The Basics of Photoynsy Lecture Series 6: Factors Affecting Photosynthing

photosynthesy of plants is influenced by internal and external factors, and the common indicator for measuring the degree of photosynthetic influence of internal and external factors on photosyntheticity is photosynthetic rate.
, photolysal rate, and the unit ofThe photolysing rate usually refers to the amount of CO2 absorption per unit of time, the amount of CO2 absorption per unit of leaf area, or the amount of release of O2, which can also be expressed by the accumulation of dry matter per unit time and per unit of leaf area. Common units are: smol CO2-m-2 s-1 (previously expressed with mg.dm-2-h-1, 1 smol-m-2-s-1=1.58mg-dm-2.h-1), smol O2-dm-2 dm-h-1 and mgDW (dry weight) and 2-h-1. CO2 absorption is measured with infrared CO2 gas analyzer, O2 release is measured with oxygen electrode oxygenation device, and dry matter accumulation can be determined by improving half-leaf method (please refer to the plant physiological experiment instructions).
some methods of measuring photosynthetic rate do not take into account such factors as breathing action (light, dark breathing) and co2 released by breathing are re-fixed for photosynthesy, so the results measured are actually table-based sightseeing rate (see photosynthetic rate) or net photosynthethethe Rate (net photosynthetic rate, Pn), such as the table touring rate plus light, dark breathing rate, you get the total photosynthetic rate (gross photosyntheticrate) or true photosynthetic rate.
, internal factors
(i) leaf development and structure
1. Leaf age newly-growed young leaves, photolyzing rate is very low.
The main reasons are: (1) leaf
tissue
development is not perfect, pores have not yet fully formed or opened small, cell gap is small, leaf meat cells and external gas exchange rate is low; (4) The breathing action of the young leaves is exuberant, thus reducing the rate of table sightseeing. However, with the growth of young leaves, the development of chlorophytes, chlorophyte content and Rubisco enzyme activity increased, photolyzing rate increased, when the leaves grow to the maximum area and thickness, the photolyzing rate usually reaches the maximum value, after that, as the leaves age, chlorophyte content and Rubisco enzyme activity decreased, and the internal structure of chlorophyte disintegrination, photoneedling rate decreased.
based on the "low-high-low" pattern of photolysaling rate with leaf age, it is available to infer the size of the relative photolymped rate of leaves in different parts of the reproductive period. In the case of cereal crops with long-term nutrient growth, the photogastic rate of the heart leaves is lower, and the photolytic rate of the falling 3 leaves is often the highest, while in the sequestration period, the photogastic rate of the leaves should be decayed from top to bottom.
2. The structure of leaves, such as leaf thickness, the ratio of fence tissue to sponge tissue, the number of yeloros and sacs, all have an effect on the photogasing rate. The structure of the leaf is controlled by genetic factors on the one hand and environmental influences on the other.
C4 plants usually have a higher rate of leaf photoplication than C3 plants, which is related to the characteristics of C4 plant leaves with wreath structure and so on. Many plants have two types of leafy tissue in their leaf tissue, which are fenced cells on the abdominal side and sponge tissue cells on the back. Fence tissue cells are slender, arranged tightly, chlorophyte density is large, chlorophyl content is high, resulting in a deep green leaf abdomen, and the chla/b ratio is high, photolytic activity is also high, while the sponge tissue is the opposite. The tissue of sun plant leaf fence, which is grown under light conditions, is more developed than that of shade plant, and the photosynthing characteristics of chlorophytes are better, so the solar leaves have a higher photosynthing rate.
the same blade, the photolyceric rate measured on different parts is often inconsistent. For example, the photoresist rate of the leaf tip of the benthon crop is lower than that of the lower and middle parts of the leaf because the tip of the leaf is thin and prone to premature aging.
