Chemical characteristics and gelling properties of agar from two Philippine Gracilaria spp. (Gracilariales, Rhodophyta)

The chemical structure of agars extracted from Philippine Gracilaria arcuata and G. tenuistipitata were determined by NMR and infrared spectroscopy. Agar with alternating 3-linked 6-O-methyl-β-D-galactopyranosyl and 4-linked 3,6-anhydro-2- O-methyl-α-L-galactopyranosyl units was isolated from G. arcuata, while the agar from G. tenuistipitata possesses the regular agarobiose repeating unit with partial methylation at the 6-position of the D-galactosyl residues. Both agars exhibit sulphate substitution at varying positions in the polymer. Chemical analyses reveal higher 3,6-anhydrogalactose and lower sulphate contents in alkali-modified than in native agar from both samples. Also, alkali modification enhanced agar gel strength and syneresis. Native G. arcuata agar produces a viscous solution (2000 cP at 75 °C) with a high gelling point (>60 °C) that forms a soft gel even after alkali modification (gel strength: <300 g cm⁻²). On the other hand, the agar from G. tenuistipitata exhibits gel qualities typical of most Gracilaria agars. This revised version was published online in June 2006 with corrections to the Cover Date.     

Old field colonization by native trees and shrubs following land use change: Could this be Victoria’s largest example of landscape recovery?

Summary Natural regeneration of farmland areas following landuse change has the potential to reinstate native vegetation and landscape processes across larger scales than intentional works. However, few examples of large‐scale natural regeneration have been reported from southern Australia. In this study we use historical air photos to document the rate of establishment of natural regeneration in central Victoria following a change from agricultural to rural residential land use. In 2009, regrowth patches occupied 8185 ha, or 12.3% of the cleared landscape in the study region, mostly on relatively low fertility soils. Most of this area (6216 ha) supported Cassinia shrubland, with eucalypts encroaching as patches get older. On average, native vegetation has regenerated over nearly 1800 ha every decade since the mid‐1960s. If this trend continues, regrowth will occupy 20% of infertile soils on private land by 2025. This region now appears to support one of the largest examples of old field succession recorded from south‐eastern Australia. Regrowth patches are likely to provide many conservation benefits, although little information exists on habitat values provided by regrowth shrublands. Since regeneration is on private land, perceptions of whether regrowth is ‘good’ or ‘bad’ will vary according to landholder goals, as will future management of regrowth patches. Consequently, considerable ecological and social research is required to understand the ecosystem services and disservices which regrowth provides to both landholders and biota.     

Comparative culture experiments with filamentous members of the Bangiales (Rhodophyta) from New Zealand: Insights into ecologic adaptation and biogeography

Gametophyte cultures of seven genetically distinct, filamentous members of the Bangiales were grown under a range of temperatures (10°C, 12°C, 15°C and 20°C) and photoperiods, as well as lowered salinity (5 psu), in order to compare their responses to differing environmental regimes, and to evaluate the utility of a range of morphological, physiological and life history characters for distinguishing these entities. Significant differences in morphological characters such as filament width and cell size were found between some lineages. While these may have some regional diagnostic value, it was concluded that the practical use of these morphometric analyses is limited given the experimental growth period and replication required. The most useful characters for delineating filamentous Bangiales taxa were found to be the germination rates of spores, growth rates of filaments, timing and amount of spore release, and mortality of filaments. Different lineages appear to be adapted to particular environmental conditions, here represented by temperature/photoperiod, and salinity. The results of these comparative culture experiments provide some explanation for the seasonal occurrence and biogeographic distribution of the tested lineages around New Zealand.     

Specificity of a Y-linked gene in the flea beetle Phyllotreta nemorum for defences in Barbarea vulgaris

A Y-linked gene (R-gene) in the flea beetle Phyllotreta nemorum L. (Coleoptera: Chrysomelidae: Alticinae) confer the ability of larvae to survive on types of the plant Barbarea vulgaris R.Br. (Brassicaceae) which are immune to attack by susceptible conspecifics. Two near-isogenic flea beetle lines were developed. The YE-line contained the Y-linked R-gene, and male larvae from this line survived on B. vulgaris. The ST-line did not contain the gene and did not survive on the plant. The YE-line had been developed through 8–9 generations of backcrosses (YE-males with ST-females) and the two lines were considered to be isogenic except for genes located on the Y-chromosome.A single copy of the Y-linked gene is sufficient to transfer a susceptible genotype (ST) into a resistant genotype (YE) which is able to utilize a plant that is immune to attack by specimens without R-genes. The Y-linked gene had no effects on survival on other plant species tested. The gene did not have any effect on developmental times and weights of adult beetles reared on other plants than B. vulgaris. Developmental times of larvae with the Y-linked gene were longer on B. vulgaris than on normal host plants, R. sativus and S. arvensis, but the adults obtained the same size on these plant species. No trade-offs of the Y-linked gene were discovered. The results suggest that the occurrence of the Y-linked gene is a derived trait which has enabled the flea beetle to expand its host plant range. The evolution of a host shift to B. vulgaris seems not to be favoured by the presence of this single gene.     

