Abstract
Abstract A model is proposed for the relationship between net photosynthetic rate (N) and light Intensity at a given concentration of CO 2 in the air ([CO 2 ] a ). The model provides a prediction of the sum of the diffusion resistances (Σr), the capacity (K) of the leaf to fix CO 2 , the concentration of CO 2 at the point of photosynthesis ([CO 2 ] g ), and the respiration rate (R). The model fits the available data well and provides a frame work by which future research may be guided. The calculated values of [CO 2 ] g decreased from [CO 2 ] g at the compensation point to a nearly constant value at high tight intensities. [CO 2 ] g high light infensitit‐s range from 32 to 144 μ/l (volume) depending on the species. When these values of [CO 2 ] g , are used in the diffusion equation, the resulting levels of the mesophyll resistance (r m ) are lower than those calculated by using the assumptions that [CO 2 ] g equals zero. The plants which had (he higher photosynthetic rates at a given light intensity and [CO 2 ] a had grealer values of [CO 2 ] g than those with lower photo‐synthetic rates. The calculated rates of respiration of wheat leaves were twice as high as those measured in the dark. This suggests that the light respiration rate may be twice as great as the dark respiration rate at the same temperature. The calculated values of K demonstrate variability within and between species. The maximum N was independent of K. A relationship between K and the maximum quantum efficiency, at constant levels of [CO 2 ] g , was demonstrated in several species. The Σr was inversely related to the maximum rate of photosynthesis for the species investigated. The values of r m calculated for cotton were inversely related to [CO 2 ] a suggesting that the transfer of [CO 2 ] in the cell may involve a concentration dependent chemical reaction in addition to or rather than a physical diffusion process.
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Claims 12
Claim · model-written summary
The model fits the available data well.
Verbatim
e3“The model fits the available data well”
Claim · model-written summary
Calculated CO2 concentration at the point of photosynthesis at high light ranges from 32 to 144 μl/l depending on species.
Verbatim
e0“The calculated values of [CO 2 ] g decreased from [CO 2 ] g at the compensation point to a nearly constant value at high tight intensities”
e1“range from 32 to 144 μ/l (volume) depending on the species”
Claim · model-written summary
Calculated CO2 concentration at the point of photosynthesis decreased from the compensation point to a nearly constant value at high light.
Verbatim
e0“The calculated values of [CO 2 ] g decreased from [CO 2 ] g at the compensation point to a nearly constant value at high tight intensities”
e1“range from 32 to 144 μ/l (volume) depending on the species”
Claim · model-written summary
Plants with higher photosynthetic rates had greater calculated CO2 concentration at the point of photosynthesis.
- Taxon
- plantsViridiplantaee2
- Treatment
- higher photosynthetic ratese2
- Outcome
- [CO 2 ] ge2
- Direction
- grealere2
Verbatim
e2“The plants which had (he higher photosynthetic rates at a given light intensity and [CO 2 ] a had grealer values of [CO 2 ] g”
Claim · model-written summary
Calculated respiration rates of wheat leaves were twice as high as rates measured in the dark.
- Taxon
- wheat leaves
Triticum aestivume4 - Outcome
- rates of respiratione4
- Direction
- twice as highe4
- Comparator
- those measured in the darke4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“The calculated rates of respiration of wheat leaves were twice as high as those measured in the dark”
Claim · model-written summary
Light respiration rate may be twice as great as dark respiration rate in wheat leaves at the same temperature.
- Taxon
- wheat leavesTriticum aestivume4
- Outcome
- light respiration ratee5
- Direction
- twice as greate5
- Comparator
- dark respiration ratee5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“The calculated rates of respiration of wheat leaves were twice as high as those measured in the dark”
e5“This suggests that the light respiration rate may be twice as great as the dark respiration rate at the same temperature”
Claim · model-written summary
Calculated values of K show variability within and between species.
Verbatim
e6“The calculated values of K demonstrate variability within and between species”
Claim · model-written summary
The maximum N was independent of K in plants.
- Taxon
- plantsViridiplantaee2
- Outcome
- maximum Ne7
- Direction
- no_changeinferrede7
- Comparator
- Ke7
Verbatim
e2“The plants which had (he higher photosynthetic rates at a given light intensity and [CO 2 ] a had grealer values of [CO 2 ] g”
e7“The maximum N was independent of K”
Claim · model-written summary
The relationship between K and maximum quantum efficiency was demonstrated in several species at constant CO2 levels.
- Taxon
- speciese0
- Outcome
- maximum quantum efficiencye0
- Qualifier
- at constant levels of [CO 2 ] ge0
- Comparator
- Ke0
Not reportedDirection
Verbatim
e0“A relationship between K and the maximum quantum efficiency, at constant levels of [CO 2 ] g , was demonstrated in several species”
Claim · model-written summary
Σr was inversely related to the maximum rate of photosynthesis across the species investigated.
Verbatim
e0“The Σr was inversely related to the maximum rate of photosynthesis for the species investigated”
Claim · model-written summary
Mesophyll resistance calculated for cotton was inversely related to CO2 concentration in air.
- Taxon
- cotton
Gossypium hirsutume0 - Treatment
- [CO 2 ] ae0
- Outcome
- r me0
- Direction
- inverselye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The values of r m calculated for cotton were inversely related to [CO 2 ] a”
Claim · model-written summary
CO2 transfer in cotton cells may involve a concentration-dependent chemical reaction in addition to or rather than physical diffusion.
- Taxon
- cottonGossypium hirsutume0
- Outcome
- transfer of [CO 2 ]e1
- Qualifier
- concentration dependent chemical reactione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The values of r m calculated for cotton were inversely related to [CO 2 ] a”
e1“the transfer of [CO 2 ] in the cell may involve a concentration dependent chemical reaction in addition to or rather than a physical diffusion process”