木槿属几种植物的染色体数目及其倍性的研究

采用去壁低渗火焰干燥法进行染色体制片分析了木槿属Hibiscus植物裂瓣槿H. schizopetalus (Masters) Hook. f.)、木芙蓉H. mutabilis L.以及扶桑H. rosa sinensis L. 4个栽培变种的染色体数目.结果表明裂瓣槿染色体数目为2n=42木芙蓉2n=92扶桑2n=84重虹中玫槿2n=105; 橙黄中玫槿2n=138; 洋红中玫槿2n=147.裂瓣槿、扶桑、重虹中玫槿、洋红中玫槿之间存在倍性关系,其染色体基数为x=21.通过对植物形态特征以及染色体数目的观察分析推测红色中玫槿可能为洋红中玫槿和裂瓣槿的杂交种.     

Effects of sequential pollination on the success of "fast" and "slow" pollen donors in Hibiscus moscheutos (Malvaceae)

Competition among pollen grains for the chance to fertilize ovules typically involves two stages: arrival times on stigmas and/or the growth of pollen tubes through styles. In a previous study of Hibiscus moscheutos, we found that individual pollen donors often differed in pollen tube competitive ability. Here we determined whether short delays in pollen arrival time altered the average success of "fast" and "slow" pollen donors when both types of pollen experienced the same delays. Hand-pollination experiments were carried out using four pairs of pollen donors that differed in competitive ability. We allowed delays of 15 or 30 min between the first and second pollen donor and then determined seed paternity using allozyme markers. The second donor typically sired fewer seeds than pollen that arrived earlier, but, contrary to expectation, "faster" pollen did not always sire significantly more seeds than "slower" pollen when each was applied after delays of the same duration. In two of the four pairs of donors, differences that were seen following simultaneous pollinations disappeared when each type of pollen was applied following identical delays of 15 or 30 min. This unexpected response suggests that the dynamics of pollen tube competition are more complex than anticipated.     

Inhibition of nitric oxide synthase (NOS) underlies aluminum-induced inhibition of root elongation in Hibiscus moscheutos

Aluminum (Al) is toxic to plants when solubilized into Al(3+) in acidic soils, and becomes a major factor limiting plant growth. However, the primary cause for Al toxicity remains unknown. Nitric oxide (NO) is an important signaling molecule modulating numerous physiological processes in plants. Here, we investigated the role of NO in Al toxicity to Hibiscus moscheutos. Exposure of H. moscheutos to Al(3+) led to a rapid inhibition of root elongation, and the inhibitory effect was alleviated by NO donor sodium nitroprusside (SNP). NO scavenger and inhibitors of NO synthase (NOS) and nitrate reductase had a similar inhibitory effect on root elongation. The inhibition of root elongation by these treatments was ameliorated by SNP. Aluminum inhibited activity of NOS and reduced endogenous NO concentrations. The alleviation of inhibition of root elongation induced by Al, NO scavenger and NOS inhibitor was correlated with endogenous NO concentrations in root apical cells, suggesting that reduction of endogenous NO concentrations resulting from inhibition of NOS activity could underpin Al-induced arrest of root elongation in H. moscheutos.     

Effect of allopolyploidy on the activity of selected enzymes inHibiscus

Mature seeds of diploid and tetraploidHibiscus species were analyzed for enzyme activity (alcohol dehydrogenase, malate dehydrogenase, leucine aminopeptidase), total protein content, DNA amount and dry weight. The recently formed tetraploid,H. radiatus, generally had enzyme and protein levels very similar to the sum of its progenitors, while the more ancient speciesH. acetosella had several lower levels. This difference may reflect the greater amount of timeH. acetosella has had to evolve dosage compensations.Michigan Agricultural Experiment Station Journal Article 9665.A part of this research was used to satisfy the requirements ofA. Hoisington for a M.S. degree at the University of South Carolina.     

Improvements in shoot apex regeneration of two fiber crops: cotton and kenaf

Cotton (Gossypium hirsutum L.) and kenaf ( Hibiscus cannabinus L.) belong to the Malvaceae family, and both are used as sources of fibers. Shoot apices from vigorous seedlings aseptically germinated from 3 different cultivars of both cotton and kenaf were used in this study. The cotton and kenaf shoot apex size was between 2–3 mm containing the meristem, unexpanded leaves, and a small portion of the cotyledon. Shoot apices were placed on 18 different media comparing full and 1/2 strength Murashige and Skoog (1962) plus vitamins, and combinations of 0, 0.1, and 1 mg l^-1 of naphthaleneacetic acid and 6-benzyladenine (BA). The shoot apices of both crops developed successfully without intervening callus formation, and no significant differences among cultivars were found. An average of 58% of the cotton shoot apices initiated shoot and rooted in full strength Murashige and Skoog (1962) plus vitamins in 6 weeks. For kenaf, an average of 92% of shoot apices initiated shoot and rooted in full strength Murashige and Skoog plus vitamins and 0.1 mg l^-1 BA in 3 weeks. All regenerated plants of both crops were phenotypically normal and set seeds. This revised version was published online in June 2006 with corrections to the Cover Date.     

