Co‐occurring increases of calcium and organellar reactive oxygen species determine differential activation of antioxidant and defense enzymes in Ulva compressa (Chlorophyta) exposed to copper excess

In order to analyse copper‐induced calcium release and (reactive oxygen species) ROS accumulation and their role in antioxidant and defense enzymes activation, the marine alga Ulva compressa was exposed to 10 µM copper for 7 d. The level of calcium, extracellular hydrogen peroxide (eHP), intracellular hydrogen peroxide (iHP) and superoxide anions (SA) as well as the activities of ascorbate peroxidase (AP), glutathione reductase (GR), glutathione‐S‐transferase (GST), phenylalanine ammonia lyase (PAL) and lipoxygenase (LOX) were determined. Calcium release showed a triphasic pattern with peaks at 2, 3 and 12 h. The second peak was coincident with increases in eHP and iHP and the third peak with the second increase of iHP. A delayed wave of SA occurred after day 3 and was not accompanied by calcium release. The accumulation of iHP and SA was mainly inhibited by organellar electron transport chains inhibitors (OETCI), whereas calcium release was inhibited by ryanodine. AP activation ceased almost completely after the use of OETCI. On the other hand, GR and GST activities were partially inhibited, whereas defense enzymes were not inhibited. In contrast, PAL and LOX were inhibited by ryanodine, whereas AP was not inhibited. Thus, copper stress induces calcium release and organellar ROS accumulation that determine the differential activation of antioxidant and defense enzymes.     

Anatomical and hnctional differences and nyctinastic leaf movements in Chenopodium album L. and Chenopodium hircinum Schrad. (Chenopodiaceae)

The anatomical structure of the leaves of Chenopodium album L. and Chenopodium hircinum Schrad. has been examined. Leaf chlorophyll content (Chl), specific leaf area (SLA), specific leaf weight (SLA^-1) and nitrogen content (N₂) were estimated in both species. Ch1, SLA and N₂ were greater in C. album than in C. hircinum. SLA^-1 data showed that C. album is more efficient than C. hircinum , because the former invests smaller quantities of dry weight to achieve a square centimetre of leaf area. The possible effects of Chl, N₂ and leaf anatomy on efficient gas exchange are discussed. The presence of nyctinastic leaf nocturnal movements was detected in both species. The meaning of this is discussed in relation to the prevention of the loss of pollen grains.     

Litter breakdown in streams of the Agüera catchment: influence of dissolved nutrients and land use

1. The breakdown of oak ( Quercus robur L.), chestnut ( Castanea sativa Miller) and eucalypt ( Eucalyptus globulus Labill.) litter enclosed in 5-mm mesh bags was compared between first-order headwaters (two with native riparian forest and two with eucalypt plantations) and a third-order reach of Agüera stream. Weight loss and dynamics of phosphorus and nitrogen in litter were studied for a period of 155 days.
2. Among the different sites, processing rates ranged from 0.0045 to 0.0080 day^–1 for chestnut leaf litter, from 0.0036 to 0.0051 day^–1 for oak, and from 0.0027 to 0.0158 day^–1 for eucalypt.
3. The availability of nutrients in water clearly influenced nitrogen and phosphorus dynamics in litter. In headwater reaches, net immobilization was not observed and losses of phosphorus and nitrogen followed mass loss. However, there was an enrichment of litter at the low reach, where influence of human settlements—located upstream—could lead to a greater availability of phosphorus in water.
4. The enhancement of litter decay by the exogenous nutrient supply depended on leaf quality, as only the processing rate of eucalypt increased at the nutrient-rich site.
5. The processing rates differed little among headwaters, suggesting that riparian forest type, i.e. deciduous forest v eucalypt plantations, did not affect litter decay in the stream.     

燕雀亚科鸟类的贝叶斯系统发生:非洲鹂雀的分类地位及朱雀属的进化与异质起源

鹂雀(Linurgus olivaceus)是非洲热带森林中一种独特的鸣禽,为鹂雀属(Linurgus)的惟一物种。在已有的研究中,通过对鹂雀和雀形目现存鸟类中每个科及亚科至少一个物种的线粒体DNA序列测定,分析了鹂雀与其它现存雀形目鸟类的系统发生关系;在遗传上,对鹂雀与金丝雀、金翅雀及燕雀亚科其它鸟类亦有比较研究。本研究共使用了燕雀亚科83种鸟类,重点对该亚科的系统发生进行了修订。使用贝叶斯法构建了系统发生树,结果表明:鹂雀属于燕雀亚科,系统发生树中聚在金翅雀族(Carduelini),与金丝雀属(Serinus)、金翅雀属(Carduelis)及交嘴雀属(Loxia)的种类形成一组;在系统发生中,鹂雀可能是一个基部物种,它同金丝雀属和金翅雀属鸟类一同进化并分歧出来。在本研究中未能涉及的一些已灭绝种类,可能与鹂雀有着较近的遗传学关系。另一方面,研究也表明锡嘴雀(Coccotharustes coccothraustes)肯定包括在欧亚蜡嘴雀(蜡嘴雀属Eophona和拟蜡嘴雀属Mycerobas)中,美洲的朱雀(Carpodacus)可能是从亚洲种类分歧出来并经过进化辐射形成。     

Anatomical structure and secretion compounds of colleters in nine Ilex species (Aquifoliaceae) from southern South America

In order to clarify whether the structures observed at the base of the petiole of the genus Ilex are colleters resulting from stipules, the anatomy, vascularization and secretions of these supposed glandular structures were analysed in nine species. This is the first report of colleters in Ilex. Stipular colleters replace the stipules in all species studied and are characterized by the presence of vascular traces. In addition to the stipular colleters, three other types of colleter were distinguished: standard and lachrymiform colleters found on the leaf teeth or crenations, and sessile colleters found on the margins of the floral bracts. Their basic structure consists of a central core of parenchymatous cells surrounded by one layer of palisade secretory epidermal cells. Histochemical tests were also performed on secretions; proteins were found in the secretions studied, but glucose was not. The glandular origin of the stipular colleters is confirmed on the basis of their position, secretions and anatomy. Analyses of the colleter‐secreted proteins distinguished two different groups of Ilex species. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 197–210.