تحلل

التعفُّنDecomposition عَرَضٌ لأمراض نباتية كثيرة تتسبب في تلف النبات. وتسببه أنواع من البكتيريا أو الفطريات التي تصيب النبات وتقتل خلاياه. ويدمر العفن، الفواكه والخضراوات سريعًا، غير أن المزارعين يكافحونه برش النباتات بالمبيدات الحشرية.

ومن الأمراض الشائعة التي تسبب التعفن التعفن المر والتعفن الأسود والتعفن البني والتعفن الجاف وآفة البطاطس المتأخرة. ويصيب العفن المر أساساً التفاح، وإن كان يصيب أيضا السفرجل والكمثرى (الإجاص)، فضلاً عن إصابته لنباتات أخرى. ويسبب العفن المر فطر يدمر الفاكهة، وعساليج وأغصان الأشجار. ويصنع الفطر بقعة بُنية اللون في الفاكهة. ثم تنمو البقعة اتساعًا وعمقًَا، وقد تُعطي الفاكهة في آخر المطاف مذاقاً مراً.

أما التعفن الأسود، فيصيب النباتات المزروعة مثل التفاح، والعنب، والكمثرى والسفرجل، والبطاطا. ويسبب المرض بقعاً بنيّة داكنة في الأجزاء المصابة. كذلك يهلك التعفن البنيّ الخوخ، وغيره من أنواع الفاكهة ذات النواة، مثل الكرز والبرقوق، حيث تظهر على الفاكهة بقع بنية صغيرة، ثم تأخذ البقع في النمو إلى أن تتعفن الفاكهة بكاملها. أما العفن الجاف فيصيب الأشجار. وأخيراً فإن آفة البطاطس المتأخرة تسبب تعفُّن البطاطس. وكانت هذه الآفة هي السبب في إخفاق محصول البطاطس في أيرلندا من عام 1845م إلى 1847م.

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 تحلل النبات

انظر أيضاً: Compost and هضم لاهوائي

A decaying peach over a period of six days. Each frame is approximately 12 hours apart, as the peach shrivels and becomes covered with mold.

الفطريات والبكتريا are very important in the decomposition of plants, accounting for approximately 80 to 90 % of the total biomass of the decomposed material (Chapin et al., Principles of Terrestrial Ecosystem Ecology).

في معظم الأنظمة البيئية للمراعي, النار هي وسيلة رئيسية للتحلل, مما يجعلها أساسية في دورة المغذيات Nutrient cycling (DeBano et al. 1998).

النواحي الكيميائية لتحلل النبات دائماً ما تتضمن اطلاق ثاني اكسيد الكربون.

 تحلل الحيوانات

النمل ينظف ثعبان ميت

Decomposition begins at the moment of death, caused by two factors: autolysis, the breaking down of tissues by the body's own internal chemicals and enzymes; and putrefaction, the breakdown of tissues by bacteria. These processes release gases that are the chief source of the characteristic odor of dead bodies. These gases swell the body.

معظم المحلِلين هم بكتريا أو فطريات.

 تحلل البشر

 المراحل

بمجرد حدوث الموت, تحلل الجسد البشري يبدأ في مراحل. عملية تكسر الأنسجة قد تأخذ أياماً لسنوات لكي تبدأ. At all stages of decomposition, insect activity occurs on the body as detailed below.

 Fresh

The fresh stage of decomposition occurs during the first few days following death. There are no physical signs of decomposition during this time. However, homeostasis of the body has ceased, allowing cellular and soft tissue changes to occur because of the process of autolysis, the destruction of cells and organs due to an aseptic chemical process. At this point, the body enters algor mortis, the cooling of the body's temperature to that of its surroundings. When the body’s cells reach the final stage of autolysis, an anaerobic environment is created, that is, an environment wherein oxygen is not present. This allows the body’s normal bacteria to break down the remaining carbohydrates, proteins, and lipids. The products from the breakdown create acids, gases, and other products which cause volatile organic compounds (VOCs) and putrefactive effects. VOCs are produced during the early stages of human decomposition.

