Abstract
Cold acclimation by sustained downregulation of PSII was studied in intact leaves of an Australian mistletoe Amyema miquelii (Lehm. ex Miq.) Tiegh. and its host Eucalyptus . The trends were followed from autumn to spring on leaves that had developed in summer and were exposed to different microclimates with progress of the seasons. In sun leaves of mistletoe, efficiency of excitation energy transfer from light-harvesting pigments to Chl a molecules in PSII core complexes was markedly reduced in winter. Concomitantly, a band in 77K fluorescence emission spectra emerged at 715 nm, in the same way as the cold-hard band found in overwintering snow gum seedlings (Gilmore and Ball 2000, Proceedings of the National Academy of Sciences USA 97, 11 098–11 101). Further, a distinct band, which presumably involves Chl- b -containing antennae complexes, appeared at 705 nm in –2°C fluorescence emission spectra with decreasing intensity of the PSII band. Much shorter PSII fluorescence lifetimes measured in sun leaves of mistletoe that were exhibiting sustained downregulation of PSII indicated enhanced thermal dissipation of excitation energy. Winter acclimation symptoms of the photosynthetic apparatus were more striking in mistletoe sun leaves compared with eucalypt sun leaves. Because the light and temperature environments of sun leaves are similar for the parasite and host, we primarily attribute the enhanced light-acclimation symptoms to the limited photosynthetic capacity of A. miquelii in winter.
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Claims 7
Claim · model-written summary
Excitation energy transfer efficiency in mistletoe sun leaves was markedly reduced in winter.
- Taxon
- Amyema miquelii
Amyema miqueliit0 - Outcome
- In sun leaves of mistletoe, efficiency of excitation energy transfer from light-harvesting pigments to Chl a molecules in PSII core complexes was markedly reduced in winter.e0
- Direction
- reducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In sun leaves of mistletoe, efficiency of excitation energy transfer from light-harvesting pigments to Chl a molecules in PSII core complexes was markedly reduced in winter.”
t0“Amyema miquelii (Lehm. ex Miq.) Tiegh.”
Claim · model-written summary
A 715 nm fluorescence band emerged in winter mistletoe leaves.
- Taxon
- Amyema miqueliiAmyema miqueliit0
- Outcome
- a band in 77K fluorescence emission spectra emerged at 715 nme0
- Value
- 715 nme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a band in 77K fluorescence emission spectra emerged at 715 nm”
t0“Amyema miquelii (Lehm. ex Miq.) Tiegh.”
Claim · model-written summary
A 705 nm fluorescence band appeared as the PSII band declined.
- Taxon
- Amyema miqueliiAmyema miqueliit0
- Outcome
- a distinct band, which presumably involves Chl- b -containing antennae complexes, appeared at 705 nm in –2°C fluorescence emission spectra with decreasing intensity of the PSII bande0
- Value
- 705 nme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a distinct band, which presumably involves Chl- b -containing antennae complexes, appeared at 705 nm in –2°C fluorescence emission spectra with decreasing intensity of the PSII band”
t0“Amyema miquelii (Lehm. ex Miq.) Tiegh.”
Claim · model-written summary
Mistletoe sun leaves under sustained PSII downregulation had shorter PSII fluorescence lifetimes.
- Taxon
- Amyema miqueliiAmyema miqueliit0
- Outcome
- Much shorter PSII fluorescence lifetimes measured in sun leaves of mistletoe that were exhibiting sustained downregulation of PSIIe0
- Direction
- shortere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Much shorter PSII fluorescence lifetimes measured in sun leaves of mistletoe that were exhibiting sustained downregulation of PSII”
t0“Amyema miquelii (Lehm. ex Miq.) Tiegh.”
Claim · model-written summary
Shorter fluorescence lifetimes indicated enhanced thermal energy dissipation.
- Taxon
- Amyema miqueliiAmyema miqueliit0
- Outcome
- indicated enhanced thermal dissipation of excitation energye0
- Qualifier
- thermal dissipation of excitation energye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“indicated enhanced thermal dissipation of excitation energy”
t0“Amyema miquelii (Lehm. ex Miq.) Tiegh.”
Claim · model-written summary
Winter photosynthetic acclimation symptoms were stronger in mistletoe sun leaves than eucalypt sun leaves.
- Taxon
- Amyema miqueliiAmyema miqueliit0
- Outcome
- Winter acclimation symptoms of the photosynthetic apparatus were more striking in mistletoe sun leaves compared with eucalypt sun leaves.e0
- Direction
- more strikinge0
- Comparator
- eucalypt sun leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Winter acclimation symptoms of the photosynthetic apparatus were more striking in mistletoe sun leaves compared with eucalypt sun leaves.”
t0“Amyema miquelii (Lehm. ex Miq.) Tiegh.”
Claim · model-written summary
The authors attribute enhanced winter acclimation symptoms mainly to limited photosynthetic capacity of A. miquelii.
- Taxon
- Amyema miqueliiAmyema miqueliit0
- Outcome
- we primarily attribute the enhanced light-acclimation symptoms to the limited photosynthetic capacity of A. miquelii in wintere0
- Qualifier
- limited photosynthetic capacitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we primarily attribute the enhanced light-acclimation symptoms to the limited photosynthetic capacity of A. miquelii in winter”
t0“Amyema miquelii (Lehm. ex Miq.) Tiegh.”