from the xenobiotics by the microsomal fraction, partially purified CYP and peroxidase C were determined. These data were used to estimate the participation of the CYP preparation and peroxidase C in oxidation of two out of the four studied xenobiotics (NMA, Sudan I) in tulip microsomes. Using such detailed study, we found that the CYP-dependent enzyme system is responsible for the oxidation of these xenobiotics in the microsomal fraction of tulip bulbs. The results demonstrate the progress in resolving the role of plant CYP and peroxidase enzymes in oxidation of xenobiotics.     

Isolation of immunochemically distinct form of cytochrome P-450 from microsomes of tulip bulbs

A highly purified cytochrome P-450 was obtained from the microsomes of tulip bulbs (Tulipa gesneriana L.). The molecular weight (Mr = 52,500) and amino acid composition of this plant cytochrome P-450 are similar to those reported for rat livers. On the contrary, Ouchterlony double diffusion analyses indicated that cytochrome P-450 isolated from tulip bulbs shares no common antigenic determinants with those of 9 other plants, in spite of the presence of comparable contents of cytochrome P-450 and/or trans-cinnamate 4-monooxygenase with tulip bulbs.     

Isolation and characterization of 5-lipoxygenase from tulip bulbs

An unique membrane bound lipoxygenase was isolated and purified from purple star tulip bulbs with a specific activity of 5.2 mu moles O2 consumed.min-1.mg-1 protein. The purified tulip enzyme exhibits regiospecificity for O2 insertion at C-5 of the arachidonic acid molecule. Identification of the reaction product was confirmed as 5-hydroperoxyeicosatetraenoic acid by analytical criteria which included: cochromatography with the authentic compound, as well as mass spectral and 1H-NMR analysis. Thus, the enzyme from tulip bulbs appears to be different from the cytosolic lipoxygenase from potato tubers, which exhibits non-regiospecificity in terms of O2 incorporation. However, the purified tulip lipoxygenase showed a strong immunological crossreactivity with antiserum raised against the purified potato lipoxygenase, indicating close immunological relationship with the other plant lipoxygenases.     

Differential responses of tiger swallowtail subspecies to secondary metabolites from tulip tree and quaking aspen

Summary Two subspecies of the eastern tiger swallowtail butterfly, Papilio glaucus, exhibit reciprocal inabilities to survive and grow on each other's preferred foodplant. P. g. canadensis R. & J. performs well on quaking aspen (Populus tremuloides Michx.) but not on tulip tree (Liriodendron tulipifera L.); P. g. glaucus L. performs well on tulip tree but not on quaking aspen. This study was designed to test the hypothesis that secondary metabolites in tulip tree and quaking aspen are responsible for these differential utilization abilities. We extracted and fractionated leaf constituents into different chemical classes, applied them to a mutually acceptable diet (black cherry, Prunus serotina, leaves), and bioassayed them against neonate larvae (survival) and penultimate instar larvae (survival, growth, digestibility and conversion efficiencies). For each plant species, one fraction in particular showed activity against the unadapted subspecies. One tulip tree fraction dramatically reduced survival of P. g. canadensis neonates, and reduced consumption rates, growth rates, and ECI's of fourth instar larvae. The tulip tree constituents most likely responsible for these effects are sesquiterpene lactones. One quaking aspen fraction greatly lowered survival of P. g. glaucus neonates, and decreased survival, consumption rates, growth rates and ECD's of fourth instar larvae. The compounds responsible for these results are probably simple phenols or phenolic glycosides. Surprisingly, P. g. glaucus and P. g. canadensis showed slightly poorer performance on the active tulip tree and quaking aspen fractions, respectively, indicating that even adapted insects incur a metabolic cost in the processing of their host's phytochemicals.     

