What are the external factors that affect photosynthesis?

The indicator of photosynthesis is the rate of photosynthesis. The photosynthetic velocity is usually expressed in the number of CO2 milligrams absorbed per square meter of leaf area per hour, and the general method of measuring the photosynthetic velocity does not take into account the respiration of the leaves, but the net photosynthesis velocity is measured, and the total photosynthesis velocity is also added to the respiration velocity, the relationship is: Total photosynthetic velocity = net photosynthetic velocity Respiration velocity In general exercises, the net photosynthetic amount (e.g., measured in the experiment) is usually informed, and the respiration volume (e.g., measured in the dark) is also informed. What is required is the total amount of photosynthesis (organic matter produced by photosynthesis, or oxygen released).

1) Light Photosynthesis is a photobiochemical reaction, so the photosynthetic rate accelerates with the increase of light intensity. However, after a certain range, the increase in photosynthetic velocity slows down until it no longer increases, because light promotes the photoreaction process, while the ability of dark reactions (CO2, catalytic efficiency of enzymes, etc.) is limited. The relationship between light intensity and photosynthetic velocity can be represented in the following diagram:

Note: Point A indicates that the amount of CO2 absorbed by photosynthesis is equal to the amount of CO2 released by respiration. Point b indicates that the rate of photosynthesis reaches the point of saturation.

The dotted curve represents shade plants, and the solid curve represents yang plants. (2) Carbon dioxide CO2 is the raw material for photosynthesis of green plants, and its concentration affects the dark reaction of photosynthesis. Increasing the CO2 concentration within a certain range can increase the photosynthetic velocity, and after the CO2 concentration reaches a certain level, the photosynthesis rate does not increase, because the products of the photoreaction are limited.

The relationship between CO2 concentration and photosynthetic velocity can be represented in the following figure: Note: The practice is the photosynthetic velocity of C3 plants, and the dotted line is the photosynthetic velocity of C4 plants.

C4 plants have a higher CO2 utilization rate than C3 plants. (3) Temperature The dark reaction in photosynthesis is a chemical reaction catalyzed by enzymes, and temperature directly affects the activity of enzymes. The relationship between temperature and the rate of photosynthesis is actually like the relationship between enzymes and temperature, there is an optimal temperature.

4) Mineral elements Mineral elements directly or indirectly affect photosynthesis. For example: n:

are the elements that make up chlorophyll, enzymes, ATP, NADP, etc. P: are the elements that make up ATP, NADP, etc.

mg: is the element that makes up chlorophyll. (5) Moisture Moisture is one of the raw materials for photosynthesis, and when it is lacking, it can reduce the photosynthetic velocity.

6) Diurnal variation Photosynthesis during the day is generally higher at noon, but in the hot summer, the rate of photosynthesis decreases at noon, and the phenomenon of "lunch break" appears.

Light intensity, temperature, humidity, carbon dioxide concentration.

Light intensity: Photosynthesis is a photobiochemical reaction, so the photosynthetic rate accelerates with the increase of light intensity, but after a certain range, the increase in photosynthetic rate slows down until it no longer increases; Carbon dioxide concentration: carbon dioxide is the raw material for photosynthesis of green plants, the concentration affects the dark reaction of photosynthesis, increasing the concentration of carbon dioxide within a certain range can increase the rate of photosynthesis, and the rate of photosynthesis does not increase after the carbon dioxide concentration reaches a certain value, this is because the products of photoreaction are limited; Temperature:

The influence of temperature on photosynthesis is more complex, because photosynthesis includes two parts: light reaction and dark reaction, light reaction mainly involves photophysical and photochemical reaction processes, especially the steps directly related to light, excluding enzymatic reactions, so the photoreaction part is less affected by temperature, or even not affected by temperature; The dark reaction is a series of enzymatic reactions, which are obviously affected and restricted by temperature changes.

The external factors that affect photosynthesis are light, carbon dioxide, temperature, mineral elements, moisture.

External factors affecting photosynthesis include light intensity, CO2 content, temperature, etc.; The internal factors include the activity of enzymes, the number of pigments, the content of five-carbon compounds, etc. The light intensity mainly affects the light reaction, the content and temperature of CO2 mainly affect the dark reaction, the number of pigments mainly affects the light reaction, and the content of the five carbon compounds mainly affects the fixation of carbon dioxide in the dark reaction mode.

In the appropriate range, the higher the temperature, the stronger the photosynthesis intensity, and when the temperature is too high, the photosynthesis intensity decreases. The higher the carbon dioxide concentration, the greater the intensity of photosynthesis. The more abundant the water, the greater the intensity of photosynthesis.

