Abstract
Water vapour flux (rate of water loss) from the mesophyll of isolated Agapanthus praecox Willd. leaf pieces without an epidermis was investigated by loss of mass into unstirred air at relative humidities (RHs) of 0.993-0.850, compared with the rate from a water atmometer (rate of evaporation). The point at which relative evaporation (RE, the rate of water loss divided by the rate of evaporation) reaches <1 inadequately identifies the onset of mesophyll regulation because values >1 were found. For RHs of 0.993-0.967, RE varied in daily cycles from 0.6 to ~3, with a period of ~24h, maxima at mid-afternoon, minima at or near dawn. For RH<0.950, the cycles were suppressed. An initial rate of RE ≈1.2, RE declined towards zero. In leaf pieces supplied with water via vascular strands (rate of transpiration), the daily cycle persisted down to RH 0.850, where maximal RE ≈ 2. Transpiration from one surface of field leaves gave the rate of transpiration in the same range. These data require the maximum RE for each vapour pressure deficit as the value identifying the onset of mesophyll regulation (possibly by aquaporins), which produces cyclic changes in the rates of water loss and transpiration. At RH<0.95, the decline of RE below 1 is probably regulated by cell wall water status. Possible functions of the two types of regulation are discussed.
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Claims 9
Claim · model-written summary
Relative evaporation below one inadequately marks the onset of mesophyll regulation.
- Taxon
- Agapanthus praecox Willd.
Agapanthus praecoxe1 - Outcome
- inadequately identifies the onset of mesophyll regulatione0
- Value
- <1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The point at which relative evaporation (RE, the rate of water loss divided by the rate of evaporation) reaches <1 inadequately identifies the onset of mesophyll regulation because values >1 were found.”
e1“Agapanthus praecox Willd.”
Claim · model-written summary
At RH 0.993-0.967, relative evaporation cycled daily from 0.6 to about 3.
- Taxon
- Agapanthus praecox Willd.Agapanthus praecoxe1
- Outcome
- RE varied in daily cyclese0
- Value
- 0.6 to ~3e0
- Qualifier
- RHs of 0.993-0.967e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For RHs of 0.993-0.967, RE varied in daily cycles from 0.6 to ~3, with a period of ~24h, maxima at mid-afternoon, minima at or near dawn.”
e1“Agapanthus praecox Willd.”
Claim · model-written summary
At RH below 0.950, daily cycles were suppressed.
- Taxon
- Agapanthus praecox Willd.Agapanthus praecoxe1
- Outcome
- the cyclese0
- Direction
- suppressede0
- Qualifier
- RH<0.950e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For RH<0.950, the cycles were suppressed.”
e1“Agapanthus praecox Willd.”
Claim · model-written summary
After initial RE near 1.2, RE declined toward zero.
- Taxon
- Agapanthus praecox Willd.Agapanthus praecoxe1
- Outcome
- REe0
- Direction
- declinede0
- Value
- ≈1.2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“An initial rate of RE ≈1.2, RE declined towards zero.”
e1“Agapanthus praecox Willd.”
Claim · model-written summary
In water supplied leaf pieces, daily cycles persisted to RH 0.850.
- Taxon
- Agapanthus praecox Willd.Agapanthus praecoxe1
- Outcome
- daily cycle persistede0
- Qualifier
- RH 0.850e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In leaf pieces supplied with water via vascular strands (rate of transpiration), the daily cycle persisted down to RH 0.850, where maximal RE ≈ 2.”
e1“Agapanthus praecox Willd.”
Claim · model-written summary
At RH 0.850, maximal RE was about 2.
- Taxon
- Agapanthus praecox Willd.Agapanthus praecoxe1
- Outcome
- maximal REe0
- Value
- ≈ 2e0
- Qualifier
- RH 0.850e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In leaf pieces supplied with water via vascular strands (rate of transpiration), the daily cycle persisted down to RH 0.850, where maximal RE ≈ 2.”
e1“Agapanthus praecox Willd.”
Claim · model-written summary
Field leaf transpiration from one surface fell in the same range.
- Taxon
- Agapanthus praecox Willd.Agapanthus praecoxe1
- Outcome
- rate of transpiratione0
- Direction
- same rangee0
- Setting
- field leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transpiration from one surface of field leaves gave the rate of transpiration in the same range.”
e1“Agapanthus praecox Willd.”
Claim · model-written summary
Authors propose maximum RE for each deficit as the threshold for mesophyll regulation.
- Taxon
- Agapanthus praecox Willd.Agapanthus praecoxe1
- Outcome
- maximum RE for each vapour pressure deficit as the value identifying the onset of mesophyll regulatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“These data require the maximum RE for each vapour pressure deficit as the value identifying the onset of mesophyll regulation”
e1“Agapanthus praecox Willd.”
Claim · model-written summary
Authors suggest cell wall water status regulates RE decline below one at low RH.
- Taxon
- Agapanthus praecox Willd.Agapanthus praecoxe1
- Outcome
- decline of RE below 1e0
- Qualifier
- cell wall water statuse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At RH<0.95, the decline of RE below 1 is probably regulated by cell wall water status.”
e1“Agapanthus praecox Willd.”