The complex structure of higher plant chloroplasts has fascinated researchers for many years. Although the spatial relationship between granum and stroma thylakoids has been known for more than 20 years, most textbooks and research papers continue to include erroneous 3D models and simplified schemes. Here we present a simple computer model, based on electron micrographs from serial section of granum—stroma assemblies, showing the striking 3D structure of the stroma membrane wound around the granum.
Posted Jan 14, Why would I recommend dosing silica?
Largely because creatures in our tanks use it, the concentrations in our tanks at least in mine are below natural levels, and the sponges, mollusks, and diatoms may not be getting enough to thrive.
Contents Silica is a chemical that is feared by many reef keepers. More recently, others have suggested that soluble silica does not, in fact, increase diatom growth in reef tanks. Much of the debate swirls around whether silica sand is a good choice for the substrate in a reef tank. According to different individuals, it can easily release soluble silica, or it cannot possibly do so.
In this case it appears that the truth is somewhere between these views. In this article I will expand on a previous article covering silica in reef tanks by Craig Bingman.
When adequate silicate is added to my reef tank, diatom growth appears to increase. Contrary to popular notions, however, the increased diatom growth actually makes my glass easier to see through than the green algae that it replaced.
In this article, I will not generally refer to silicic acid or silicate unless I am specifying one or the other. The concentration of soluble silica in the ocean is highly variable.
In near surface waters, diatoms are very efficient at sucking it out of solution to make their SiO2 frustules. A diatom bloom in the ocean can drive the concentration of silica down from a value not atypical for the whole ocean, 45 mM 2.
This input is approximately balanced by the deposition of silica on the ocean bottom. The average residence time for a single silicon atom in the oceans is only about years, before it gets deposited in some fashion.
All ocean waters are undersaturated with respect to amorphous silica allowing the silica structures in diatoms and radiolarians to dissolveand most waters are undersaturated even with respect to quartz,5 although its dissolution is kinetically slow, allowing beaches to exist.
A view through the front glass of my reef tank a few hours after scraping the glass. Marine Organisms that Use Silica: Diatoms There are a variety of marine organisms that use silica.
In the oceans, the primary consumers are diatoms. They use silica to form frustules that provide them with a hard, silica-containing cell wall. These frustules form a dizzying array of beautiful patterns, and are well represented at the interface between science, art, and photography.
A view through the front glass of my reef tank 5 days after scraping the glass. With one exception discussed below all diatoms require silica for growth, and low silica levels cause significant changes in the cell cycle.
There have been many studies on the uptake of silica by diatoms. Most diatoms take up silica in the form of silicic acid, although one has been shown to take up the silicate form.
Different diatom species have different abilities to absorb silica from the water. That is, as the silica concentration drops, some diatoms can continue to pull silica from the water while others cannot.
Most diatoms have half maximal rates of silica absorption of 0. Nevertheless, it is obvious that this facilitates the deposition process, and inhibits dissolution of the existing frustule.
Diatoms apparently use proteins to guide the deposition process, where soluble silica is converted into the intricate solid frustule, but exactly how this role is accomplished is not known. Many reef tanks may, in fact, be selecting for diatoms that are able to get enough silica at the low concentrations typically available.
Contents Contents Preface Acronyms. Some Russian and English Geographical Names Introduction. Chapter 1. History Of Regular Observations Over The Kerch Strait And The Data Sets Available. Iron (Fe) Deficiency i*n *Cyanobacteria Fe in cyanobacteria serves as an essential redox component important to diverse metabolic pathways. Fe-rich systems in cyanobacteria such as the photosynthetic apparatus and the respiratory electron transport system are dependent on Fe supply (Raven et al., ). TOXIC METALS IN PLANTS. Copper in plants. Cobre em plantas. Inmaculada Yruela. Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), .
Are diatoms silica-limited in reef tanks? That question is addressed experimentally below. In the oceans, diatoms are silica limited in some natural settings like the polar regions and the Sargasso Sea, where the ambient silica concentration is less than 1 mM 0.
In reef tanks, where nitrogen and phosphorus are often not in short supply, it makes sense that silica could be limiting. In case you were thinking that silica limitation to diatom growth is necessarily a good thing, there are drawbacks. The limitation of silica, inhibiting the growth of diatoms that would otherwise take up the limiting nutrients nitrogen and phosphorus, has even been implicated in blooms of cyanobacteria.Use: Calcium Chloride is an excellent water soluble crystalline Calcium source for uses compatible with chlorides.
Chloride compounds can conduct electricity when fused or dissolved in water. a) Iron deficiency in the blue-green alga Anacystis nidulans: changes in pigmentation and photosynthesis.
Physiol Plant 30–37; Öquist G ( b) Iron deficiency in the blue-green alga Anacystis nidulans: fluorescence and absorption spectra recorded at 77K. Physiol Plant 55–58; Pakrasi HB, Goldenberg A, Sherman LA ( Complete Planted Aquarium Information; Substrate, bio available carbon (CO2), Nutrients, GH, KH, pH, lighting.
Aquarium plant resources, algae control & fish.
Iron (Fe) Deficiency i*n *Cyanobacteria Fe in cyanobacteria serves as an essential redox component important to diverse metabolic pathways. Fe-rich systems in cyanobacteria such as the photosynthetic apparatus and the respiratory electron transport system are dependent on Fe supply (Raven et al., .
Since the low solubility of Fe +++ above neutral pH in oxic ecosystems severely limits the biological availability of iron to aquatic microorganisms, cyanobacteria and other microbes have developed a number of responses to cope with iron deficiency.
Cyanobacterial responses to iron stress include the synthesis of an efficient, siderophore-based system to scavenge iron and the substitution of ferredoxin . Iron Deficiency and Iron Reconstitution in the Cyanobacterium Synechocystis sp. PCC [w] Abhay K. Singh, Lauren M. McIntyre, and Louis A.
Sherman* Many other changes are associated with Fe deficiency in cyanobacteria and cells continue to grow, although the growth rate is .