Effects of temperature on photosynthesis

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temperature photosynthesis effects

Terrestrial plants are regularly subjected to strong temperature variations. These variations can reach an amplitude of 40°C or even more, both in polar regions and in hot desert areas. Being rooted, they have reduced mobility and must cope with changes in their environment. The assimilation of CO2 by plants via photosynthesis is the gateway to carbon in the biosphere. What is the thermal amplitude that allows it to function? How does photosynthesis reacts to rapid and slow temperature variations? What is the diversity of responses? What are the physiological processes that limit it? Crucial questions tare o be considered in the context of global warming.

1. Plant production and climate change

The current increase in greenhouse gas emissions will cause an increase in atmospheric temperature of 2 to 3°C in the next 50 years (see A carbon cycle disrupted by human activities). At the same time, heat waves and extreme heat periods will be more frequent and of longer duration [1]. Agricultural production and the functioning of forests will therefore be greatly affected. Models based on large-scale observations indicate that, in the absence of agronomic adaptation, the decrease in crop yields can reach 17% for each 1°C increase in the temperature of the growing season [2].

The production of higher plants depends in particular (but not only [3]) on leaf photosynthesis (see Shedding light on photosynthesis & The The path of carbon in photosynthesis). CO2 enters the leaf where its reduction in the chloroplasts is accompanied by O2 production. Its entry is almost exclusively through the stomata (Figure 1). For each molecule of CO2 absorbed, 50 to 300 molecules of water are transpired from the leaves, depending on the plant. This water allows, among other things, the cooling of the leaf (see Focus Leaf transpiration and heat protection).

photosynthesis-CO2-absorption
Figure 1. During photosynthesis, CO2 is absorbed and O2 is released mainly through the stomatal opening (ostiole). The water vapour (transpiration of the leaf) passes mainly through the ostiole but also through the epidermis. Transpiration allows the leaf to cool down in the light. [Source: Author’s diagram]
The leaf is a converter of solar energy into chemical energy and, like any energy converter, requires a permanent cooling system.

The climate changes that are currently occurring make it necessary to understand the effects of temperature on photosynthesis.

2. The thermal optimum of photosynthesis

2.1. Diagram of the thermal response

Photosynthetic CO2 uptake varies with temperature. In most cases its response to temperature is rapidly reversible between about 10 and 34°C. In this range of temperatures it presents a maximum value: a thermal optimum.

photosynthesis assimilation CO2
Figure 2. Diagram of the variation of CO2 assimilation by an intact leaf. It highlights the temperature range in which  variations are generally rapidly reversible. [Source: Author’s diagram]
Below 10°C and above 34°C plants start to set up protective mechanisms. For these extreme values, CO2 assimilation is often unstable and can be cancelled more or less quickly: the leaf is then under stress (Figure 2).

2.2. A thermal optimum based on the average temperature of the environment

Plants in cold environments or with a cold growing season have a higher photosynthesis at low temperatures. Plants in warm environments, or growing during the warm season, have a higher photosynthesis at high temperatures.

deschampsia antartica optimum thermal
Figure 3. Deschampsia antarctica is one of two flowering plants found in Antarctica. It is often subjected to negative temperatures. The snow that frequently covers it protects it from extreme temperatures. [Source: Lomvi2, CC BY-SA 3.0, via Wikimedia Commons]
For example, the thermal optimum for CO2 assimilation [4] in Deschampsia antarctica (Figure 3) and Colobanthus quitensis, the only two Antarctic flowering plants, is between 8 and 15°C, while it is around 45°C in Tridestomia oblongifolia, a warm desert plant from Central America. The latter species probably holds the world record for flowering plants in this respect.

2.3. Acclimatization to the thermal conditions of the environment

temperature photosynthesis plant
Figure 4. Variations in CO2 assimilation as a function of leaf temperature, in a plant grown at 10°C (red) or 25°C. Measurements made on Pea, under a light close to saturation. CO2 content in ambient air: 390 ppm. [Source: Author’s diagram]
Differences in the thermal response of photosynthesis are also found in individuals of the same species growing at different temperatures. Figure 4 shows CO2 assimilation in pea grown at 10 or 25°C.

In the first case (cultivation at 10°C) the thermal optimum is about 16°C, while it is higher than 25°C in the second (cultivation at 25°C). At low temperatures, CO2 assimilation is higher in plants grown at 10°C.

In this case the adjustment to cool conditions is a gain for the plant.

2.4. Acclimatization can be rapid

temperature Wadi Rum Remth
Figure 5. Remth (Hammada scoparia), a characteristic plant of the Wadi Rum desert (Jordan). [Source: Ji-Elle, CC BY-SA 4.0, via Wikimedia Commons]
For example, the photosynthesis of Hammada scoparia, a bush in the deserts of the Middle East (Negev, Wadi Rum) follows the seasonal variations in temperature: its thermal optimum varies from 29°C in early spring to 41°C in summer and then to 28°C in autumn

temperature photosynthesis encelia californica
Figure 6. Encelia sp. (Yellow flowers) is a typical plant of dry areas in California (here Palm Canyon trail). [Source: © Stan Shebs, via Wikimedia commons CC BY-SA 3.0]
Changes in the thermal optimum can be even more rapid and of great amplitude. For example, in a seaside clone [5] of Encelia californica, a change in growth temperature from 30°C (constant day and night temperature) to 15°C during the day and 2°C during the night for three days is sufficient to lower the thermal optimum by about ten degrees.

In general, these changes can be measured in both growing and mature leaves, with the response being of greater amplitude in growing leaves.

2.5. Heat-sensitive versus cold-sensitive species

Warm acclimation of cool-adapted species (or ecotypes [6]) occurs with an increase in thermal optimum but a general decrease in photosynthesis.

This is, for example, the case of Atriplex sabulosa. One can then wonder about the interest of this change. The opposite may be true for plants strictly adapted to warm conditions, such as Tridestomia oblongifolia. Figure 7 illustrates the case of Atripex lentiformis, [7] a perennial leafy plant, which occurs in California in both Death Valley and in cool, wet coastal habitats:

  • The assimilation of the desert ecotype (Figure 7A) and the coastal ecotype (Figure 7B) show almost the same response to temperature when grown under 23°C during the day and 18°C at night (in red in Figure 7).
  • photosynthesis medium hot cool
    Figure 7. Variations in CO2 assimilation of Atriplex lentiformis ecotypes from a warm environment (A) and a cool, moist environment (B). [Source: Author’s diagram, after Pearcy (1977)] Right, Atripex lentiformis (salt bush) [Source: Forest & Kim Starr, CC BY 3.0, via Wikimedia Commons]
    Under the alternating 43°C day and 30°C night (blue in Figure 7), only the desert ecotype shows plasticity, maintaining high CO2 assimilation under these new conditions. The activity of the coastal ecotype is low at all temperatures. Only the displacement of the thermal optimum remains of its acclimatization capabilities [8].