Identification of Factors that Cause Heterophylly in Ludwigia arcuata Walt. (Onagraceae)

Abstract: The submerged leaves of Ludwigia arcuata are much narrower than the terrestrial leaves. Such heterophyllous changes in leaf shape have been observed in other aquatic angiosperms, such as Callitriche heterophylla, Hippuris vulgaris and Ranunculus flabellaris, but the cause of the formation of heterophyllous leaves in L. arcuata seems to be quite different. In contrast to other species, in which the shapes of epidermal cells have been changed, the change of leaf shape in L. arcuata was found to be due to changes in the numbers of epidermal cells aligned in transverse sections. The susceptibility of leaves to changes in shape above and below the water is dependent on the developmental stages: leaves younger than the fourth leaf responded to a change in environment, while leaves older than the fifth leaf did not. Treatment with ACC (1-aminocyclopropane-1-carboxylic acid), a precursor to ethylene, induced the formation of submerged-type leaves on terrestrial shoots, implying that ethylene might be the endogenous factor responsible for the change in leaf shape. The results are discussed with reference to the significance of the acclimation of plants to environmental changes.     

新疆豆科短命植物弯果胡卢巴根瘤与根瘤菌的特性

[目的]对弯果胡卢巴根瘤增殖特性、根瘤显微结构、根瘤菌遗传聚类以及根瘤菌各种抗性进行观察、分析和鉴定.[方法]分别利用不同基质培养、石蜡切片和树脂半超薄切片以及16S rRNA基因序列扩增和序列分析等技术方法对弯果胡卢巴根瘤和根瘤菌进行研究.[结果]①在混合土(养花土:白杨林下土:沙土=1:1:1)中有明显结瘤且植株结荚最多,多数根瘤呈掌状和姜形;②显微结构显示根瘤由表及里分为表层、皮层、维管束、已侵染细胞与未侵染细胞几部分;③对根瘤菌16S rRNA基因全长序列(1377bp)测序并分析,结果显示其与苜蓿中华根瘤菌16S rRNA基因的同源性达99.9%;④根瘤菌抗逆性鉴定结果显示,在温度为4℃～60℃(20 Min)、pH值为6.0～12.0、NaCl浓度为0%～2%的范围内根瘤菌均可正常生长;低浓度的卡那霉素、链霉素及头孢霉素等抗生素(25μg/mL,)就能完全抑制根瘤菌的生长,但仍能在100μg/mL的氨苄青霉素中正常生长.[结论]弯果胡卢巴结瘤需要较好的土壤及通气条件;根瘤簇生,瘤内含大量被根瘤菌侵染的细胞;弯果胡卢巴根瘤菌与苜蓿中华根瘤菌(sinorhizobium meliloti,)同源性最高,是一类较耐高温和强碱的菌株.     

Spread and potential host range of the invasive oak lace bug [Corythucha arcuata (Say, 1832) – Heteroptera: Tingidae] in Eurasia

1. The North American oak lace bug feeds on leaves of ‘white oaks” in its native range. In Europe, it was first discovered in northern Italy in 2000. In recent years, it has subsequently spread rapidly and population outbreaks have been observed in several European countries. In the present study, we summarize the steps of its expansion.
2. To predict its potential host range, we checked 48 oak species in 20 sentinel gardens in seven countries between 2013 and 2018.
3. In total, 27 oak species were recorded as suitable hosts; 13 of them are globally new ones, 23 out of the 29 in section Quercus (～ white oaks, an intrageneric taxonomic unit within genus Quercus), including Asian oaks, native to Japan, Korea and China, and four out of five in section Cerris (another intrageneric unit of the same genus), were accepted as hosts. None of the species in section Lobatae (red oaks) or in the Ilex group was accepted.
4. Host records were also collected in forest stands of 10 countries. We found 11 oak species that were infested. Outbreak populations were most commonly found on Quercus robur, Quercus frainetto, Quercus petraea and Quercus cerris, comprising widespread and outstandingly important oaks species in Europe.
5. Based on our findings, we conclude that suitable hosts for oak lace bug are present in most of Europe and Asia. This means that a lack of hosts will likely not restrict further range expansion.