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From Wikipedia

Fibrous root system

A fibrous root system (sometimes also called adventitious root system) is the opposite of a taproot system. It is usually formed by thin, moderately branching roots growing from the stem. A fibrous root system is universal in monocotyledonous plants and ferns.

Most trees begin life with a taproot, but after one to a few years change to a wide-spreading fibrous root system with mainly horizontal surface roots and only a few vertical, deep anchoring roots. A typical mature tree 30-50 m tall has a root system that extends horizontally in all directions as far as the tree is tall or more, but well over 95% of the roots are in the top 50 cm depth of soil.

A few plants with fibrous root systems:


List of poisonous plants

Below is an extensive, if incomplete, list of plants containing poisonous parts that pose a serious risk of illness, injury, or death to humans or animals.

Poisonous food plants

Many food plants possess toxic parts, are toxic unless processed, or are toxic at certain stages of their life. Notable examples include:

  • Apple(Malus domestica). Seeds containcyanogenic glycosides; in most species, the amount found in a single fruit won't kill a person; but it is possible to ingest enough seeds to provide a fatal dose.
  • Cassava(Manihot esculenta) Toxic in the unprocessed form.
  • Cherry(Prunus cerasus), as well as other species (Prunus spp) such aspeach (Prunus persica), plum (Prunus domestica), almond (Prunus dulcis), and apricot (Prunus armeniaca). Leaves and seeds contain cyanogenic glycosides.
  • Chocolate. Containstheobromine at levels toxic to dogs and cats.
  • Indian pea(Lathyrus sativus). A legume grown in Asia and East Africa as an insurance crop for use during famines. Containsoxalyl-L-α,β-diaminopropionic acid (ODAP), a neurotoxin causing wasting and paralysis if eaten over a long period.
  • Kidney beanor common bean (Phaseolus vulgaris). Contains the lectinphytohaemagglutinin, which causes gastric upset. Toxicity removed by thorough cooking.
  • Nutmeg(Myristica fragrans). Containsmyristicin.
  • Lima beanor Butter Bean (Phaseolus lunatus). Raw beans contain dangerous amounts oflinamarin, a cyanogenicglucoside.
  • Lupin. Some varieties have edible seeds. Sweet Lupins have less, and Bitter Lupins have more of the toxic alkaloidslupinine and sparteine.
  • Onions and garlic. Onions and garlic (genus Allium) containthiosulphate, which in high doses is toxic to dogs, cats and some other livestock.
  • Potato(Solanum tuberosum). Foliage and green-tinged tubers are toxic, containing the glycoalkaloidsolanine, which develops as a result of exposure to light. Causes intense digestive disturbances, nervous symptoms, and in high enough doses, death.
  • Rhubarb(Rheum rhaponticum). Leaf blades, but notpetioles, contain oxalic acidsalts, causing kidney disorders, convulsions, coma. Rarely fatal.
  • Tomato(Solanum lycopersicum). Foliage and vines containalkaloid poisons which cause digestive upset and nervous excitement.

Other poisonous plants

  • Aconitum(Aconite, wolfsbane, monkshood) (Aconitum napellus). The poison is concentrated in the unripe seed pods and roots, but all parts are poisonous. Causes digestive upset, nervous excitement. The juice in plant parts is often fatal. It is a quick-acting poison often used to coat poisonous arrows in Asia.
  • Adenium obesum. Also known as Sabi Star, Kudu or Desert-rose.The plant exudes a highly toxic sap which is used by the Akie and Hadza in Tanzania, to coat arrow-tips for hunting.
  • Agave. The juice of a number of species causes acute contact dermatitis, with blistering lasting several weeks and recurring itching for several years thereafter.
  • Abrus precatorius, known commonly as Jequirity, Crab's Eye, Rosary Pea, 'John Crow' Bead, Precatory bean, Indian Licorice, Akar Saga, Giddee Giddee orJumbie Bead inTrinidad & Tobago. Particularly dangerous as the brightly-coloured seeds (usually black and red) are commonly used in jewellry and easily eaten by children.
  • Angel's Trumpet (Brugmansia). All parts of the plant contains the tropane alkaloidsscopolamine and atropine. Often fatal.
  • Asparagus. The berries are poisonous.
  • Autumn crocus. The bulbs are poisonous and cause nausea, vomiting, diarrhea. Can be fatal.
  • Azalea. (Azalea ssp.) All parts of the plant are poisonous and cause nausea, vomiting, depression, breathing difficulties, coma. Rarely fatal.
  • Bittersweet nightshade

