Role of resting cysts in Chilean Alexandrium catenella dinoflagellate blooms revisited

The detection of sparse Alexandrium catenella-resting cysts in sediments of southern Chilean fjords has cast doubts on their importance in the recurrence of massive toxic dinoflagellate blooms in the region. The role of resting cysts and the existence of different regional Chilean populations was studied by culturing and genetic approaches to define: (1) cyst production; (2) dormancy period; (3) excystment success; (4) offspring viability and (5) strain mating compatibility. This study newly revealed a short cyst dormancy (minimum 69 days), the role of key abiotic factors (in decreasing order salinity, irradiance, temperature and nutrients) controlling cyst germination (max. 60%) and germling growth rates (up to 0.36–0.52 div. day⁻¹). Amplified fragment length polymorphism (AFLP) characterization showed significant differences in genetic distances (GD) among A. catenella populations that were primarily determined by the geographical origin of isolates and most likely driven by oceanographic dispersal barriers. A complex heterothallic mating system pointed to variable reproductive compatibility (RCs) among Chilean strains that was high among northern (Los Lagos/North Aysén) and southern populations (Magallanes), but limited among the genetically differentiated central (South Aysén) populations. Field cyst surveys after a massive 2009 bloom event revealed the existence of exceptional high cyst densities in particular areas of the fjords (max. 14.627 cysts cm⁻³), which contrast with low cyst concentrations (<221.3 cysts cm⁻³) detected by previous oceanographic campaigns. In conclusion, the present study suggests that A. catenella resting cysts play a more important role in the success of this species in Chilean fjords than previously thought. Results from in vitro experiments suggest that pelagic–benthic processes can maintain year-round low vegetative cell concentrations in the water column, but also can explain the detection of high cysts aggregations after the 2009-bloom event. Regional drivers that lead to massive outbreaks, however, are still unknown but potential scenarios are discussed.     

温度对叶用莴苣春化的影响

为了探讨温度对叶用莴苣春化的影响,进而明确其春化类型,本试验选用两个易抽薹叶用莴苣品种GB-30和GB-31为试材,分别进行20 d的4、20和25 ℃处理,然后均进行高温胁迫促进抽薹,采用石蜡切片观察茎尖花芽分化进程,并结合后期抽薹开花情况来判断是否进行春化,并确定其春化类型.结果表明:两个品种在前期经过3种温度处理后,在高温胁迫第8天时均有不同程度的抽薹.两个品种不同温度处理下花芽均进行了分化,前期4 ℃处理并没有使其花芽分化明显提前,后期的高温胁迫可以明显促进花芽分化进程.两品种间在不同温度处理下完成各发育阶段所需天数存在差异,两品种各处理从催芽到开花以及从高温到开花的有效积温也存在差异.前期未经低温处理的叶用莴苣也进入花芽分化、抽薹、现蕾及开花阶段,表明叶用莴苣为非低温春化型植物,后期高温处理能明显促进其抽薹开花,而且从催芽开始只有有效积温达到约2500 ℃·d才能开花.     

冷激对高温胁迫下番茄幼苗生长及花芽分化的影响

为了解苗期冷激锻炼对番茄幼苗生长和花芽分化的影响,试验采用人工气候箱模拟夏季设施高温环境,每天对番茄幼苗进行10 ℃、10 min的冷激锻炼,研究冷激处理对高温胁迫下番茄幼苗生长、叶片超微结构和花芽分化进程的影响,并观察定植后开花和坐果情况.结果表明：在4叶期经过冷激锻炼的番茄幼苗茎粗、壮苗指数分别比对照提高了7.2%和55.5%;经过冷激锻炼处理的番茄幼苗叶片中叶绿体和线粒体等细胞器形状及结构正常完整,一定程度上缓解了高温对番茄幼苗叶肉细胞超微结构的破坏;冷激锻炼显著提高了番茄幼苗早期花芽分化的分化进程,但随着苗龄的延长这种差异变得不显著.定植后经冷激处理的番茄幼苗第1、2穗果的坐果数和坐果率显著高于未经冷激处理.表明冷激锻炼不仅能够缓解高温对番茄幼苗细胞超微结构的伤害和生长的胁迫,还有利于早期花芽分化进程的提前,提高番茄坐果数和坐果率.     

