Abstract
Plants have been hypothesized to maintain strong control over xylem tension by closing stomata and to operate at a water potential above or near the critical potential at which cavitation commences. An alternative hypothesis holds that cavitation temporarily relieves water stress and stomatal closure is insufficient to prevent short term “run-away” cavitation. The objectives of this study were to investigate the leaf conductivity loss at noon (Loss) of 13 woody species differing in leaf phenology at two sites on karst topography in the wet season in southwestern China; the hydraulic architecture of woody species has rarely been reported previously. Loss was predicted from minimum field leaf water potentials (Ψmin) and laboratory-generated vulnerability curves. We also measured the maximum quantum efficiency of photosystem II using chlorophyll a fluorescence (Fv/Fm) and other associated leaf traits. Loss in the field varied substantially, from 1.39% in evergreen Itea chinensis to 90.07% in deciduous Sapium sebiferum. However, the Loss did not significantly decrease the efficiency of photosystem II. The water potential at which a 50% loss in leaf conductivity occurred (Ψ50) was not correlated to Ψmin. The co-occurring evergreen and deciduous species differed significantly in some stem hydraulic and associated leaf traits. Deciduous species had higher hydraulic conductance, photosynthetic rate, stomatal conductance, lower cavitation-resistance and minimum water potential than co-occurring evergreen species. There was no sign that karst woody species in southwestern China could control xylem tension above the threshold to avoid substantial xylem cavitation in the wet season. There was no association between Loss and Fv/Fm among the studied species. This “isohydric” regulation behaviour, as well as abundant rainfall in the wet season, may explain why large variations of Loss existed across karst woody species in southwestern China.
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Claims 10
Claim · model-written summary
Field leaf conductivity loss ranged from 1.39% in Itea chinensis to 90.07% in Sapium sebiferum.
- Taxon
- Itea chinensis
Itea chinensise0 - Outcome
- Loss in the fielde0
- Value
- 1.39%e0
- Qualifier
- evergreene0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Loss in the field varied substantially, from 1.39% in evergreen Itea chinensis to 90.07% in deciduous Sapium sebiferum.”
Claim · model-written summary
Sapium sebiferum had 90.07% field leaf conductivity loss.
- Taxon
- Sapium sebiferum
Triadica sebiferae0 - Outcome
- Loss in the fielde0
- Value
- 90.07%e0
- Qualifier
- deciduouse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Loss in the field varied substantially, from 1.39% in evergreen Itea chinensis to 90.07% in deciduous Sapium sebiferum.”
Claim · model-written summary
Leaf conductivity loss did not significantly decrease photosystem II efficiency.
- Taxon
- woodyt0
- Treatment
- Losse0
- Outcome
- efficiency of photosystem IIe0
- Direction
- did not significantly decreasee0
Not reportedOrgan / stage
Verbatim
e0“However, the Loss did not significantly decrease the efficiency of photosystem II.”
t0“woody plants”
Claim · model-written summary
Ψ50 was not correlated with Ψmin.
Verbatim
e0“The water potential at which a 50% loss in leaf conductivity occurred (Ψ50) was not correlated to Ψmin.”
t0“woody plants”
Claim · model-written summary
Co-occurring evergreen and deciduous species differed in some stem hydraulic and leaf traits.
Verbatim
e0“The co-occurring evergreen and deciduous species differed significantly in some stem hydraulic and associated leaf traits.”
t0“woody plants”
Claim · model-written summary
Deciduous species had higher hydraulic conductance, photosynthetic rate and stomatal conductance than evergreen species.
Verbatim
e0“Deciduous species had higher hydraulic conductance, photosynthetic rate, stomatal conductance, lower cavitation-resistance and minimum water potential than co-occurring evergreen species.”
t0“woody plants”
Claim · model-written summary
Deciduous species had lower cavitation resistance and minimum water potential than evergreen species.
Verbatim
e0“Deciduous species had higher hydraulic conductance, photosynthetic rate, stomatal conductance, lower cavitation-resistance and minimum water potential than co-occurring evergreen species.”
t0“woody plants”
Claim · model-written summary
Karst woody species showed no sign of controlling xylem tension above the cavitation threshold in the wet season.
- Taxon
- karst woody speciese0
- Outcome
- control xylem tension above the thresholde0
- Qualifier
- in the wet seasone0
- Setting
- southwestern Chinae0
Not reportedDirection
Verbatim
e0“There was no sign that karst woody species in southwestern China could control xylem tension above the threshold to avoid substantial xylem cavitation in the wet season.”
Claim · model-written summary
Loss and Fv/Fm were not associated among the species studied.
Verbatim
e0“There was no association between Loss and Fv/Fm among the studied species.”
t0“woody plants”
Claim · model-written summary
The authors suggest isohydric regulation and wet-season rainfall may explain the broad variation in conductivity loss.
Verbatim
e0“This “isohydric” regulation behaviour, as well as abundant rainfall in the wet season, may explain why large variations of Loss existed across karst woody species in southwestern China.”