Biosynthesis of abscisic acid by the non-mevalonate pathway in plants, and by the mevalonate pathway in fungi

The biosynthetic pathways to abscisic acid (ABA) were investigated by feeding [1-(13)C]-D-glucose to cuttings from young tulip tree shoots and to two ABA-producing phytopathogenic fungi. 13C-NMR spectra of the ABA samples isolated showed that the carbons at 1, 5, 6, 4', 7' and 9' of ABA from the tulip tree were labeled with 13C, while the carbons at 2, 4, 6, 1', 3', 5', 7', 8' and 9' of ABA from the fungi were labeled with 13C. The former corresponds to C-1 and -5 of isopentenyl pyrophosphate, and the latter to C-2, -4 and -5 of isopentenyl pyrophosphate. This finding reveals that ABA was biosynthesized by the non-mevalonate pathway in the plant, and by the mevalonate pathway in the fungi. 13C-Labeled beta-carotene from the tulip tree showed that the positions of the labeled carbons were the same as those of ABA, being consistent with the biosynthesis of ABA via carotenoids. Lipiferolide of the tulip tree was also biosynthesized by the non-mevalonate pathway.     

Food choice from endemic North Carolina tree species by captive prosimians (Lemur fulvus)

Seven captive-born lemurs (Lemur fulvus) at the Duke University Primate Center were presented with leaves of different maturity from five species of North Carolina trees. The animals demonstrated three distinct behaviors toward the novel plant material. They sniffed, tasted, and/or ingested it. New leaves were sniffed, but little tasting and ingestion was observed. Intermediate pine needles were sniffed and ingested but little tasted. Mature leaves were sniffed equally, but the mature leaves of tulip trees and honeysuckle were tasted significantly more than pine, sweetgum, and red maple. Pine, sweetgum, and red maple were ingested significantly more than tulip trees and honeysuckle. Male lemurs ate significantly more mature pine needles and new sweetgum leaves than did the females. Chemical analysis of these plant materials indicated that the new and mature leaves of tulip tree and honeysuckle contained alkaloids. Captive-born lemurs apparently use their sense of smell and taste in choosing what to eat and seem just as capable as free-ranging animals in finding food when faced with the chemical defenses that protect trees from insect predation.     

Developmental changes and tissue distribution of lectin in Tulipa

A sensitive enzyme-immunoassay was developed to quantify the tulip lectin and used to follow its distribution during the life cycle of tulips cv. Attila.The tulip lectin is predominantly located in the bulbs. At planting time the absolute lectin concentration is approximately the same in all bulb scales. However, as the shoot grows and the plant turns on to flowering, the lectin concentration rapidly decreases, first in the inner bulb scales but later also in the outer bulb scale. Soon after flowering the lectin rapidly accumulates in the new daughter bulbs.Lectin levels in leaves, stems and flowers are very low. The lectin in these tissues is already present before the sprout emerges. During the first two weeks after planting, there is a small increase in lectin concentration, followed by a rapid decrease as the plant turns on to flowering. By flowering time all the lectin has disappeared from the aerial parts.Abbreviations DW dry weight - ELISA enzyme-linked immunosorbent assay - FW fresh weight - PBS phosphate-buffered saline - PBSN phosphate-buffered saline containing 0.02% sodium azide - PBST phosphate-buffered saline containing 0.02% sodium azide and 0.05% Tween 20 - TL tulip lectin - Tris 2-amino-2-(hydroxymethyl)-1,3-propanediol     

Comparing the Effects of Rust on Plot Yield, Plant Yield, Yield Components, and Vegetative Parts of Soybean

