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Andreas Rigling - One of the best experts on this subject based on the ideXlab platform.
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effects of Mistletoe removal on growth n and c reserves and carbon and oxygen isotope composition in scots pine hosts
Tree Physiology, 2016Co-Authors: Caifeng Yan, Andreas Rigling, Matthias Dobbertin, Arthur Gessler, Xingguo HanAbstract:Most Mistletoes are xylem-tapping hemiparasites, which derive their resources from the host's xylem solution. Thus, they affect the host's water relations and resource balance. To understand the physiological mechanisms underlying the Mistletoe-host relationship, we experimentally removed Viscum album ssp. austriacum (Wiesb.) Vollmann from adult Pinus sylvestris L. host trees growing in a Swiss dry valley. We analyzed the effects of Mistletoe removal over time on host tree growth and on concentrations of nonstructural carbohydrates (NSC) and nitrogen (N) in needles, fine roots and sapwood. In addition, we assessed the δ(13)C and δ(18)O in host tree rings. After Mistletoe removal, δ(13)C did not change in newly produced tree rings compared with tree rings in control trees (still infected with Mistletoe), but δ(18)O values increased. This pattern might be interpreted as a decrease in assimilation (A) and stomatal conductance (gs), but in our study, it most likely points to an inadequacy of the dual isotope approach. Instead, we interpret the unchanged δ(13)C in tree rings upon Mistletoe removal as a balanced increase in A and gs that resulted in a constant intrinsic water use efficiency (defined as A/gs). Needle area-based concentrations of N, soluble sugars and NSC, as well as needle length, single needle area, tree ring width and shoot growth, were significantly higher in trees from which Mistletoe was removed than in control trees. This finding suggests that Mistletoe removal results in increased N availability and carbon gain, which in turn leads to increased growth rates of the hosts. Hence, in areas where Mistletoe is common and the population is large, Mistletoe management (e.g., removal) may be needed to improve the host vigor, growth rate and productivity, especially for relatively small trees and crop trees in xeric growth conditions.
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Mistletoe induced crown degradation in scots pine in a xeric environment
Tree Physiology, 2010Co-Authors: Andreas Rigling, Britta Eilmann, Roger Koechli, Matthias DobbertinAbstract:Summary Increasing Scots pine (Pinus sylvestris L.) mortality has been recently observed in the dry inner valleys of the European Alps. Besides drought, infection with pine Mistletoe (Viscum album ssp. austriacum) seems to play an important role in the mortality dynamics of Scots pines, but how Mistletoes promote pine decline remains unclear. To verify whether pine Mistletoe infection weakens the host via crown degradation, as observed for dwarf Mistletoes, we studied the negative effects of pine Mistletoe infestation on the photosynthetic tissues and branch growth of pairs of infested and noninfested branches. Pine Mistletoe infection leads to crown degradation in its host by reducing the length, the radial increment, the ramification, the needle length and the number of needle years of the infested branches. This massive loss in photosynthetic tissue results in a reduction in primary production and a subsequent decrease in carbohydrate availability. The significant reduction in needle length due to Mistletoe infection is an indication for a lower water and nutrient availability in infested branches. Thus, Mistletoe infection might lead to a decrease in the availability of water and carbohydrates, the two most important growth factors, which are already shortened due to the chronic drought situation in the area. Therefore, pine Mistletoe increases the risk of drought-induced mortality of its host when growing in a xeric environment.
