The Botanical Review最新文献

There are few studies focused on spore and pollen clumps in paleopalynological samples, and these are only reports from the Northern Hemisphere. These aggregates may be of animal or floral origin. The goal of this contribution is to provide the first detailed study of spore and pollen clumps from the Southern Hemisphere, and to discuss their possible origin, botanical affinities, and pollination modes, based on their morphological characteristics, preservation and comparison with putative living representatives. Three fern spore clumps and 18 angiosperm pollen clumps were recognized in Maastrichtian-Danian La Colonia Formation sediments that outcrop at Chubut Province, Patagonia, Argentina. Most clumps are monospecific and composed of undamaged elements but some of them have two types of spore/pollen with corroded and/or fragmented exines. These findings represent the most diverse and abundant record of fern and angiosperm clumps from the Late Cretaceous and early Paleocene so far known from South America and the Southern Hemisphere. These results are indicative of the need for comprehensive large-scale studies on pollination of modern taxa and careful processing of palynological samples to lessen the already large bias in paleopalynological interpretations. The paucity of information on clumps in the fossil record has impaired our comprehension of dispersion/pollination in deep time.

Taxonomic data is essential to advance the discovery and description of biodiversity, as well as the study of evolutionary processes. Emerging large-scale datasets and new methods of analysis have provided different approaches to describe biodiversity. Here, we present a review of the taxonomic history in Cycadales including an analysis of historical taxonomic concepts and approaches used for species delimitation. We examine the trends in the publication of new species following taxonomic works in books, journals and horticultural catalogues, monographic projects and floras where species treatments were published. In addition, we review the studies concerning species delimitations using the literature available in scientific journals appearing in the database ISI Web of Knowledge. The approaches used were discussed throughout all research focused on empirical and theoretical considerations in each study. We review the current state of the studies on causal processes that have given rise to the currently recognized diversity. The trend shows that taxonomic work on discovery and description of species has been intensive in the last 40 years culminating in 38.8% of binomials published. As a result, we consider the relevance of the monographs and floras for identification of species for other biological disciplines and the content of these contributions is compared and discussed. A total of six criteria (diagnosability, phenetic, phylogenetic, genotypic cluster, niche specialization and coalescent) were detected from the following three approaches to species delimitation within Cycadales: traditional, integrative taxonomy, and monophyletic. In all cases, the results from these species delimitations not only provided a taxonomic treatment or proposed a new species, but also supposedly clarified the other species involved as a result of the new taxonomic concept of the new species described. Most investigations of species delimitation used the traditional approach or a phenetic criteria. Finally, we discuss evolutionary studies on causal processes involved in cycad diversity. This is considered in the context of species delimitation as hypothesis testing for a successful evaluation of variation in both genetic and morphological understanding.

Apomixis is considered to be a natural mode of clonal propogation from seed to seed, in which progeny serves as a replica of maternal genotype. The process evades creation of variation by circumventing sexual fusion and recombination, offering great advantage to fix heterosis or hybrid vigour in plants. As this would permit the conservation of complex favourable genotypes that are of agricultural value, it has immense potential in crop seed production. In order to accomplish this, a comprehensive knowledge on the genetic basis and the molecular mechanisms regulating different components of apomixis stands as a key prerequisite. So far, despite of the persistent interest and extensive research on apomixis, the underlying gene regulatory networks and their evolutionary origins are not well deciphered and still remain unclear. From the developmental perspective, apomixis is widely accepted to be controlled or deviated form of sexual reproduction and studies based on comparative analysis of genes or mutants regulating sexual and apomictic pathways revealed their resemblance across various plant species. Since apomixis is a complex, yet well regulated phenomenon that constantly requires action of specific genes during all developmental stages, the present review summarises recent advances in apomixis and compiles information on vital genes and mutants involved in regulating apomixis during various stages of development.

Graphical abstract

Graphical abstract: Brief illustration on mechanisms of apomictic and sexual life cycle in angiosperms. Apomixis avoids the process of meiosis and recombination offering advantage over sexuals by conservation of heterosis or vigor for several generations, easy maintenance of superior genotypes and rapid production of homozygous lines. In sexuals owing to nuclear division and fertilization, fixation of heterosis cannot be achieved and maintenance/development of homozygous lines becomes intricate.*Based on the fertilization the ploidy of endosperm may vary.

