Abstract
Effects of water deficits on leaf turgor maintenance processes were analyzed for pear trees (Pyrus communis L. cv. "Barlett") grown in 120-liter containers. Four irrigation treatments were applied: a well-watered control treatment, a spring water stress cycle (Sp), a summer water stress cycle (Su), and a spring plus summer water stress cycle (Sp + Su). For the Sp treatment, water application was progressively reduced from 100 to 20% of the control dose over a period of 27 days in spring. For the Su treatment, water application was progressively reduced over 23 days in summer, from 100 to 20% of the control dose. The Sp + Su treatment comprised both the spring and summer drought stress cycles. Pressure-volume (P-V) curves were constructed and stomatal conductances were determined for pear leaves from each treatment during the spring and summer stress cycles. Leaf water potential (Psi(pi) (0)) and relative water content (R(0)) at the turgor loss point of control leaves tended to decrease from spring to summer. Changes in leaf osmotic water potential at full turgor (Psi(pi) (100)) and in symplast water fraction (R(s)) did not explain the seasonal decrease in Psi(pi) (0). The water stress treatments had no effect on Psi(pi) (100), but R(s) was reduced by the water stress treatments, particularly during the summer stress cycle of the Su and Sp + Su treatments. The decrease in R(s) was correlated with an increase in the slope of the linear region of the P-V curve. Such a coupled adjustment would lead to increased water uptake capacity of water-stressed trees only under non-turgor conditions. Furthermore, pear leaves did not actively accumulate solutes. We conclude, therefore, that changes in leaf tissue water relations as a result of leaf acclimation to water stress are unlikely to facilitate maintenance of fruit productivity under drought.
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Claims 8
Claim · model-written summary
Control pear leaf water potential and relative water content at turgor loss tended to decline from spring to summer.
- Taxon
- pear trees
_Poirier_Fleurs_et_feuilles.jpg?width=60)
Pyrus communise1 - Organ / stage
- leavese0
- Outcome
- Leaf water potential (Psi(pi) (0)) and relative water content (R(0))e0
- Direction
- decreasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_Poirier_Fleurs_et_feuilles.jpg?width=500)
Verbatim
e0“Leaf water potential (Psi(pi) (0)) and relative water content (R(0)) at the turgor loss point of control leaves tended to decrease from spring to summer”
e1“pear trees (Pyrus communis L. cv. "Barlett")”
Claim · model-written summary
Changes in full-turgor osmotic water potential and symplast water fraction did not explain the seasonal decline in turgor-loss water potential.
- Taxon
- pear treesPyrus communise1
- Outcome
- seasonal decrease in Psi(pi) (0)e0
- Qualifier
- leaf osmotic water potential at full turgor (Psi(pi) (100)) and in symplast water fraction (R(s))e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Changes in leaf osmotic water potential at full turgor (Psi(pi) (100)) and in symplast water fraction (R(s)) did not explain the seasonal decrease in Psi(pi) (0)”
e1“pear trees (Pyrus communis L. cv. "Barlett")”
Claim · model-written summary
Water stress did not change pear leaf osmotic water potential at full turgor.
- Taxon
- pear treesPyrus communise1
- Treatment
- water stress treatmentse0
- Outcome
- Psi(pi) (100)e0
- Direction
- no effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The water stress treatments had no effect on Psi(pi) (100)”
e1“pear trees (Pyrus communis L. cv. "Barlett")”
Claim · model-written summary
Water stress reduced symplast water fraction, especially in summer stress cycles.
- Taxon
- pear treesPyrus communise1
- Treatment
- water stress treatmentse0
- Outcome
- R(s)e0
- Direction
- reducede0
- Qualifier
- particularly during the summer stress cycle of the Su and Sp + Su treatmentse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“R(s) was reduced by the water stress treatments, particularly during the summer stress cycle of the Su and Sp + Su treatments”
e1“pear trees (Pyrus communis L. cv. "Barlett")”
Claim · model-written summary
Reduced symplast water fraction was correlated with a steeper linear pressure-volume curve.
- Taxon
- pear treesPyrus communise1
- Outcome
- slope of the linear region of the P-V curvee0
- Direction
- increasee0
- Qualifier
- decrease in R(s)e0
- Comparator
- decrease in R(s)e0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The decrease in R(s) was correlated with an increase in the slope of the linear region of the P-V curve”
e1“pear trees (Pyrus communis L. cv. "Barlett")”
Claim · model-written summary
The coupled adjustment would increase water uptake capacity only without turgor.
- Taxon
- pear treesPyrus communise1
- Outcome
- water uptake capacitye0
- Qualifier
- only under non-turgor conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Such a coupled adjustment would lead to increased water uptake capacity of water-stressed trees only under non-turgor conditions”
e1“pear trees (Pyrus communis L. cv. "Barlett")”
Claim · model-written summary
Pear leaves did not actively accumulate solutes.
- Taxon
- pearPyrus communise0
- Organ / stage
- leavese0
- Outcome
- did not actively accumulate solutese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pear leaves did not actively accumulate solutes”
Claim · model-written summary
The authors conclude acclimation of pear leaf water relations is unlikely to sustain fruit productivity under drought.
- Taxon
- pear treesPyrus communise1
- Outcome
- maintenance of fruit productivity under droughte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“changes in leaf tissue water relations as a result of leaf acclimation to water stress are unlikely to facilitate maintenance of fruit productivity under drought”
e1“pear trees (Pyrus communis L. cv. "Barlett")”