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pine Mistletoe viscum album ssp austriacum contributes to scots pine pinus sylvestris mortality in the rhone valley of switzerland
Forest Pathology, 2006Co-Authors: Matthias Dobbertin, Andreas RiglingAbstract:Summary In recent years unusual high mortality of Scots pine (Pinus sylvestris) has been observed in the Swiss Rhone Valley. The exact causes, however, are not known. At a 2-ha monitoring plot, tree mortality and crown condition have been monitored since 1996. Between 1996 and 2004, 59% of the Scots pines died, most of them following the drought periods 1996–1998 and 2003–2004, while only 15% of the deciduous trees died. Crown transparency, needle discolouration, dead branch percentage, Mistletoe (Viscum album ssp. austriacum) rating, Tomicus sp. shoot feeding, male flowering effect, tree stem diameter, crown shading and social tree class assessed in 1998 were used in a logistic regression model to predict tree mortality. Crown transparency, Mistletoe rating and percentage of dead branches were found significant in the model and the probability of tree mortality increased with increasing rankings of these parameters. Needle discolouration could be used to substitute dead branch percentage as predictor. While crown transparency increased with Mistletoe rating, for trees in the same transparency class, trees with medium and heavy Mistletoe infection were two to four times more likely to die than trees with no or only low Mistletoe infection. For the surviving trees we found that trees with Mistletoes showed a significantly higher increase in transparency in the year following a drought than trees without, while in a drought year the opposite was true. At the beginning of the observations no significant differences in transparency had been found between the trees with and without Mistletoe. However, by the end of the observation period trees with Mistletoe had significantly higher crown transparency. We conclude that Mistletoe infection can be considered as both a predisposing factor for tree death, by increasing needle loss following drought and a contributing factor by increasing water stress during drought.
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the upward shift in altitude of pine Mistletoe viscum album ssp austriacum in switzerland the result of climate warming
International Journal of Biometeorology, 2005Co-Authors: Matthias Dobbertin, Nadine Hilker, Martine Rebetez, Niklaus E Zimmermann, Thomas Wohlgemuth, Andreas RiglingAbstract:Pine Mistletoe (Viscum album ssp. austriacum) is common in natural Scots pine (Pinus sylvestris L.) forests in the alpine Rhone Valley, Switzerland. This semi-parasite, which is regarded as an indicator species for temperature, increases the drought stress on trees and may contribute to the observed pine decline in the region. We recorded Mistletoes on representative plots of the Swiss National Forest Inventory ranging from 450 to 1,550 m a.s.l. We found Mistletoe on 37% of the trees and on 56% of all plots. Trees infested with Mistletoe had a significantly higher mortality rate than non-infested trees. We compared the current Mistletoe occurrence with records from a survey in 1910. The current upper limit, 1,250 m, is roughly 200 m above the limit of 1,000-1,100 m found in the earlier survey 100 years ago. Applying a spatial model to meteorological data we obtained monthly mean temperatures for all sites. In a logistic regression mean winter temperature, pine proportion and geographic exposition significantly explained Mistletoe occurrence. Using mean monthly January and July temperatures for 1961-1990, we calculated Skre's plant respiration equivalent (RE) and regressed it against elevation to obtain the RE value at the current Mistletoe elevation limit. We used this RE value and temperature from 1870-1899 in the regression and found the past elevation limit to be at 1,060 m, agreeing with the 1910 survey. For the predicted temperature rise by 2030, the limit for Mistletoe would increase above 1,600 m altitude.
Matthias Dobbertin - One of the best experts on this subject based on the ideXlab platform.
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effects of Mistletoe removal on growth n and c reserves and carbon and oxygen isotope composition in scots pine hosts
Tree Physiology, 2016Co-Authors: Caifeng Yan, Andreas Rigling, Matthias Dobbertin, Arthur Gessler, Xingguo HanAbstract:Most Mistletoes are xylem-tapping hemiparasites, which derive their resources from the host's xylem solution. Thus, they affect the host's water relations and resource balance. To understand the physiological mechanisms underlying the Mistletoe-host relationship, we experimentally removed Viscum album ssp. austriacum (Wiesb.) Vollmann from adult Pinus sylvestris L. host trees growing in a Swiss dry valley. We analyzed the effects of Mistletoe removal over time on host tree growth and on concentrations of nonstructural carbohydrates (NSC) and nitrogen (N) in needles, fine roots and sapwood. In addition, we assessed the δ(13)C and δ(18)O in host tree rings. After Mistletoe removal, δ(13)C did not change in newly produced tree rings compared with tree rings in control trees (still infected with Mistletoe), but δ(18)O values increased. This pattern might be interpreted as a decrease in assimilation (A) and stomatal conductance (gs), but in our study, it most likely points to an inadequacy of the dual isotope approach. Instead, we interpret the unchanged δ(13)C in tree rings upon Mistletoe removal as a balanced increase in A and gs that resulted in a constant intrinsic water use efficiency (defined as A/gs). Needle area-based concentrations of N, soluble sugars and NSC, as well as needle length, single needle area, tree ring width and shoot growth, were significantly higher in trees from which Mistletoe was removed than in control trees. This finding suggests that Mistletoe removal results in increased N availability and carbon gain, which in turn leads to increased growth rates of the hosts. Hence, in areas where Mistletoe is common and the population is large, Mistletoe management (e.g., removal) may be needed to improve the host vigor, growth rate and productivity, especially for relatively small trees and crop trees in xeric growth conditions.