With about 11,100 islands and islets of which ca. 250 are regularly inhabited by human, the Mediterranean Sea represents one of the regions of the world with the most islands and archipelagos. These numerous islands represent a significant component of the Mediterranean biodiversity, notably with the presence of range-restricted species and peculiar vegetation types. The aim of this review is to provide a balanced view of this highly diverse phytoecological heritage, but also taking into account the medium sized islands and the smaller ones that have not been highlighted so far. Mediterranean islands constitute both a museum for ancient lineages (paleoendemic taxa) and cradle for recent plant diversification. The complex historical biogeography (paleogeographical events of the Neogene, Messinian salinity crisis, climatic and eustatic changes of the Pleistocene, influence of glacial events) has profoundly influenced the current patterns of plant diversity. These insular landscapes were also precociously impacted by prehistoric man, possibly by Neanderthals. Among the 157 large Mediterranean islands (i.e. with a surface area exceeding 10 km²), 49 have a surface greater than 100 km². The main patterns and dynamics of vegetation on the largests islands (Balearic Islands, Corsica, Sardinia, Sicily, Croatian islands, Greek islands, Crete, Cyprus) are summarized. Then, the specific ecosystem functioning (disturbance, plant-animal interactions) and vegetation structures of the small Mediterranean islands (i.e. a surface area less than 10 km² or 1000 ha), are highlighted by evoking successively the small rocky islands, the volcanic ones, and the sandy and flat islands. Owing to their uniqueness and fragility, Mediterranean islands urgently need some integrated and ambitious conservation planning, aiming at the long-term preservation of their outstanding biotic and cultural heritage.

The genus Empetrum (Ericaceae) is controversially classified taxonomically. It is conservatively treated as comprising one variable widespread circumboreal/circumarctic species, E. nigrum, usually known as black crowberry (although there are other fruit colors), and a comparatively localized circumantarctic species, E. rubrum, called red crowberry. For millennia in the Northern Hemisphere crowberries have been a valuable source of berries for Indigenous Peoples, and indeed Empetrum is one of the most important berry crops of the Arctic. It has recently begun to be marketed as a commercial processed fruit crop, with increasing evidence of possessing phenolic compounds of high value for nutrition and medicine. Ecologically, Empetrum is a keystone species, sustaining numerous birds and mammals, and dominating many tundra and heathland ecosystems through allelopathic toxins that exclude competitive plants. With climate change expected to greatly alter the northern world in the near future, there is considerable concern about the welfare of Empetrum.

Alzheimer’s Disease (AD), a progressive neurodegenerative disorder linked to increasing age, is the primary cause of dementia in the world. Clinically, it is characterized by cognitive impairments, progressive memory deficits and diminished learning ability. Despite the comprehensive research in AD, none of the existing treatments prevents the onset and progression of the disease. The use of medicinal plants is a fundamental component of the African traditional healthcare system due to its accessibility and affordability in many parts of rural Africa. However, there is a dearth of an updated comprehensive compilation of potential medicinal plants from the African continent commonly used in the management of AD. The primary focus of the present article is to review evidence from selected African plants in experimental and preclinical studies which have promising prospects to be developed as novel therapeutic agents for the treatment of AD. To achieve this, major scientific databases such as Science Direct, Pubmed, Scopus, Web of Science and Google Scholar have been searched to investigate and gather information on African traditional medicinal plants useful for the treatment of cognitive deficits, memory impairments and AD. Our search results showed several commonly used medicinal plants and their possible mechanisms of action including inhibition of acetylcholinesterase activity, modification of Aβ processing, protection against oxidative stress and regulation of antioxidant enzymes activity. This review therefore provides a compilation of medicinal plants that could be further studied for their bioactive constituents; these may become safe, effective and novel therapeutic candidates for the treatment of AD.

Wheat and barley are among the most important staple foods, originally exploited, cultivated and domesticated in the Near East, in places between the Eastern shores of the Mediterranean Sea and Western slopes of the Zagros Mountains, at the beginning of the Holocene epoch. Almost all wild progenitors of the domesticated species of wheat and barley naturally grow in Iran, a Near Eastern Country, and were frequently exploited by the residents of the Iranian plateau throughout history. The cultivation of grains was initiated by hunter-gatherers dwelled in Iran as a supplementary source of food in the 12th millennium BP; however, the domestication of wheat and barley, in the 10th millennium BP, revolutionized life-style of the Iranian people, and led to a gradual but steady increase in the complexity of human societies in Iran. Every aspects of grain cultivation and its technical difficulties pushed forward human societies to develop more and more efficient methods of cultivation, irrigation, transportation, storage and reservation, food preparation, trade and commercialization, governmental taxation and scientific exploration and invention, which were reviewed briefly in the current manuscript on the basis of the available archaeological and archaeobotanical literature, covering a timespan from 12th millennium BP to 1st millennium AD.