UVB exposure does not accelerate rates of litter decomposition in a semi-arid riparian ecosystem

Aboveground litter decomposition is controlled mainly by substrate quality and climate factors across terrestrial ecosystems, but photodegradation from exposure to high-intensity ultraviolet-B (UVB) radiation may also be important in arid and semi-arid environments. We investigated the interactive effects of UVB exposure and litter quality on decomposition in a Tamarix-invaded riparian ecosystem during the establishment of an insect biological control agent in northern Nevada. Feeding by the northern tamarisk beetle (Diorhabda carinulata) on Tamarix spp. trees leads to altered leaf litter quality and increased exposure to solar UVB radiation from canopy opening. In addition, we examined the dynamics of litter decomposition of the invasive exotic Lepidium latifolium, because it is well-situated to invade beetle-infested Tamarix sites. Three leaf litter types (natural Tamarix, beetle-affected Tamarix, and L. latifolium) differing in substrate quality were decomposed in litterbags for one year in the field. Litterbags were subjected to one of three treatments: (1) Ambient UVB or (2) Reduced UVB (where UVB was manipulated by using clear plastic films that transmit or block UVB), and (3) No Cover (a control used to test for the effect of using the plastic films, i.e. a cover effect). Results showed a large cover effect on rates of decomposition and nutrient release, and our findings suggested that frequent cycles of freeze-thaw, and possibly rainfall intensity, influenced decomposition at this site. Contrary to our expectations, greater UVB exposure did not result in faster rates of decomposition. Greater UVB exposure resulted in decreased rates of decomposition and P release for the lower quality litter and no change in rates of decomposition and nutrient release for the two higher quality litter types, possibly due to a negative effect of UVB on soil microbes. Among litter types, rates of decomposition and net release of N and P followed this ranking: L. latifolium > beetle-affected Tamarix > natural Tamarix. Altered nutrient dynamics with beetle introduction as well as the rapid decomposition rates exhibited by L. latifolium are consistent with vulnerability to secondary invasion. In this desert ecosystem, decomposition and nutrient release were strongly affected by litter type and much less so by UVB exposure.     

早春短命植物独行菜天然种衣与水分的关系

早春短命植物独行菜（Lepidium apetalum Willd.）的种子遇水后在种子外部形成一层粘液层--种衣,种衣遇水后迅速膨胀,种子的重量和大小都发生了变化,种衣的存在对独行菜种子的萌发、幼苗的生长及种群的延续有重要的生态意义.     

云南栽培玛咖的营养成分分析与评价

对云南栽培的玛咖营养成分进行了分析,并与文献报道的秘鲁产玛咖进行了比较.结果表明:云南栽培玛咖含有16.7×104mg·kg-1的蛋白质、21.5×104·mg·kg-1粗纤维、9.30%氨基酸、多种无机元素、多种维生素等营养成分,脂肪含量低;所含营养成分的种类与秘鲁产玛咖类似,其中对人体有益的蛋白质、粗纤维、钙、铁、锌、VC等成分的含量较高,表明云南栽培玛咖的营养丰富,具有开发利用价值.     

低海拔引种栽培玛咖主要有效成分分析

为给低海拔地区栽培玛咖的开发和推广提供参考依据,以引种栽培基地湖南省湘西自治州不同海拔样地的玛咖为材料,采用醇浸取法和高效液相色谱法,对其生物碱、玛咖酰胺和玛咖烯等主要有效成分进行了测定与分析。测定结果表明:其总生物碱含量为0.707%~2.376%;玛咖酰胺含量为0.083 8%~0.529 2%,玛咖烯含量为0.008 3%~0.070 6%,玛咖酰胺+玛咖烯含量为0.099 7%~0.537 6%。分析结果表明:湘西低海拔地区栽培的玛咖其主要有效成分含量与秘鲁原产地的相当,说明海拔高度对玛咖有效成分含量无显著影响。文中因此认为,玛咖可以在低海拔地区大量推广栽培。     

NaCl胁迫对宽叶独行菜种子萌发的影响

对宽叶独行菜的种子进行了不同浓度的盐处理试验,结果表明:盐胁迫下种子萌发受到显著抑制,并且随着浓度增加其抑制作用越明显;宽叶独行菜种子萌发的NaCl临界浓度是200mmoL/L。     

独行菜属植物的研究进展

对独行菜属植物的资源研究与利用情况进行了总体概述,重点总结独行菜属植物化学成分与耐逆生理生化机制研究的进展,并提出了今后一段时间对独行菜属植物资源研究与利用的思考。     

宽叶独行菜组培体系的建立和初步优化

以宽叶独行菜(Lepidium latifolium L.)的叶片和茎段为外植体,接种于MS培养基上进行愈伤诱导和植株再生培养,研究不同浓度激素对愈伤和再生苗生长状况的影响。结果表明,当激素浓度为1.5 mg/L2,4-D+1.0 mg/L IAA+0.5 mg/L 6-BA时,再生植株长势最好;当激素浓度为0.5 mg/L 2,4-D+1.0 mg/L IAA+1.5 mg/L 6-BA时愈伤组织长势最好;适当增加6-BA的浓度,可以促进再生植株根系的生长。     

独行菜属药学研究概况

在广泛文献检索基础上,对独行菜属植物的种类、成分、药理及临床应用进行了概述,为深入开发利用提供参考。     

粘液繁殖体植物抱茎独行菜TTG1基因转化拟南芥的表型研究

[目的]将过量表达典型粘液繁殖体植物抱茎独行菜TTG1基因(LpTTG1)的转基因拟南芥株系表型与野生型和突变体进行比较,为深入研究LpTTG1基因的功能提供参考依据.[方法]在体视显微镜下,通过对拟南芥野生型、ttg1突变体及LpTTG1基因过表达转基因株系的植株表型,幼苗叶表皮毛、下胚轴和根毛以及种子形态进行观察比较.[结果]拟南芥ttg1突变体与野生型和LpTTG1过表达转基因型的幼苗在下胚轴的颜色、根毛着生方式、真叶表皮毛等方面有显著差异,但后两者表型间无显著差异.[结论]缺失TTG1基因可导致拟南芥幼苗形态发生显著变化,但此基因过量表达不一定对拟南芥形态产生影响.     

外源水杨酸处理对采后豇豆抗冷性的影响

试验研究了不同浓度的外源永杨酸溶液处理对采后豇豆冷藏效果的影响.结果表明,采用水杨酸处理可以有效地抑制豇豆表面水浸状凹陷斑扩大,改善豇豆冷藏期间的贮藏品质,延缓豇豆豆荚中叶绿素的降解,抑制细胞膜透性的增加和丙二醛含量的积累,并使过氧化物酶和过氧化氢酶活性始终维持在较高水平.其中以1.0 mmol/L浓度的水杨酸溶液处理的效果最佳.