Influences of temperature, humidity, and CO2 concentration on the photosynthesis and respiration of three-year-oldBetula platyphylla was investigated. Light compensation point, saturation point and CO2 compensation po...Influences of temperature, humidity, and CO2 concentration on the photosynthesis and respiration of three-year-oldBetula platyphylla was investigated. Light compensation point, saturation point and CO2 compensation point were also determined. The results showed that the optimal temperature of photosynthesis and dark respiration was 24 °C and 30 °C, respectively, at ambient CO2. When relative humidity was 80%,Betula platyphylla could maintain strong photosynthesis. There was no significant correlation between respiration and relative humidity. The light compensation and saturation point was 25 μmol·m?2·s?1 and 1 375 μmol·m?2·s?1, respectively. The CO2 compensation point was 180 μL·L?1. The results showed thatBetula platyphylla still had potential to assimilate CO2 when CO2 concentration was above 2 400 μL·L?1.展开更多
Under high light conditions, ammonium nutrition has a negative effect on plant growth. This suggests that the adverse effects of ammonium nutrition on plant growth may be related to carbon gain, photosynthesis, and ph...Under high light conditions, ammonium nutrition has a negative effect on plant growth. This suggests that the adverse effects of ammonium nutrition on plant growth may be related to carbon gain, photosynthesis, and photorespiration. However, there is no consistent evidence of a specific mechanism that could explain the plant growth reduction under ammonium supply. It is generally accepted that during the light reaction, a surplus of nicotinamide adenine dinucleotide hydrogen phosphate （NADPH） is produced, which is not completely used during the assimilation of CO2, Nitrate reduc- tion in the leaf represents an additional sink for NADPH that is not available to ammonium-grown plants. Nitrate and ammonium nutrition may use different pathways for NADPH consumption, which leads to differences in photosynthesis and photorespiration. The morphological （i.e., cell size, mesophyll thickness, and chloroplast volume） and enzymic （i.e., ribulose-1,5-bisphosphate carboxylase/oxygenase （Rubisco）, phosphoenolpyruvate carboxylase （PEPCase）, and glutamine synthetase/glutamate synthetase （GS/GOGAT）） differences that develop when plants are treated with either nitrate or ammonium nitrogen forms are related to photosynthesis and photorespiration. The differences in photorespiration rate for plants treated with nitrate or ammonium are related to the conversion of citrate to 2-oxoglutarate （2-OG） and photorespiratory CO2 refixation.展开更多
Soil respiration induced by soybean cultivation over its entire growing season and the factors influencing soil respiration were investigated to examine the seasonal pattern of soil respiration induced by soybean cult...Soil respiration induced by soybean cultivation over its entire growing season and the factors influencing soil respiration were investigated to examine the seasonal pattern of soil respiration induced by soybean cultivation, explore soybean growth and photosynthesis on soil respiration, and determine the temperature dependence on soil respiration. Soil respiration in a pot experiment with and without soybean plants was sampled using the static chamber method and measured using gas chromatograph. Air temperature was a dominant factor controlling soil respiration rate in unplanted soil. Additionally, rhizosphere respiration comprised 62% to 98% of the soil respiration rate in the soybean-planted soil varying with the soybean growth stages. Harvesting aerial parts of soybean plant caused an immediate drop in the soil respiration rate at that stage. After harvesting the aerial parts of the soybean plant, a highly significant correlation between soil respiration rate and air temperature was found at the flowering stage （P 〈 0.01）, the pod stage （P 〈 0.01）, and the seed-filling stage （P 〈 0.05）. Thus, rhizosphere respiration during the soybean-growing period not only made a great contribution to soil respiration, but also determined the seasonal variation pattern of the soll respiration rate.展开更多
Aims Black spruce(Picea mariana[Mill.]B.S.P.)and white spruce(Picea glauca[Moench]Voss.)are congeneric species.Both are moderately shade tolerant and widely distributed across North American boreal forests.Methods To ...Aims Black spruce(Picea mariana[Mill.]B.S.P.)and white spruce(Picea glauca[Moench]Voss.)are congeneric species.Both are moderately shade tolerant and widely distributed across North American boreal forests.Methods To understand light effects on their ecophysiological responses to elevated CO_(2),1-year-old seedlings were exposed to 360µmol mol−1 and 720µmol mol−1 CO_(2)at three light conditions(100%,50%and 30%of full light in the greenhouse).Foliar gas exchanges were measured in the mid-and late-growing season.Important Findings Elevated CO_(2)increased net photosynthesis(Pn)and photosynthetic water use efficiency,but it reduced stomatal conductance and transpiration.The stimulation of photosynthesis by elevated CO_(2)was greatest at 50%light and smallest at 100%.Photosynthesis,maximum carboxylation rate(Vcmax)and light-saturated rate of electron transport(Jmax)all decreased with decreasing light.Elevated CO_(2)significantly reduced Vcmax across all light treatments and both species in mid-growing season.However,the effect of elevated CO_(2)became insignificant at 30%light later in the growing season,with the response being greater in black spruce than in white spruce.Elevated CO_(2)also reduced Jmax in white spruce in both measurements while the effect became insignificant at 30%light later in the growing season.However,the effect on black spruce varied with time.Elevated CO_(2)reduced Jmax in black spruce in mid-growing season in all light treatments and the effect became insignificant at 30%light later in the growing season,while it increased Jmax later in the season at 100%and 50%light.These results suggest that both species benefited from elevated CO_(2),and that the responses varied with light supply,such that the response was primarily physiological at 100%and 50%light,while it was primarily morphological at 30%light.展开更多
基金This paper was supported by the National Natural Science Foundation of China (No. 39970627) and the Key Project of State Department of Science Technology (2002BA515B05).
