Abstract
A study was made of the short- and long-term effects of partial defoliation (cutting at 15 cm above the crown) of lucerne plants (Medicago sativa L. cv. Hunter River) on the net photosynthesis, transpiration, photorespiration and CO2 transfer resistances of remaining leaves. The response in gas-exchange properties of leaves of different ages to partial defoliation of the plant was also investigated. Partial defoliation always induced rejuvenation in photosynthetic rate of remaining leaves. Young and middle-aged leaves rejuvenated to rates comparable to those of recently expanded leaves but old leaves only partially rejuvenated. Time after defoliation to attain peak rates increased as leaves aged; values were 5, 9 and 12 days for plants partially defoliated on days 16, 30 and 65 of regrowth respectively. Peak rates were maintained for only 3 or 4 days before declining. Rates of photorespiration and photosynthesis were closely coupled. Transpiration rates varied over time in a similar but more erratic pattern to net photosynthetic rates. Changes in net photosynthetic rates associated with senescence, defoliation treatments and irradiance levels were largely attributable to changes in intracellular resistance to CO2 transfer. Intracellular resistances ranged from 2.6 to 30 s cm-1, constituting 67-95 % of the total resistance to photosynthesis. Stomatal resistance to CO2 diffusion remained low, 0.2 - 1.0 s cm-1, for all but very old leaves. Partial defoliation followed by continual removal of new crown and stubble shoots induced very high net photosynthetic rates, c. 15 days later. Highest net photosynthetic rate was 238 ng CO2 cm-2 s-1. Possible mechanisms responsible for photosynthetic rejuvenation following partial defoliation are discussed, together with ecological implications of this phenomenon.
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Claims 13
Claim · model-written summary
Partial defoliation always induced rejuvenation of photosynthetic rate in remaining lucerne leaves.
- Taxon
- Medicago sativa
Medicago sativae0 - Treatment
- Partial defoliatione1
- Outcome
- photosynthetic ratee1
- Direction
- rejuvenatione1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Partial defoliation always induced rejuvenation in photosynthetic rate of remaining leaves”
Claim · model-written summary
After partial defoliation, young and middle-aged leaves rejuvenated to photosynthetic rates comparable to recently expanded leaves.
- Taxon
- Medicago sativaMedicago sativae0
- Organ / stage
- Young and middle-aged leavese2
- Treatment
- Partial defoliatione1
- Outcome
- photosynthetic ratee1
- Direction
- rejuvenatede2
- Comparator
- recently expanded leavese2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Partial defoliation always induced rejuvenation in photosynthetic rate of remaining leaves”
e2“Young and middle-aged leaves rejuvenated to rates comparable to those of recently expanded leaves”
Claim · model-written summary
After partial defoliation, old leaves only partially rejuvenated in photosynthetic rate.
- Taxon
- Medicago sativaMedicago sativae0
- Organ / stage
- old leavese2
- Treatment
- Partial defoliatione1
- Outcome
- photosynthetic ratee1
- Direction
- partially rejuvenatede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Partial defoliation always induced rejuvenation in photosynthetic rate of remaining leaves”
e2“old leaves only partially rejuvenated”
Claim · model-written summary
Time after defoliation to attain peak photosynthetic rates increased as leaves aged: 5, 9 and 12 days for plants defoliated on days 16, 30 and 65 of regrowth.
- Taxon
- Medicago sativaMedicago sativae0
- Treatment
- partially defoliated on days 16, 30 and 65 of regrowthe1
- Outcome
- Time after defoliation to attain peak ratese1
- Direction
- increasede1
- Value
- 5, 9 and 12 dayse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Time after defoliation to attain peak rates increased as leaves aged; values were 5, 9 and 12 days for plants partially defoliated on days 16, 30 and 65 of regrowth respectively”
Claim · model-written summary
Peak photosynthetic rates were maintained for only 3 or 4 days before declining.
- Taxon
- Medicago sativaMedicago sativae0
- Outcome
- Peak rates were maintainede1
- Value
- 3 or 4 dayse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Peak rates were maintained for only 3 or 4 days before declining”
Claim · model-written summary
Rates of photorespiration and photosynthesis were closely coupled.
- Taxon
- Medicago sativaMedicago sativae0
- Outcome
- Rates of photorespiratione1
- Direction
- closely couplede1
- Comparator
- photosynthesise1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Rates of photorespiration and photosynthesis were closely coupled”
Claim · model-written summary
Transpiration rates varied over time in a pattern similar to net photosynthetic rates but more erratic.
- Taxon
- Medicago sativaMedicago sativae0
- Outcome
- Transpiration ratese1
- Qualifier
- similar but more erratic pattern to net photosynthetic ratese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Transpiration rates varied over time in a similar but more erratic pattern to net photosynthetic rates”
Claim · model-written summary
Changes in net photosynthetic rates with senescence, defoliation and irradiance were largely attributable to changes in intracellular resistance to CO2 transfer.
- Taxon
- Medicago sativaMedicago sativae0
- Treatment
- defoliation treatmentse1
- Outcome
- net photosynthetic ratese1
- Qualifier
- changes in intracellular resistance to CO2 transfere1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Changes in net photosynthetic rates associated with senescence, defoliation treatments and irradiance levels were largely attributable to changes in intracellular resistance to CO2 transfer”
Claim · model-written summary
Intracellular resistances ranged from 2.6 to 30 s cm-1.
- Taxon
- Medicago sativaMedicago sativae0
- Outcome
- Intracellular resistancese1
- Value
- 2.6 to 30 s cm-1e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Intracellular resistances ranged from 2.6 to 30 s cm-1”
Claim · model-written summary
Intracellular resistances constituted 67-95% of the total resistance to photosynthesis.
- Taxon
- Medicago sativaMedicago sativae0
- Outcome
- total resistance to photosynthesise1
- Value
- 67-95 %e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“constituting 67-95 % of the total resistance to photosynthesis”
Claim · model-written summary
Stomatal resistance to CO2 diffusion remained low, 0.2-1.0 s cm-1, for all but very old leaves.
- Taxon
- Medicago sativaMedicago sativae0
- Outcome
- Stomatal resistance to CO2 diffusione1
- Direction
- lowe1
- Value
- 0.2 - 1.0 s cm-1e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Stomatal resistance to CO2 diffusion remained low, 0.2 - 1.0 s cm-1, for all but very old leaves”
Claim · model-written summary
Partial defoliation followed by continual removal of new crown and stubble shoots induced very high net photosynthetic rates about 15 days later.
- Taxon
- Medicago sativaMedicago sativae0
- Treatment
- Partial defoliation followed by continual removal of new crown and stubble shootse1
- Outcome
- net photosynthetic ratese1
- Direction
- very highe1
- Qualifier
- c. 15 days latere1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Partial defoliation followed by continual removal of new crown and stubble shoots induced very high net photosynthetic rates, c. 15 days later”
Claim · model-written summary
The highest net photosynthetic rate was 238 ng CO2 cm-2 s-1.
- Taxon
- Medicago sativaMedicago sativae0
- Outcome
- Highest net photosynthetic ratee1
- Value
- 238 ng CO2 cm-2 s-1e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Medicago sativa L. cv. Hunter River”
e1“Highest net photosynthetic rate was 238 ng CO2 cm-2 s-1”
The same questions in other papers
pruning · physiology: photosynthesis · Medicago sativa (alfalfa)Results agree
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See all 6 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.