Ion-mediated increase in the hydraulic conductivity of Laurel stems: role of pits and consequences for the impact of cavitation on water transport

Changes in hydraulic conductivity (K(h)) were measured in stems of Laurus nobilis L. during perfusion with KCl, NaCl or sucrose solutions. Ionic solutes induced marked increase of K(h) with respect to deionized water but sucrose had no effect. The kinetics of KCl-induced K(h) increase was measured together with changes in [K(+)] of the perfused solution. K(h) increases were paralleled by increases in the [K(+)](out)/[K(+)](in) ratio. Samples of different lengths or with increasing percentage loss of conductivity (PLC) due to xylem cavitation were tested, with the aim of increasing radial flow through intervessel pits. KCl solutions enhanced the K(h) of 12-cm-long samples with a concentration-dependent effect up to 100 mm KCl. DeltaK(h) increased from 3 to 30% in 1.5- and 12-cm-long samples, respectively and remained constant for longer samples. Increasing PLC induced an exponential increase in DeltaK(h). PLC measured with KCl solutions was significantly less than that measured with deionized water, suggesting that measurements of PLC can be affected by the composition of the perfused solution. Experiments support the hypothesis that the 'ionic effect' is mediated by physico-chemical changes of pectins of the pit membranes and raise the possibility that plants might alter the ionic composition of the xylem sap to alleviate the hydraulic impact of cavitation.     

Contact toxicity of Azadirachta indica (Adr. Juss.), Eucalyptus camaldulensis (Dehn.) and Laurus nobilis (L.) essential oils on mortality cotton aphids,Aphis gossypii Glover (Hem.: Aphididae)

Essential oils from three species of plants comprising three plant families were obtained by Clevenger-type water distillation. The major compounds in these essential oils were identified with GC-MS and their insecticidal activity against adult cotton aphid, Aphis gossypii Glover tested with dosage-mortality bioassays. We examined mortality only for viviparous adults because sizeable aphid populations on cucumber (Cucurbitaceae) hosts are largely produced by these wingless, parthenogenic females. Three of the oils were directly applied to aphid females in randomised blocks at 25?±?2?°C and 60?±?5% R.H. and under a L16:D8 photoperiod. Essential oils were mixed with a non-toxic emulsifying agent, Tween 80. Results show adverse contact effects of essential oils studied in the control of cotton aphid. Probit analysis and LC₅₀ at concentrations at different exposures showed aphids were incapacitated and killed by aliphatic aldehydes, phenols and monocyclic terpenes contained in Azadirachta indica, Eucalyptus camaldulensis and Laurus nobilis. LC₅₀ on cotton aphid, for azadirachtin eucalyptus and laurel essential oils were respectively 5389, 9515 and 13730?ppm. In the current study, efficacy in respect to the contact toxicity (LC₅₀) followed the order: A. indica?>?E. camaldulensis?>?L. nobilis after 24?h treatment. Our results show quantitative and qualitative differences in the chemical composition and insecticidal activities of our essential oils. All oils became insect toxic as concentration increased. According to the results, essential oils of all the three plants have the potential to be employed in the pest management programmes that can be used in protection of greenhouse conditions against cotton aphid.     

Frugivory in European Laurel: how extinct seed dispersers have been substituted

Capsule Extinction of ancient frugivores during the Quaternary has led to a depauperated seed disperser community for Laurus nobilis and a tight mutualism between the plant and the Blackbird Turdus merula.

Aims To describe a present-day frugivore assemblage of natural Laurel populations in southern Spain.

Methods Eight fruiting trees of different size were monitored with binoculars during 52 hours spread across one ripening season, and the identity and behaviour of foraging birds were recorded. Additional point counts were used to record the avifauna of the surroundings.

Results Despite a diverse frugivore community being present, Laurel fruits are almost exclusively (99%) consumed by Blackbird and rarely (1%) by Blackcap Sylvia atricapilla. Blackbirds concentrate at fruiting trees and individuals may remain there for several days. Birds usually forage in small groups and return at intervals of 12–14 minutes.

Conclusion The Blackbird population of the study area forages extensively on the energy-rich Laurel fruits, while the plants depend exclusively on this bird species for seed dispersal. Consequences of the depauperate frugivore community and the tight mutualism between Blackbirds and Laurels on plant recruitment and conservation are discussed.     