To determine the plant variable for coupling a disease model to a soybean growth model, effects of soybean rust (caused by Phakopsora pachyrhizi) on soybean were quantified at four levels: vegetative parts, yield components, plant yield, and plot yield. Path analysis was conducted to determine the most correlated components to disease in each level. The responses of vegetative parts, such as shoot weight and branches/plant, to disease effects were inconsistent among cultivars. Yield components responded consistently to disease effects among the cultivars, indicated by the high values of correlation coefficients between disease and the components. Path coefficients indicated that reduction of 100-seed weight was the most important cause of yield loss in this level. No significant within-plant compensation was detected using path coefficient analysis except for that between pod length to pod width. The most consistent response to disease effect was at population level. Correlation of disease to plant yield was as significant as these to plot yield. Correlations between disease and these plant levels were in the order of plot yield, plant yield, yield components, and vegetative parts. Regression between plot yield and green leaf area duration (GLAD) from flowering to seed full size was highly significant (P < 0,001). This study suggests that green leaf area at population level was the best variable for coupling disease model to crop model.     

Changes in diffusible indole-3-acetic acid from various parts of tulip plant during rapid elongation of the flower stalk

In order to chemically identify the putative indole-3-acetic acid (IAA) and to confirm the native source of auxins account for rapid elongation of the floral stalk of tulip, we examined diffusible IAA from various parts of tulip plant during rapid elongation of the flower stalk. IAA was identified in the diffusates collected from the leaves, internodes, and floral organs with gas chromatography (GC)–mass spectrometry. The amount of diffusible IAA from different plant organs followed the order of that the internodes > flower organs > leaves during the period of rapid elongation of the floral stalk. The diffusible IAA from internodes reached its peak amount at different time than did diffusible IAA from the flower. The results obtained indicated that the top internode is probably the major source of auxins account for rapid elongation of the flower stalk.     

上海地区郁金香引种栽培与品种综合评价

通过建立郁金香(Tulipa gesneriana)品种评价体系,筛选生长适应性好、观赏价值高,适宜应用于园林景观的郁金香品种。对29个郁金香进口品种在上海地区进行引种栽培,观察记录其物候期,并对植株高、冠幅等12个生长特性,以及开花整齐度、花型、花色等32个观赏特性进行了观测。从观测指标中筛选出了包括开花整齐度、花色均匀度、花色等27个评价指标,使用层次分析法与灰色关联度分析法建立了评价体系。综合评价将29个品种分成了4个等级：Ⅰ级包含10个品种, Ⅱ级12个品种,而Ⅲ级和Ⅳ级包含品种数较少,分别只有4和3个品种。Ⅰ、Ⅱ级品种普遍具有较高的观赏价值,同时适应性较强,适合今后推广应用于上海及周边地区园林绿化。这对筛选适于上海及周边地区园林种植的郁金香品种有重要的指导作用,建立的评价体系对评价其他郁金香品种在园林中应用也有积极参考意义。     

A Simple Model for the Cold Requirement of the Tulip

A simple model is proposed that qualitatively describes someimportant features of the cold requirement of the tulip. Themodel may be used as a basis for quantitative experimental investigationsinto the response of tulip growth and development to differentperiods of bulb storage at low temperatures.     

Why does land-use history facilitate non-native plant invasion? A field experiment with Celastrus orbiculatus in the southern Appalachians

Although historic land use is often implicated in non-native plant invasion of forests, little is known about how land-use legacies might actually facilitate invasion. We conducted a 2-year field seeding experiment in western North Carolina, USA, to compare germination and first-year seedling survival of Celastrus orbiculatus Thunb. in stands that had been cultivated and abandoned a century earlier and were dominated by tulip poplar (Liriodendron tulipifera L.), and in paired stands that had never been cultivated and were dominated by oaks (Quercus spp.). Experiments were conducted at five sites with paired tulip poplar and oak stands by varying litter mass (none, low, or high) and litter type (tulip poplar or oak). We also performed reciprocal soil translocations using pots seeded with C. orbiculatus. Soil moisture and temperature were measured throughout the growing season. Germination and survival were highest in the tulip poplar stands. Germination was also higher in plots with low litter mass. Seedling survival was highest in plots with low litter mass or no litter. Soil moisture was higher in tulip poplar stands and under low-mass litter. Differences in germination and survival among the potted plants were minimal, suggesting that soil type and ambient site conditions were less important than litter conditions for C. orbiculatus establishment. Our results suggest that the low litter mass and mesic soil conditions that are characteristic of tulip poplar stands may confer higher invasibility and explain the higher abundance of C. orbiculatus in areas with successional overstory communities associated with historically cultivated forests.     

