Berveiller Daniel, Kierzkowski Daniel, Damesin Claire
Laboratoire Ecologie, Systématique et Evolution (ESE), CNRS & Université Paris Sud, Bâtiment 362, 91405 Orsay Cedex, France.
Tree Physiol. 2007 Jan;27(1):53-61. doi: 10.1093/treephys/27.1.53.
The photosynthetic characteristics of current-year stems of six deciduous tree species, two evergreen tree species and ginkgo (Ginkgo biloba L.) were compared. Gas exchange, chlorophyll concentration, nitrogen concentration and maximum quantum yield of PSII were measured in stems in summer and winter. A light-induced decrease in stem CO(2) efflux was observed in all species. The apparent gross photosynthetic rate in saturating light ranged from 0.72 micromol m(-2 )s(-1) (ginkgo, in winter) to 3.73 micromol m(-2) s(-1) (Alnus glutinosa (L.) Gaertn., in summer). Despite this variability, a unique correlation (slope = 0.75), based on our results and those reported in the literature, was found between gross photosynthetic rate and dark respiration rate. Mass-based gross photosynthetic rate decreased with stem mass per area and correlated to chlorophyll concentration and nitrogen concentration, both in summer and winter. The radial distribution of stem chlorophyll differed among species, but all species except ginkgo had chlorophyll as deep as the pith. In summer, the maximum quantum yield of stem PSII (estimated from the ratio of variable to maximal fluorescence; F (v)/F (m)) of all species was near the optimal value found for leaves. By contrast, the values were highly variable in winter, suggesting large differences in sensitivity to low-temperature photoinhibition. The winter values of Fv/Fm were only 31-60% of summer values for the deciduous species, whereas the evergreen conifer species maintained high F (v)/F (m) in winter. The results highlight the interspecific variability of gross photosynthesis in the stem and its correlation with structural traits like those found for leaves. The structural correlations suggest that the selection of photosynthetic traits has operated under similar constraints in stems and leaves.
比较了六种落叶树种、两种常绿树种和银杏（Ginkgo biloba L.）当年生茎的光合特性。在夏季和冬季测量了茎中的气体交换、叶绿素浓度、氮浓度和PSII的最大量子产率。在所有物种中均观察到光诱导的茎CO₂ 通量下降。饱和光下的表观总光合速率范围为0.72微摩尔·米⁻²·秒⁻¹（银杏，冬季）至3.73微摩尔·米⁻²·秒⁻¹（欧洲桤木（Alnus glutinosa (L.) Gaertn.），夏季）。尽管存在这种变异性，但根据我们的结果和文献报道，发现总光合速率与暗呼吸速率之间存在独特的相关性（斜率 = 0.75）。基于单位面积茎质量的总光合速率随茎质量下降，并与夏季和冬季的叶绿素浓度和氮浓度相关。不同物种茎叶绿素的径向分布有所不同，但除银杏外，所有物种的叶绿素都深至髓心。在夏季，所有物种茎PSII的最大量子产率（根据可变荧光与最大荧光的比率估算；F(v)/F(m)）接近叶片的最佳值。相比之下，冬季这些值变化很大，表明对低温光抑制的敏感性存在很大差异。落叶树种的Fv/Fm冬季值仅为夏季值的31 - 60%，而常绿针叶树种在冬季保持较高的F(v)/F(m)。结果突出了茎中总光合作用的种间变异性及其与叶片结构特征的相关性。结构相关性表明，光合特性的选择在茎和叶中受到类似的限制。
