We analysed Ball's empirical model of stomatal conductance (Ball, Woodrow and Berry, 1987). The o... more We analysed Ball's empirical model of stomatal conductance (Ball, Woodrow and Berry, 1987). The original interpretation was found to be flawed, and a new one is proposed which views the model as a description of the relationship between CO2 flux rate and stomatal conductance, rather than as a model of stomatal conductance alone. It is shown that this model is useful for describing changes in intercellular CO2 concentration. The model was tested against data from experiments in which the responses of stomatal conductance and CO2 flux density to humidity and temperature were measured in leaves of Hedera helix. It was found that the responses to temperature and humidity are not treated in a satisfactory way in the model whereas the response of the model to other variables is realistic. An alternative to Ball's model is described and tested. It is concluded that Ball's model is a useful starting point for development of simulation models to be used as submodels in canopy and regional models. However, as any empirical model, it is of no use for defining causal relationships.
The experiments and simulations reported in this paper show that, for stomata sensitive to both C... more The experiments and simulations reported in this paper show that, for stomata sensitive to both CO2 and water vapour concentrations, responses of stomatal conductance (gws) to boundary layer thickness have two components, one resulting from changes in intercellular CO2 concentration (χci) and another from changes in leaf surface water vapour saturation deficit (Dws). The experiments and simulations also show that the boundary layer conductance (gwb) can significantly alter the apparent response of gws to ambient air CO2 mole fraction (χca) and water vapour mole fraction (χwa). Because of the feedback loop involved the responses of gws for χca and χwa each include responses to both χci and Dws. The boundary layer alters the state of the variables sensed by the guard cells—i.e. χci and Dws—and so it is a source of feedback. Thus, when scaling up from responses of stomata to the response of gws for a whole leaf, the effect of the boundary layer must be considered. The results indicate that, for given responses of gws to χci and Dws, the apparent responses of gws to Dwa and χca depend on the size of the leaf and wind speed, showing that this effect of the boundary layer should be considered when comparing data measured under different conditions, or with different methods.
Abstract. The objective of the work reported was to answer the following questions: (1) Do stomat... more Abstract. The objective of the work reported was to answer the following questions: (1) Do stomata respond to both humidity and temperature? (2) Do these responses interact in such a way that relative humidity at the leaf surface is a more appropriate variable than water vapour saturation deficit at the leaf surface and yields a simpler description of the compound response? To answer these questions, we measured the response of leaf conductance to humidity under constant leaf temperature, and the response to increasing leaf temperature under constant relative humidity and under constant water vapour saturation deficit. We found that, in Hedera helix subsp. canariensis (Willd.) Coutinho, there was a reversible response to humidity under constant temperature, and that there was also a response to temperature under constant relative humidity. The relationship between leaf conductance and relative humidity was different when measured at the same temperature rather than at different temperatures. An inversely proportional response was consistently obtained when stomatal conductance was expressed in relation to water vapour saturation deficit. The interaction between the effects of leaf temperature and water vapour saturation deficit was not compatible with a mechanism of response to humidity and temperature based solely on relative humidity. From these data, we conclude that water vapour saturation deficit is a more appropriate variable for describing stomatal responses to humidity.
Tulevaisuuden ilmastossa eri kasvutekijät eivät välttämättä korreloi toistensa kanssa samalla tav... more Tulevaisuuden ilmastossa eri kasvutekijät eivät välttämättä korreloi toistensa kanssa samalla tavalla kuin tällä hetkellä, ja kokeellisella tutkimuksella voidaan selvittää puiden menestymistä uusissa olosuhteissa. Joensuun dasotronit ovat erikoisvalmisteisia kasvukammioita, joissa ilman ja maan lämpötilaa voidaan säädellä erikseen, samoin kuin valotasoa, päivänpituutta ja ilman kosteutta.
Abstract In contrast to earlier beliefs, it is now known that boron (B) can be retranslocated com... more Abstract In contrast to earlier beliefs, it is now known that boron (B) can be retranslocated complexed with sugar alcohols in some plant species. Conifers had been thought not to translocate sugar alcohols in the phloem. However, 1 d after applying 10 B enriched boric acid to shoots of Scots pine and Norway spruce seedlings, we found increases in both the amount and proportion of 10 B in the root systems in both species.
