Like in animals, the first line of defense of plants is the skin - the epidermis and the periderm.
If the first line of defense is penetrated, the second line of defense is the triggering of two different immune responses, which involves extensive genetic reprogramming.
The first being a chemical attack that would isolate the pathogen and prevent spread of infection. This immune response is a hypersensitive response called Pathogen-Associated Molecular Pattern (PAMP) triggered immunity. A hypersensitive response is a local cell and tissue death that would occur at and near the site of infection. It can restrict the spread of the pathogen, but also be a consequence of the overall defense response. It involves transcriptional activation of over 10% of the plant's genes that can encode enzymes that would hydrolyze components of cell walls of pathogens. Effector triggered immunity also stimulates the formation of lignin and cross linking of molecules within plant cell walls.
The second response is only triggered if PAMP is not sufficient. The second response is known as a systemic acquired resistance. This arises from plant-wide expression or defensive genes. Methylsalicylic acid is produced around the infection site and carried by the phloem throughout the plant, where it is converted to salicyclic acid in areas remote from sites of infection. The salicyclic acid activates signal transduction pathways that poises the defense system to respond rapidly to another infection. This response generally lasts for a while in order to ensure that infection is completely protected from.
Sunday, March 22, 2015
Plants Spawning Invertebrates for Protection
Herbivores are organisms that solely rely on plants as their source of nutrients. Herbivores are a large threat to the plants as it reduces the size of the plants, hindering their ability to acquire resources to survive. Herbivores also restrict growth because many species of plants would focus their energy on developing an adaptation to defend themselves. Herbivores also opens up portals for infectious pathogens to infect the plants. Some plants would develop physical defensive mechanisms such as thorns or trichomes, and others would acquire chemical defenses such as a chemical that makes them taste bad or poisonous.
Some plants, such as corn are able to produce "green leaf volatile compounds" when it's leaves are chewed on. These compounds are a mixture of many chemicals, the most prevalent being terpenoid and phenolic (both of which are very attractive to parasitic wasps). The wasps would fly to the plant being eaten and the wasp would target the threat. The wasp would employ different defensive strategies depending on the species. Some species such as the digger wasps would pick up the host and relocate it elsewhere. Other wasps are more deadly, they would lay eggs in the threat. The eggs would hatch in a day or two and kill the host from within.
Some plants, such as corn are able to produce "green leaf volatile compounds" when it's leaves are chewed on. These compounds are a mixture of many chemicals, the most prevalent being terpenoid and phenolic (both of which are very attractive to parasitic wasps). The wasps would fly to the plant being eaten and the wasp would target the threat. The wasp would employ different defensive strategies depending on the species. Some species such as the digger wasps would pick up the host and relocate it elsewhere. Other wasps are more deadly, they would lay eggs in the threat. The eggs would hatch in a day or two and kill the host from within.
Plant Response to Various Stresses
Flooding
Too much water could cause the plant to suffocate because the soil would lack air spaces that provides oxygen for the roots to perform cellular respiration.
Oxygen deprivation generally will stimulate the production of ethylene and cause many cells in the root cortex to die. Destruction of the root cortex would create new air bubbles that would function as "snorkels", providing oxygen to the submerged roots.
Salt
Excess amounts of salt can lower the water potential of the soil solution, causing water deficiency in plants. When the water potential of soil solution become more negative, the water potential gradient from soil to roots is lowered, reducing the plant's water intake. NaCl and other ionic salts are toxic to plants when there is high concentrations of them.
Plants typically respond by produce solutes that are well tolerated at high concentrations, mainly organic compounds that can keep water potential of cells more negative then that of the soil solution while not admitting toxic quantities of ionic salts.
Heat
Heat could be detrimental to a plant's survivability as it could denature many enzymes, killing the plants.
Transpiration helps to keep the leaves cool by evaporative cooling. Hot and dry weather tends to dehydrate plants, closing off the stomate would help to conserve water loss but it would compromise the plant's ability for evaporative cooling, Many plants have a backup response, especially when the temperature exceeds 40 degrees Celsius - plants would synthesize heat-shock proteins that would help protect other proteins from the extreme heat.
Too much water could cause the plant to suffocate because the soil would lack air spaces that provides oxygen for the roots to perform cellular respiration.
Oxygen deprivation generally will stimulate the production of ethylene and cause many cells in the root cortex to die. Destruction of the root cortex would create new air bubbles that would function as "snorkels", providing oxygen to the submerged roots.
