Since the discovery two decades ago that transgenes are efficiently integrated into the genome of Physcomitrella patens by homologous recombination, this moss has been a premier model system to study evolutionary developmental biology questions, stem cell reprogramming, and the biology of nonvascular plants. P patens was the first non-seed plant to have its genome sequenced. With this level of genomic information, together with increasing molecular genetic tools, a large number of reverse genetic studies have propelled the use of this model system. A number of technological advances have recently opened the door to forward genetics as well as extremely efficient and precise genome editing in P patens Additionally, careful phylogenetic studies with increased resolution have suggested that P patens emerged from within Physcomitrium Thus, rather than Physcomitrella patens, the species should be named Physcomitrium patens Here we review these advances and describe the areas where P patens has had the most impact on plant biology.
We recently published an account on an exceptionally well-preserved non-marine thalloid organism from the Triassic of the Transantarctic Mountains.8 This organism, Litothallus ganovex, occurs as compressions of rosette-like thalli (Fig. 1A) with associated cellular sheets (Fig. 1C and D). The exquisite preservation of the fossils enabled a detailed study of the peculiar anatomy of the organism. The thallus of L. ganovex consists of densely spaced, vertical cellular filaments that are laterally fused to form a sheet- or crust-like structure (Fig. 1B). Thalloid bodies containing such pseudotissues only occur in certain algae and lichens. It appears most likely that L. ganovex represents a freshwater macroalga based on its striking resemblance to certain extant freshwater representatives of the red algal order Hildenbrandiales. We speculated that L. ganovex may have been a widespread constituent of certain Triassic freshwater ecosystems that was simply overlooked by earlier workers because of its inconspicuous appearance; Litothallus superficially resembles a coaly film on a sediment bedding plane. Recently we had the opportunity to study the large collection of Mesozoic plant fossils from various localities in Antarctica housed at the Natural History Museum and Biodiversity Research Center of the University of Kansas, Lawrence, KS. It appeared that many slabs with Triassic plant fossils also contain abundant Litothallus specimens, which demonstrates that this organism was in fact more common than we had originally envisaged. In some of the slabs large accumulations of thalli may even form thin coaly layers in the sediment.
Mosses and liverworts are some of the many organisms found in Arches that most people do not associate with deserts. Mosses can tolerate long periods of complete dehydration and occupy a variety of habitats in the park, including exposed rocks, biological soil crusts, riparian areas and sometimes trees. They do best in shady canyons, north-facing slopes and at the bases of shrubs. Most liverworts must be near water to survive, and are very rare in the park.
Like all photosynthetic organisms, mosses are primary producers that build biomass through photosynthesis. They enrich ecosystems with organic matter, forming the basis of the food chain. As a component of biological soil crusts, mosses trap airborne soil particles, reduce erosion, retain water and may enhance water infiltration.
Fragmentation in multicellular or colonial organisms is a form of asexual reproduction or cloning, where an organism is split into fragments. Each of these fragments develops into mature, fully grown individuals that are clones of the original organism.
The organism may develop specific organs or zones to shed or be easily broken off. If the splitting occurs without the prior preparation of the organism, both fragments must be able to regenerate the complete organism for it to function as reproduction.
Molds, yeasts and mushrooms, all of which are part of the Fungi kingdom, produce tiny filaments called hyphae. These hyphae obtain food and nutrients from the body of other organisms to grow and fertilize. Then a piece of hyphae breaks off and grows into a new individual and the cycle continues.
Sponges and coral colonies naturally fragment and reproduce. Many species of annelids and flatworms produce by this method.When the splitting occurs due to specific developmental changes, the terms orchiectomy, laparotomy, and budding are used. In'architomy' the animal splits at a particular point and the two fragments regenerate the missing organs and tissues. The splitting is not preceded by the development of the tissues to be lost. Before splitting, the animal may develop furrows at the zone of splitting. The headless fragment must regenerate a completely new head.In 'paratomy', the split occurs perpendicular to the antero-posterior axis and the split is preceded by the "pregeneration" of the anterior structures in the posterior portion. The two organisms have their body axis aligned i.e. they develop in a head to tail fashion. Budding is similar to paratomy except that the body axes need not be aligned: the new head may grow toward the side or even point backward (e.g. Convolutriloba retrogemma an acoel flat worm).