2.6. C3 plants versus C4 plants

Temperature photosynthesis forest
Figure 8. Primary forest in southern Argentina. Almost all trees are C3 plants. [Source: © G. Cornic]
C3 plants were the first to appear and constitute about 85% of current plant species. They mainly colonize cool and humid environments (or seasons). Trees, for example, with rare exceptions, are C3 plants (Read The path of carbon in photosynthesis) (Figure 8).

C4 plants, of which there are traces only from the end of the Tertiary Era, constitute only 5% of the species. They tend to colonize hot and dry environments (or seasons) (See Restoring savannas and tropical herbaceous ecosystems). Maize and sugarcane are examples.

On average, the thermal optimum of C4 plants is located at higher temperatures than that of C3 plants.

However, C3 plants are the most plastic. In fact, their thermal optimum varies from around 7 to 35 ° C, while that of C4 plants oscillates, with a few exceptions, between 30 and 40 ° C. In addition, when the temperature is below 20 ° C, the photosynthesis of C4 plants is on average lower than that of C3 plants.

3. CO2 assimilation results from the interaction of processes whose response to temperature is different

The absorption of light at the collecting antennae (Figure 9) and the transfer of its energy to the PSII reaction centres are not temperature sensitive.
Are temperature sensitive:

  • The diffusion of CO2 from the ambient air to the chloroplasts: its speed increases with temperature.
  • The fixation of CO2 on Ribulose 1,5-bisphosphate (RuBP), a sugar whose skeleton is formed by 5 carbon atoms (Read Focus Deciphering the Benson-Bassham-Calvin cycle)
  • The transfer of electrons from PSII to PSI.

CO2 photosynthetic fixation
Figure 9. Diagram of the interacting processes during photosynthetic CO2 fixation (case of a C3 plant). PSI and PSII: respectively photosystem I and II. They are included in the thylakoid membrane, which is made up of two lipid layers forming “sacs” in the chloroplast. The interior of the thylakoid is the lumen. RubisCO: enzyme that catalyzes the fixation of CO2 on a sugar with 5 carbon atoms (Ribulose 1,5-bisphosphate: C5). Benson-Calvin cycle: allows the regeneration of C5, and at the same time gives the plant the necessary carbon. ATP is synthesized when protons from the lumen return to the stroma through an ATPase using inorganic phosphate, Pi. The lumen protons have two origins: (1) oxidation of water in the lumen by PSII which also provides electrons, e- and (2) operation of a proton pump in the thylakoid that passes protons from the stroma into the lumen. [Source: Author’s diagram]
The regeneration of RuBP occurs via the operation of the Benson-Calvin cycle (This is the “biochemistry” of the process) which uses reducing power (in the form of NADPH) provided by electron transfer to function. The necessary ATP is synthesized when protons accumulated in the lumen pass into the stroma through an ATPase (Figure 9).
The formation of reducing power and the synthesis of ATP have a thermal sensitivity close to that of electron transfer.

4. What are the processes at work in setting the thermal optimum for CO2 assimilation in C3 and C4 plants?

4.1. Photosystem activity and the resulting electron transfer are not involved

Measured in vitro on isolated thylakoids (see legend Figure 9), in the presence of artificial acceptors, electron transfer increases with temperature and shows a clear thermal optimum. It is located around 30°C and corresponds to that of CO2 assimilation when the latter is saturating [9]. The activity of PSII has a thermal optimum identical to that of the electron transfer chain.

  • PSI activity is not inhibited at high temperatures (above 30°C, up to 45°C) where it remains stable or even increases: it is the activity of PSII that limits the activity of the electron chain.
  • Moreover, PSII is very sensitive to high temperatures which damage the protein complex that allows the oxidation of water (see Figure 9).

The thermal response of electron transfer is similar in C3 and C4 plants. However, there are organizational differences between these two types of plants (see The path of carbon in photosynthesis).
The supply of energy cannot therefore explain the differences in thermal optimum. It is the way in which the energy produced is used that makes the difference.

4.2. An answer? Comparison of the effect of atmospheric O2 on CO2 assimilation of C3 and C4 plants

  • In normal air [10], 21% O2 (+ N2) + 360 ppm CO2: the thermal optimum is 27°C in Maize (C4 plant), while it is only 22°C in Pea (C3 plant) (Figure 10): the thermal optimum of the C4 plant is higher than that of the C3 plant (see also section 2.6).
  • In an oxygen-deficient atmosphere, 1% O2 (+ N2) + 360 ppm CO2: the CO2 uptake of Maize is not affected, while that of Pea is stimulated above about 17°C, with a shift in its thermal optimum to near that of Maize.
  • In C3 plants, atmospheric oxygen inhibits CO2 uptake when the leaf temperature is sufficiently high, whereas it has no effect (or negligible effect) in C3 plants
  • assimilation CO2 temperature
    Figure 10. Variation of CO2 assimilation measured in leaves of Pea (A; Pisum sativum) and Maize (B; Zea mays) as a function of leaf temperature. The plants were grown in natural light at a temperature of 20 ± 2°C. [Source: Author’s diagram – royalty-free image / Pixabay]
    Note that the variation in electron transfer estimated in vivo, by measuring chlorophyll fluorescence emission as a function of temperature, is very similar in 1% and 21% O2 in Pea: the variation in thermal optimum is therefore not due to a change in photochemistry.

4.3. Rubisco properties explain the difference in response

  • Case of C3 plants

COand Ocompete to occupy the active sites of Rubisco: This enzyme has a carboxylase function and an oxygenase function. CO2 enters the Benson-Calvin cycle and the photosynthetic fixation of O2 is at the origin of a metabolic pathway responsible for photorespiration (Figure 11; see also The path of carbon in photosynthesis).

CO2 occupies a high number of active sites on the Rubisco when the O2 content of the ambient air is low (1% for example) or that of COis high.

O2 is mainly fixed if its content increases or if that of CO2 decreases (the latter then releases active sites which are then occupied by O2).

In normal air, there are two reasons why O2 fixation increases (and consequently CO2 fixation decreases) when the temperature increases [11].

  1. The affinity of Rubisco forCO2 decreases more than that for O2; a factor that favours the assimilation of O2.
  2. The water solubility coefficient of CO2 decreases more than that of O2, leading to a more rapid decrease in the amount of CO2 than O2 in the chloroplast; this is a factor that favours O2 fixation.

In an O2-poor atmosphere (Figure 10), competition between O2 and CO2 is very reduced. Energy is then used mainly for CO2 assimilation, which increases in value until around 30°C and then decreases as the energy supply decreases (see section 4.1).