Abstract Soil temperature is a main factor limiting root growth in the boreal forest. To simulate... more Abstract Soil temperature is a main factor limiting root growth in the boreal forest. To simulate the possible soil-warming effect of future climate change, 5-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were subjected to three simulated growing seasons in controlled environment rooms. The seedlings were acclimated to a soil temperature of 16 C during the first (GS I) and third growing seasons (GS III), but were assigned to random soil-temperature treatments of 9, 13, 18 and 21 C during the second growing season (GS II).
Abstract We analysed Ball's empirical model of stomatal conductance (Ball, Woodrow and Berry, 198... more Abstract We analysed Ball's empirical model of stomatal conductance (Ball, Woodrow and Berry, 1987). The original interpretation was found to be flawed, and a new one is proposed which views the model as a description of the relationship between CO 2 flux rate and stomatal conductance, rather than as a model of stomatal conductance alone. It is shown that this model is useful for describing changes in intercellular CO 2 concentration.
Abstract Photomorphogenic responses triggered by low fluence rates of ultraviolet B radiation (UV... more Abstract Photomorphogenic responses triggered by low fluence rates of ultraviolet B radiation (UV-B; 280–315 nm) are mediated by the UV-B photoreceptor UV RESISTANCE LOCUS8 (UVR8). Beyond our understanding of the molecular mechanisms of UV-B perception by UVR8, there is still limited information on how the UVR8 pathway functions under natural sunlight.
Abstract We studied the effects of light quality and nutrient supply on growth and nitrogen accum... more Abstract We studied the effects of light quality and nutrient supply on growth and nitrogen accumulation in silver birch (Betula pendula Roth) seedlings to test three hypotheses:(1) growth of birch seedlings is sensitive to changes in light quality;(2) the response of birch seedling growth to light quality depends on nutrient supply; and (3) assimilation and allocation of nitrogen by birch seedlings are affected by light quality.
Abstract Five-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were subjected to three ... more Abstract Five-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were subjected to three simulated growing seasons in controlled environment chambers. Plants were acclimated to a soil temperature of 16 C during the first and third growing seasons, but were allocated at random to soil temperature treatments of 9, 13, 18 and 21 C during the second growing season.
Seasonal variation in leaf phenolic composition may be important for acclimation of plants to sea... more Seasonal variation in leaf phenolic composition may be important for acclimation of plants to seasonal changes in their biotic and abiotic environment. For a realistic assessment of how plants respond to solar UV-B (280-315 nm) and UV-A (315-400 nm) radiation, seasonal variation in both environment and plant responses needs to be taken into account. This also has implications for studies concerning stratospheric ozone depletion and resulting increased UV-B radiation, as other environmental variables and/or plant phenology could interact with UV radiation. To elucidate this, we established a field experiment using plastic films attenuating different parts of the solar UV spectrum. The concentration of individual phenolic compounds was measured during one growing season in leaves of grey alder (Alnus incana) and white birch (Betula pubescens) trees. Our results showed changes in concentration of, e.g. hydrolyzable tannins in birch that suggest an effect of UV-A alone and e.g. chlorogenic acids in alder indicate a quadratic effect of UV-B irradiance and both linear and quadratic effect for UV-A in second-degree polynomial fits. Further, there was interaction between treatment and sampling time for some individual metabolites; hence, the UV response varied during the season. In addition to the UV effects, three temporal patterns emerged in the concentrations of particular groups of phenolics. Possible implications for both sampling methods and timing are discussed. Moreover, our results highlight differences in responses of the two tree species, which are taken to indicate differences in their ecological niche differentiation.
Go to AGRIS search. Silva Fennica (2002). Leaf life span and the mobility of "non-mo... more Go to AGRIS search. Silva Fennica (2002). Leaf life span and the mobility of "non-mobile" mineral nutrients : the case of boron in conifers. ...
