栓皮栎地上部分构型及生物量分配

研究秦岭南坡商洛地区不同径级栓皮栎的地上部分构型、生物量及其分配和构型与生物量的关系.结果表明： 不同径级栓皮栎地上部分构型与生物量的分配存在差异.随着径级的增大,栓皮栎树高、胸径和冠幅逐渐增大;平均递减率先增大后减小;栓皮栎总体分枝率和逐步分枝率先增加后下降;不同径级栓皮栎垂直方向上的比叶面积为0.02～0.03,叶重比、叶面积指数和叶面积比的较大值在径级为Ⅰ、Ⅱ、Ⅲ时出现于树干中、上部,在径级为Ⅳ、Ⅴ、Ⅵ时出现在树干中部,径级进一步增大则在垂直方向上出现2个峰值,分别位于树干中下部和中上部.栓皮栎地上部分生物量中,树干生物量占71.8%～88.4%,枝生物量占5.8%～19.6%,叶生物量占4.2%～8.6%.随着径级的增大,树干生物量所占比例先减小后增大,而枝、叶生物量所占比例呈先增大后减小再增大的趋势.栓皮栎地上部分生物量与树高、胸径、冠幅和逐步分枝率(R_2∶1)呈显著正相关,与总体分枝率和逐步分枝率(R_3∶2)呈正相关趋势,但相关性不显著.树干生物量、地上总生物量与树干递减率呈负相关趋势,枝生物量、叶生物量与树干递减率呈正相关趋势,但相关性均不显著.     

木槿的化学成分研究

为了解木槿(Hibiscus syriacus)茎的化学成分,采用MCI-gel中压柱层析、硅胶柱层析、Sephadex LH-20凝胶柱层析和高效液相色谱等色谱方法,从木槿茎85%乙醇提取物中分离得到13个化合物。根据理化性质和波谱数据,其结构分别鉴定为methyl 4-[2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl) ethyl] sinapate (1)、2,6,2′,6′-四甲氧基-4,4′-二(2,3-环氧-1-羟基丙基)二苯(2)、3,4,5-三甲氧基肉桂酸甲酯(3)、3,4-二甲氧基肉桂酸甲酯(4)、对羟基肉桂酸甲酯(5)、咖啡酸甲酯(6)、阿魏酸甲酯(7)、丁香脂素(8)、clemaphenol A (9)、(E)-3-hydroxyanetholeβ-D-glucopyranoside (10)、荭草苷(11)、木犀草素(12)和芹菜素(13)。其中化合物1～10为木脂素类,化合物11～13为黄酮类,化合物1为新天然产物,化合物1～12为首次从该植物中分离得到。采用MTS法检测,40μmol/L的化合物1～10对人白血病HL-60细胞和人肺癌A-549细胞株体外生长均未显示出较好的抑制活性。     

喀斯特断陷盆地区不同恢复阶段群落物种组成与多样性特征

研究自然植被恢复过程中的物种组成、群落结构及生物多样性的变化,能够为人工促进植被恢复的树种选择与群落结构的优化配置提供重要依据。本研究以空间代替时间对喀斯特断陷盆地典型区云南省建水县不同天然植被(草丛、灌丛、乔木林)进行群落学调查,对不同恢复阶段的植物群落按乔木、灌木、草本进行分层,分析各恢复阶段植物群落的物种组成、水平和垂直结构、生物多样性。结果表明:在总面积为3200 m^2的12个样地中,共记录43科72属94种维管束植物,优势种以壳斗科(Fagaceae)、鼠李科(Rhamnaceae)、紫金牛科(Myrsinaceae)、蔷薇科(Rosaceae)、木犀科(Oleaceae)等科的植物为主;在草丛→灌丛→乔木林的恢复过程中,群落物种组成中的科数、属数、种数逐渐增加,低矮和小径级植物个体数所占比例逐渐减少,但整体仍以低矮的小径级植物为主。草本植物的丰富度和Shannon指数在植被恢复的初期即草丛阶段最大,而均匀度指数则以灌丛阶段最大;木本植物的丰富度和Shannon指数随着植被的恢复逐渐增大,但均匀度指数随着植被的恢复逐渐下降;随着植被的恢复,草本层和乔木层的生态优势度逐渐增大,灌木层的生态优势度逐渐减小;草本植物由早期一年或多年生的喜阳、耐旱、耐贫瘠的草本向抗逆性强的多年生草本过渡,并逐渐向中性和阴性转变,其中刺芒野古草(Arundinella setosa)能够很好地适应该地区的环境;薄叶鼠李(Rhamnus leptophylla)、铁仔(Myrsine africana)、假虎刺(Carissa spinarum)、小石积(Osteomeles anthyllidifolia)等阳性树种为该地区植被恢复的先锋种,其早期的出现为其他植物的恢复创造条件,后期又逐渐被喜阴的植物替代,在植被恢复初期可利用这些物种;在植被恢复后期,壳斗科的铁橡栎(Quercus cocciferoides)成为建群种,可在灌丛阶段植被恢复时利用该物种,也可以选择使用该物种植树造林;在整个植被恢复过程中,优势度从以矮小植物为主朝着高大植物发展、优势种寿命越来越长的趋势十分明显。     

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.     

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.