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Mistletoe induced crown degradation in scots pine in a xeric environment
Tree Physiology, 2010Co-Authors: Andreas Rigling, Britta Eilmann, Roger Koechli, Matthias DobbertinAbstract:Summary Increasing Scots pine (Pinus sylvestris L.) mortality has been recently observed in the dry inner valleys of the European Alps. Besides drought, infection with pine Mistletoe (Viscum album ssp. austriacum) seems to play an important role in the mortality dynamics of Scots pines, but how Mistletoes promote pine decline remains unclear. To verify whether pine Mistletoe infection weakens the host via crown degradation, as observed for dwarf Mistletoes, we studied the negative effects of pine Mistletoe infestation on the photosynthetic tissues and branch growth of pairs of infested and noninfested branches. Pine Mistletoe infection leads to crown degradation in its host by reducing the length, the radial increment, the ramification, the needle length and the number of needle years of the infested branches. This massive loss in photosynthetic tissue results in a reduction in primary production and a subsequent decrease in carbohydrate availability. The significant reduction in needle length due to Mistletoe infection is an indication for a lower water and nutrient availability in infested branches. Thus, Mistletoe infection might lead to a decrease in the availability of water and carbohydrates, the two most important growth factors, which are already shortened due to the chronic drought situation in the area. Therefore, pine Mistletoe increases the risk of drought-induced mortality of its host when growing in a xeric environment.
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pine Mistletoe viscum album ssp austriacum contributes to scots pine pinus sylvestris mortality in the rhone valley of switzerland
Forest Pathology, 2006Co-Authors: Matthias Dobbertin, Andreas RiglingAbstract:Summary In recent years unusual high mortality of Scots pine (Pinus sylvestris) has been observed in the Swiss Rhone Valley. The exact causes, however, are not known. At a 2-ha monitoring plot, tree mortality and crown condition have been monitored since 1996. Between 1996 and 2004, 59% of the Scots pines died, most of them following the drought periods 1996–1998 and 2003–2004, while only 15% of the deciduous trees died. Crown transparency, needle discolouration, dead branch percentage, Mistletoe (Viscum album ssp. austriacum) rating, Tomicus sp. shoot feeding, male flowering effect, tree stem diameter, crown shading and social tree class assessed in 1998 were used in a logistic regression model to predict tree mortality. Crown transparency, Mistletoe rating and percentage of dead branches were found significant in the model and the probability of tree mortality increased with increasing rankings of these parameters. Needle discolouration could be used to substitute dead branch percentage as predictor. While crown transparency increased with Mistletoe rating, for trees in the same transparency class, trees with medium and heavy Mistletoe infection were two to four times more likely to die than trees with no or only low Mistletoe infection. For the surviving trees we found that trees with Mistletoes showed a significantly higher increase in transparency in the year following a drought than trees without, while in a drought year the opposite was true. At the beginning of the observations no significant differences in transparency had been found between the trees with and without Mistletoe. However, by the end of the observation period trees with Mistletoe had significantly higher crown transparency. We conclude that Mistletoe infection can be considered as both a predisposing factor for tree death, by increasing needle loss following drought and a contributing factor by increasing water stress during drought.
