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.