We examined the quality and decomposition of naturally abscised leaves of silver birch (Betula pe... more We examined the quality and decomposition of naturally abscised leaves of silver birch (Betula pendula) seedlings subjected to three different levels of fertilization under ambient and elevated levels of temperature and CO2. At the end of the second growing season, the chemical composition of the litter collected from the seedlings was analyzed. Whole-leaf samples from pooled litter from each of
We analysed Ball's empirical model of stomatal conductance (Ball, Woodrow and Berry, 1987). The o... more We analysed Ball's empirical model of stomatal conductance (Ball, Woodrow and Berry, 1987). The original interpretation was found to be flawed, and a new one is proposed which views the model as a description of the relationship between CO2 flux rate and stomatal conductance, rather than as a model of stomatal conductance alone. It is shown that this model is useful for describing changes in intercellular CO2 concentration. The model was tested against data from experiments in which the responses of stomatal conductance and CO2 flux density to humidity and temperature were measured in leaves of Hedera helix. It was found that the responses to temperature and humidity are not treated in a satisfactory way in the model whereas the response of the model to other variables is realistic. An alternative to Ball's model is described and tested. It is concluded that Ball's model is a useful starting point for development of simulation models to be used as submodels in canopy and regional models. However, as any empirical model, it is of no use for defining causal relationships.
The experiments and simulations reported in this paper show that, for stomata sensitive to both C... more The experiments and simulations reported in this paper show that, for stomata sensitive to both CO2 and water vapour concentrations, responses of stomatal conductance (gws) to boundary layer thickness have two components, one resulting from changes in intercellular CO2 concentration (χci) and another from changes in leaf surface water vapour saturation deficit (Dws). The experiments and simulations also show that the boundary layer conductance (gwb) can significantly alter the apparent response of gws to ambient air CO2 mole fraction (χca) and water vapour mole fraction (χwa). Because of the feedback loop involved the responses of gws for χca and χwa each include responses to both χci and Dws. The boundary layer alters the state of the variables sensed by the guard cells—i.e. χci and Dws—and so it is a source of feedback. Thus, when scaling up from responses of stomata to the response of gws for a whole leaf, the effect of the boundary layer must be considered. The results indicate that, for given responses of gws to χci and Dws, the apparent responses of gws to Dwa and χca depend on the size of the leaf and wind speed, showing that this effect of the boundary layer should be considered when comparing data measured under different conditions, or with different methods.
Abstract. The objective of the work reported was to answer the following questions: (1) Do stomat... more Abstract. The objective of the work reported was to answer the following questions: (1) Do stomata respond to both humidity and temperature? (2) Do these responses interact in such a way that relative humidity at the leaf surface is a more appropriate variable than water vapour saturation deficit at the leaf surface and yields a simpler description of the compound response? To answer these questions, we measured the response of leaf conductance to humidity under constant leaf temperature, and the response to increasing leaf temperature under constant relative humidity and under constant water vapour saturation deficit. We found that, in Hedera helix subsp. canariensis (Willd.) Coutinho, there was a reversible response to humidity under constant temperature, and that there was also a response to temperature under constant relative humidity. The relationship between leaf conductance and relative humidity was different when measured at the same temperature rather than at different temperatures. An inversely proportional response was consistently obtained when stomatal conductance was expressed in relation to water vapour saturation deficit. The interaction between the effects of leaf temperature and water vapour saturation deficit was not compatible with a mechanism of response to humidity and temperature based solely on relative humidity. From these data, we conclude that water vapour saturation deficit is a more appropriate variable for describing stomatal responses to humidity.
Tulevaisuuden ilmastossa eri kasvutekijät eivät välttämättä korreloi toistensa kanssa samalla tav... more Tulevaisuuden ilmastossa eri kasvutekijät eivät välttämättä korreloi toistensa kanssa samalla tavalla kuin tällä hetkellä, ja kokeellisella tutkimuksella voidaan selvittää puiden menestymistä uusissa olosuhteissa. Joensuun dasotronit ovat erikoisvalmisteisia kasvukammioita, joissa ilman ja maan lämpötilaa voidaan säädellä erikseen, samoin kuin valotasoa, päivänpituutta ja ilman kosteutta.
Abstract In contrast to earlier beliefs, it is now known that boron (B) can be retranslocated com... more Abstract In contrast to earlier beliefs, it is now known that boron (B) can be retranslocated complexed with sugar alcohols in some plant species. Conifers had been thought not to translocate sugar alcohols in the phloem. However, 1 d after applying 10 B enriched boric acid to shoots of Scots pine and Norway spruce seedlings, we found increases in both the amount and proportion of 10 B in the root systems in both species.
