Guy Robert D, Reid David M, Krouse H Roy
Biology Department, University of Calgary, T2N 1N4, Calgary, Alberta, Canada.
Physics Department, University of Calgary, T2N 1N4, Calgary, Alberta, Canada.
Oecologia. 1980 Jan;44(2):241-247. doi: 10.1007/BF00572686.
The total carbon δC values of two C halophytes,Salicornia europaea L. ssp.rubra (Nels.) Breitung andPuccinellia muttalliana (Schultes) Hitch., native to inland saline areas of Alberta, Canada, were determined for plants grown under controlled conditions of supplied NaCl in the nutrient solution, and for plants found growing in the field. Field specimens were collected along line transects which ran from areas of high salinity to areas of low salinity across the pattern of species zonation. The δC value of the two species seemed to reflect the water potential of the soil (ψ ) as measured arbitrarily at a depth of 10 cm, becoming less negative as the ψ decreased. Over a linear distance of 5.55 m,S. europaea spp.rubra showed a shift of +5.3‰ as the ψ went from-25x10 kPa to a minimum of-73x10 kPa. ForP. nuttalliana, the δC values differed by 3.4‰ over a distance of 7.45 m where the maximum difference in ψ was 12.7x10 kPa. However, δC values ofP. nuttalliana only roughly reflected the spatial trends in ψ at the time of collection. In the growth chamber, the δC value ofS. europaea ssp.rubra changed by a maximum of +8.0‰ when the solute potential of the nutrient solution (ψ ) was dropped from-0.25x10 kPa to-64.25x10 kPa; while the δC value ofP. nuttalliana changed by a maximum of +10.8‰ when the ψ was dropped from-0.25x10 kPa to-40.25x10 kPa. Linear regression analyses indicated that the δC values of both species were strongly correlated (P<0.2%) with ψ . The observed shifts in δC may represent changes in the mode of photosynthetic CO fixation. However, a number of other explanations, some of which are discussed in the text, are also possible. A proper ecophysiological interpretation of such shifts in δC values of C plants awaits a better understanding of the isotope fractionation mechanisms involved.
对加拿大艾伯塔省内陆盐碱地区的两种C4盐生植物——欧洲海蓬子（Salicornia europaea L. ssp. rubra (Nels.) Breitung）和穆氏碱茅（Puccinellia muttalliana (Schultes) Hitch.），测定了在营养液中供应不同NaCl浓度的受控条件下生长的植株以及田间生长植株的总碳δC值。田间样本是沿着从高盐度区域到低盐度区域穿过物种分带模式的样线采集的。这两个物种的δC值似乎反映了在10厘米深度任意测量的土壤水势（ψ），随着ψ降低，负值变小。在5.55米的直线距离上，随着ψ从-25×10³千帕降至最低-73×10³千帕，欧洲海蓬子ssp. rubra的δC值变化了+5.3‰。对于穆氏碱茅，在ψ最大差值为12.7×1平方厘米的7.45米距离内，δC值相差3.4‰。然而，穆氏碱茅的δC值仅大致反映了采集时ψ的空间趋势。在生长室中，当营养液的溶质势（ψs）从-0.25×10³千帕降至-64.25×10³千帕时，欧洲海蓬子ssp. rubra的δC值最大变化了+8.0‰；而当ψs从-0.25×10³千帕降至-40.25×10³千帕时，穆氏碱茅的δC值最大变化了+10.8‰。线性回归分析表明，两个物种的δC值与ψs都显著相关（P<0.2%）。观察到的δC变化可能代表光合CO₂固定模式的变化。然而，也有许多其他解释，其中一些在文中进行了讨论。对C4植物δC值这种变化进行恰当的生态生理学解释，有待于对所涉及的同位素分馏机制有更好的理解。