峨眉山珍稀植物鹅掌楸组培过程中的膜脂过氧化

鹅掌楸(Liriodendron chinense(Hemsl.) Sarg.)是中国特有珍稀树种.鉴于目前还鲜有野生鹅掌楸组培过程生理生化变化的相关报道.本研究以峨嵋山野生鹅掌楸茎尖芽为外植体进行组织培养,并对其继代培养再生过程中超氧阴离子自由基(O_2~-)、过氧化氢(H_2O_2)和丙二醛(MDA)含量的变化进行了测定.研究结果表明,随着培养时间的延长,植物体中O_2~-和MDA含量呈现逐渐增加的变化趋势.这表明在连续继代培养条件下,植物体内活性氧会积累,引起膜脂过氧化.H_2O_2含量"S"形曲线变化,并随着再生芽的分化而上升,因此,H_2O_2不仅参与了膜脂过氧化过程,还可能作为一种细胞信号物质参与诱导细胞分化和再生芽的形成.该研究也为进一步用组织培养法保存峨眉山珍稀植物鹅掌楸种质资源提供了参考.     

The significance of biological races of Ditylenchus dipsaci and their hybrids

Pure cultures of six races of Ditylenchus dipsaci derived from a single female, namely, lucerne race (LR), red clover race (RCR), white clover race (WCR), narcissus race (NR), tulip race (TR) and oat race (OR) were inoculated into eight plant species growing in pots. Onion was host to all six races, and tulip to all except RCR, whereas lucerne was susceptible only to LR and slightly to WCR. Hyacinth was not very susceptible to any race. The TR and OR were the most polyphagous. Severe symptoms were not necessarily associated with large nematode populations. Parthenogenesis did not occur. Ten fertile hybrids between races were produced and the host range of five of these was tested. On average the hybrids multiplied less than their parent races and their host ranges showed no relationship to those of their parent races. RCR and TR inoculated together into tulip produced significantly fewer nematodes than did TR alone and more than RCR alone. Mixed populations of races occur in nature which are probably a mixture of parental races, their hybrids and back-crosses. Repeated back-crossing of the hybrids with parental types and the slower multiplication of the hybrids is an explanation for the variation in host range of known races and the failure to record new races.     

An escape response behaviour in the brittle star ophiopteris papillosa (echinodermata: Ophiuroidea)

This study describes a behaviour of the brittle star Ophiopteris papillosa and tests two hypotheses concerning its possible function. During this behaviour an individual rapidly raises all five arms above its disk as the brittle star falls through the water column. The final position, with the five arms held tightly together above the disk, is termed the tulip position. Individuals in the tulip position fell faster, thus reaching the bottom sooner, than individuals not in the tulip position when tested in the laboratory. Individuals in the tulip position were consumed less frequently than individuals not in the tulip position when tested in the field. I conclude that the tulip position increases the likelihood of a brittle star reaching the protective cover of the bottom and escaping fatal predation.     

金叶马褂木叶片特性及其 RAPD 分子鉴定

金叶马褂木是从当地金边马褂木中发现的春季至初夏间全叶呈金黄色至淡黄色的芽变材料。对该芽变种质的叶片特性进行了连续8年的观察与调查,同时结合RAPD技术进行了初步的分子鉴定。叶片特性观察与调查结果表明,金叶马褂木叶片大小与金边马褂木、北美马褂木差异不大,但叶片叶绿素含量显著少于金边马褂木和北美马褂木,叶片色泽也与金边马褂木有显著性差异。结合RAPD分子鉴定结果,认为金叶马褂木是一个发生变异的新种质。     