In normal air, the effect of O2 on photosynthetic CO2 fixation (Figure 11) is very low (or even nil) when the temperature is low: competition on the carboxylation sites is in favour of CO2.

fixation CO2 O2 plant
Figure 11. Schematic of CO2 and O2 fixation on RuBP (Ribulose 1,5-bisphosphate) in a C3 plant. APG: 3-phosphoglyceric acid, 3 C compound; TP: Trioses phosphate. The carbon leaves the Calvin cycle to feed the synthesis of sucrose. PG: phosphoglycolate, 2C compound. Two PGs give a serine (Ser) containing 3C with the production of CO2 from photorespiration. C = Carbon atom. Source: Author’s diagram]

On the other hand, when the temperature increases, the competition on these sites favours the fixation of O2 which then consumes an increasing part of the energy produced by the activity of the photosystems. This energy is therefore no longer available for CO2 fixation, which reaches its maximum value around 22°C.

  • Case of C4 plants.

COis concentrated at the Rubisco by a mechanism that is insensitive to oxygen. Its content can reach 800 to 2000 ppm depending on the plant in C4: that is to say contents from 2 to 5 times higher than its current atmospheric content.

Under these conditions, photosynthetic O2 fixation is weak or even non-existent because the active sites of the Rubisco are all occupied by CO2. The energy supplied by the activity of the photosystems is therefore used only in the fixation of CO2 when the leaf temperature increases, explaining the higher thermal optimum in this type of plant.

C4 plants evolved from C3 plants during the global decrease in atmospheric CO2 content at the end of the Tertiary Era [12].

This decrease would then have “released” the oxygenase function of the Rubisco of C3 plants, resulting in a loss of fixed carbon via photorespiration.

The establishment of a CO2 concentration mechanism is an advantage because it prevents this carbon loss. We currently find species that are “intermediates” between C3 and C4.

5. The thermal optimum of C3 photosynthesis is modulated by certain environmental parameters

5.1. The CO2 content in the atmosphere

The thermal optimum increases with increasing ambient CO2 content. In the case shown in Figure 12, it increases from about 10°C when the content is 100 ppm to more than 30°C when it is 800 ppm.

assimilation CO2 photosynthesis
Figure 12. Variations in CO2 uptake as a function of leaf temperature measured on a Pea leaf placed at different ambient CO2 levels. Light near saturation. [Source: © G. Cornic, unpublished]
This effect is explained by the competition between CO2  and O2 for the occupation of the active sites of the Rubisco: at 800 ppm CO2 the active sites are occupied mainly by CO2 ; at 100 ppm CO2 the occupation of these sites by atmospheric O2 is in majority.

human activities temperature atmosphere
Figure 13. Human activities lead to an increase in carbon dioxide in the atmosphere. Its content went from 320 to 415 ppm in the space of 50 years. This increase has consequences on the temperature of the atmosphere and the activity of the vegetation. [Source : Royalty-free image / Pixabay]
 In a world with steadily increasing atmospheric CO(Figure 13), the thermal optimum of C3 plants is expected to increase. This does not mean, however, that plant production will then be higher (see note 3 section 1): episodes of high heat will, like droughts, certainly be more frequent.

5.2. Lack of water

The photosynthetic apparatus is resistant to drought. It retains all its capacity to absorb CO2 on the Rubisco, and to produce energy until the leaves have lost about 30% of their water [13].

  • CO2 uptake decreases in this range of water loss, because the stomata close (see Focus Leaf transpiration and heat protection). This closure slows down the entry of CO2  into the leaf and consequently leads to a decrease of the CO2 content in the mesophyll.
  • However, the O2 content in the chloroplasts remains high. Indeed, its content in the atmosphere (21% or 210,000 ppm) is, compared to that of CO2 (@ 400 ppm), very high and in any case sufficient for a very substantial quantity to pass through the epidermis even when the stomata are closed.
  • The competition between CO2 and O2 for the occupation of the active sites of the Rubisco is thus in favour of O2.

photosynthesis lack water
Figure 14. A, Variations in CO2 assimilation as a function of leaf temperature. Leaves with different amounts of water loss found in air with an ambient CO2 content of 400 ppm. B, The electron transfer rate estimated on the same leaves by measuring the chlorophyll fluorescence emission. [Source: Author’s diagram, after Cornic et al. ref. 14]
Therefore, the thermal optimum for photosynthesis must lower in C3 plants that dry out.

This is shown in Figure 14A, in which the thermal optimum drops from about 23°C, in a Pea leaf at maximum turgor, to 17°C when it has lost 20% of its water.

Electron transfer in the thylakoid membrane is not affected by water loss in the range shown (Figure 14B). When water loss is 20%, the energy produced by photosystem activity is primarily used to bind atmospheric oxygen to RuBP [14], resulting in increased photorespiration.

6. Why, from its thermal optimum, CO2 assimilation decreases as temperature decreases or increases?

6.1. When the temperature lowers

Several reasons probably all contribute, to varying degrees, to this decrease :

  • The rate of RuBP turnover decreases: there is a slowdown in the activity of some enzymes controlling this turnover, notably that of a Fructose 1,6-bisphosphate (see Figures 9 and 11).
  • Sequestration of phosphorylated compounds in chloroplasts. The triose phosphate is no longer (or less) exported when sucrose synthesis is inhibited. The inorganic phosphate in the chloroplast is no longer renewed leading to a decrease in ATP synthesis.
  • Inhibition of the electron transfer chain (see section 4.1), resulting in reduced energy production (reducing power and ATP).

In C4 plants it is the activity of the Rubisco that appears to be preponderant, although the cold sensitivity of enzymes involved in CO2 accumulation at the Rubisco is well known.

6.2. As the temperature increases

In C3 plants the increase in photorespiration decreases the fraction of electrons produced by PSII and used to assimilate CO2. However, other factors are at play since CO2 assimilation measured (1) in an atmosphere with little or no photorespiration (ambient O2 content of 1%), and (2) measured in a normal atmosphere in a C4 plant decreases in both cases (Figure 10).

Several reasons can be given:

  • The slowing down of PSII activity leading to that of the electron transfer chain from PSII to PSI.
  • To perform its role Rubisco must be activated by an enzyme called Rubisco activase, the activity of which decreases when the temperature is higher than about 33°C (incidentally, high-temperature resistant activases appear in some plants subjected to periods of high heat [15]). However, since activase must itself be activated by an electron transfer-dependent process, it cannot be ruled out that the latter is also involved in limiting [15].
  • The “catalytic misfiring” of Rubisco increases with temperature and increasing amounts of an inhibitor of the enzyme (Xylulose-1,4-bisphosphate), which is structurally close to RuBP (see Figures 9 and 11), are synthesized.

In C4 plants (case of Maize) the activation and activity of enzymes that participate in the CO2 concentration system at the Rubisco are not very sensitive to high temperatures. The same reasons as above may explain the decrease in COassimilation when the temperature increases beyond that of the thermal optimum.