Substances produced during the fresh stage of decomposition attract a variety of insects. Insects belonging to the order Diptera begin to lay their eggs on the body during this stage, especially members of the Calliphoridae family. There is also considerable activity by soil dwelling insects around a body that it is on the ground or buried in the soil. The reasoning for this is simple: a dead human body serves as an excellent source of decaying matter to feed on in a very hospitable environment.

 Putrefaction

Odor, color changes, and bloating of the body during decomposition are the results of putrefaction. The lower part of the abdomen turns green due to bacteria activity in the cecum. Bacteria break down hemoglobin into sulfhemoglobin, which causes the green color. A formation of gases enters the abdomen, which forces liquids and feces out of the body. The gases also enter the neck and face, causing swelling of the mouth, lips, and tongue. Due to this swelling and misconfiguration of the face, identification of the body can be difficult. Bacteria also enter the venous system causing blood to hemolyze. This leads to the formation of red streaks along the veins. This color soon changes to green through a process known as marbelization. It can be seen on the chest and shoulder area and on the thighs. The skin can develop blisters containing serous fluid. The skin also becomes fragile, leading to skin slippage, making it difficult to move a body. Body hair comes off easily. The change of the green discoloration to brown marks the transition of the early stage of putrefaction to the advanced decomposition stages.

During the putrefaction stage of decomposition the majority of insect activity again comes from members of the Calliphoridae family, and includes: Formicidae, Muscidae, Sphaeroceridae, Silphidae, Lepidoptera, Hymenoptera, Sarcophagidae, Histeridae, Staphylinidae, Phalangida, Piophilidae, Araneae, Sepsidae, and Phoridae. As with the fresh stage of decomposition if the body is on the ground or buried in soil there is also considerable insect activity by the soil-inhabiting arthropods.

 Black putrefaction

After the body goes through the bloating stage it begins the black putrefaction stage. At this point the body cavity ruptures, the abdominal gases escape and the body darkens from its greenish color. These activities allow for a greater invasion of scavengers, and insect activity increases greatly. This stage ends as the bones become apparent, which can take anywhere from 10 to 20 days after death depending on the surrounding environmental conditions. This period is also dependent on the degree to which the body is exposed to each and any of the varying elements and conditions.

During the black putrefaction stage of decomposition, insects that can be found living in the body are: Calliphoridae larvae, Staphylinidae, Histeridae, Gamasid mites, Ptomaphila, Trichopterygidae, Piophilid larvae, Parasitic wasps, Staphylinid larvae, Trichopterygid larvae, Histerid larvae, Ptomaphila larvae, Dermestes, Tyroglyphid mites, Tineid larvae, and the Dermestes larvae. Some insects can also be found living in the soil around the body such as: Isopoda, Collembola, Dermaptera, Formicidae, Pseudoscorpiones, Araneae, Plectochetos, Acari, Pauropoda, Symphyla, Geophilidae, and Protura. The types of insects will differ based on where the body is, although Diptera larvae can be found feeding on the body in almost all cases.

 Butyric fermentation

After the early putrefaction and black putrefaction phases have taken place, the body begins mummification, in which the body begins to dry out. Once the human carcass has mummified it goes through saponification, the formation of adipocere (grave wax), referring to the loss of body odor and the formation of a cheesy appearance on the cadaver. Mummification is considered a post-active stage because there is less definite distinction between changes as indicated by reduced skin, cartilage, and bone. Mummification is also indicated when all of the internal organs are lost due to insect activity.

Insects that can be found on the body during mummification include most of the same insects as in the putrefaction stage, but also include: Acarina, Nitidulidae, Cleridae, Dermestes caninus, and Trogidae. The main soil-inhabiting arthropods include Dermaptera and Formicidae.