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the upward shift in altitude of pine Mistletoe viscum album ssp austriacum in switzerland the result of climate warming
International Journal of Biometeorology, 2005Co-Authors: Matthias Dobbertin, Nadine Hilker, Martine Rebetez, Niklaus E Zimmermann, Thomas Wohlgemuth, Andreas RiglingAbstract:Pine Mistletoe (Viscum album ssp. austriacum) is common in natural Scots pine (Pinus sylvestris L.) forests in the alpine Rhone Valley, Switzerland. This semi-parasite, which is regarded as an indicator species for temperature, increases the drought stress on trees and may contribute to the observed pine decline in the region. We recorded Mistletoes on representative plots of the Swiss National Forest Inventory ranging from 450 to 1,550 m a.s.l. We found Mistletoe on 37% of the trees and on 56% of all plots. Trees infested with Mistletoe had a significantly higher mortality rate than non-infested trees. We compared the current Mistletoe occurrence with records from a survey in 1910. The current upper limit, 1,250 m, is roughly 200 m above the limit of 1,000-1,100 m found in the earlier survey 100 years ago. Applying a spatial model to meteorological data we obtained monthly mean temperatures for all sites. In a logistic regression mean winter temperature, pine proportion and geographic exposition significantly explained Mistletoe occurrence. Using mean monthly January and July temperatures for 1961-1990, we calculated Skre's plant respiration equivalent (RE) and regressed it against elevation to obtain the RE value at the current Mistletoe elevation limit. We used this RE value and temperature from 1870-1899 in the regression and found the past elevation limit to be at 1,060 m, agreeing with the 1910 survey. For the predicted temperature rise by 2030, the limit for Mistletoe would increase above 1,600 m altitude.
Graham L. Strong - One of the best experts on this subject based on the ideXlab platform.
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Water relations of temperate Mistletoes on various hosts.
Functional plant biology : FPB, 2002Co-Authors: Graham L. Strong, Peter BannisterAbstract:The daily field water relations and gas exchange of the temperate Mistletoes Ileostylus micranthus (Hook.f.) Tiegh. and Tupeia antarctica Cham. et Schlecht. on various hosts were examined seasonally in Dunedin, New Zealand during 1996–1998. Mistletoes commonly have higher transpiration rates (E) than their hosts, and this is generally cited as the reason why Mistletoes develop lower water potentials (ψ) than their hosts. The Mistletoe-host pairs that we examined showed no significant overall differences in E and stomatal conductance (g), and we used them to test the hypothesis that lowered ψ in Mistletoes result from higher E. Despite the lack of differences in E and g, osmotic potentials, predawn and daily minimum ψ (ψmin) were significantly more negative in Mistletoes, although differences between host and Mistletoe ψ were less on hosts with low osmotic potentials and ψ. Mistletoes maintained lower ψ than their hosts both when unshaded and under artificial shading, had lower ψ than hosts at equal E, but had shoot hydraulic resistances similar to that of their hosts. E and ψ of hosts and Mistletoes tended to be coordinated only in summer, when hosts were most water-stressed. Mistletoes maintained higher relative water contents at turgor loss, symplastic water contents, and bulk moduli of elasticity (e) than their hosts. We conclude that the lower ψ in these temperate Mistletoes are a consequence of greater Mistletoe E only when host ψ are low, but are otherwise maintained by greater succulence and higher e than in their hosts.
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Differential accumulation of nutrient elements in some New Zealand Mistletoes and their hosts.