Micropropagation of Ranunculus Asiaticus: A Review and Perspectives

Ranunculus asiaticus is an important ornamental species mainly cultivated in the countries surrounding the Mediterranean sea. So far the multiplication of this plant has been mainly carried out by seed and rhizome division; however, these systems present many drawbacks. Tissue culture is an attractive alternative for accelerated propagation of selected and indexed genotypes. In this paper we review the work carried out on in vitro culture of R. asiaticus and present a flow chart for its commercial production, using axillary budding and embryogenesis. Although the price of micropropagated plants is higher compared to traditional material (seedlings and rhizomes from seed populations), it should be considered that tissue cultured plants have a better rhizome yield per plant; moreover, the tissue culture approach allows to offer clonal material of selected lines.     

A Review of Ship Breaking and Rig Scrapping in the Gulf of Mexico

Ship breaking and rig scrapping is the process in which a unit is broken down and recycled into salvageable components, cut into pieces, and transported to a domestic steel mill or exported on a cargo vessel. Breaking is a labor-intensive, low-technology, and relatively homogeneous industry. Work conditions in breaking yards are difficult, dangerous, and potentially hazardous, with operations that are not well suited for mechanization. Ship breaking and rig scrapping share many common features in workflows, worker safety, and environmental issues, but also have notable differences in breaking cost and industry structure. Ship breaking and rig scrapping do not play a major role in the material handled by scrap processors in the United States, but they are part of the unique industrial landscape associated with the offshore energy industry. The purpose of this article is to review the scrap and storage markets for ships and rigs in the Gulf of Mexico. The disposal alternatives, inventory statistics, and the factors that influence breaking and disposal cost are reviewed. The primary environmental protection and worker safety statutes are also outlined.     

Fragment Propagation and Colonization Ability Enhanced and Varied at Node Level after Escaping from Apical Dominance in Submerged Macrophytes

Aquatic plants develop strong fragment propagation and colonization ability to endure the natural disturbances. However,detailed research of ability to endure the natural disturbances has been lacking to date. Therefore, reproduction (shoot) and colonization (root) of shoot fragments of Potamogeton crispus L. with or without apices were investigated for the effect of apical dominance, and the growth of decapitated shoot fragments at three lengths (2, 4, 6cm) was compared. Meanwhile,fragment propagation at levels of bud position was studied for bud position effect after escaping from apical dominance.The results showed significant increases occurred in the outgrowth of lateral branches on fragments decapitated compared with the fragments with apices, implying that apical dominance exists. Different lengths of fragments showed little difference in biomass allocations, but significant differences were noted in their propagation. Meanwhile, the effect of bud position was verified, due to the significant difference of average reproduction per node among the three length groups. Thus, the present study has made progress in the current understanding of aquatic plant dispersion among natural systems and contributes to improve methods of in vitro propagation for re-implantation purposes.     

Overexpression of a wheat α-amylase type 2 impact on starch metabolism and abscisic acid sensitivity during grain germination

Despite being of vital importance for seed establishment and grain quality, starch degradation remains poorly understood in organs such as cereal or legume seeds. In cereals, starch degradation requires the synergetic action of different isoforms of α-amylases. Ubiquitous overexpression of TaAmy2 resulted in a 2.0–437.6-fold increase of total α-amylase activity in developing leaf and harvested grains. These increases led to dramatic alterations of starch visco-properties and augmentation of soluble carbohydrate levels (mainly sucrose and α-gluco-oligosaccharide) in grain. Interestingly, the overexpression of TaAMY2 led to an absence of dormancy in ripened grain due to abscisic acid (ABA) insensitivity. Using an allosteric α-amylase inhibitor (acarbose), we demonstrated that ABA insensitivity was due to the increased soluble carbohydrate generated by the α-amylase excess. Independent from the TaAMY2 overexpression, inhibition of α-amylase during germination led to the accumulation of soluble α-gluco-oligosaccharides without affecting the first stage of germination. These findings support the hypotheses that (i) endosperm sugar may overcome ABA signalling and promote sprouting, and (ii) α-amylase may not be required for the initial stage of grain germination, an observation that questions the function of the amylolytic enzyme in the starch degradation process during germination.