Photosynthesis usually refers to the process by which green plants (including algae) absorb light energy and synthesize carbon dioxide and water into energetic organic matter, while releasing oxygen.

Photosynthesis Reaction Process:

Light reaction stage: The chemical reaction in the first stage of photosynthesis must have light energy to proceed, and this stage is called the light reaction stage. The chemical reaction in the photoreaction stage is carried out on the thylakoids within the chloroplast.

Dark Reaction Stage: The chemical reaction in the second stage of photosynthesis, which can be carried out without light energy, is called the dark reaction stage. The chemical reactions in the dark reaction phase are carried out in the matrix within the chloroplast.

The light reaction stage and the dark reaction stage are a whole, and in the process of photosynthesis, the two are closely related and indispensable.

The importance of photosynthesis: Photosynthetic auspiciousness provides material and energy for the survival of almost all living things, including humans. Therefore, photosynthesis is of great significance for humans and the entire biological world.

Light intensity, carbon dioxide concentration in the environment, temperature, moisture content in the soil, mineral element content in the soil are external factors that affect photosynthesis. The photosynthetic rate increases with the increase of light intensity, but before the intensity reaches full sunlight, the rate at which photosynthesis has reached the light saturation point, that is, the photosynthetic rate does not increase if the light intensity increases.

Temperature:

The carbon reaction in the photosynthetic process is a chemical reaction catalyzed by enzymes, and temperature directly affects the activity of enzymes, therefore, temperature also has a great influence on photosynthesis. With the exception of a few examples, plants can photosynthesize normally at 10 35, with 25 30 being the most suitable, and at 35 or more the synthesis begins to decline, and at 40 50 it stops completely. At low temperatures, enzymatic reactions are reduced, thus limiting the progress of photosynthesis.

At high temperature, on the one hand, high temperature destroys the structure of chloroplast and cytoplasm, and passivates the enzymes of chloroplasts; On the other hand, when dark respiration and photorespiration are strengthened, the photosynthetic rate decreases.

The amount of mineral elements in the soil

Mineral elements directly or indirectly affect photosynthesis. Nitrogen, magnesium, iron, manganese, etc. are mineral elements necessary for the biosynthesis of chlorophyll and so on; Copper, iron, sulfur and chlorine are involved in photosynthetic electron transport and water cracking processes. Potassium and phosphorus are involved in the metabolism of sugars, and when they are deficient, they affect the transformation and transportation of sugars, which indirectly affects photosynthesis At the same time, phosphorus also participates in the transformation and energy transfer of photosynthesis intermediates, so it has a great impact on photosynthesis.

The moisture content of the soil

The water required for photosynthesis is only a small part (less than 1%) of the water absorbed by plants, so the lack of water mainly indirectly affects the decrease of photosynthesis rate. Specifically, the lack of water closes the stomata of the leaves, affecting the entry of CO2 into the leaves. Water deficiency strengthens the hydrolysis of leaf starch, accumulates sugars, and slows the output of photosynthetic products, which will reduce the photosynthetic rate.

Internal factors affecting photosynthesis: the content of pigments in chloroplasts, enzyme activity; External factors: light intensity, light quality, light time, CO2 concentration, amount of water, temperature, mineral elements (fertilizer).

Photosynthesis usually refers to the process in which green plants (including algae) absorb the energy of light, synthesize carbon dioxide and water into energetic organic matter, and release oxygen when the cavity is open. It mainly includes two stages: light reaction and dark reaction, which involves important reaction steps such as light absorption, electron transfer, photosynthetic phosphorylation, and carbon assimilation, which is of great significance for realizing the energy conversion in nature and maintaining the carbon-oxygen balance of the atmosphere.

The process by which green plants use the sun's light energy to assimilate carbon dioxide (CO2) and water (H2O) to make organic matter and release oxygen is called photosynthesis. The organic matter produced by photosynthesis is mainly carbohydrates, and the energy is released by the release of circular sensitivity.

While assimilating inorganic carbides, plants convert solar energy into chemical energy, which is stored in the organic compounds formed. The solar energy assimilated by photosynthesis is about 10 times the amount of energy required by humans every year. The chemical energy stored in organic matter, in addition to the use of the plant itself and all heterotrophs, is more important for the energy of human nutrition and activity**.

Hence it can be said that photosynthesis provides the main energy source today. Greenery is a giant energy conversion station.

Turn inorganic matter into organic matter.

The scale on which plants produce organic matter through photosynthesis is enormous. It is estimated that plants can absorb about 71 011 tonnes of CO2 and synthesize about 500 billion tonnes of organic matter per year. 40% of the carbon assimilated by autotrophic plants on Earth is assimilated by phytoplankton, and the remaining 60% is assimilated by terrestrial plants.

