Abstract
Abstract Rates of apparent photosynthesis (AP), dark respiration, photorespiration, mesophyll resistance, and concentrations of soluble starch, sugars, chlorophyll and nitrogen were measured in alfalfa leaves ( Medicago sativa L.) grown under high or low light levels in an attempt to evaluate the effect of nonstructural carbohydrate concentration on net CO 2 assimilation. Leaf N and chlorophyll levels of high light plants exceeded those of low‐light plants. Constant light increased both starch and sugar levels in low‐light plants, but had little effect on high‐light plants. Rates of AP declined in low‐light plants upon transfer to constant light conditions, apparently due to increases in stomatal and mesophyll resistance. Leaf starch levels were negatively correlated (P > 0.05) with rates of AP and positively correlated with mesophyll resistance in both groups of plants but leaf sugar content was not correlated with either AP or mesophyll resistance. Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness, while low‐light plants were less affected. Rates of AP declined in both groups of plants due to increases in both mesophyll and stomatal resistances. Neither sugar nor starch levels were correlated with AP or mesophyll conductance in this treatment. The data support the hypothesis of feedback inhibition of photosynthesis, mediated through an increase in mesophyll resistance, which is associated with high levels of starch in the leaves.
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Claims 16
Claim · model-written summary
High-light plants had greater leaf nitrogen than low-light plants.
- Taxon
- Alfalfa
Medicago sativat0 - Treatment
- high light plantse0
- Outcome
- Leaf Ne0
- Direction
- exceedede0
- Comparator
- low‐light plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf N and chlorophyll levels of high light plants exceeded those of low‐light plants”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
High-light plants had greater chlorophyll than low-light plants.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- high light plantse0
- Outcome
- chlorophyll levelse0
- Direction
- exceedede0
- Comparator
- low‐light plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf N and chlorophyll levels of high light plants exceeded those of low‐light plants”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Constant light increased starch in low-light plants.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- Constant lighte0
- Outcome
- starche0
- Direction
- increasede0
- Qualifier
- low‐light plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Constant light increased both starch and sugar levels in low‐light plants”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Constant light increased sugar in low-light plants.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- Constant lighte0
- Outcome
- sugar levelse0
- Direction
- increasede0
- Qualifier
- low‐light plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Constant light increased both starch and sugar levels in low‐light plants”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Constant light had little effect on high-light plants.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- Constant lighte1
- Outcome
- little effecte0
- Direction
- little effecte0
- Qualifier
- high‐light plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but had little effect on high‐light plants”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Apparent photosynthesis declined in low-light plants transferred to constant light.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- constant light conditionse0
- Outcome
- Rates of APe0
- Direction
- declinede0
- Qualifier
- low‐light plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
The decline in photosynthesis under constant light was apparently due to increased stomatal resistance.
- Taxon
- AlfalfaMedicago sativat0
- Outcome
- Rates of APe2
- Qualifier
- increases in stomatale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“apparently due to increases in stomatal and mesophyll resistance”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Leaf starch was negatively correlated with apparent photosynthesis in both groups.
- Taxon
- AlfalfaMedicago sativat0
- Compound
- Leaf starche0
- Outcome
- rates of APe0
- Direction
- negatively correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf starch levels were negatively correlated (P > 0.05) with rates of AP”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Leaf starch correlated positively with mesophyll resistance in both groups.
- Taxon
- AlfalfaMedicago sativat0
- Organ / stage
- plantse0
- Outcome
- mesophyll resistancee0
- Direction
- positively correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“positively correlated with mesophyll resistance in both groups of plants”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Leaf sugar was not correlated with apparent photosynthesis or mesophyll resistance.
- Taxon
- AlfalfaMedicago sativat0
- Compound
- leaf sugare0
- Outcome
- AP or mesophyll resistancee0
- Direction
- not correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leaf sugar content was not correlated with either AP or mesophyll resistance”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Starch declined substantially in high-light plants transferred to darkness.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- constant darknesse0
- Outcome
- Starche0
- Direction
- declinede0
- Qualifier
- high‐light plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Sugar declined substantially in high-light plants transferred to darkness.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- constant darknesse0
- Outcome
- sugar levelse0
- Direction
- declinede0
- Qualifier
- high‐light plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Low-light plants were less affected by transfer to darkness.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- constant darknesse3
- Outcome
- less affectede0
- Direction
- less affectede0
- Qualifier
- low‐light plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“while low‐light plants were less affected”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Apparent photosynthesis declined in both groups in darkness.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- constant darknesse3
- Outcome
- Rates of APe0
- Direction
- declinede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rates of AP declined in both groups of plants due to increases in both mesophyll and stomatal resistances”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
Neither sugar nor starch correlated with photosynthesis or mesophyll conductance in darkness.
- Taxon
- AlfalfaMedicago sativat0
- Outcome
- AP or mesophyll conductancee0
- Direction
- Neithere0
- Qualifier
- this treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Neither sugar nor starch levels were correlated with AP or mesophyll conductance in this treatment”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
Claim · model-written summary
The authors support starch-associated feedback inhibition of photosynthesis via mesophyll resistance.
- Taxon
- AlfalfaMedicago sativat0
- Outcome
- feedback inhibition of photosynthesise0
- Qualifier
- increase in mesophyll resistancee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The data support the hypothesis of feedback inhibition of photosynthesis, mediated through an increase in mesophyll resistance, which is associated with high levels of starch in the leaves”
t0“Alfalfa”
e1“Constant light increased both starch and sugar levels in low‐light plants”
e2“Rates of AP declined in low‐light plants upon transfer to constant light conditions”
e3“Starch and sugar levels of high‐light plants declined substantially upon transfer to constant darkness”
The same questions in other papers
light · physiology: photosynthesis · Medicago sativa (alfalfa)Positive and negative results
3 papers in the same direction as this paper · 3 in the opposite direction
- positive
- positive
- positive
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See all 7 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.