Name: plant carbon fixation in hot climates
Uploaded: 2019-03-11T09:21:13.000Z
Duration: 1 min 27 s
Channel: JoVE

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C4 Pathway and CAM

- [Рассказчик] Некоторые растения, такие как кукуруза,адаптировали альтернативные способы исправить углеродболее эффективно в жарких сухих условиях. 
В одном, путь С4. 
На первом этапе углеродной фиксацииуглекислый газ, CO2, проникает в мезофильные клеткии через фермент PEP карбоксилазу,в сочетании с трехуглеродным соединением ПКП,чтобы образовать 4-х угольное соединение, оксалоацетата,который затем превращается в другую органическую кислоту,в этом случае малат. 
Малат транспортируется в клетки оболочки пучкаглубоко в листе, где кислород ограничени сломался, выпуская CO2,который затем может пройти через цикл Кальвинаи работать с Rubisco, чтобы производить разные виды сахара. 
Другие растения, такие как ананасы,используют метаболизм Crassulacean кислоту,или путь CAM, чтобы исправить углерод. 
CAM растения открывают свои устьицы только ночью,чтобы предотвратить потерю воды в течение дня. 
Подобно пути C4,CO2 сначала фиксируется PEP-карбоксилазой в оксалоацетат,который затем преобразуется в малат. 
Вместо того, чтобы транспортировать малат к части листа,Растения САМ хранят его в вакуолях мезофильных клеток,выпуская его в дневное время,так что, цикл Кальвина может продолжатьсянаряду со световыми реакциями при фотосинтезе.

<ol>
	<li>Эдвардс, Э.Д. Эволюционные траектории, доступность и другие метафоры: случай фотосинтеза C4 и CAM. Новый фитолог. 223 (4), 1742-1755 (2019).</li>
</ol>

Пути c4 и cam

<h4>Обзор</h4>

Некоторые растения, такие как сахарный тростник и кукуруза, которые растут в жарких условиях, используют альтернативный процесс, называемый C 4 путем связывания углерода. Цикл начинается с CO 2 из атмосферы, попадающего в клетки мезофилла, где он используется для образования оксалоацетата - четырехуглеродной молекулы - из фосфоенолпирувата (PEP). Затем оксалоацетат превращается в малат и транспортируется в клетки оболочки пучка, где концентрация кислорода низкая. Здесь CO 2 высвобождается из малата и вступает в цикл Кэльвина, где он превращается в сахара. Путь CAM осуществляется у растений, таких как кактусы, которые также нуждаются в экономии воды в течение дня. CAM-растения пропускают CO 2 в листья ночью и производят малат, который хранится в вакуолях до следующего дня. Затем малат высвобождается из вакуолей и обрабатывается в цикле Кальвина. Путь C 4 разделяет различные процессы локально, а путь CAM разделяет их в хронологическом порядке.

<h4>Путь C4</h4>

Некоторые растения, такие как кукуруза и сахарный тростник, разработали альтернативные способы фиксации углерода, которые помогают избежать потери воды в жарких, сухих условиях. Одним из таких методов является путь C4. На первом этапе, CO2 входит в мезофилл клетки, и фермент фосфоэнлпируват (PEP) карбоксилазы добавляет его в 3-углеродного соединения PEP для формирования 4-углеродного соединения оксалоацетата. Оксалоацетат затем преобразуется в органическую кислоту, называемую малатом.

Впоследствии малат транспортируется в пучок оболочки клеток глубоко в листе, где концентрация кислорода низкая. Малат разбит, высвобождая молекулу CO2, которая затем попадает в цикл Кэльвина, где фермент рубиско преобразует его в сахар. Путь C4 предлагает преимущество в жарких, засушливых условиях, так как растения закрывают свою стомату для сохранения воды. В результате, они могут держать концентрацию кислорода низкой и, следовательно,связаться скорее с СО 2 рубиско, а не O2. Когда концентрация кислорода выше, рубиско связывает O2 вместо CO2– процесс, называемый фотореспирацией, который бы остановил фотосинтез и потреблял энергию.

<h4>Путь CAM</h4>

Другие растения, такие, как кактусы и ананас, используют грубый метаболизм кислоты (CAM) путь для фиксации углерода. CAM растения в первую очередь открывают их стомату ночью, чтобы предотвратить потерю воды в жаркий день. Ночью CO2 попадает в мезофилл клетки, где он сочетается с PEP для формирования оксалоацетата и в конечном итоге малат. Малат затем хранится в вакуолях до следующего дня, когда он высвобождается из вакуолей и входит в цикл Кэльвина. Первые этапы фотосинтеза продолжаются в течение дня, поскольку они зависят от света, в то время как светозависимые реакции цикла Кэльвина происходят в ночное время. Таким образом, CAM растения разделяют процессы CO2 фиксации и синтеза сахара, производя их в разное время дня.

Пути C4 и CAM

Большинство растений используют путь C3 для фиксации углерода. Однако некоторые растения, такие как сахарный тростник, кукуруза и кактусы, которые растут в жарких условиях, используют альтернативные...

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plant carbon fixation in hot climates

Plant carbon fixation in hot climates can follow the C4 pathway or the CAM pathway. These alternative pathways help some plants reduce energy loss from photorespiration. Photorespiration happens when oxygen levels are high and rubisco, the enzyme in the Calvin cycle, binds O2 instead of CO2. When that happens, photosynthesis slows and energy is used up.

The C4 pathway is used by plants such as corn and sugarcane. In mesophyll cells, CO2 first joins with PEP, or phosphoenolpyruvate, through the action of PEP carboxylase. This forms the 4-carbon compound oxaloacetate, which is then changed into organic acids, mostly malate.

Malate moves into the bundle sheath cells deep in the leaf, where oxygen levels are low. There, malate is broken down and releases CO2. That CO2 enters the Calvin cycle and is turned into sugar with the help of RuBisCo. In hot, dry conditions, this separation of carbon fixing and sugar production helps the plant close its stomata and save water while keeping oxygen low.

Other plants, such as cacti and pineapple, use the CAM pathway, or crassulacean acid metabolism. CAM plants open their stomata at night to limit water loss during the day. CO2 enters the mesophyll cells at night and combines with PEP to form oxaloacetate and then malate.

The malate is stored in vacuoles until the next day. During the day, it is released so the Calvin cycle can begin. In CAM plants, carbon fixation happens at night, while sugar synthesis follows during the day with energy from the light-dependent reactions. This time-based separation helps these plants survive hot, dry environments.

Plant Carbon Fixation in Hot Climates

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Photosynthesis uses light energy to turn carbon dioxide into carbohydrates. It also releases oxygen as a by-product. These products help support most food webs and make aerobic life possible. Photosynthesis has two main stages, and they happen in different parts of the chloroplast. The light-dependent reactions take place in the thylakoid membranes. Chlorophyll absorbs light energy there and helps split water molecules. This releases O2 and makes ATP and NADPH. The light-independent reactions...

c4 pathway and cam

Plant carbon fixation in hot climates can follow the C4 pathway or the CAM pathway. These alternative pathways help some plants reduce energy loss from photorespiration. Photorespiration happens when oxygen levels are high and rubisco, the enzyme in the Calvin cycle, binds O2 instead of CO2. When that happens, photosynthesis slows and energy is used up. The C4 pathway is used by plants such as corn and sugarcane. In mesophyll cells, CO2 first joins with PEP, or phosphoenolpyruvate, through the...

key terms and concepts

Learn how C4 and CAM pathways help plants like corn, sugarcane, cacti, and pineapple reduce photorespiration and save water in hot climates.

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Plant Carbon Fixation in Hot Climates

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