五爪金龙凋落叶腐解物的化感潜力研究

采用莴苣种子为受体,测试了五爪金龙凋落叶早期腐解物的化感作用,并与其鲜叶及凋落叶的化感潜力进行了比较分析。结果如下:凋落叶40d的腐解物、鲜叶及凋落叶的水提取液均具有较强的化感潜力,并表现出低促高抑的浓度效应,在FW0.1g﹒mL-1高质量浓度下的综合化感抑制强度为凋落叶未能加土壤的腐解物>鲜叶>凋落叶加土壤的腐解物>凋落叶,而在FW0.005g﹒mL-1低质量浓度下的综合化感促进作用是凋落叶>鲜叶>凋落叶加土壤的腐解物>凋落叶未加土壤的腐解物。鲜叶的抑制强度较凋落叶的大,表明叶片在衰老过程中抑制作用减弱。凋落叶未加土壤仅在空气微生物作用下的腐解物抑制作用最强,促进作用最小,而加入土壤后在土壤微生物作用下的腐解物的抑制作用却有所减弱,抑制强度介于鲜叶和凋落叶的之间,促进作用却小于鲜叶和凋落叶,说明凋落叶腐解过程中微生物的参与对化感作用产生了复杂的影响。     

入侵物种三裂叶蟛蜞菊挥发物的化感作用研究

对华南地区重要外来入侵物种三裂叶蟛蜞菊挥发物的化感作用进行了研究,以揭示该物种的入侵机制。采用水蒸气蒸馏法提取三裂叶蟛蜞菊地上部分的挥发油,提取率为2.58‰(质量比)。以稗草、三叶鬼针草和青葙3种杂草种子为供试对象,用种子萌发法测定了三裂叶蟛蜞菊挥发物的化感作用活性。结果表明:三裂叶蟛蜞菊的茎叶在密闭系统中产生的挥发性物质对稗草、三叶鬼针草和青葙的幼苗生长有显著抑制作用。稗草的根长、苗高和鲜质量分别比对照减少49.1%、35.0%和27.3%,三叶鬼针草的分别比对照减少18.8%、20.9%和28.6%,青葙的分别比对照减少62.9%、21.2%和50.0%。水蒸气蒸馏法所得的挥发油对稗草、三叶鬼针草和青葙的幼苗生长也有显著抑制作用,且抑制作用随着浓度的增大而增强。稗草的根长、苗高和鲜质量分别比对照减少88.2%、58.3%和45.5%,三叶鬼针草的根长、苗高和鲜质量分别比对照减少38.6%、34.5%和71.4%,青葙的根长、苗高和鲜质量分别比对照减少83.7%、51.5%和75.0%。结论:三裂叶蟛蜞挥发物具有化感作用,其作用机理值得深入研究。     

常乐稀土复合肥对玉米（Zea may L.）的细胞毒性和遗传毒性效应

为了研究常乐稀土多元复合肥对主要农作物--玉米(Zea mays L.)是否产生细胞毒性和遗传毒性效应,采用不同梯度质量浓度的稀土复合肥溶液对玉米进行处理,观察其根尖生长状况,统计分析细胞死亡率、微核率、有丝分裂指数以及对细胞DNA的损伤情况.结果表明,质量浓度为10mg·L-1以下时,常乐稀土复合肥能够促进玉米根尖的生长,100mg·L-1以上时抑制根尖生长;随着试验浓度的递增,细胞死亡率、微核率、DNA损伤率逐渐上升并具有正相关性,表现出明显的剂量-效应关系,而有丝分裂指数却随着浓度的增加逐渐下降.以上结果表明,常乐稀土复合肥对玉米确有一定的细胞毒性和遗传毒性效应,其细胞毒性阈值和遗传毒性阈值皆为100mg·L-1.     