论鲢、鳙对微囊藻的消化利用

1980年—1985年7—8月在水温30℃,溶氧8mg/L以上,pH值7—8,光照度2800lx的限制摄食量条件下,鲢、鳙鱼种对微囊藻干物质的消化率分别为29.45±4.37、26.07±2.15％;蛋白质消化率分别为39.20±3.44、33.71±2.93％;脂肪消化率分别为34.03±5.38、30.29±2.16％;碳水化合物消化率分别为36.61±4.15、30.39±2.81％。鱼种对微囊藻日需量分别为其体重的54.44和60.53％。鱼的生长与其生活水体中藻类的初始浓度有密切关系:(1)藻类浓度在0.4—0.8g/L时鲢、鳙分别增重1.55—7.41和0.78～6.21％;(2)藻类浓度在1.0—1.3g/L时鲢、鳙分别减重2.0—5.9和2.2—8.3％。0.8g/L为鲢、鳙滤食微囊藻的最大浓度。     

月桂叶精油成分及逐月动态变化

采用毛细柱 GC-MS 和弹性石英毛细柱 GC Kovats 指数的鉴定方法,从月桂(Laurusnobilis L.)叶精油中鉴定出45个化合物,其中1,4-桉叶油素、水合桧烯等19个系该种植物中首次报道。系统地研究了月桂干叶与鲜叶、不同产地、当年生与多年生成分,首次报道月桂叶精油成分逐月动态变化,表明其得率和主成分1,8-桉叶油素含量均以7月最高。     

Xylem cavitation and hydraulic control of stomatal conductance in Laurel (Laurus nobilis L.)

The possible link between stomatal conductance (g_L), leaf water potential ( Ψ _L) and xylem cavitation was studied in leaves and shoots of detached branches as well as of whole plants of Laurus nobilis L. (Laurel). Shoot cavitation induced complete stomatal closure in air‐dehydrated detached branches in less than 10 min. By contrast, a fine regulation of g_L in whole plants was the consequence of Ψ _L reaching the cavitation threshold ( Ψ _CAV) for shoots. A pulse of xylem cavitation in the shoots was paralleled by a decrease in g_L of about 50%, while Ψ _L stabilized at values preventing further xylem cavitation. In these experiments, no root signals were likely to be sent to the leaves from the roots in response to soil dryness because branches were either detached or whole plants were growing in constantly wet soil. The stomatal response to increasing evaporative demand appeared therefore to be the result of hydraulic signals generated during shoot cavitation. A negative feedback link is proposed between g_L and Ψ _CAV rather than with Ψ _L itself.     

Microsatellite loci isolated from the scleractinian coral, Acropora nobilis

We report the isolation and characterization of eight microsatellite loci from the scleractinian coral, Acropora nobilis. The microsatellite loci were obtained using compound SSR primers or an enrichment protocol. All the loci were polymorphic with four to eight alleles per locus and observed heterozygosities ranging from 0.22 to 0.76. Some of the primers developed for the two congeners, Acropora palmata and Acropora millepora were applicable to A. nobilis. These loci are useful for studying the connectivity among A. nobilis populations in Okinawa, southern Japan.     

人工培养条件下君子兰雄配子体发育与核酸、蛋白质合成的研究

作者建立了离体培养君子兰雄配子体的简易方法并观察了其发育过程。应用核酸、蛋白质合成抑制剂和放射自显影技术,研究不同发育阶段雄配子体的核酸和蛋白质的合成。发现四分孢子释放以后,DNA 的合成仅在有丝分裂间期的细胞核内进行;散粉前96小时至精细胞形成,营养核、生殖核和精于核中均未见~3H-胸苷掺入。RNA 和蛋白质合成的动态相似,各有三次高峰和两次停顿。抑制剂的种类和加入的时间、数量对发育的影响不同,显示了 DNA、RNA 和蛋白质合成间及生物大分子合成与雄配子体形态发育间的相关性。     

利用17个微卫星标记分析鳙鱼的遗传多样性

选用本实验室克隆的17个鳙鱼微卫星分子标记分析四川泸州和江西鄱阳湖的两个种群鳙鱼的遗传多样性及种质特性,计算和统计了杂合度、多态信息含量（PIC）、有效等位基因数、等位基因频率、遗传距离、遗传相似系数、Hardy-Weinberg平衡偏离指数等方面内容。结果表明：选择使用17个微卫星标记,其中有4个为单态标记,13个为多态标记。江西和四川鳙鱼群体每个微卫星位点的平均等位基因数分别为3.325及3.882,平均有效等位基因数分别为3.531及2.676,多态位点百分率分别为82.4及70.5, 17个微卫星标记共有等位基因71个,多态微卫星位点的PIC在0.114~0.960之间变动,平均为0.417 ,两群体位点平均观测杂合度为0.385和0.452,平均期望杂合度为0.360和0.422,两个群体间的遗传相似系数为0.897,群体间的遗传距离为0.109。