Plant pathology

Plant pathology (also phytopathology) is the scientific study of plant diseases caused by pathogens (infectious diseases) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like organisms, phytoplasmas, protozoa, nematodes and parasitic plants. Not included are ectoparasites like insects, mites, vertebrate or other pests that affect plant health by consumption of plant tissues. Plant pathology also involves the study of pathogen identification, disease etiology, disease cycles, economic impact, plant disease epidemiology, plant disease resistance, how plant diseases affect humans and animals, pathosystem genetics, and management of plant diseases.

Plant pathogens

Fungi

The majority of phytopathogenic fungi belong to the Ascomycetes and the Basidiomycetes.

The fungi reproduce both sexually and asexually via the production of spores. These spores may be spread long distances by air or water, or they may be soil borne. Many soil borne spores, normally zoospores, are capable of living saprotrophically, carrying out the first part of their lifecycle in the soil.

Fungal diseases can be controlled through the use of fungicides in agriculture, however new races of fungi often evolve that are resistant to various fungicides.

thumb|left|[[Rice blast]], a necrotrophic fungus

Biotrophic fungal pathogens colonize living plant tissue and obtain nutrients from living host cells. Necrotrophic fungal pathogens infect and kill host tissue and extract nutrients from the dead host cells. See Powdery Mildew and Rice Blast images below.

Significant fungal plant pathogens include:

Ascomycetes

Basidiomycetes

Oomycetes

The oomycetes are not true fungi but are fungal-like organisms. They include some of the most destructive plant pathogens including the genusPhytophthora which includes the causal agents of potato late blight and sudden oak death.

Despite not being closely related to the fungi, the oomycetes have developed very similar infection strategies and so many plant pathologists group them with fungal pathogens.

Significant oomycete plant pathogens

Bacteria

Most bacteria that are associated with plants are actually saprotrophic, and do no harm to the plant itself. However, a small number, around 100 species, are able to cause disease. Bacterial diseases are much more prevalent in sub-tropical and tropical regions of the world.

Most plant pathogenic bacteria are rod shaped (bacilli). In order to be able to colonize the plant they have specific pathogenicity factors. Five main types of bacterial pathogenicity factors are known:

1. Cell wall degrading enzymes– used to break down the plant cell wall in order to release the nutrients inside. Used by pathogens such as Erwiniato causesoft rot.

2. ToxinsThese can be non-host specific, and damage all plants, or host specific and only cause damage on a host plant.

3. Effector proteins These can be secreted into the extracellular environment or directly into the host cell, often via the Type three secretion system. Some effectors are known to suppress host defense processes.

4. Phytohormones– for example From Yahoo Answers

Question:It helps a plant climb along a surface. B. It provides food for animals. C. It stores nutrients. D. It pulls nutrients from the soil. E. It prevents soil from washing away.

Answers:E... Plants with fibrous root systems are used to prevent soil erosion.

Question:

Answers:The primary root is the first-formed, main root, originating from the radicle of a seed embryo. In plants, not developing or dieing back this root, arise fibrous roots, often from stem or leaf tissue. That`s why they are considered as adventitious. http://www.cactus-art.biz/note-book/Dictionary/Dictionary_R/dictionary_root_system_apparatus.htm

Question:

Answers:Fiberous roots are in the ground to anchor the plant and absorb water and nutrients. They are numerous and thin. Turf grass is a good example. Aerial roots are suspended in the air and do not go into the soil. The best example of that is an orchid. They normally sit in the fork of a tree in the rainforset many feet from the ground and absorb water directly from the air. This explains why orchids are in the humid rainforests but not in deserts.

Question:2. What soil conditions might fibrous roots prefer and what conditions might the tap root prefer? 3. What type of root structure would you think a very large plant be best with? Explain your answer.

Answers:1. There are a whole lot of secondary roots instead of a big primary root. They spread out through the soil instead of just going down through the soil. So they hold the soil together a lot better. 2. ? 3. I think a fibrous root system might be more sturdy than a taproot system. It might "grip" the soil better and be more stable.