Abstract
Abstract. The effect of water‐stress on photosynthetic carbon metabolism in spinach ( Spinacia oleracea L.) has been studied in experiments in which water‐stress was induced rapidly by floating leaf discs on sorbitol solutions or wilting detached leaves, and in experiments in which water‐stress was allowed to develop gradually in whole plants as the soil dried out. In both short‐ and long‐term water stress, the rate of photosynthesis in saturating CO 2 did not decrease until leaf water potential decreased below ‐1.0 MPa. However, at smaller water deficits there was already an inhibition of starch synthesis, while sucrose synthesis remained constant or increased. This change in partitioning was accompanied by an increase in activation of sucrose‐phosphate synthase (revealed as an increase in activity assayed in the presence of low hexose‐phosphate and inorganic phosphate, while the activity assayed with saturating hexosephosphates remained unaltered). Water‐stressed leaves had a two‐ to three‐fold higher sucrose content at the end of the night, and contained less starch than non‐stressed leaves. When leaves were held in the dark, sucrose was mobilized initially, while starch was not mobilized until the sucrose had decreased to a low level; in water‐stressed leaves, starch mobilization commenced at a two‐fold higher sucrose content. It is concluded that water‐stressed leaves maintain higher sucrose and lower starch levels than non‐stressed leaves. This response is found in rapid and long‐term stress, and represents an inherent response to water deficits.
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Claims 8
Claim · model-written summary
The rate of photosynthesis in spinach did not decrease until leaf water potential fell below -1.0 MPa in short- and long-term water stress.
- Taxon
- Spinacia oleracea
Spinacia oleraceae0 - Outcome
- rate of photosynthesise1
- Qualifier
- until leaf water potential decreased belowe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic carbon metabolism in spinach ( Spinacia oleracea L.)”
e1“the rate of photosynthesis in saturating CO 2 did not decrease until leaf water potential decreased below”
Claim · model-written summary
At smaller water deficits, starch synthesis in spinach leaves was inhibited.
- Taxon
- Spinacia oleraceaSpinacia oleraceae0
- Treatment
- smaller water deficitse2
- Outcome
- starch synthesise2
- Direction
- inhibitione2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic carbon metabolism in spinach ( Spinacia oleracea L.)”
e2“at smaller water deficits there was already an inhibition of starch synthesis, while sucrose synthesis remained constant or increased”
Claim · model-written summary
At smaller water deficits, sucrose synthesis in spinach leaves remained constant or increased.
- Taxon
- Spinacia oleraceaSpinacia oleraceae0
- Treatment
- smaller water deficitse2
- Outcome
- sucrose synthesise2
- Direction
- remained constant or increasede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic carbon metabolism in spinach ( Spinacia oleracea L.)”
e2“at smaller water deficits there was already an inhibition of starch synthesis, while sucrose synthesis remained constant or increased”
Claim · model-written summary
Water-stressed spinach leaves had a two- to three-fold higher sucrose content at the end of the night than non-stressed leaves.
- Taxon
- Spinacia oleraceaSpinacia oleraceae0
- Treatment
- Water‐stressed leavese3
- Outcome
- sucrose contente3
- Direction
- highere3
- Value
- two‐ to three‐folde3
- Comparator
- non‐stressed leavese3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic carbon metabolism in spinach ( Spinacia oleracea L.)”
e3“Water‐stressed leaves had a two‐ to three‐fold higher sucrose content at the end of the night, and contained less starch than non‐stressed leaves”
Claim · model-written summary
Water-stressed spinach leaves contained less starch than non-stressed leaves.
- Taxon
- Spinacia oleraceaSpinacia oleraceae0
- Treatment
- Water‐stressed leavese3
- Outcome
- starche3
- Direction
- lesse3
- Comparator
- non‐stressed leavese3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic carbon metabolism in spinach ( Spinacia oleracea L.)”
e3“Water‐stressed leaves had a two‐ to three‐fold higher sucrose content at the end of the night, and contained less starch than non‐stressed leaves”
Claim · model-written summary
In spinach leaves held in the dark, starch was not mobilized until sucrose had decreased to a low level.
- Taxon
- Spinacia oleraceaSpinacia oleraceae0
- Treatment
- held in the darke4
- Outcome
- starch was not mobilizede4
- Qualifier
- until the sucrose had decreased to a low levele4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic carbon metabolism in spinach ( Spinacia oleracea L.)”
e4“When leaves were held in the dark, sucrose was mobilized initially, while starch was not mobilized until the sucrose had decreased to a low level”
Claim · model-written summary
In water-stressed spinach leaves, starch mobilization began at a two-fold higher sucrose content.
- Taxon
- Spinacia oleraceaSpinacia oleraceae0
- Treatment
- water‐stressed leavese5
- Outcome
- starch mobilizatione5
- Qualifier
- commenced at a two‐fold higher sucrose contente5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic carbon metabolism in spinach ( Spinacia oleracea L.)”
e5“in water‐stressed leaves, starch mobilization commenced at a two‐fold higher sucrose content”
Claim · model-written summary
Water stress was accompanied by an increase in activation of sucrose-phosphate synthase in spinach leaves.
- Taxon
- Spinacia oleraceaSpinacia oleraceae0
- Gene
- sucrose‐phosphate synthasee6
- Outcome
- activatione6
- Direction
- increasee6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic carbon metabolism in spinach ( Spinacia oleracea L.)”
e6“an increase in activation of sucrose‐phosphate synthase”