7. Hardening after plant exposure to cool (≤ about 10°C) and high (≥ about 37°C) temperatures

Maintaining plants at cool or high temperatures causes, along with the changes in photosynthesis described above, increase in their resistance to otherwise lethal temperatures(frost and high temperature). This is hardening.

In this process, temperature and light interact and the metabolic changes induced are sometimes very rapid (from minutes to hours).

Thus, cold hardening can be achieved at ordinary temperature by modulating the length of the light period or its spectral composition in the red [16]. However, cold is still required to achieve full hardening. Also the lack of light in the cold prevents hardening to varying degrees.

  • At elevated temperatures : the transmitted signals activate the synthesis of chaperone proteins (HSPs: Heat Schock Proteins) that repair denaturing proteins, also prevent their coagulation or even help mark them for degradation.
  • At cool temperatures: the synthesis of chaperone proteins is also activated. It is accompanied by (i) the synthesis of “antifreeze” proteins that interfere with ice crystal formation and (ii) an increase in sugar synthesis tending to increase osmotic pressure in the cells.

Note that the signaling pathways and their interactions inducing the genome response are only partially known. The references given in “Learn More” and an attached Focus allow for further exploration of this evolving point.

8. Effects of temperature on photosynthesis: summary diagram

The summary diagram (Figure 15) classifies the effects of temperature on photosynthesis according to the speed of temperature change and the extent of its variation. Note that hardening allows leaf maintenance in perennial leaf plants and therefore minimizes energy loss under extreme temperature conditions.

photosynthetic temperature effects
Figure 15. Scheme classifying the effects of temperature on photosynthesis. [Source: Author’s diagram]
The rapidity of current climate change makes it necessary to delve deeper into the responses of plants to their environment: the hope is to be able to maintain sufficient primary production to keep the biosphere functioning.

9. Messages to remember

  • The uptake of CO2 by a leaf has a thermal optimum close to the average temperature of its growth environment.
  • This thermal optimum can change rapidly when the conditions of the environment are durably modified: this is a process acclimatization.
  • This thermal optimum is on average less in C3 plants than in C4 plants: this is mainly due to photosynthetic fixation of atmospheric O2 via Rubisco activity in C3 plants.
  • This optimum depends on the CO2 content of the ambient air in C3 plants: at high content it becomes identical to that in C4 plants.
  • This optimum depends on the hydration state of the leaf.
  • Subjected to cool or hot temperatures plants bring into play processes hardening to otherwise lethal temperatures. These processes involve protein syntheses and changes in the fluidity of chloroplast and cell membranes.

Notes and references

Cover image. Sunset over the Sonora Arizona desert. [Source: royalty free / Pixabay]

[1] Meehl GA, Stocker TF, Collins WD, Riedlingstein P, Gaye AT, Gregory JM, Kitoh A, Knutti R, Murphy JM, Noda A & Raper SCB (2007). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press

[2] Yamori W, Hikosaka K & Way DA. (2014). Temperature response of photosynthesis in C3, C4, and CAM plants: temperature acclimation and temperature adaptation. Photosynthesis Res. 119, 101- 117.

[3] For example, when growing plants are subjected to drought, the amount of carbon they assimilate decreases initially because leaf growth is inhibited. The mechanisms for CO2 fixation in the leaf are not then inhibited. Boyer JS (1970) Plant Physiol.46, 233-235

[4] The values of thermal optima given here, are from measurements made in “normal air”, containing 21% O2 and about 400 ppm CO2. When this is not the case the O2 and CO2 contents are shown. The CO2 uptake in air containing 21% O2 is saturated from about 1200 ppm CO2 when light is close to saturation. The evaporative power of the air is also regulated in most cases during the measurements. It is estimated by the saturation deficit of the partial pressure of water vapor in the ambient air around the leaves.

[5] Plants from the same individual by vegetative reproduction. They are genetically identical.

[6] Ecotype: Plants of the same species from different environments, which, grown from seed to flower under identical conditions show different physiological characteristics.

[7] It fetches water from as far as the water table, hence its name of phreatophyte plant.

[8] Pearcy RW (1971). Acclimation of photosynthetic and respiratory CO2 exchange to growth temperature in Atriplex lentiJormis (Torr.) Wats. Plant Physiol. 59, 795-799

[9] Yamasaki T, Yamakawa T, Yamane Y, koike H, Satoh K & Katoh S. (2002) Temperature acclimation of photosynthesis and related changes in photosystem II electron transport in winter wheat. Plant Physiol. 128 1087-1097.

[10] See note #4, section 2.2

[11] Jordan DB & Ogren WL (1984). The CO2/O2 specificity of ribulose 1,5-bisphosphate carboxylase/oxygenase. Dependence on ribulose bisphosphate concentration, pH and temperature. Planta 161, 308-313

[12] Ehleringer JR, Sage RF, Flanagan LB & Pearcy RW (1991). Climate change and the evolution of C4 photosynthesis. Trends in Ecology and Evolution 6, 95-99

[13] Cornic G & Massacci A (1996). Leaf photosynthesis under drought stress. In Advances in Photosynthesis (vol 5) Photosynthesis and the environment, 347-366. Neil R Baker (ed.) Kluwer Academic publishers Dordrecht.

[14] Cornic G, Badeck F-W, Ghashghaie J & Manuel N (1999). Effect of temperature on net CO2 uptake, stomatal conductance for CO2 and quantum yield of photosystem II photochemistry of dehydrated pea leaves. In Sanchez Dias M, Irigoyen JJ, Aguirreolea J & Pithan K (eds) Crop development for cool and wet regions of Europe. European community. ISBN 92-828-6947-4.

[15] Crafts-Brandner SJ, van de Loo FJ & Salvucci ME (1997). The two forms of ribulose-1,5-bisphosphate carboxylase/oxygenase activase differ in sensitivity to elevated temperature. Plant Physiol. 114, 439-444.

[16] Puhakainen T, Li C, Boije-Malm M, Kangasjärvi J, Heino P & Palva ET. (2004). Short-day potentiation of low temperature-induced gene expression of a C-repeat-binding factor-controlled gene during cold acclimation in Silver Birch. Plant Physiol.136, 4299-4307


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To cite this article: CORNIC Gabriel (September 27, 2021), Effects of temperature on photosynthesis, Encyclopedia of the Environment, Accessed December 9, 2024 [online ISSN 2555-0950] url : https://www.encyclopedie-environnement.org/en/life/effects-temperature-on-photosynthesis/.

