Abstract
Abstract Key message Austropuccinia psidii infection and increase in diseased leaf area resulted in a reduction of photosynthesis, an upregulation of stomatal conductance, and an increase in leaf starch and sucrose content. Abstract Austropuccinia psidii is a biotrophic rust pathogen that causes myrtle rust, affecting over 480 species in the Myrtaceae family. The development of chlorotic and necrotic leaf areas following A. psidii infection has been shown to affect leaf gas exchange. In this study, we quantified photosynthesis, stomatal conductance, and non-structural carbohydrates in seedlings of a long-lived tree, Metrosideros excelsa (pōhutukawa), following A. psidii infection in a glasshouse experiment (infected and control seedlings) conducted over 20 weeks. The diseased leaf area rose from 8% in week 2 to 95% in week 20 after A. psidii inoculation. The photosynthetic rate declined by over 90% within 6 weeks after inoculation and was associated with biochemical damage in CO 2 fixation. Stomatal conductance decreased over the first 4 weeks after inoculation and then increased. An increase in lesions and necrotic cells may inhibit stomatal regulation. Starch content was threefold higher in infected than control leaves 20 weeks after inoculation. Increased starch accumulation in the infected leaf area could be due to reduced export of newly fixed carbon from the infected leaves. Meanwhile, glucose + fructose content was 31% lower in infected leaves at the experiment’s end, likely because of leaf necrosis. If the pathogen-induced damage and loss of leaves, reduction in photosynthesis and changes in non-structural carbohydrates shown in this study also occur in wild M. excelsa seedlings and reduces their biomass, this may in turn reduce their competitive ability in the primary successions that they currently often dominate.
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Claims 10
Claim · model-written summary
Diseased leaf area increased from 8% at week 2 to 95% at week 20 after inoculation.
- Taxon
- Metrosideros excelsa
Metrosideros excelsat0 - Interactor
- A. psidii
.jpg?width=60)
Austropuccinia psidiie0pathogen - Outcome
- diseased leaf areae0
- Direction
- rosee0
- Value
- 8% in week 2 to 95% in week 20e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“The diseased leaf area rose from 8% in week 2 to 95% in week 20 after A. psidii inoculation”
t0“Metrosideros excelsa”
Claim · model-written summary
Photosynthetic rate fell over 90% within six weeks after inoculation.
- Taxon
- Metrosideros excelsaMetrosideros excelsat0
- Treatment
- inoculatione0
- Outcome
- photosynthetic ratee0
- Direction
- declinede0
- Value
- over 90%e0
- Qualifier
- within 6 weekse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The photosynthetic rate declined by over 90% within 6 weeks after inoculation”
t0“Metrosideros excelsa”
Claim · model-written summary
The photosynthetic decline was associated with biochemical damage in CO 2 fixation.
- Taxon
- Metrosideros excelsaMetrosideros excelsat0
- Outcome
- biochemical damage in CO 2 fixatione0
- Qualifier
- was associated withe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“was associated with biochemical damage in CO 2 fixation”
t0“Metrosideros excelsa”
Claim · model-written summary
Stomatal conductance declined during the first four weeks after inoculation.
- Taxon
- Metrosideros excelsaMetrosideros excelsat0
- Outcome
- Stomatal conductancee0
- Direction
- decreasede0
- Qualifier
- first 4 weeks after inoculatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Stomatal conductance decreased over the first 4 weeks after inoculation”
t0“Metrosideros excelsa”
Claim · model-written summary
Stomatal conductance subsequently rose.
- Taxon
- Metrosideros excelsaMetrosideros excelsat0
- Outcome
- Stomatal conductancee1
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“and then increased”
t0“Metrosideros excelsa”
e1“Stomatal conductance decreased over the first 4 weeks after inoculation”
Claim · model-written summary
Lesions and necrotic cells may inhibit stomatal regulation.
- Taxon
- Metrosideros excelsaMetrosideros excelsat0
- Outcome
- stomatal regulatione0
- Qualifier
- lesions and necrotic cellse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“An increase in lesions and necrotic cells may inhibit stomatal regulation”
t0“Metrosideros excelsa”
Claim · model-written summary
Infected leaves had threefold higher starch than controls at 20 weeks.
- Taxon
- Metrosideros excelsaMetrosideros excelsat0
- Treatment
- infectede0
- Outcome
- Starch contente0
- Direction
- highere0
- Value
- threefolde0
- Qualifier
- 20 weeks after inoculatione0
- Comparator
- control leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Starch content was threefold higher in infected than control leaves 20 weeks after inoculation”
t0“Metrosideros excelsa”
Claim · model-written summary
Reduced export of newly fixed carbon could explain starch buildup.
- Taxon
- Metrosideros excelsaMetrosideros excelsat0
- Outcome
- Increased starch accumulatione0
- Qualifier
- reduced export of newly fixed carbon from the infected leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increased starch accumulation in the infected leaf area could be due to reduced export of newly fixed carbon from the infected leaves”
t0“Metrosideros excelsa”
Claim · model-written summary
Infected leaves had 31% lower glucose and fructose at the end.
- Taxon
- Metrosideros excelsaMetrosideros excelsat0
- Treatment
- infected leavese0
- Outcome
- glucose + fructose contente0
- Direction
- lowere0
- Value
- 31%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“glucose + fructose content was 31% lower in infected leaves at the experiment’s end”
t0“Metrosideros excelsa”
Claim · model-written summary
The authors suggest leaf necrosis may explain lower glucose and fructose.
- Taxon
- Metrosideros excelsaMetrosideros excelsat0
- Outcome
- glucose + fructose contente0
- Qualifier
- leaf necrosise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“glucose + fructose content was 31% lower in infected leaves at the experiment’s end, likely because of leaf necrosis”
t0“Metrosideros excelsa”