Abstract Soil temperature is a main factor limiting root growth in the boreal forest. To simulate... more Abstract Soil temperature is a main factor limiting root growth in the boreal forest. To simulate the possible soil-warming effect of future climate change, 5-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were subjected to three simulated growing seasons in controlled environment rooms. The seedlings were acclimated to a soil temperature of 16 C during the first (GS I) and third growing seasons (GS III), but were assigned to random soil-temperature treatments of 9, 13, 18 and 21 C during the second growing season (GS II).
Abstract We analysed Ball's empirical model of stomatal conductance (Ball, Woodrow and Berry, 198... more Abstract We analysed Ball's empirical model of stomatal conductance (Ball, Woodrow and Berry, 1987). The original interpretation was found to be flawed, and a new one is proposed which views the model as a description of the relationship between CO 2 flux rate and stomatal conductance, rather than as a model of stomatal conductance alone. It is shown that this model is useful for describing changes in intercellular CO 2 concentration.
Abstract Photomorphogenic responses triggered by low fluence rates of ultraviolet B radiation (UV... more Abstract Photomorphogenic responses triggered by low fluence rates of ultraviolet B radiation (UV-B; 280–315 nm) are mediated by the UV-B photoreceptor UV RESISTANCE LOCUS8 (UVR8). Beyond our understanding of the molecular mechanisms of UV-B perception by UVR8, there is still limited information on how the UVR8 pathway functions under natural sunlight.
Abstract We studied the effects of light quality and nutrient supply on growth and nitrogen accum... more Abstract We studied the effects of light quality and nutrient supply on growth and nitrogen accumulation in silver birch (Betula pendula Roth) seedlings to test three hypotheses:(1) growth of birch seedlings is sensitive to changes in light quality;(2) the response of birch seedling growth to light quality depends on nutrient supply; and (3) assimilation and allocation of nitrogen by birch seedlings are affected by light quality.
Abstract Five-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were subjected to three ... more Abstract Five-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were subjected to three simulated growing seasons in controlled environment chambers. Plants were acclimated to a soil temperature of 16 C during the first and third growing seasons, but were allocated at random to soil temperature treatments of 9, 13, 18 and 21 C during the second growing season.
Seasonal variation in leaf phenolic composition may be important for acclimation of plants to sea... more Seasonal variation in leaf phenolic composition may be important for acclimation of plants to seasonal changes in their biotic and abiotic environment. For a realistic assessment of how plants respond to solar UV-B (280-315 nm) and UV-A (315-400 nm) radiation, seasonal variation in both environment and plant responses needs to be taken into account. This also has implications for studies concerning stratospheric ozone depletion and resulting increased UV-B radiation, as other environmental variables and/or plant phenology could interact with UV radiation. To elucidate this, we established a field experiment using plastic films attenuating different parts of the solar UV spectrum. The concentration of individual phenolic compounds was measured during one growing season in leaves of grey alder (Alnus incana) and white birch (Betula pubescens) trees. Our results showed changes in concentration of, e.g. hydrolyzable tannins in birch that suggest an effect of UV-A alone and e.g. chlorogenic acids in alder indicate a quadratic effect of UV-B irradiance and both linear and quadratic effect for UV-A in second-degree polynomial fits. Further, there was interaction between treatment and sampling time for some individual metabolites; hence, the UV response varied during the season. In addition to the UV effects, three temporal patterns emerged in the concentrations of particular groups of phenolics. Possible implications for both sampling methods and timing are discussed. Moreover, our results highlight differences in responses of the two tree species, which are taken to indicate differences in their ecological niche differentiation.
Go to AGRIS search. Silva Fennica (2002). Leaf life span and the mobility of "non-mo... more Go to AGRIS search. Silva Fennica (2002). Leaf life span and the mobility of "non-mobile" mineral nutrients : the case of boron in conifers. ...
We examined the quality and decomposition of naturally abscised leaves of silver birch (Betula pe... more We examined the quality and decomposition of naturally abscised leaves of silver birch (Betula pendula) seedlings subjected to three different levels of fertilization under ambient and elevated levels of temperature and CO2. At the end of the second growing season, the chemical composition of the litter collected from the seedlings was analyzed. Whole-leaf samples from pooled litter from each of
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