Functional plant biology : FPB, 2002Co-Authors: Peter Bannister, Graham L. Strong, Inge AndrewAbstract:It has been generally assumed that differential accumulation of mineral nutrients, leading to greater accumulation of elements in Mistletoe tissues, is associated with greater transpiration in the Mistletoe than in the host. Only a few investigations have measured both tissue element concentrations and transpiration, or transpiration-related parameters such as carbon isotope ratios (δ13C). Seasonal means for foliar concentrations of Ca, Mg, K, Na, P, N, transpiration and δ13C were obtained from ten Mistletoe–host pairs, nine involving the Mistletoe Ileostylus micranthus and one with Tupeia antarctica. Annual means of transpiration and δ13C were similar in Mistletoes and hosts, but hosts showed greater variation in both transpiration and δ13C than Mistletoes. Foliar concentrations of Ca and Mg in Mistletoes were similar to those of their hosts, N concentrations were less, and foliar concentrations of K, Na and P were greater in Mistletoes than in their hosts. Ratios of foliar concentrations of Ca, Mg and P in Mistletoes to those in their hosts (M/H) were greatest when host transpiration was low, when host δ13C was least negative, and when the difference between Mistletoe and host δ13C was most negative. The lack of a phloem connection between host and Mistletoe, combined with circulation of elements in the host phloem and their transfer into the host xylem, provides a mechanism that explains the accumulation of phloem-mobile elements in the Mistletoe.
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Carbon and nitrogen isotope ratios, nitrogen content and heterotrophy in New Zealand Mistletoes
Oecologia, 2001Co-Authors: Peter Bannister, Graham L. StrongAbstract:The carbon isotope ratio (δ13C) of New Zealand Mistletoes (-29.51±0.10‰) and their hosts (-28.89±0.12‰) is generally more negative, and shows less difference between Mistletoes and their hosts, than found in previous studies. In 37% of the examined pairs, the δ13C of Mistletoes was less negative than that of their hosts. These reversals were not associated with the relative position (proximal or distal) of the host material with regard to the Mistletoe. Differences between host and Mistletoe tended to be greater on hosts with less negative δ13C. Both nitrogen content and isotope ratio (δ15N) of the Mistletoe leaves were strongly correlated with those of their hosts. Nitrogen contents of Mistletoe leaves were similar to those of their hosts at low nitrogen contents but proportionately less on hosts with a high nitrogen content, whereas δ15N of Mistletoes was consistently similar to that of their hosts. The δ13C of Mistletoes was related to both host nitrogen content and δ15N, but δ13C in host tissue was related to neither, suggesting that the Mistletoes derived both nitrogen and carbon from their hosts. The δ13C of both hosts and Mistletoes were significantly related to leaf conductance and carbon dioxide concentration but relationships with transpiration and water use efficiency were not significant. In all cases there was no clear separation between the responses of hosts and Mistletoes. This may be related to the similarity of stomatal conductance, transpiration and photosynthesis in the studied Mistletoes and their hosts and is consistent with the small differences in δ13C between Mistletoes and hosts found in this study. Consequently, the estimation of Mistletoe heterotrophy from carbon discrimination is confounded, as the small difference between host and Mistletoe carbon discrimination could equally well result from either similarities in photosynthesis and water relations or heterotrophic assimilation of host-derived carbon. The differences between our study and previous studies (which are mostly from seasonally dry or semi-arid to arid environments) may be related to the temperate environment in which these Mistletoes grow. Water is freely available so that the Mistletoe is able to obtain sufficient water and dissolved nutrients without having to maintain the high transpiration rate and low water potentials that are needed to extract water from a water-stressed host. Similarly, Mistletoe photosynthesis is less inhibited by water stress. The physiological similarities between Mistletoe and hosts from a temperate environment are reflected in their similar δ13C values.