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温度对光合作用的影响

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temperature photosynthesis effects

       陆生植物经常受到温度剧烈变化的影响,无论是在极地还是在炎热的沙漠地区,温度的变化幅度可以达到40 °C甚至更高。陆生植物扎根后就几乎不能移动,因此,它们必须应对原位环境的变化。植物通过光合作用同化二氧化碳,这是碳进入生物圈的起点。光合作用正常工作的温度范围是多少?光合作用对快速和缓慢的温度变化如何响应?不同植物的响应有何差异?限制光合作用的生理过程是什么?这些关键问题都需要我们在全球变暖的背景下加以考虑。

1. 植物生产与气候变化

  从目前温室气体排放增加的趋势来看,未来50年内大气温度可能升高2-3°C(见“被人类活动干扰的碳循环)。与此同时,热浪和极端高温事件将更加频发,持续时间也会更长[1]。农业生产和森林的功能将受到巨大的影响。基于大规模观察的模型表明,在缺乏农业适应性措施的情况下,生长季温度每升高1°C,作物产量下降可达17%[2]

  高等植物的生产力尤其(但不只是[3])依赖叶片的光合作用(参见“揭示光合作用的真相以及“光合作用的碳代谢路径”)。二氧化碳(CO2)进入叶片后在叶绿体中被还原,同时伴随着氧气(O2)的产生。二氧化碳几乎完全是通过保卫细胞进入叶片的(图1),每一个二氧化碳分子进入叶片,就会蒸发掉50-300个水分子,具体数值取决于植物种类和状态。蒸腾损失的水分除了其他功能外,还能使叶片冷却(参见“叶片蒸腾和热保护”)。

环境百科全书-光合作用-蒸腾作用
图1. 在光合作用过程中,二氧化碳和氧气主要通过气孔(小孔)进出,水蒸气(叶片的蒸腾作用)也是如此,但表皮也能蒸腾水分。蒸腾作用可以使照光的叶片降温。[图片来源:作者自制]

  叶片将太阳能转化为化学能,与任何能量转化器一样,它需要一个持久工作的冷却系统

  当前,气候变化正在发生,了解温度对光合作用的影响则更为必要。

2. 光合作用的最适温度

2.1. 温度响应图

  光合作用中二氧化碳的吸收速率随温度而变化。大多数情况下,当温度在10-34 °C之间变化时光合速率也会发生快速可逆的变化,并出现一个最大速率:即光合作用的最适温度

环境百科全书-光合作用-二氧化碳吸收速率
图2. 活体叶片的二氧化碳吸收速率随温度变化示意图。图中显示了吸收速率快速可逆变化的温度范围。[图片来源:作者自制]

  10°C以下和34°C以上对植物来说属于胁迫条件,它们会启动保护机制,以应对此类极端温度。在此胁迫条件下,叶片的二氧化碳同化过程往往是不稳定的,甚至可能停止(图2)。

2.2. 基于环境平均温度的最适温度

  在寒冷环境或寒冷季节生长的植物,低温下的光合速率更高;相反,在温暖环境或温暖季节生长的植物,高温下的光合速率更高。

环境百科全书-光合作用-南极发草
图3. 南极发草(Deschampsia antarctica)是在南极洲发现的两种开花植物之一,那里的气温经常处于零度以下,它常因积雪覆盖而免受极端低温的影响。[图片来源:Lomvi2, CC BY-SA 3.0, 通过维基共享资源]

  例如,南极仅有两种开花植物南极发草(Deschampsia antarctica,图3)和南极漆姑草(Colobanthus quitensis),它们的二氧化碳同化的最适温度都在8~15°C之间[4],而来自中美洲炎热沙漠的植物(Tridestomia oblongifolia)的最适温度在45°C左右,这可能是有花植物的世界纪录。

2.3. 对环境温度条件的适应

环境百科全书-光合作用-豌豆叶片二氧化碳吸收速率
图4 . 生长在10 °C(红色)或25 °C的豌豆叶片二氧化碳吸收速率与叶片温度的函数关系。测定条件为光强接近饱和,空气中的二氧化碳浓度为390 μL/L。[图片来源:作者自制]

       生长在不同温度下的同种植物个体,其光合作用对温度的响应也存在差异。图4显示了在10 °C和25 °C下生长的豌豆的二氧化碳吸收速率。

        第一种情形为在10 °C下培养植物,其叶片光合作用的最适温度约为16 °C;而在第二种情形下,植物的培养温度是25 °C,此时的最适温度则高于25 °C。而且在较低温度下,在10 °C条件下生长的植物二氧化碳吸收速率更高。

       在这种情况下,适应较冷的温度条件对植物来说是有利的。

2.4. 可以快速适应

环境百科全书-光合作用-雷姆斯
图5. 雷姆斯(Hamada scoparia)是瓦迪拉姆沙漠(Wadi Rum,约旦)的特色植物。[图片来源:Ji-Elle, CC BY-SA 4.0, 通过维基共享资源]

  例如,中东沙漠(内盖夫的瓦迪拉姆)中的一种灌木雷姆斯(Hamada scoparia)的光合作用随温度的季节变化而变化:最适温度从早春的29 °C升高到夏季的41 °C,再回落到秋季的28 °C。

环境百科全书-光合作用-脆菊木属植物
图6. 脆菊木属植物(Encelia sp.,图中开黄色花的)是加州干旱地区的典型植物(此处为棕榈峡谷小道)。[图片来源:©Stan Shebs, CC BY-SA 3.0,通过维基共享资源]

  光合最适温度的变化甚至可以更快,幅度也更大。例如,在加利福尼亚海滨的加州脆菊木(Encelia california)株丛[5],当其生长温度从30 °C(昼夜恒定)变为白天15 °C、夜间2 °C,只需3天,其光合最适温度就会降低约10 °C。

  一般来说,无论是还在生长的叶片还是已经成熟的叶片,都可以测量到这样的变化,生长中的叶片响应幅度往往更大。

2.5. 热敏植物与冷敏植物的比较

  生活在冷凉环境的植物物种(或生态型[6])对高温的适应会伴随着最适温度的升高,同时光合速率往往会降低

  例如,裂叶滨藜(Atriplex sabulosa)就是如此。这种变化的意义值得思考。而对于那些严格适应温暖环境的植物来说,情况可能正好相反,如Tridestomia oblongifolia。图7展示了大滨藜(Triplex lentiformis)的情况,它是一种多年生密丛生小灌木[7],既分布在加州的死亡谷,也生长在凉爽湿润的沿海地带:

  • 当生长温度为白天23 °C、夜间18 °C(图7中红色部分) 时,沙漠生态型(图7A)和滨海生态型(图7B)的二氧化碳吸收对温度变化的反应几乎相同。
  • 环境百科全书-光合作用-大滨藜
    图7. 左图为生活在温暖环境(A)和凉爽湿润环境(B)的两种大滨藜(Atriplex lentiformis)生态型二氧化碳吸收速率的差异。[图片来源:作者自制,见Pearcy(1977)]。右图为大滨藜(盐木)[图片来源:Forest & Kim Starr, CC BY 3.0, 通过维基共享资源]
    在白天43 °C、夜间30 °C的生长环境中(图7中蓝色部分),只有沙漠生态型表现出适应性,在新生长条件下保持了高的二氧化碳吸收速率;而滨海生态型在所有叶片温度下的光合速率都较低,只有最适温度的升高体现了它一定的适应能力[8]

