Palaeoenvironmental and palaeobiogeographical implications of fossil seeds and charophytes from the Lameta Formation (Late Cretaceous), Jabalpur,Madhya Pradesh,India

A Late Cretaceous fossil flora composed of five fossil seed genera and two charophyte genera was discovered and reported here from the siltstone and green marl band of the Lameta Formation at the Chui Hill section and the Chhota Simla Hill section in the Jabalpur area. On the basis of comparative studies, including thin-section and XRD analysis, the palaeoenvironment is deduced to be arid to semi-arid fluvial-lacustrine. The recovered flora suggests Laurasian palaeobiogeographic affinity and shows the dispersal route from Europe to India via Africa.     

水稻种子内生泛菌(Pantoea spp.)系统发育多样性及其促生功能

【目的】Pantoea菌株是广泛分布在自然界中的一类功能多样的细菌。本研究对分离自水稻种子内生的Pantoea菌株进行系统发育分析及功能评价,从而确定分类地位、种类多样性、分布特征及功能特性。【方法】采用乙醇-次氯酸钠联合灭菌方法进行水稻种子的表面灭菌,进行内生细菌的分离与纯化;其次将纯化后的菌株进行16Sr RNA基因PCR扩增及序列分析,通过MEGA7软件构建系统发育树;将分离得到的菌株进行功能实验检测,如溶磷、产IAA、产铁载体、拮抗病原真菌等特性,最后检测菌株的溶血性;水稻分型采用SSR方法,并对水稻农学性状如分蘖数、株高、植株重及产量进行调查。【结果】本研究对分离自8个不同基因型水稻种子中的146株内生Pantoea菌株进行系统发育分析及功能评价,结果发现所分离到的泛菌菌株主要属于Pantoea dispersa、Pantoea agglomerans、Pantoea cypripedii以及Pantoea brenneri四个种,其中P. dispersa的菌株数量最多,分布最广,并且存在于所有的8个水稻种子样品中。对其中66株菌进行功能检测,发现86.3%和69.7%的菌株具有溶磷和产IAA能力,有7株菌具有产铁载体能力,未发现对真菌病害Fusarium moniliforme有拮抗作用的菌株,并发现3株菌具有溶血性;本实验未发现泛菌组成与水稻系统发育及农学性状存在明显的相关性。【结论】本研究首次对水稻种子中泛菌的多样性及其功能进行报道,发现不同基因型的水稻种子所含Pantoea种类及组成存在差异,种子选择性地积累了Pantoea类群,大部分菌株具有一定的促生特性。该研究结果有助于进一步探究微生物与植物的共进化、种子微生物的传播途径及作用方式。     

Cryopreservation of shoot tips of recalcitrant and tropical species: Advances and strategies

There is a pressing need for practical and successful conservation efforts to establish long-term germplasm collections of recalcitrant and tropical species, given the challenge and threat that these plants are facing. Cryopreservation is the only way of conserving some of these species, especially those with temperature or desiccation sensitive (recalcitrant) seeds. This review covers reports on cryopreservation studies of shoot tips (apical and axillary) of tropical and subtropical plants. Since many of these species have recalcitrant seeds, the cryopreservation successes, failures and problems involved with these seeds are also discussed. The methodologies, important factors and steps involved in successful cryopreservation protocols are analyzed. Finally strategies are suggested to develop a successful cryopreservation protocol for new plant species, in particular those with tropical recalcitrant seeds.     

Seed germination ecology and salt stress response in eight Mediterranean populations of Sarcopoterium spinosum (L.) Spach