Identification of jasmonic acid and its methyl ester as gum-inducing factors in tulips

The purpose of this study was to identify endogenous factors that induce gummosis and to show their role in gummosis in tulip (Tulipa gesneriana L. cv. Apeldoorn) stems. Using procedures to detect endogenous factors that induce gum in the stem of tulips, jasmonic acid (JA) and methyl jasmonate (JA-Me) were successfully identified using gas–liquid chromatography–mass spectrometry. Total amounts of JA and JA-Me designated as jasmonates in tulip stems were also estimated at about 70–80 ng/g fresh weight, using deuterium-labeled jasmonates as internal standards. The application of JA and JA-Me as lanolin pastes substantially induced gums in tulip stems with ethylene production. The application of ethephon, an ethylene-generating compound, however, induced no gummosis although it slightly affected jasmonate content in tulip stems. These results strongly suggest that JA and JA-Me are endogenous factors that induce gummosis in tulip stems.     

Jasmonates are essential factors inducing gummosis in tulips: mode of action of jasmonates focusing on sugar metabolism

The purpose of this study was to know the mechanism of jasmonates to induce gummosis in tulip (Tulipa gesneriana L. cv. Apeldoorn) shoots, especially on the focus of sugar metabolism. Gummosis in the first internode of tulip plants was induced by the application of methyl jasmonate (JA-Me, 1% w/w in lanolin) and jasmonic acid (JA, 1% w/w in lanolin) 5 days after application and strongly stimulated by the simultaneous application of ethylene-releasing compound, ethephon (2-chloroethylphosphonic acid, 1% w/w in lanolin), although ethephon alone had little effect. JA-Me stimulated ethylene production of the first internodes of tulips, ethylene production increasing up to more than 5 times at day 1 and day 3 after the application. On the other hand, application of ethephon did not increase endogenous levels of jasmonates in tulip stems. Analysis of composition of tulip gums revealed that they were consisted of glucuronoarabinoxylan with an average molecular weight of ca. 700 kDa. JA-Me strongly decreased the total amount of soluble sugars in tulip stems even in 1 day after application, being ca. 50% of initial values 5 days after application, but ethephon did not. However, both JA-Me and ethephon had almost no effect on the neutral sugar compositions of soluble sugars mainly consisting of glucose, mannose and xylose in ratio of 20:2:1 and traces of arabinose. Both JA-Me and ethephon applied exogenously stimulated senescence of tulip shoots shown by the loss of chlorophyll. These results strongly suggest that the essential factor of gummosis in tulips is jasmonates affecting the sugar metabolism in tulip shoots. The mode of action of jasmonates to induce gummosis of tulip shoots is discussed in relation to ethylene production, sugar metabolism and senescence.     

Proton Efflux from the Outer Layer of the Peduncle of Tulip in Gravitropism and Circumnutation*

Epidermal plus hypodermal peels from tulip peduncles produced bands of acidity on agar containing bromocresol purple. Peels from horizontally oriented peduncles gave rise to an acidity band which corresponded to the lower side of the peduncle. The band began 3–6 cm beneath the flower and extended basipetally within the region of gravitropic bending. No corresponding band appeared in an agar layer laid on the cortical surface exposed by peeling. Peduncles growing in the normal vertical position showed circumnutations with a period in the range of 4 h. The peels from these stalks produced one or two bands more acid than the remaining part of the peel. Since the acidity band in horizontally positioned stalks corresponds to the zone of faster growth causing gravitropic bending, we infer that the band(s) produced by vertical stalks also correspond to zones of differential growth involved in circumnutation. On the basis of a previous finding that tulip leaves give rise to an oscillating acidity pattern, we infer that vertical stalks also show such a pattern. This inference fits the model proposing the involvement of an internal oscillator in circumnutation. However, the ratio of the circumnutation period to the gravitropic lag phase in tulip peduncles is such as predicted by the gravitropic-feedback model of circumnutation.