广州城郊环境梯度下马尾松针叶元素质量分数变化特征

城市化、工业化迅速发展及人类活动的加剧给城市及其周边地区森林生态系统带来前所未有的干扰和压力。植物冠层是植物与大气直接进行气体交换的界面,冠层叶组织化学分析已成为评价环境污染对森林树木健康的影响,指示环境污染的有效手段。文章以广州黄埔工业区(丹水坑风景区)、城郊接壤区(华南植物园)和近郊(帽峰山森林公园)这一环境梯度为对象,在各研究点上选定自然生长的、成熟健康的马尾松(Pinus massonianaL.)5株,分别采集树冠中部向阳枝条上的当年生(Current,C)和一年生(Current 1,C 1)针叶,然后将每组针叶区分为带叶鞘针叶、去叶鞘针叶和叶鞘3个组分进行样本制备,测定N、Al、Cu、Cd、Pb、Zn、Cr、Ni元素质量分数,旨在探讨利用马尾松针叶不同组分的元素质量分数用于指示城郊梯度环境质量变化的适宜性和可靠性。研究结果表明:①当年生带叶鞘针叶中Al质量分数显著高于当年生去叶鞘针叶(p<0.05),其余元素在当年生和一年生的去叶鞘针叶与带叶鞘的完整针叶间均无显著差异;②Ni在当年生针叶及其叶鞘间没有显著差异(p<0.05),其它被测定的金属元素无论在当年生还是一年生针叶中,均表现为叶鞘中的元素质量分数均显著高于去叶鞘针叶(p<0.05),体现了针叶与叶鞘在形态结构上的差异引起重金属积累的差异;而非金属元素N质量分数则针叶显著高于叶鞘;③一年生针叶中Ni质量分数显著低于当年生针叶,但Al、Pb、Zn质量分数显著高于当年生针叶,一年生叶鞘中所有金属元素的质量分数都显著高于当年生叶鞘,表现出随暴露时间和针叶寿命的延长而持续累积的特征;而营养元素N质量分数在当年生针叶和一年生针叶以及当年生叶鞘和一年生叶鞘间无显著差异;④城乡环境梯度下生长的马尾松为研究环境质量演变提供了一个天然的实验室,受人类活动干扰大的城区马尾松一年生针叶的Cd和N质量分数及其叶鞘中的Cu、Cr、Ni质量分数显著高于受人为干扰较少的郊区,表明植物组织中元素化学特征反映了城市发展过程中人类活动的足迹。在城市环境尤其是重金属污染的监测中,成熟的一年生叶鞘更具指示意义,效果更显著。     

三种类型油菜(Brassica spp.)和野芥菜(B. juncea var.gracilis Tsen et Lee)杂交亲和性及F1的适合度--潜在基因转移的研究

通过人工去雄授粉，采用荧光显微镜观察了3种类型栽培油菜花粉在两地采集的野芥菜柱头上的萌发生长情况，结合杂交后的结实率，探讨了3种类型油菜和野芥菜杂交的亲和性．结果表明，甘蓝型油菜和芥菜型油菜与野芥菜的亲和性都非常高，亲和性指数达10．0以上，而白菜型油菜和野芥菜的亲和性较低，亲和指数小于0．2．子一代的适合度研究结果表明，芥菜型油菜向野芥菜杂交一代的适合度没有降低，而甘蓝型及白菜型和野芥菜杂交一代的适合度明显下降，表现在花粉活力降低，结实率极低．上述结果表明，白菜型油菜和野芥菜的基因转移可能性最小，甘蓝型居中，而芥菜型极易向野芥菜发生基因转移．     

水分和氮素供应对菠菜硝酸盐累积和钾素吸收的影响

研究了水分和氮素供应对露地秋菠菜的硝酸盐累积和钾、氮吸收的影响。结果表明：与传统的水氮管理措施相比，采用水分平衡法和氮素专家系统进行的水氮供应并没有造成作物减产，但对钾、氮元素的吸收却有明显的影响，同氮素吸收相比，作物对钾素的吸收数量更高；并且作物对钾、氮的吸收比例随氮素供应水平的增加而降低，试验还动态监测了菠菜最新展开叶的叶柄汁液中的硝酸盐和K^ 浓度在一天内的变化情况。结果表明，不同水氮处理的菠菜叶柄汁液的硝酸盐浓度在白天均没有发生显著变化；叶柄汁液中的K^ 浓度和NO3^-／K^ 的浓度比在白天受氮素供应水平的影响很大，供氮量高，K^ 浓度和NO3^-／K^ 浓度比的变化也大，但受灌水量影响不大。图3表2参17。     

不同AM真菌对三叶草耐油性的影响

在盆栽条件下研究了4个油浓度（0、5000、10000和50000w/mgkg^-1）下接种辽河油田污染土壤中分离出的3种AM真菌（Glomus mosseae，G.geospora，G.constrictum）对三叶草耐油性的影响。试验结果表明：1）随着油浓度的增加，侵染率亦增加，10000mgkg^-1时G.geospora和G.constrictum的侵染率分别为67.65％和82.86％；2）从侵染率、地上部生物量和菌根依赖性来看，随着油浓度的增加，最适的AM真菌亦不一样，油浓度为0、5000和10000mgkg^-1时，最适AM真菌分别是G.geospora、G.mosseae和G.constrictum；3）油污染土壤上接种AM真菌能促进植株的地下部和地上部的生长，接菌处理的茎干重比相应的对照增加62.2％-267.1％；4）随着油浓度的增加和植物的生育进程，AM真菌的接种效应在增强。图3表3参14     

Twenty-five years of biomonitoring lead in the Frankfurt/Main area

The present study is an example of the historical monitoring of heavy metals. The specific question it aims to explore is: to what extent has the lead content of selected organisms used for biomonitoring in Frankfurt/Main—one of the cities in Germany most heavily affected by automobile traffic—changed as a result of legislation on leaded gasoline?