2.6. C3植物和C4植物的比较

环境百科全书-光合作用-阿根廷南部的原始森林
图8. 阿根廷南部的原始森林,几乎所有的树木都是C3植物。[来源:©G. Cornic]

  C3植物是最早出现的植物类群,约占现存植物物种的85%。它们主要生长在凉爽湿润的环境(或季节)。例如,树木中除了极个别外,其他都是C3植物(阅读“光合作用的碳代谢路径”)(图8)。

  C4植物始现于第三纪末期,仅占现存植物物种总数的5%。它们更喜爱炎热、干燥的环境(或季节)(参见“恢复热带稀树草原和热带草本生态系统”)。玉米和甘蔗就是C4植物。

  平均而言,C4植物的最适温度高于C3植物。

  但是,C3植物具有极强的适应性。事实上,它们的最适温度范围很宽,从大约7 °C到35 °C左右,而C4植物的最适温度一般在30-40°C之间,只有很少例外。而且当温度低于20 °C时,C4植物的平均光合速率低于C3植物。

3. 二氧化碳同化是温度响应特征不同的诸过程相互作用的结果

  捕集天线对光的吸收(图9)和将光能转移到PSII反应中心的过程对温度不敏感

  温度敏感的过程包括:

  • 二氧化碳从环境空气到叶绿体的扩散过程:扩散速度随着温度的增加而提高。
  • 1,5-二磷酸核酮糖(RuBP)固定二氧化碳的过程,RuBP是一种由5个碳原子构成的糖(“破译本森-巴萨姆-卡尔文循环”)。
  • 从PSII到PSI的电子传递过程
环境百科全书-光合作用-光合作用中的相互作用过程示意图
图9. 固定二氧化碳的光合作用中的相互作用过程示意图(以C3植物为例)。PSI和PSII:分别为光系统I和II,它们位于类囊体膜上,类囊体膜是脂质双分子层成,在叶绿体中形成“空腔”,即类囊体内部的囊腔。RubisCo:催化5碳糖(1,5-二磷酸核酮糖:C5) 固定二氧化碳的酶。本森-卡尔文循环:使得C5再生,同时为植物固定CO2。当类囊体腔内的质子跨过类囊体膜进入叶绿体基质的时候,就会驱动ATP酶消耗无机磷酸盐Pi,合成ATP。类囊体腔内的质子有两个来源:(1) PSII氧化腔内的水,同时生成电子e-,(2)通过类囊体上的质子泵将质子从基质运输到腔内。[图片来源:作者自制]

  RuBP的再生是通过本森-卡尔文循环(Benson-Calvin cycle)(这是光合作用的“生物化学”过程)完成的,该循环需要电子传递生成的还原力(以NADPH的形式),还需要ATP,ATP是类囊体腔内积累的质子跨膜进入叶绿体基质时,推动ATP酶合成的(图9)。

  生成还原力、合成ATP以及电子传递三个过程的温度敏感性相当。

4. C3和C4植物中,决定CO2同化最适温度的过程是什么?

4.1. 与光系统活性及此产生的电子传递过程无关

  当存在人工电子受体时,对离体类囊体测量(见图9中的图例)发现,电子传递随温度升高而加快,明显存在最适温度,大约为30 °C,与二氧化碳饱和时叶片吸收CO2的最适温度相当[9]。PSII活性的最适温度与电子转移链的最适温度相同。

  • PSI活性不受高温抑制(30°C以上,45°C以下)。高温时,其活性保持稳定甚至有所增加:是PSII的活性限制了电子传递链的活性。
  • PSII对高温非常敏感,高温会破坏PSII中使水氧化的蛋白质复合物(见图9)。

  C3C4植物中电子传递对温度的反应相似。但是,这两类植物的光合器官在结构上存在着差异(参见:“光合作用的碳代谢路径”)。

  因此,能量供应并不能解释这两类植物光合最适温度的差异,对能量的使用方式不同才是决定性因素。

4.2. 这是答案吗?大气中的氧气对C3和C4植物二氧化碳同化的影响

  • 含有21%的O2(+ N2)+ 360 μL/L CO2正常空气中[10]:玉米(C4植物)的最适温度为27 °C,而豌豆(C3植物)仅为22 °C(图10),C4植物的最适温度高于C3植物(另见2.6节)。
  • 含有1% 的O2(+ N2)+ 360 μL/L CO2低氧空气中:玉米的二氧化碳吸收不受影响,而豌豆的二氧化碳吸收速率在17°C以上时得以提高,并且最适温度提高到与玉米接近。
  • 当叶温很高时,大气中的氧会抑制C3植物的二氧化碳吸收,但对C4植物没有影响(或影响可以忽略)。
  • 环境百科全书-光合作用-二氧化碳吸收速率与叶温的关系
    图10. 豌豆(A, Pisum sativum)和玉米(B, Zea mays)叶片二氧化碳吸收速率与叶温的关系。植物生长于20±2 °C的自然光下。[图片来源:作者自制图表和 Pixabay免版税图片]
           注意,通过测量活体豌豆叶片发出的叶绿素荧光与温度的关系,发现电子传递速率在空气含氧量为1%和21%时基本相同,表明光合最适温度的变化与光化学过程无关

4.3. Rubisco的性质是差异的关键

  • C3植物的情形

  二氧化碳和氧气竞争Rubisco的活性位点:该酶同时具有羧化酶功能和加氧酶功能。二氧化碳通过其羧化酶功能进入本森-卡尔文循环的同时,其氧化酶功能导致光合氧气固定,这是光呼吸代谢途径的起点(图11;另见:“光合作用的碳代谢路径”)。

  当环境空气中氧气含量较低(例如1%)或二氧化碳含量较高时,二氧化碳会占据大量的Rubisco活性位点。

  如果氧气含量增加,或者二氧化碳含量减少(释放出Rubisco酶的活性位点,并被氧气占据),该酶就会主要固定氧气。

  在正常的空气中,当温度升高氧气的固定增加(因而二氧化碳的固定减少),原因有两个[11]

  一是Rubisco对二氧化碳的亲和力下降幅度大于对氧气的亲和力,因而有利于氧气吸收。

  二是二氧化碳在水中的溶解系数比氧气下降更多,导致叶绿体中二氧化碳的含量下降比氧气快,这也有利于氧气固定。

  在缺氧的大气中(图10),氧气和二氧化碳对Rubisco活性位点的竞争会大大减弱,捕集的光能主要用于二氧化碳的吸收,二氧化碳吸收速率会随着叶片温度的升高而增加,直到30 °C左右达到最大,然后随着能量的减少而降低(见第4.1节)。