文摘Influences of temperature, humidity, and CO2 concentration on the photosynthesis and respiration of three-year-oldBetula platyphylla was investigated. Light compensation point, saturation point and CO2 compensation point were also determined. The results showed that the optimal temperature of photosynthesis and dark respiration was 24 °C and 30 °C, respectively, at ambient CO2. When relative humidity was 80%,Betula platyphylla could maintain strong photosynthesis. There was no significant correlation between respiration and relative humidity. The light compensation and saturation point was 25 μmol·m?2·s?1 and 1 375 μmol·m?2·s?1, respectively. The CO2 compensation point was 180 μL·L?1. The results showed thatBetula platyphylla still had potential to assimilate CO2 when CO2 concentration was above 2 400 μL·L?1.
基金Project supported by the National Basic Research Program of China (No.2005CB121101)National Natural Science Foundation of China (Nos.30400279 and 30671233)International Foundation for Science (IFS)(No.C/3799-1)
文摘Under high light conditions, ammonium nutrition has a negative effect on plant growth. This suggests that the adverse effects of ammonium nutrition on plant growth may be related to carbon gain, photosynthesis, and photorespiration. However, there is no consistent evidence of a specific mechanism that could explain the plant growth reduction under ammonium supply. It is generally accepted that during the light reaction, a surplus of nicotinamide adenine dinucleotide hydrogen phosphate （NADPH） is produced, which is not completely used during the assimilation of CO2, Nitrate reduc- tion in the leaf represents an additional sink for NADPH that is not available to ammonium-grown plants. Nitrate and ammonium nutrition may use different pathways for NADPH consumption, which leads to differences in photosynthesis and photorespiration. The morphological （i.e., cell size, mesophyll thickness, and chloroplast volume） and enzymic （i.e., ribulose-1,5-bisphosphate carboxylase/oxygenase （Rubisco）, phosphoenolpyruvate carboxylase （PEPCase）, and glutamine synthetase/glutamate synthetase （GS/GOGAT）） differences that develop when plants are treated with either nitrate or ammonium nitrogen forms are related to photosynthesis and photorespiration. The differences in photorespiration rate for plants treated with nitrate or ammonium are related to the conversion of citrate to 2-oxoglutarate （2-OG） and photorespiratory CO2 refixation.
基金Project supported by the National Science Fund for Distinguished Young Scholars (No. 40125004)the KnowledgeInnovation Project of Chinese Academy of Sciences (No. KZCX1-SW-01-05).
文摘Soil respiration induced by soybean cultivation over its entire growing season and the factors influencing soil respiration were investigated to examine the seasonal pattern of soil respiration induced by soybean cultivation, explore soybean growth and photosynthesis on soil respiration, and determine the temperature dependence on soil respiration. Soil respiration in a pot experiment with and without soybean plants was sampled using the static chamber method and measured using gas chromatograph. Air temperature was a dominant factor controlling soil respiration rate in unplanted soil. Additionally, rhizosphere respiration comprised 62% to 98% of the soil respiration rate in the soybean-planted soil varying with the soybean growth stages. Harvesting aerial parts of soybean plant caused an immediate drop in the soil respiration rate at that stage. After harvesting the aerial parts of the soybean plant, a highly significant correlation between soil respiration rate and air temperature was found at the flowering stage （P 〈 0.01）, the pod stage （P 〈 0.01）, and the seed-filling stage （P 〈 0.05）. Thus, rhizosphere respiration during the soybean-growing period not only made a great contribution to soil respiration, but also determined the seasonal variation pattern of the soll respiration rate.
基金by Natural Sciences and Engineering Research Council of Canada Discovery grants to Q.L.Dang(Project No.203198-2013-RGPIN)Lakehead University Graduate Assistantships to J.Marfo.
文摘Aims Black spruce(Picea mariana[Mill.]B.S.P.)and white spruce(Picea glauca[Moench]Voss.)are congeneric species.Both are moderately shade tolerant and widely distributed across North American boreal forests.Methods To understand light effects on their ecophysiological responses to elevated CO_(2),1-year-old seedlings were exposed to 360µmol mol−1 and 720µmol mol−1 CO_(2)at three light conditions(100%,50%and 30%of full light in the greenhouse).Foliar gas exchanges were measured in the mid-and late-growing season.Important Findings Elevated CO_(2)increased net photosynthesis(Pn)and photosynthetic water use efficiency,but it reduced stomatal conductance and transpiration.The stimulation of photosynthesis by elevated CO_(2)was greatest at 50%light and smallest at 100%.Photosynthesis,maximum carboxylation rate(Vcmax)and light-saturated rate of electron transport(Jmax)all decreased with decreasing light.Elevated CO_(2)significantly reduced Vcmax across all light treatments and both species in mid-growing season.However,the effect of elevated CO_(2)became insignificant at 30%light later in the growing season,with the response being greater in black spruce than in white spruce.Elevated CO_(2)also reduced Jmax in white spruce in both measurements while the effect became insignificant at 30%light later in the growing season.However,the effect on black spruce varied with time.Elevated CO_(2)reduced Jmax in black spruce in mid-growing season in all light treatments and the effect became insignificant at 30%light later in the growing season,while it increased Jmax later in the season at 100%and 50%light.These results suggest that both species benefited from elevated CO_(2),and that the responses varied with light supply,such that the response was primarily physiological at 100%and 50%light,while it was primarily morphological at 30%light.