 Dry decay

When the last of the soft-tissue has been removed from the body, the final stage of decomposition, skeletonization, occurs. This stage encompasses the deterioration of skeletal remains, and is the longest of the decomposition processes. Skeletonization differs markedly from the previous stages, not only in length, but in the deterioration process itself.

The strength and durability of bone stems from the unique protein-mineral bond present in skeletal formation. Consequently, changes to skeletal remains, known as bone diagenesis, occur at a substantially slower rate than stages of soft-tissue breakdown. As the protein-mineral bond weakens after death, however, the organic protein begins to leach away, leaving behind only the mineral composition. Unlike soft-tissue decomposition, which is influenced mainly by temperature and oxygen levels, the process of bone breakdown is more highly dependent on soil type and pH, along with presence of groundwater. However, temperature can be a contributing factor, as higher temperature leads the protein in bones to break down more rapidly. If buried, remains decay faster in acidic-based soils rather than alkaline. Bones left in areas of high moisture content also decay at a faster rate. The water leaches out skeletal minerals, which corrodes the bone, and leads to bone disintegration.

At the dry decay stage commonly found insects include: Sphaeroceridae, Acarina, Nitidulidae, Cleridae, Dermestes caninus, Trogidae, Tyroglyphid mites, and the Tineid larvae. The soil-inhabiting arthropods are: Collembola, Dermaptera, Heteroptera, Coleoptera and their larvae, parasitic Hymenoptera, Formicidae, Diptera larvae, Pseudoscorpiones, Aranae, Plectochetos, Acari, Pauropoda, Symphyla, Geophilidae, Protura, and Aphididae.

 أهميته للطب الشرعي

للمزيد من المعلومات: Forensic entomological decomposition

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 العوامل المؤثرة على التحلل

للمزيد من المعلومات: Environmental effects on forensic entomology

معدل وطريقة التحلل في جسم الحيوان تتأثر بدرجة كبيرة بعدد من العوامل. في ترتيب (تقريباً) تنازلي لدرجة الأهمية, العوامل هي:

• درجة الحرارة
• تواجد الاكسجين
• تحنيط مسبق
• سبب الوفاة
• الدفن, وعمق الدفن
• Access by scavengers
• Trauma, بما فيها الجروح
• الرطوبة, أو الابتلال
• سقوط الأمطار
• حجم ووزن الجسم
• الملابس
• السطح الموجود عليه الجسد
• الطعام/الأشياء داخل السبيل الهضمي

 انظر أيضاً

• Cadaverine
• Decompiculture
• Putrescine
• Staling

 المصادر

• المعرفية الشاملة
• Statheropoulos, M, Agapiou, A., Spiliopoulou, C., Pallis, G.C., and Sianos, E. "Environmental aspects of VOCs evolved in the early stages of human decomposition." Science of The Total Environment. 385(2007): 221-227.
• Eberhardt, Terry L., and Elliot, D. A. "A Preliminary investigation of insect colonisation and succession on remains in New Zealand." Forensic Science International 176(2008): 217-223.
• Kulshrestha, Pankaj, and Satpathy, D.K. "Use of beetles in forensic entomology." Forensic Science International 120(2001): 15-17.
• Schmitt, Aurore, Cunha, E., and Pinheiro, J.. Forensic Anthropology and Medicene: Complementary Sciences Frome Recovery to Cause of Death. 1st ed. Totowa, NJ: Humana Press, 2006.
• Haglund, William D., and Sag, M. H.. Forensic Taphonomy: The Postmortem Fate of Human Remains. 1st ed. Boca Raton: CRC Press, 1997.
• Smith, K. G. V.. A Manual of Forensic Entomology. 3rd. Ithaca, N.Y.: Cornell University Press, 1986.
• Eberhardt, Terry L., and Elliot, Douglas A. A preliminary investigatio of insect colonisation and succession on remains in new Zealand. University of auckland, department of chemistry, forensic science programme, 2006. Forensic science international 176 (2008) 217-223