Abstract
The responses of photosynthesis, chlorophyll fluorescence, and de-epoxidation state of the xanthophyll cycle pigments (DEPS) of micropropagated apple trees ( Malus × domestica ) were investigated under whole-root water stress (WRS) and half-root water stress (HRS) induced by polyethylene glycol 6000 to simulate whole and partial root zone drying. Compared with control plants without water stress, plants under WRS and HRS exhibited reduced leaf net photosynthetic rate (P n ) and stomatal conductance ( g S ) with a greater reduction in WRS than in HRS plants. However, intercellular CO 2 concentration (Ci) increased under WRS as water stress was prolonged, signifying a non-stomatal limitation of P n . Regarding HRS, decreased P n was mainly the result of a stomatal limitation explained by a relatively low Ci. Changes in photosynthesis and chlorophyll parameters indicate that severe and slight damage occurred to the photosynthetic apparatus of WRS and HRS leaves, respectively, starting at Day 3 after initiating water stress. This damage was not evident on the donor side but was expressed as a reduced capacity of the acceptor side of the photosystem II reaction centers. To prevent damage from excess light, the DEPS of WRS leaf increased. Decreased g S could explain reduced water use under an irrigation strategy of partial root zone drying in fruit trees.
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Claims 12
Claim · model-written summary
Whole-root water stress reduced leaf net photosynthetic rate compared with control plants without water stress.
- Taxon
- Apple Trees
Malus domesticat1 - Treatment
- WRSe0
- Outcome
- leaf net photosynthetic ratee0
- Direction
- reducede0
- Comparator
- control plants without water stresse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Apple Trees”
e0“Compared with control plants without water stress, plants under WRS and HRS exhibited reduced leaf net photosynthetic rate”
Claim · model-written summary
Half-root water stress reduced leaf net photosynthetic rate compared with control plants without water stress.
- Taxon
- Apple TreesMalus domesticat1
- Treatment
- HRSe0
- Outcome
- leaf net photosynthetic ratee0
- Direction
- reducede0
- Comparator
- control plants without water stresse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Apple Trees”
e0“Compared with control plants without water stress, plants under WRS and HRS exhibited reduced leaf net photosynthetic rate”
Claim · model-written summary
Whole-root water stress reduced stomatal conductance compared with control plants without water stress.
- Taxon
- Apple TreesMalus domesticat1
- Treatment
- WRSe1
- Outcome
- stomatal conductancee1
- Direction
- reducede1
- Comparator
- control plants without water stresse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Apple Trees”
e0“Compared with control plants without water stress, plants under WRS and HRS exhibited reduced leaf net photosynthetic rate”
e1“reduced leaf net photosynthetic rate (P n ) and stomatal conductance ( g S ) with a greater reduction in WRS than in HRS plants”
Claim · model-written summary
Half-root water stress reduced stomatal conductance compared with control plants without water stress.
- Taxon
- Apple TreesMalus domesticat1
- Treatment
- HRSe1
- Outcome
- stomatal conductancee1
- Direction
- reducede1
- Comparator
- control plants without water stresse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Apple Trees”
e0“Compared with control plants without water stress, plants under WRS and HRS exhibited reduced leaf net photosynthetic rate”
e1“reduced leaf net photosynthetic rate (P n ) and stomatal conductance ( g S ) with a greater reduction in WRS than in HRS plants”
Claim · model-written summary
Whole-root water stress caused a greater reduction in leaf net photosynthetic rate than half-root water stress.
- Taxon
- Apple TreesMalus domesticat1
- Treatment
- WRSe1
- Outcome
- leaf net photosynthetic ratee1
- Direction
- greater reductione1
- Comparator
- HRSe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Apple Trees”
e1“reduced leaf net photosynthetic rate (P n ) and stomatal conductance ( g S ) with a greater reduction in WRS than in HRS plants”
Claim · model-written summary
Intercellular CO2 concentration increased under whole-root water stress as water stress was prolonged.
- Taxon
- Apple TreesMalus domesticat1
- Treatment
- WRSe2
- Outcome
- intercellular CO 2 concentratione2
- Direction
- increasede2
- Qualifier
- as water stress was prolongede2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Apple Trees”
e2“intercellular CO 2 concentration (Ci) increased under WRS as water stress was prolonged”
Claim · model-written summary
Under half-root water stress, decreased photosynthetic rate was mainly due to stomatal limitation with low intercellular CO2.
- Taxon
- Apple TreesMalus domesticat1
- Treatment
- HRSe3
- Outcome
- decreased P ne3
- Qualifier
- a stomatal limitation explained by a relatively low Cie3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Apple Trees”
e3“Regarding HRS, decreased P n was mainly the result of a stomatal limitation explained by a relatively low Ci”
Claim · model-written summary
Whole-root water stress caused damage to the photosynthetic apparatus starting at Day 3 after initiating water stress.
- Taxon
- Apple TreesMalus domesticat1
- Treatment
- WRSe4
- Outcome
- damage occurred to the photosynthetic apparatuse4
- Qualifier
- starting at Day 3 after initiating water stresse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Apple Trees”
e4“severe and slight damage occurred to the photosynthetic apparatus of WRS and HRS leaves, respectively, starting at Day 3 after initiating water stress”
Claim · model-written summary
Half-root water stress caused slight damage to the photosynthetic apparatus starting at Day 3 after initiating water stress.
- Taxon
- Apple TreesMalus domesticat1
- Treatment
- HRSe4
- Outcome
- damage occurred to the photosynthetic apparatuse4
- Qualifier
- starting at Day 3 after initiating water stresse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Apple Trees”
e4“severe and slight damage occurred to the photosynthetic apparatus of WRS and HRS leaves, respectively, starting at Day 3 after initiating water stress”
Claim · model-written summary
The damage under whole-root water stress was expressed as reduced capacity of the acceptor side of photosystem II reaction centers and was not evident on the donor side.
- Taxon
- Apple TreesMalus domesticat1
- Outcome
- capacity of the acceptor side of the photosystem II reaction centerse5
- Direction
- reducede5
- Qualifier
- not evident on the donor sidee5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Apple Trees”
e5“This damage was not evident on the donor side but was expressed as a reduced capacity of the acceptor side of the photosystem II reaction centers”
Claim · model-written summary
The de-epoxidation state of xanthophyll cycle pigments increased in whole-root water stress leaves.
- Taxon
- Apple TreesMalus domesticat1
- Treatment
- WRSe6
- Outcome
- DEPSe6
- Direction
- increasede6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Apple Trees”
e6“To prevent damage from excess light, the DEPS of WRS leaf increased”
Claim · model-written summary
Decreased stomatal conductance could explain reduced water use under partial root zone drying in fruit trees.
Verbatim
e7“Decreased g S could explain reduced water use under an irrigation strategy of partial root zone drying in fruit trees”
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See all 10 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.