  当温度较低时,在正常空气中的氧气对光合二氧化碳固定的影响(图11)非常低(甚至为零):此时二氧化碳在羧化位点上的竞争更有优势

环境百科全书-光合作用-二氧化碳和氧气与RuBP结合示意图
图11. 在C3植物中二氧化碳和氧气与RuBP(1,5-二磷酸核酮糖)结合示意图。APG: 3-磷酸甘油酸,3C化合物。TP:磷酸丙糖。离开卡尔文循环的碳是蔗糖合成的原料。PG:磷酸乙醇酸,2C化合物。两个PG生成一个含有3C的丝氨酸(Ser),通过光呼吸释放1个二氧化碳。C = 碳原子。[资料来源:作者自制]

  另一方面,当温度升高时,这些活性位点上的竞争有利于氧气的固定,光系统捕获的太阳能越来越多地被氧气固定所消耗,而非用于二氧化碳的固定。二氧化碳固定速率在22 °C左右达到最大值。

  • C4植物的情形

  二氧化碳通过一种对氧不敏感的机制在Rubisco附近富集,在不同C4植物叶片中含量可以达到8002000 μL/L:也就是比当前大气中的含量高25

  在此条件下,由于Rubisco的活性位点全部被二氧化碳占据,光合作用对氧气的固定作用很弱,甚至完全没有。因此,即使叶片温度升高,光系统捕集的太阳光能也仅用于二氧化碳固定,这就是C4植物的光合最适温度较高的原因。

  C4植物是在第三纪末期全球大气二氧化碳浓度下降的过程中,C3植物演化而来的[12]

  大气CO2浓度的降低使得C3植物Rubisco的加氧酶功能得以“发挥”,并通过光呼吸途径损失固定的碳。

  因而,建立二氧化碳富集机制就成了一个优势,可以防止光呼吸碳损失。我们现在还能够发现C3和C4“过渡类型”的植物物种。

5. C3光合途径的最适温度受某些环境因子的调控

5.1. 大气二氧化碳浓度

  光合最适温度随环境二氧化碳含量的增加而提高。如图12所示,从二氧化碳含量为100 μL/L时的10 °C左右提高到含量为800 μL/L时的30 °C以上。

环境百科全书-光合作用-豌豆叶片二氧化碳吸收速率与叶片温度的关系
图12. 在不同环境的二氧化碳浓度下,豌豆叶片的二氧化碳吸收速率与叶片温度的关系。测量时光强接近饱和。 [图片来源:©G. Cornic]

  这一效应可以用二氧化碳和氧气竞争Rubisco的活性位点来解释:在二氧化碳浓度为800 μL/L时,活性位点主要被二氧化碳占据;而在二氧化碳浓度为100 μL/L时,氧气会占据大多数的活性位点。

环境百科全书-光合作用-大气二氧化碳浓度升高
图13. 人类活动导致大气中二氧化碳浓度升高,其含量在50年间从320 μL/L上升到了415 μL/L,影响了大气温度和植被活动。[来源:Pixabay免版税图片]

  在大气二氧化碳浓度稳步增加的情况下(图13),C3植物的最适温度有望提升,但这并不意味着植物生产力的提高(参见第1部分注释3):因为像干旱一样,高温时期肯定会更频繁地出现

5.2. 缺水

  光合工具叶绿体本身有较强的抗旱性,叶绿体可以保持Rubisco吸收二氧化碳和固定光能的能力,直到叶片失去其含水量的30%[13]

  • 在这种缺水情况下,气孔逐渐关闭(参见“叶片蒸腾和热保护”),二氧化碳吸收会减少。气孔关闭减缓了二氧化碳进入叶片的速度,导致叶肉细胞中二氧化碳含量减少
  • 然而,叶绿体中的氧气浓度仍然很高。事实上,与二氧化碳(约 400 μL/L)相比,大气中氧气的浓度(21%或210 000 μL/L)非常高。在任何情况下,即使气孔关闭,也会有相当数量的氧气通过表皮进入叶片内部。
  • 因此,二氧化碳和氧气之间对Rubisco活性位点的竞争对氧气有利
环境百科全书-光合作用-水分含量不同的三种叶片二氧化碳吸收速率与叶温的关系
图14. 环境二氧化碳浓度为400 μL/L时,水分含量不同的三种叶片中二氧化碳吸收速率与叶温的关系(A);以及根据叶绿素荧光测量计算得到的电子转移速率(B)。[来源:作者自制图表,自Cornic等,参考文献14]

  因此,C3植物的叶片在逐渐失水的过程中,其光合作用的最适温度也必须降低。

  如图14A所示,豌豆叶片的最适温度从叶片水分饱和时的23 °C,下降到失去20%水分时的17 °C。

  在实验中的水分丧失范围内(图14B),类囊体膜上的电子传递速率不受影响。当水分损失达20%时,光系统捕集的太阳能主要用于氧与RuBP结合[14],导致光呼吸增加。

6. 为什么无论温度较最适宜温度升或降,二氧化碳吸收速率总是降低的?

6.1. 当温度低于最适温度时

  可能有几个原因不同程度地导致了同化速率降低:

  • RuBP周转速度降低。控制RuBP周转的一些酶的活性降低,尤其是果糖1,6-二磷酸酶(见图9和11)。
  • 叶绿体中的磷被磷酸化化合物固定。由于蔗糖合成受到抑制,磷酸丙糖输出终止(或减少),使得无机磷酸盐不再与磷酸丙糖交换进入叶绿体,导致ATP合成因无机磷缺乏而下降。
  • 抑制电子传递链(见第4.1节),导致能量 (还原力和ATP) 产生减少。

       在C4植物中,光合作用对低温的响应主要受Rubisco活性的影响,当然,参与二氧化碳固定的其他酶对低温敏感也是众所周知的。

6.2. 当温度高于最适温度时

  C3植物中,随着温度升高,光呼吸增加, PSII产生的电子中用于同化二氧化碳的比例下降。除此之外,还有其他因素也在起作用:(1)即使在很少或没有光呼吸的大气条件(环境氧气含量为1%)下测量,也会发现光合速率随温度升高而降低;(2)在正常的大气条件下C4植物也有相同的表现 (图10)。可能的原因有:

  • PSII活性的降低导致了从PSII到PSI的电子传递速率减慢。
  • Rubisco要发挥作用,必须被一种叫做Rubisco激酶的酶激活。当温度超过约33°C时,该酶的活性就会下降(不过,在一些生长期会经历高温的植物中存在耐高温的激酶[15])。但是,由于激酶本身的激活必须依赖电子传递的过程,因此不能排除电子传递也参与限制Rubisco活性[15]
  • 随着温度的升高,与RuBP结构相近的Rubisco酶抑制剂(木糖糖-1,4-二磷酸)的合成量增加,Rubisco的“催化失效”越来越明显(见图9和11)。

