Use diffusion to extract nutrients from the water. Not plants or animals, but protists. Evolved from terrestrial plants and have tissues that are specialized for certain tasks. Use roots and rhizomes to extract nutrients from the sediment; use leaves for extracting nutrients from the water.
Besides, seaweed lacks vascular tissues, while seagrass has vascular tissues. Thus, this is another significant difference between seaweed and seagrass. Moreover, seaweed is not differentiated into true stem, roots and leaves while seagrass has a differentiated structure with a true stem, roots and leaves.
Below infographic lists more differences between seaweed and seagrass in tabular form for side by side comparison. Seaweeds are marine macroalgae. They are not true plants. They lack true stems, leaves and roots. Moreover, they lack vascular tissues. Seagrasses are actual grasses or plants. They are marine flowering plants that have true stems, roots and leaves. They also have vascular tissues. Seaweeds belong to kingdom Protista while seagrasses belong to kingdom Plantae.
Seaweeds reproduce via spores. They do not produce flowers, fruits or seeds. Seagrasses produce flowers, fruits and seeds. Seaweeds are made up of a special combination of substances, which are very different from the ones typically found in terrestrial plants and which allow them to play a distinctive role in human nutrition.
Most notably, the mineral content of seaweeds is 10 times as great as that found in plants grown in soil; as a consequence, people who regularly eat seaweeds seldom suffer from mineral deficiencies.
In addition, marine algae are endowed with a wide range of trace elements and vitamins. Because they contain a large volume of soluble and insoluble dietary fiber, which are either slightly, or else completely, indigestible, seaweeds also have a low calorie count.
A wild strain of Chondrus crispus , or Hana-Tsunomata in Japanese, appeals to both the eye and the palate. This seaweed has a distinct crunchy texture and a milder taste than most other sea vegetables. Its flamboyant colors—pink, green, and yellow—are completely natural.
Marine algae possess a fantastic ability to take up and concentrate certain substances from seawater. For example, the iodine concentration in konbu and other types of kelp is up to , times as great in the cells of the seaweeds as in the surrounding water, and the potassium concentration is 20—30 times greater. On the other hand, the sodium content is appreciably lower than that of salt water.
Depending on the species, fresh seaweeds are 70—90 percent water by weight. The composition of the dry ingredients in the different types of seaweeds can vary a great deal, but the approximate proportions are about 45—75 percent carbohydrates and fiber, 7—35 percent proteins, less than 5 percent fats, and a large number of different minerals and vitamins.
Broadly speaking, the proteins in seaweeds contain all the important amino acids, especially the essential ones that cannot be synthesized by our bodies and that we therefore have to ingest in our food. Porphyra has the greatest protein content 35 percent and members of the order Laminariales the lowest 7 percent.
Three groups of carbohydrates are found in seaweeds: sugars, soluble dietary fiber, and insoluble dietary fiber.
Many of these carbohydrates are different from those that make up terrestrial plants and, furthermore, they vary among the red, the green, and the brown species of algae.
The sugars, in which we include sugar alcohols such as mannitol in brown algae and sorbitol in red algae, can constitute up to 20 percent of the seaweeds. The seaweed cells make use of several types of starch-like carbohydrates for internal energy storage; again, these vary according to species. For example, the brown algae contain laminarin, which is of industrial importance as it can be fermented to make alcohol. Norwegian winged kelp Alaria esculenta is appearing on the menus of top restaurants.
Soluble dietary fiber, which is situated in between the seaweed cells and binds them together, constitutes up to 50 percent of the organism. Composed of three distinct groups of carbohydrates, namely, agar, carrageenan, and alginate, fiber can absorb water in the human stomach and intestines and form gelatinous substances that aid in the digestive process. Insoluble dietary fiber derived from the stiff cell walls of the seaweeds is present in lesser quantities, typically amounting to between 2 percent and 8 percent of the dry weight.
Cellulose is found in all three types of algae and xylan another type of complex carbohydrate in the red and green ones. The primary mineral components in seaweeds are iodine, calcium, phosphorous, magnesium, iron, sodium, potassium, and chlorine.
Added to these are many important trace elements such as zinc, copper, manganese, selenium, molybdenum, and chromium. The mineral composition, especially, varies significantly from one seaweed species to another. Konbu contains more than —1, times as much iodine as nori. On average, dulse—a widely eaten red seaweed—is the poorest choice in terms of mineral and vitamin content but, on the other hand, it is far richer in potassium salts than in sodium salts.
In general, marine algae are a much better source of iron than foods such as spinach and egg yolks. Seaweeds contain iodine, although the exact quantities again vary greatly by species. The iodine content is dependent on where the seaweed grew and how it has been handled after harvest. Furthermore, the iodine is not evenly distributed, being most abundant in the growing parts and least plentiful in the blades.
In particular, the brown seaweeds contain large amounts of iodine. It is not known for certain why brown seaweeds contain so much iodine, but this is probably linked to their capacity for rapid growth. Iodide was found to act as the main antioxidant for this tissue. In addition, the study showed that the action of iodide was not accompanied by an accumulation of organically bound iodine.
The history of the discovery of iodine as an element actually begins with seaweeds. He noticed that his chemical experiments with the seaweed ash gave rise to a violet-colored vapor that condensed as crystals on his copper vessels and, unfortunately, caused them to corrode.
Courtois convinced first his French, and later his English, fellow chemists that his discovery had important dimensions. Their work then rapidly led to the identification of the substance that was the source of the vapors. It turned out to be a previously unknown element and, as the color violet is called iodes in Greek, the new element was given the name iodine. Terrestrial plants are a poor source of iodine, which can result in iodine deficiency in vegetarians and vegans.
The accidental discovery of iodine in seaweeds is a wonderful example of how research and an open mind on the part of the researcher can lead to results that have a major significance for the economy and for human health. Despite their importance to human diet, seaweeds have often been regarded with disdain. That unpleasant smell is due to a number of gases that are not dangerous, but are the source of odors that we consider offensive.
In a bowl mix together the oats, seeds, seaweeds, salt, and baking powder. Add water and mix well until the dough becomes sticky. Divide the dough into two and place one part on a piece of baking paper. On top of the dough add another piece of baking paper and roll the dough out as thinly as possible between the two. With a knife or pizza wheel cut the top baking paper and divide the dough into squares without cutting through the bottom paper.
Remove the top baking paper and place the dough and the bottom paper on a baking sheet. Some seaweeds are microscopic, such as the phytoplankton that live suspended in the water column and provide the base for most marine food chains. Most are medium-sized, come in colors of red, green, brown, and black, and randomly wash up on beaches and shorelines just about everywhere.
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