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Are Mistletoes Shade Plants? CO2Assimilation and Chlorophyll Fluorescence of Temperate Mistletoes and their Hosts
Annals of Botany, 2000Co-Authors: Graham L. Strong, Peter Bannister, David J. BurrittAbstract:Abstract Mistletoes usually have slower rates of photosynthesis than their hosts. This study examines CO 2 assimilation, chlorophyll fluorescence and the chlorophyll content of temperate host–parasite pairs (nine hosts parasitized by Ileostylus micranthus and Carpodetus serratus parasitized by Tupeia antarctica ). The hosts of I. micranthus had higher mean annual CO 2 assimilation (3.59 ± 0.41 μmol m −2 s −1 ) than I. micranthus (2.42 ± 0.20 μmol m −2 s −1 ), and C. serratus (2.41 ± 0.43 μmol m −2 s −1 ) showed higher CO 2 assimilation than T. antarctica (0.67 ± 0.64 μmol m −2 s −1 ). Hosts saturated at significantly higher electron transport rates (ETR) and light levels than Mistletoes. The positive relationship between CO 2 assimilation and electron transport suggests that the lower CO 2 assimilation rates in Mistletoes are a consequence of lower electron transport rates. When photosynthetic rates, ETR and chlorophyll a / b ratios were adjusted for photosynthetically active radiation, hosts did not have significantly higher CO 2 assimilation (3.21 ± 0.37 μmol m −2 s −1 ) than Mistletoes (2.54 ± 0.41 μmol m −2 s −1 ), but still had significantly higher ETR and chlorophyll a / b ratios. The electron transport rates, saturating light and chlorophyll a / b ratios of sun leaves from Mistletoes were similar to host shade leaves. These responses indicate that in comparison with their hosts, Mistletoe leaves have the photosynthetic characteristics of the leaves of shade plants.
Peter Bannister - One of the best experts on this subject based on the ideXlab platform.
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Water relations of temperate Mistletoes on various hosts.
Functional plant biology : FPB, 2002Co-Authors: Graham L. Strong, Peter BannisterAbstract:The daily field water relations and gas exchange of the temperate Mistletoes Ileostylus micranthus (Hook.f.) Tiegh. and Tupeia antarctica Cham. et Schlecht. on various hosts were examined seasonally in Dunedin, New Zealand during 1996–1998. Mistletoes commonly have higher transpiration rates (E) than their hosts, and this is generally cited as the reason why Mistletoes develop lower water potentials (ψ) than their hosts. The Mistletoe-host pairs that we examined showed no significant overall differences in E and stomatal conductance (g), and we used them to test the hypothesis that lowered ψ in Mistletoes result from higher E. Despite the lack of differences in E and g, osmotic potentials, predawn and daily minimum ψ (ψmin) were significantly more negative in Mistletoes, although differences between host and Mistletoe ψ were less on hosts with low osmotic potentials and ψ. Mistletoes maintained lower ψ than their hosts both when unshaded and under artificial shading, had lower ψ than hosts at equal E, but had shoot hydraulic resistances similar to that of their hosts. E and ψ of hosts and Mistletoes tended to be coordinated only in summer, when hosts were most water-stressed. Mistletoes maintained higher relative water contents at turgor loss, symplastic water contents, and bulk moduli of elasticity (e) than their hosts. We conclude that the lower ψ in these temperate Mistletoes are a consequence of greater Mistletoe E only when host ψ are low, but are otherwise maintained by greater succulence and higher e than in their hosts.
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Differential accumulation of nutrient elements in some New Zealand Mistletoes and their hosts.
Functional plant biology : FPB, 2002Co-Authors: Peter Bannister, Graham L. Strong, Inge AndrewAbstract:It has been generally assumed that differential accumulation of mineral nutrients, leading to greater accumulation of elements in Mistletoe tissues, is associated with greater transpiration in the Mistletoe than in the host. Only a few investigations have measured both tissue element concentrations and transpiration, or transpiration-related parameters such as carbon isotope ratios (δ13C). Seasonal means for foliar concentrations of Ca, Mg, K, Na, P, N, transpiration and δ13C were obtained from ten Mistletoe–host pairs, nine involving the Mistletoe Ileostylus micranthus and one with Tupeia antarctica. Annual means of transpiration and δ13C were similar in Mistletoes and hosts, but hosts showed greater variation in both transpiration and δ13C than Mistletoes. Foliar concentrations of Ca and Mg in Mistletoes were similar to those of their hosts, N concentrations were less, and foliar concentrations of K, Na and P were greater in Mistletoes than in their hosts. Ratios of foliar concentrations of Ca, Mg and P in Mistletoes to those in their hosts (M/H) were greatest when host transpiration was low, when host δ13C was least negative, and when the difference between Mistletoe and host δ13C was most negative. The lack of a phloem connection between host and Mistletoe, combined with circulation of elements in the host phloem and their transfer into the host xylem, provides a mechanism that explains the accumulation of phloem-mobile elements in the Mistletoe.