This study aims to deepen the analysis of seed germination ecology and salinity tolerance of Sarcopoterium spinosum (Rosaceae). Germination tests were conducted to evaluate the effect of the fruit’s spongy tissue and the intraspecific variability in seed germination among eight populations of the species on responses to light and total darkness, constant and alternating temperatures, salt stress and germination recovery. The effect of the presence of the spongy tissue varied among populations, with significant results for seed germination. For all populations, optimum germination temperatures were observed in the range of 10–20°C, indicating that S. spinosum and its germination in the field might occur preferably in the period between autumn and early spring. The high water availability due to rainfall during this period could be a considerable advantage for the seed germination of this species. Seeds of S. spinosum showed the ability to germinate in up to 250 mM NaCl in the substrate, and their ability to recover after salt exposure may be interpreted as adaptation to the coastal habitats in which they generally grow. These results give this species a halo-tolerant character. Great inter-population variability is detected in this study in several aspects, which indicated that the Mediterranean populations of S. spinosum differ considerably and are adapted to their local conditions. This study provides new information about S. spinosum seed ecology, which could help to preserve and apply effective conservation measures for this species, which in several areas of its distribution range is endangered.     

An Introduction to a Special Issue on Large‐Scale Submerged Aquatic Vegetation Restoration Research in the Chesapeake Bay: 2003–2008

The Chesapeake Bay is one of the world's largest estuaries. Dramatic declines in the abundance and distribution of submerged aquatic vegetation (SAV) in the Chesapeake Bay over the last few decades led to a series of management decisions aimed at protecting and restoring SAV populations throughout the bay. In 2003, the Chesapeake Bay Program established a goal of planting 405 ha of SAV by 2008. Realizing that such an ambitious goal would require the development of large‐scale approaches to SAV restoration, a comprehensive research effort was organized, involving federal and state agencies, academia, and the private sector. This effort differs from most other SAV restoration programs due to a strong emphasis on the use of seeds rather than plants as planting stock, a decision based on the relatively low labor requirements of seeding. Much of the research has focused on the development of tools and techniques for using seeds in large‐scale SAV restoration. Since this research initiative began, an average of 13.4 ha/year of SAV has been planted in the Chesapeake Bay, compared to an average rate of 3.6 ha/year during the previous 21 years (1983–2003). The costs of conducting these plantings are on a downward trend as the understanding of the limiting factors increases and as new advances are made in applied research and technology development. Although this effort was focused in the Chesapeake Bay region, the tools and techniques developed as part of this research should be widely applicable to SAV restoration efforts in other areas.     

Assessment of Age-Related Polyploidy in Quercus Robur L. Somatic Embryos and Regenerated Plants Using DNA Flow Cytometry

Flow cytometric analysis with 4,6-diamidino-2-phenylindole (DAPI) staining was used to screen for chromosomal changes in Quercus robur during in vitro culture. The initiated cell lines (1992 until 1999) were maintained via secondary embryogenesis on P24 medium with 0.9 M 6-benzylaminopurine (BAP) in regular subculture intervals of 6 weeks. Regenerated plants established in the greenhouse and in vitro plantlets derived from encapsulated somatic embryos were screened. The embryogenic cell lines were characterized as individual clones by isoenzyme analysis. Flow cytometric relative DNA content analysis of the first screening period revealed that somaclonal variation in form of tetraploidy occurred in two out of 26 tested somatic embryo clones (Alt and Jung). These two clones lost their ability to convert into plantlets. Intraspecific relative DNA content variation including technical variation was below 3 %. In the second screening period, however, 3 out of 37 clones (Alt, E4.31H9 and P3.27H) contained tetraploid cells leading to the assumption that the frequency of tetraploidy seems to be correlated with the duration of in vitro culture. No chromosomal differences were detected in regenerated plants. However, tetraploidy occurred in 8 % of the tested clones over a culture period of 7 years.     

Regeneration failure of lakeshore plants under an artificially altered water regime

To reveal the effects of artificial alteration of water level regime on the regeneration of lakeshore plants from seeds, we examined the factors causing regeneration failure in Lake Kasumigaura, Japan. A survey of microtopography within and around a remnant fragment of lakeshore vegetation revealed that, over a large range, the habitat is frequently inundated in spring under the current water regime, although it was rarely inundated under past water regimes. Analysis of the patterns of seedling emergence and establishment at microsites at various elevations revealed a significant negative correlation between number of inundation days and abundance or species-richness of seedlings that emerged in the spring. Most seedling deaths occurred when the study site was inundated. We suggest that regeneration failure caused by the artificial raising of the lakes water level is one of the principal mechanisms of the recent vegetational decline in the lake.