The food, oil, fiber, wood, sugar, fruits, etc., all needed by human beings come from photosynthesis, and without photosynthesis, human beings will have no food and various daily necessities. In other words, there can be no human survival and development without photosynthesis.

Maintain the carbon-oxygen balance of the atmosphere.

The reason why the atmosphere can maintain 21% oxygen content on a regular basis is mainly dependent on photosynthesis (about the amount of oxygen released during photosynthesis). On the one hand, photosynthesis provides the conditions for aerobic respiration, and on the other hand, the accumulation gradually forms the ozone (O3) layer of the atmospheric surface. The ozone layer absorbs the intense ultraviolet radiation from sunlight that is harmful to living organisms.

Although photosynthesis in plants removes a large amount of CO2 from the atmosphere, the concentration of CO2 in the atmosphere is still increasing, mainly due to urbanization and industrialization.

The intrinsic factors of photosynthesis are mainly the number of chloroplasts, the content of pigments, the number and activity of enzymes, and the genes and gene expression. Photosynthesis is the sum of a series of complex metabolic reactions, which is the basis for the survival of the biological world and an important medium of the earth's carbon and oxygen cycle.

Photosynthesis is the synthesis of light energy, which is a biochemical process in which plants, algae and certain bacteria, under the irradiation of visible light, undergo light reaction and dark reaction, use photosynthetic pigments to convert carbon dioxide (or hydrogen sulfide) and water into organic matter, and release oxygen (or hydrogen). Photosynthesis is the sum of a series of complex metabolic reactions, which is the basis for the survival of the biological world, and is also an important medium for the carbon and oxygen cycle of the geoculture stove.

Photosynthesis can be divided into two phases, i.e., light reaction and dark reaction. The former must be carried out under light and enhance with the increase in light intensity, while the latter can be carried out with or without light. The dark reaction requires light to provide energy and [h], and plants growing in low light have a slower light reaction, so the rate of photosynthesis does not increase when the carbon dioxide concentration is increased.

Transpiration increases with increased light to avoid leaf burns, but in the middle of the hot summer, when the light is too strong at noon, in order to prevent excessive water loss in the plant's body, the stomata are closed through adaptive adjustment by the plant. Although the photoreaction produces enough ATP and H in the ample burial, the stomata are closed, and the number of molecules of CO2 entering the chloroplast of mesophyll cells is reduced, which affects the production of glucose in the dark reaction.

There is light, carbon dioxide and temperature.

Illumination: Photosynthesis is a photobiochemical reaction, so the photosynthetic rate accelerates as the intensity of light increases. But beyond a certain range, the increase in photosynthetic rate slows down until it no longer increases.

The photosynthetic rate can be expressed in terms of the amount of CO2 absorbed, and the greater the amount of CO2 absorbed, the faster the photosynthetic rate.

Carbon dioxide: CO2 is the raw material for photosynthesis of green plants, and its concentration affects the progress of the dark reaction of photosynthesis. Increasing the concentration of CO2 within a certain range can increase the rate of photosynthesis, and the rate of photosynthesis does not increase after the concentration of CO2 reaches a certain value, because the products of the photoreaction are limited.

Temperature: The effect of temperature on photosynthesis is complex. Since photosynthesis includes two parts, light reaction and dark reaction, light reaction mainly involves photophysical and photochemical reaction processes, especially the steps that are directly related to light, excluding enzymatic reactions, so the photoreaction part is less affected by temperature, or even not affected by temperature; The dark reaction is a series of enzymatic reactions, which are obviously affected and restricted by temperature changes.

When the temperature is higher than the optimal temperature for photosynthesis, the photosynthetic rate obviously decreases with the increase of temperature, which is due to the passivation, denaturation and even destruction of the relevant enzymes that catalyze the dark reaction caused by high temperature, and the chloroplast structure will be changed and damaged by high temperature. The high temperature aggravates the respiration of plants, and the decrease in carbon dioxide solubility exceeds the decrease in oxygen solubility, which is conducive to photorespiration and not conducive to photosynthesis. At high temperatures, the transpiration rate of the leaves increases, the leaves lose water seriously, resulting in the closure of the stomata and the lack of carbon dioxide, and the combined effect of these factors will inevitably lead to a sharp decrease in the photosynthetic rate. When the temperature rises to the thermal limit, the net photosynthetic rate drops to zero, and if the temperature continues to rise, the leaves will wilt and even dry up and die due to severe water loss.