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Carbon and nitrogen isotope ratios, nitrogen content and heterotrophy in New Zealand Mistletoes
Oecologia, 2001Co-Authors: Peter Bannister, Graham L. StrongAbstract:The carbon isotope ratio (δ13C) of New Zealand Mistletoes (-29.51±0.10‰) and their hosts (-28.89±0.12‰) is generally more negative, and shows less difference between Mistletoes and their hosts, than found in previous studies. In 37% of the examined pairs, the δ13C of Mistletoes was less negative than that of their hosts. These reversals were not associated with the relative position (proximal or distal) of the host material with regard to the Mistletoe. Differences between host and Mistletoe tended to be greater on hosts with less negative δ13C. Both nitrogen content and isotope ratio (δ15N) of the Mistletoe leaves were strongly correlated with those of their hosts. Nitrogen contents of Mistletoe leaves were similar to those of their hosts at low nitrogen contents but proportionately less on hosts with a high nitrogen content, whereas δ15N of Mistletoes was consistently similar to that of their hosts. The δ13C of Mistletoes was related to both host nitrogen content and δ15N, but δ13C in host tissue was related to neither, suggesting that the Mistletoes derived both nitrogen and carbon from their hosts. The δ13C of both hosts and Mistletoes were significantly related to leaf conductance and carbon dioxide concentration but relationships with transpiration and water use efficiency were not significant. In all cases there was no clear separation between the responses of hosts and Mistletoes. This may be related to the similarity of stomatal conductance, transpiration and photosynthesis in the studied Mistletoes and their hosts and is consistent with the small differences in δ13C between Mistletoes and hosts found in this study. Consequently, the estimation of Mistletoe heterotrophy from carbon discrimination is confounded, as the small difference between host and Mistletoe carbon discrimination could equally well result from either similarities in photosynthesis and water relations or heterotrophic assimilation of host-derived carbon. The differences between our study and previous studies (which are mostly from seasonally dry or semi-arid to arid environments) may be related to the temperate environment in which these Mistletoes grow. Water is freely available so that the Mistletoe is able to obtain sufficient water and dissolved nutrients without having to maintain the high transpiration rate and low water potentials that are needed to extract water from a water-stressed host. Similarly, Mistletoe photosynthesis is less inhibited by water stress. The physiological similarities between Mistletoe and hosts from a temperate environment are reflected in their similar δ13C values.
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Are Mistletoes Shade Plants? CO2Assimilation and Chlorophyll Fluorescence of Temperate Mistletoes and their Hosts
Annals of Botany, 2000Co-Authors: Graham L. Strong, Peter Bannister, David J. BurrittAbstract:Abstract Mistletoes usually have slower rates of photosynthesis than their hosts. This study examines CO 2 assimilation, chlorophyll fluorescence and the chlorophyll content of temperate host–parasite pairs (nine hosts parasitized by Ileostylus micranthus and Carpodetus serratus parasitized by Tupeia antarctica ). The hosts of I. micranthus had higher mean annual CO 2 assimilation (3.59 ± 0.41 μmol m −2 s −1 ) than I. micranthus (2.42 ± 0.20 μmol m −2 s −1 ), and C. serratus (2.41 ± 0.43 μmol m −2 s −1 ) showed higher CO 2 assimilation than T. antarctica (0.67 ± 0.64 μmol m −2 s −1 ). Hosts saturated at significantly higher electron transport rates (ETR) and light levels than Mistletoes. The positive relationship between CO 2 assimilation and electron transport suggests that the lower CO 2 assimilation rates in Mistletoes are a consequence of lower electron transport rates. When photosynthetic rates, ETR and chlorophyll a / b ratios were adjusted for photosynthetically active radiation, hosts did not have significantly higher CO 2 assimilation (3.21 ± 0.37 μmol m −2 s −1 ) than Mistletoes (2.54 ± 0.41 μmol m −2 s −1 ), but still had significantly higher ETR and chlorophyll a / b ratios. The electron transport rates, saturating light and chlorophyll a / b ratios of sun leaves from Mistletoes were similar to host shade leaves. These responses indicate that in comparison with their hosts, Mistletoe leaves have the photosynthetic characteristics of the leaves of shade plants.