(ii) the output of photolysal products
the rate at which photosynthing products (sucrose) are exported from the blades affects the photolysaling rate of the blades. For example, the removal of flowers, fruits, top buds, etc. will temporarily hinder the output of photosynthemum products, reducing the photolysaling rate of leaves, especially adjacent leaves; For apples and other fruit branches ring cutting, because the photochemide products can not be shipped, will make the ring cutting on the top branches of the leaf photocheming rate decreased significantly.
photolysal products accumulate to a certain level and affect the photolysal rate for a number of reasons:
(1) feedback suppression. For example, the accumulation of sucrose feedback inhibits the activity of sucrose phosphate synthase, SPS), which inhibits the synthesis of sucrose, which increases F6P. The accumulation of F6P, and feedback inhibits fructose 1,6-phosphate enzyme activity, so that cytocytes and the content of propylene phosphate in the carbapenems increased, thereby affecting the fixation of CO2;
(2) starch particles. The accumulation of sucrose in leaf meat cells will promote the synthesis of starch and the formation of starch grains in the leafy body substation, too many starch particles on the one hand will compress and damage the sacs, on the other hand, because starch particles block the light, thus directly hindering the absorption of light by the photogastory membrane.
three external factors(i) Lighting
light is the driving force of photosynthmatics and the necessary condition for the formation of coliogens, carbases and normal leaves, and light also significantly regulates the activity of photosynthelase and the opening of the pores, so light directly restricts the rate of photosynthelization. Lighting factors include light strength, light quality and light time, which have profound effects on photosynthresity.
1. Light Strength
(1) Light Strength-Photolithic Curve
Dark Blades do not carry out photocodyne, only respiratory action releases CO2. As the light strength increases, the photosynthelation rate increases accordingly, and when a light strength is reached, the photoresponsion rate of the blade is equal to the breathing rate, i.e. the CO2 absorption is equal to the CO2 release, and the table touring rate is zero, at which point the light force is called the light compensation point. In low-light-strength regions, the photo-enseture rate increases proportionally with the increase of light-strength (proportional stage, linear A);
when the light is called the light saturation point when the light is beginning to reach the maximum photosynthing rate, and the stage after this point is called the saturation phase (straight line C). The proportion stage is mainly light forced about the photolycing rate, while the CO2 diffusion and fixed rate in the saturation stage are the main limiting factors. The slope of the light-photoresculation curve (table sightseeing rate/light strength) of the proportional stage can be used to calculate the quantum yield of the table sightseeing.
the light-glossy curves of different plants, the light compensation points and the light saturation points are also very different.
The light saturation point of plants with high light compensation point is also high, and the light compensation point and light saturation point of herbs are usually higher than that of woody plants; Light compensation points and light saturation points can be used as the main indicators of plant light demand characteristics to measure the amount of light required. Plants with low light compensation points are more resistant to yin, such as soybean light compensation points of only 0.5klx, so can be made with corn, in the corn line can still grow normally.
At the light compensation point, photolyceride accumulation is offset against respiratory consumption, and if night-time breathing consumption is taken into account, there is a deficit in the photolyceride product, so the minimum light strength required by the plant must be higher than the light compensation point throughout the day. For the group, the light strength received by the upper blades tends to exceed the light saturation point, while the light strength of the lower and middle blades is still below the light saturation point, such as the light saturation point of the rice single leaf is 40 to 50klx, and the group is 60 to 80lx, so improve the lighting of the lower and middle blades, and strive to make the lower and middle blades receive more light is an important condition for high yield.
plants' light compensation points and light saturation points are not fixed values and vary with external conditions, for example, when the CO2 concentration increases or the temperature decreases, the light compensation point decreases, and when the CO2 concentration increases, the light saturation point increases. In closed greenhouses, the temperature is higher and CO2 is less, which increases the light compensation point and is detrimental to the accumulation of photolycery. In this case, room temperature should be appropriately reduced, ventilation, or co2 can be added to ensure the smooth progress of photocodychroid.
In general light strength, C4 plants do not appear light saturation phenomenon, the reason is:
(1) C4 plant assination CO2 consumption of assination force is higher than C3 plant (2) PEPC to CO2 affinity, and has "CO2 pump", so the concentration of CO2 in the air is not usually C4 plant photocodynical limiting factors.
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