Plants that have structures that transport food and water throughout the plant are called vascular plants. Examples of vascular plants are trees and flowering plants. Examples of nonvascular plants are moss, liverworts, and hornworts. A plant stem gives a plant structure and supports the growth of the plant. Tubes within a plant stem move water and nutrients upwards from the plant roots, allowing the plant to grow.
Back in centuries, different taxonomists aimed to classify organisms in groups (taxonomy). They identified the differences ad characteristics and grouped them. Similarly, the plants, constituting the largest Kingdom with a wide range of plants from lower to high ordered plants, were classified.
The classification of plants or any other organism is a continuous process going on for centuries. Thus, botanical nomenclature international rules constitute revisions for plant classification based on several factors such as gymnosperms (Penhallow and others) that do not show characteristics up to international standards. However, the recently revised classification pattern of plants classification consists of the following divisions and sub-division:
Plants, either vascular or non-vascular, are a way to a better environment and important for different living organisms. However, vascular plants are widely spread and provide several benefits to creatures, including birds, animals, and humans.
The benchmarks are based on toxicity values from scientific studies that EPA reviewed and used to estimate risk to freshwater organisms from exposure to pesticides and their degradates in their most recent publicly available ecological risk assessments and preliminary Problem Formulations written in support of pesticide registration or registration review. The toxicity studies are responsive to data requirements specified in U.S. Code of Federal Regulations (40 CFR 158). EPA uses Harmonized Test Guidelines and the Evaluation Guidelines for Ecological Toxicity Data in the Open Literature to evaluate the quality and utility of the studies. For each of the chemicals listed, the table provides a link to the source documents from which each of the benchmarks is extracted.
Autotrophs: an organism that makes its own food from light energy or chemical energy without eating. Most green plants, many protists and most bacteria are autotrophs. Autotrophs are the base of the food chain and can also be called producers.
Ballast water: water carried in ship's for stability. Water is pumped into a ship's hold to steady it; when the water is released in other oceans the organisms in it may become pests (or invasives).
Parasitism: similar to predation in that one species benefits from the relationship and the other is harmed; differs from predation in that parasitism generally not fatal to adversely affected organism.
Producer: autotroph; organism that creates energy-rich compounds from sunlight (through photosynthesis) or certain chemicals (through chemosynthesis); first level in any food web; in estuarine systems, most abundant producers are phytoplankton.
Water column: the area of water from the seafloor up to the water surface. The water column contains free swimming, or pelagic, organisms and plankton (tiny drifting and floating organisms). The water column is a part of all bays, sloughs, lagoons and coastal areas; and is therefore part of an estuary.
Nonvascular plants can be classified as bryophytes. Bryophytes include mosses, hornworts, and liverworts. Some algae, including green algae, are also nonvascular, but are not classified as bryophytes.
Nonvascular means there is no vascular system. In nonvascular plants, there is no vascular system, or xylem and phloem, to transport water and nutrients. Nonvascular plants absorb nutrients through their cells.
Nonvascular plants are defined as a classification of plants without a vascular system (xylem and phloem). Also referred to as lower plants, nonvascular plants are the earliest form of terrestrial plants. They evolved from algae an estimated 500 million years ago. Nonvascular plants are distinguished from other classifications of plants including angiosperms (flowering plants), gymnosperms, and ferns because they lack flowers, fruits, seeds, leaves, roots, and stems. Mosses, hornworts, and liverworts are nonvascular plants called Bryophytes. There are an estimated 17,000 species of bryophytes and occupy almost every habitat type. Some species of algae are also considered nonvascular plants, particularly green algae. This lesson will review the characteristics of Bryophytes, provide examples, and discuss the importance of these plants. 041b061a72