Data on the lead content of the moss speciesBryum argenteum Hedw. from the years 1974, 1975 and 1978 and data on the lead content of the outer bark of the ash speciesFraxinus excelsior L. from 1973 served as the basis for the repeated measurements. Remeasurement was successful in 76.5% (i.e. 124 trees at 26 growth sites). The study produced the following results:

• ? As was expected, the lead content of the short-term accumulatorBryum argenteum Hedw. was distinctly lowered with a decreasing particulate lead concentration. However, the reduction factor varied greatly between the different growth sites.
• ? On the other hand, the lead content measured in the outer bark layers ofFraxinus excelsior L. has risen markedly during the past two decades. Whereas in 1973 nearly all trees examined displayed very low concentrations of lead (< 38 ppm), only 9.5% were still in this category in 1997 and nearly 30% exhibited high or even unacceptable lead concentrations (< 150 ppm → > 225 ppm). Various factors have to be taken into account to explain this increase. First of all, bark is a long-term accumulator for heavy metals like lead and its enrichment capacity could have increased as the surface becomes rougher over time. Furthermore, lead is most probably leached out of the bark to a lesser degree now than in the 1970s, owing to the reduced concentration of sulphuric acid in the rain. The dramatic growth of automobile traffic in the Frankfurt/Main area during the period covered by the study undoubtedly plays an important role as well.

     

Quantum dots enhance Cu2+-induced hepatic L02 cells toxicity

As a new class of xenogenous nanoparticle,quantum dots (QDs) possess the potential to co-exist with Cu2+ in human liver.The combined toxicity is thus concerned.Considering QDs and Cu2+ are known ROS (reactive oxygen species) inducer,we investigated the combined oxidative stress and corresponding protective strategy using human hepatic L02 cells.The results demonstrated that the presence of a small amount of MPA-CdTe QDs (2 μg/mL) in a Cu2+ solution (2.5-20 μg/mL) resulted in a higher toxicity with up to 8-fold cell viability decrease,which was accompanied by cell morphology changes.The combined toxicity was then confirmed as ROS associated oxidative stress with up to 300% and 35% increase of the intracellular ROS level and glutathione S-transferase (GST) activity,respectively.N-acetylcysteine (NAC) can also provide almost complete protection against the induced toxicity.Therefore,the ROS associated oxidant injury might be responsible for the QDs-Cu2+/Cu2+ induced toxicity and could be balanced through cytoprotective antioxidant enzyme GST.     

Variations between rice cultivars in iron and manganese plaque on roots and the relation with plant cadmium uptake

To understand certain mechanisms causing variations between rice cultivars with regard to cadmium uptake and tolerance, pot soil experiments were conducted with two rice cultivars of di erent genotypes under di erent soil Cd levels. The relationships between plant Cd uptake and iron/manganese (Fe/Mn) plaque formation on roots were investigated. The results showed that rice cultivars di ered markedly in Cd uptake and tolerance. Under soil Cd treatments, Cd concentrations and accumulations in the cultivar Shanyou 63 (the genotype indica) were significantly higher than those in the cultivar Wuyunjing 7 (the genotype japonica) (P < 0.01, or P < 0.05), and Shanyou 63 was more sensitive to Cd toxicity than Wuyunjing 7. The di erences between the rice cultivars were the largest at relatively low soil Cd level (i.e., 10 mg/kg). Fe concentrations in dithionite-citrate-bicarbonate root extracts of Shanyou 63 were generally lower than that of Wuyunjing 7, and the di erence was the most significant under the treatment of 10 mg Cd/kg soil. The results indicated that the formation of iron plaque on rice roots could act as a barrier to soil Cd toxicity, and may be a “bu er” or a “reservoir” which could reduce Cd uptake into rice roots. And the plaque may contribute, to some extent, to the genotypic di erences of rice cultivars in Cd uptake and tolerance.