Julio J Camarero - One of the best experts on this subject based on the ideXlab platform.
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drought and Mistletoe reduce growth and water use efficiency of scots pine
Forest Ecology and Management, 2013Co-Authors: Gabriel Sanguesabarreda, Juan Carlos Linares, Julio J CamareroAbstract:Abstract To what extent do Mistletoes contribute to growth decline in drought-prone forests? Can the rising atmospheric CO2 concentrations offset the negative impacts of drought and Mistletoe infestation on tree growth? Long-term data on growth and intrinsic water use efficiency (iWUE) may allow answering both questions. We used dendrochronology to assess long-term changes in radial growth and iWUE in Scots pine (Pinus sylvestris) trees severely infested by Mistletoe (Viscum album) as compared to non-infested trees. The relationships among tree variables and Mistletoe infestation were quantified using structural equation models. Linear mixed-effects models of basal area increment as a function of climate were fitted to severely infested and non-infested trees. Infested trees showed higher stem and crown diameters because they grew faster than non-infested trees in the past. Mistletoe infestation enhanced defoliation and reduced radial growth for more than 10 years prior to sampling, while iWUE was significantly lower on severely infested trees only for the last 5 years. Severely infested trees had higher growth responsiveness to drought stress than non-infested trees. Although infested and non-infested trees displayed similar rising iWUE temporal trends, the combined effect of drought stress and Mistletoe infestation caused a reduction in growth and reversed the CO2-induced increase of iWUE in infested trees. We conclude that rising atmospheric CO2 concentrations cannot compensate for the impacts of drought and Mistletoe on tree growth and iWUE.
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Mistletoe effects on scots pine decline following drought events insights from within tree spatial patterns growth and carbohydrates
Tree Physiology, 2012Co-Authors: Gabriel Sanguesabarreda, Juan Carlos Linares, Julio J CamareroAbstract:Forest decline has been attributed to the interaction of several stressors including biotic factors such as Mistletoes and climate-induced drought stress. However, few data exist on how Mistletoes are spatially arranged within trees and how this spatial pattern is related to changes in radial growth, responses to drought stress and carbon use. We used dendrochronology to quantify how Mistletoe (Viscum album L.) infestation and drought stress affected long-term growth patterns in Pinus sylvestris L. at different heights. Basal area increment (BAI) trends and comparisons between trees of three different infestation degrees (without Mistletoe, ID1; moderately infested trees, ID2; and severely infested trees, ID3) were performed using linear mixed-effects models. To identify the main climatic drivers of tree growth tree-ring widths were converted into indexed chronologies and related to climate data using correlation functions. We performed spatial analyses of the 3D distribution of Mistletoe individuals and their ages within the crowns of three severely infested pines to describe their patterns. Lastly, we quantified carbohydrate and nitrogen concentrations in needles and sapwood of branches from severely infested trees and from trees without Mistletoe. Mistletoe individuals formed strongly clustered groups of similar age within tree crowns and their age increased towards the crown apex. Mistletoe infestation negatively impacted growth but this effect was stronger near the tree apex than in the rest of sampled heights, causing an average loss of 64% in BAI (loss of BAI was ∼51% at 1.3 m or near the tree base). We found that BAI of severely infested trees and moderately or non-infested trees diverged since 2001 and such divergence was magnified by drought. Infested trees had lower concentrations of soluble sugars in their needles than non-infested ones. We conclude that Mistletoe infestation causes growth decline and increases the sensitivity of trees to drought stress.