Salt
Excess amounts of salt can lower the water potential of the soil solution, causing water deficiency in plants. When the water potential of soil solution become more negative, the water potential gradient from soil to roots is lowered, reducing the plant's water intake. NaCl and other ionic salts are toxic to plants when there is high concentrations of them.
Plants typically respond by produce solutes that are well tolerated at high concentrations, mainly organic compounds that can keep water potential of cells more negative then that of the soil solution while not admitting toxic quantities of ionic salts.
Heat
Heat could be detrimental to a plant's survivability as it could denature many enzymes, killing the plants.
Transpiration helps to keep the leaves cool by evaporative cooling. Hot and dry weather tends to dehydrate plants, closing off the stomate would help to conserve water loss but it would compromise the plant's ability for evaporative cooling, Many plants have a backup response, especially when the temperature exceeds 40 degrees Celsius - plants would synthesize heat-shock proteins that would help protect other proteins from the extreme heat.
Mechanical Stimuli Response
A plant's response to mechanical stimuli is called thigmomorphogenesis.
Plants are very sensitive when it comes to mechanical stress; for example, a ruler barely grazing a leaf could greatly alter its subsequent growth. Mechanical perturbation on a plant could result in many consequences.
Plants are very sensitive when it comes to mechanical stress; for example, a ruler barely grazing a leaf could greatly alter its subsequent growth. Mechanical perturbation on a plant could result in many consequences.
Gravitropism/Geotropism
Plants are able to detect gravity by utilizing their settlements of statoliths, or dense cytoplasmic components that settle under the influence of gravity to the lower portions of the cell. In roots, the statoliths are located in certain cells in the root cap.
Light's Effect on Plants
A photoperiod is the amount of time that an organism experiences sunlight as well as night time. Photoperiodism is a physiological response to photoperiod, typically for the purpose of flowering. It also helps the plant be able to detect seasonal changes.
Photoperiodism influences flowering because it allows the plant to know when they should flower according to whether they are short-day plants or long-day plants. Short-day plants tend to flower in seasons such as winter due to their lack of need for sunlight. Long-day plants require long term exposure to the sun, so they tend to flower during seasons such as spring and summer.
Plants can also grow in response to light that they are exposed to. In the picture below, it shows the plants' growth being manipulated in accordance to the little variables present.
Photoperiodism influences flowering because it allows the plant to know when they should flower according to whether they are short-day plants or long-day plants. Short-day plants tend to flower in seasons such as winter due to their lack of need for sunlight. Long-day plants require long term exposure to the sun, so they tend to flower during seasons such as spring and summer.
Plants can also grow in response to light that they are exposed to. In the picture below, it shows the plants' growth being manipulated in accordance to the little variables present.
In the control, the plant leans towards the light, growing in the direction of the illuminated side. Since the tip of the plant is the main variable in the detection of light due to the high numbers of photoreceptors. As the tip of the plant is removed, the plant grows straight upwards. The same occurs when the tip is covered by an opaque cap. The plant with the tip covered with the opaque cap grows straight because phototropism only occurs if the tip is exposed to light, and light is being completely shielded from the tip. A plant with the tip covered in a transparent cap is the closest resemblance to the control as the transparent cap does not prevent the tip from being exposed to the light, thus promoting the plant to lean towards the light source. The base covered by the opaque shield does curve towards the source of light, but the base remains straighter than that of the control. Since the tip is exposed to light, it is supposed to lean, but the base is voided from light thus making it grow straight. The tip separated by a gelatin block does not do much in preventing the curvature of the plant towards the light. The gelatin block is similar to the transparent cap as it allows light to penetrate through and come into contact with the plant. The tip separated by mica is a unique case. Although the tip is separated by the impermeable mica suggested that the chemical signal was a growth stimulant as the phototropic response involves faster cell elongation on the shady side than on the illuminated side.
http://www.sciencebuddies.org/Files/3834/5/PlantBio_img032.jpg
Apoptosis Post-Reproduction
Post-reproduction, plants use apoptosis to senescence, or the programmed death of certain cells, organs, or the entire plant. Cells, organs, and plants are genetically programmed to die on a schedule. They do not simply, "shut down", and die. During apoptosis, newly formed enzymes would breakdown many chemical components that include: chlorophyll, DNA, RNA, proteins, and membrane lipids. The plant would salvage many of the products from the breakdown. A burst of a hormone, typically ethylene, is usually prevalent with apoptosis during senescence.
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