  在C4植物 (如玉米)中,负责二氧化碳富集在Rubisco周围的酶的激活及其活性对高温不太敏感。因此,C4植物在最适温度以上时,二氧化碳同化速率随着温度升高而下降。

7. 植物的低温(≤10 °C左右)和高温(≥37°C左右)锻炼

  当植物停留在低温或高温环境下时,除了引发光合作用的上述变化外,还能增强它们对致死温度(霜冻和高温)的抵抗力,这就是抗性锻炼

  在此过程中,温度和光照共同作用,引起代谢变化,这个变化有时非常快(从几分钟到几小时)。

  因此,通过改变光周期的长度或光谱中的红光成分[16],可以在正常温度下实现抗寒锻炼。然而,要使抗性能力完全表现出来,仍然需要低温处理。同样地,低温并缺乏光照的条件也会不同程度地降低抗寒锻炼的效果。

  • 高温:产生信号激活分子伴侣性蛋白(热激蛋白,HSPs)的合成,修复变性蛋白,还会防止其凝固,甚至做上标记,使其降解。
  • 低温:也会激活分子伴侣性蛋白的合成,随后(i)合成干扰冰晶形成的“抗冻”蛋白和(ii)增加糖的合成,以提高细胞内的渗透压。

  请注意,抗性锻炼过程中的信号通路以及它们如何相互作用以诱导基因组反应,目前已知内容有限。读者可以阅读“了解更多”中列出的参考资料和本文的推荐文献,进一步探索这一不断发展的主题。

8. 温度对光合作用的影响:总结图

  总结图(图15)根据温度变化的速度和程度,将温度对光合作用的影响进行了分类。请注意,抗性锻炼可以使植物的多年生叶片得以在极端温度条件下维持活性,因而最大限度地减少光能损失。

环境百科全书-光合作用-温度对光合作用影响的分类图
图15. 温度对光合作用影响的分类图。[来源:作者自制]

  当前气候变化速度如此之快,我们必须更深入地研究植物对其环境的反应:以期维持足够的初级生产力,保持生物圈功能的可持续性。

9. 需要记住的信息

  • 叶片对二氧化碳吸收有最适温度,与接近其生长环境的平均温度。
  • 当环境条件被持久地改变时,最适温度也会迅速改变:这是一个驯化过程。
  • C3植物的最适温度总体上低于C4植物:这主要是由于C3植物的Rubisco在光合固碳的同时还固定大气中的氧气。
  • C3植物的最适温度受环境空气中的二氧化碳浓度影响:当二氧化碳浓度高时,它们的最适温度与C4植物相当。
  • 叶片光合最适温度受叶片水分状况影响
  • 植物经受低温或高温条件时,会通过生理过程的抗性锻炼应对致命温度。这些过程涉及蛋白质合成,以及叶绿体和细胞膜流动性的变化。

 


参考资料及说明

封面图片:亚利桑那州索诺兰沙漠的日落。[来源:免版税/ Pixabay]

[1] Meehl GA、Stocker TF、Collins WD、Riedlingstein P、Gaye AT、Gregory JM、Kitoh A、Knutti R、Murphy JM、Noda A & Raper SCB(2007)《气候变化2007:物理科学基础》。第一工作组对政府间气候变化专门委员会第四次评估报告的贡献。剑桥大学出版社

[2] Yamori W, Hikosaka K & Way DA(2014)。C3、C4和CAM植物光合作用的温度响应:温度驯化和温度适应。光合作用 119, 101- 117。

[3] 例如,当植物遭受干旱时,叶片生长首先被抑制,导致碳固定速率下降。但是叶绿体中的二氧化碳固定过程没有受到抑制。Boyer JS (1970) Plant Physiol.46, 233-235

[4] 这里给出的最适温度是在21%的氧气和约400 μL/L二氧化碳的“正常空气”中测量得出的。其他条件则标出了氧气和二氧化碳的含量。当接近饱和光强、含21% 氧气的空气条件下,光合速率的二氧化碳饱和点约为1200 μL/L。很多时候在测量过程中空气蒸发能力也会影响光合速率,这个参数是通过叶片周围空气中水汽分压的饱和亏缺来估算的。

[5] 通过营养繁殖从同一个体长出的不同植株,具有相同的基因。

[6] 生态型:生长在不同环境的同种植物,即使种植在相同的条件下,它们在从种子萌发到开花结实的过程中,也会表现出不同的生理特征。

[7] 它可以吸收土壤深处的地下水,因此被称为地下水湿生植物。

[8] Pearcy RW(1971)。triplex lentiJormis (Torr.)光合和呼吸二氧化碳交换对生长温度的适应寺庙。植物生理。59,795-799

[9] Yamasaki T, Yamakawa T, Yamane Y, koike H, Satoh K & Katoh S.(2002)冬小麦光合作用的温度适应及其光系统II电子传递的相关变化。Plant Physiol. 128 1087-1097

[10] 见2.2节的注释#4

[11] Jordan DB & Ogren WL(1984)。的有限公司2/ 氧气 核酮糖1,5-二磷酸羧化酶/加氧酶的特异性。二磷酸核酮糖浓度、pH和温度的依赖性。161年足底,308 – 313

[12] Ehleringer JR, Sage RF, Flanagan LB & Pearcy RW(1991)。气候变化与C4光合作用的演化。生态与进化趋势6,95-99

[13] Cornic G & Massacci A(1996)。干旱胁迫下的叶片光合作用。In Advances In光合作用(第5卷)光合作用与环境,347-366。尼尔R·贝克(主编)Kluwer学术出版社Dordrecht。

[14] Cornic G, Badeck F-W, Ghashghaie J & Manuel N(1999)。温度对CO净吸收二氧化碳、气孔导度的影响2 以及脱水豌豆叶片光系统II光化学的量子产率。In Sanchez Dias M, Irigoyen JJ, agureolea J & Pithan K (eds)欧洲凉爽潮湿地区的作物发育。欧洲共同体。ISBN 92-828-6947-4。

[15] Crafts-Brandner SJ, van de Loo FJ & Salvucci ME(1997)。两种形式的核酮糖-1,5-二磷酸羧化酶/加氧酶激活酶对高温的敏感性不同。植物生理。114,439-444。

[16] Puhakainen T, Li C, Boije-Malm M, Kangasjärvi J, Heino P & Palva ET.(2004)。在银桦冷驯化过程中,低温诱导c -重复结合因子控制基因表达的短日增强。植物136, 4299 – 4307


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To cite this article: CORNIC Gabriel (March 14, 2024), 温度对光合作用的影响, Encyclopedia of the Environment, Accessed December 9, 2024 [online ISSN 2555-0950] url : https://www.encyclopedie-environnement.org/zh/vivant-zh/effects-temperature-on-photosynthesis/.

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