Chemopreventive properties of Hibiscus sabdariffa L. on human gastric carcinoma cells through apoptosis induction and JNK/p38 MAPK signaling activation

Gastric cancer is a common malignancy in many countries of the world, especially in Asia. Prevention is likely to be the most effective means of not only reducing the incidence but also mortality from this disease. The term 'chemoprevention' has been referred to the prevention of cancer using specific agents to suppress or reverse the carcinogenic process. In recent years, attention has been focused on the anticancer properties of edible plants, an important role in the prevention of disease. Hibiscus sabdariffa Linne (Malvaceae), an attractive plant believed to be native to Africa, is cultivated in the Sudan and Eastern Taiwan. The purpose of this study was to examine whether the plant, H. sabdariffa extracts (HSE), affects the apoptosis of AGS cells. Using a set of apoptotic detection assays, they showed that HSE induced cytotoxicity and apoptosis of AGS cells in a concentration-dependent manner but is ineffective in Chang liver cells. The result also revealed increased phosphorylation in p38, JNK and c-Jun, cytochrome c release, and expression of Fas, FasL, Bax, and t-Bid in the HSE-treated AGS cells. We further used MAPK inhibitors to evaluate their effect on the HSE-induced AGS death. The data showed that SB203580 (p38 inhibitor), JNK inhibitor I and II or transfection with the mutant JNK expression vector had strong potential in inhibiting AGS cells apoptosis and related proteins expression. Finally, we suggested that HSE mediated AGS apoptosis via the JNK/p38 signaling cascade. According to these results, HSE could be developed as a chemopreventive agent.     

The absolute configuration of (-)-3-hydroxy-alpha-calacorene

3-Hydroxy-alpha-calacorene was identified in extracts from cold-shocked seedlings of cotton (Gossypium hirsutum L.) and kenaf (Hibiscus cannabinus L.), both of which are members of the Malvaceae family. (-)-3-Hydroxy-alpha-calacorene was isolated from Heterotheca inuloides Cass. (Asteraceae). HPLC on a chiral stationary phase column showed that the 3-hydroxy-alpha- calacorene from cotton and kenaf had the same relative configuration, while that from H. inuloides was of the opposite configuration. X-ray crystallographic analysis established the absolute configuration of the compound in H. inuloides as (8R)-(-)-3-hydroxy-alpha-calacorene.     

木槿叶片结构的发育可塑性研究

对4个木槿种下类群叶片结构的发育可塑性进行了比较研究。(1)木槿 4 个种下类群的叶片在栅栏组织厚度、下表皮厚度、上表皮气孔密度、上下表皮气孔密度比,叶片厚度以及中脉维管组织等性状上均表现出较大的发育可塑性,这种可塑性对叶片适应植株光热综合因子的时空异质性具有重要意义。(2)木槿 4 个种下类群的同类型叶片在解剖学性状上的变异很小,即性状具有很大的稳定性。针对这一特点,对 4 个木槿种下类群一年生茎初生叶片结构的比较研究表明,紫花单瓣木槿和白花重瓣木槿之间的亲缘关系较近,雅致木槿和牡丹木槿亦存在较近的亲缘关系。研究结果支持将牡丹木槿和紫花单瓣木槿提升为亚种等级,并建议将白花重瓣木槿和雅致木槿分别看作紫花单瓣木槿和牡丹木槿的变型。     

Pollen competition as a reproductive isolating mechanism between two sympatric Hibiscus species

Differences in pollen tube growth rates (certation) between heterospecific (foreign) and conspecific pollen may strongly influence whether hybrid offspring are produced after mixed pollen loads are delivered to a stigma. For both members of a sympatric species pair, Hibiscus moscheutos and H. laevis, pollination by pure loads of foreign pollen resulted in fruit set that was not significantly different from conspecific pollination, indicating that pure loads of foreign pollen could readily result in hybrid offspring. However, the number of seeds per fruit from pure foreign pollinations was significantly less than that of pure conspecific pollination. Simultaneous mixed pollination resulted in a proportion of hybrid seeds (detected by an electrophoretic marker enzyme) that was significantly lower than expected based upon the capacity of foreign pollen to effect fertilization when applied in pure pollinations. After these 50/50% pollen mixtures were applied to stigmas, 8.0 and 7.4% hybrids were produced when H. moscheutos and H. laevis were the ovule parents, respectively. For these Hibiscus species, pollen competition appears to function as a barrier to hybridization that is of moderate intensity compared with similar barriers occurring between other recently studied sympatric species pairs.