Viktor A, Cramer M D
Botany Department, University of Stellenbosch, Private Bag XI, Matieland 7602 South Africa.
New Phytol. 2003 Jan;157(1):45-54. doi: 10.1046/j.1469-8137.2003.00650.x.
• The contribution to the carbon budget and growth by root acquisition of inorganic carbon and the influence that this has on NO and NH uptake and assimilation has not been adequately quantified. • The influence of varying root-zone CO concentrations on tissue δ C and δ N was used to estimate the contribution to the carbon budget of root-assimilated carbon in tomato ( Lycopersicon esculentum ) seedlings. • Biomass accumulation was greater at 0.5% and 1% (v/v) root-zone CO in NO and NH -fed plants than with 0% root-zone CO . The plant δ C values were not altered by 1% CO with δ C = -29.00‰, but they were increased when supplied with 1% CO with δ C = -10.91‰. The δ N values of NO -fed plants were unchanged by variation in root-zone CO concentration. In NH -fed plants the δ N values were c. 1.5‰ higher at 1% CO . • Changes in δ C values with increased CO concentration (δ C = -10.91‰) were ascribed to root incorporation of CO . Less than 5% of carbon was derived from root dark fixation and thus cannot explain increases in growth on a mass basis. Reduced discrimination with NH nutrition at 1% CO could be related to increased exudation of NH and organic nitrogen and also reduced uptake.
• 通过根系获取无机碳对碳预算和生长的贡献以及这对硝酸盐和铵盐吸收与同化的影响尚未得到充分量化。
• 利用根际不同二氧化碳浓度对组织δ¹³C和δ¹⁵N的影响来估算番茄（Lycopersicon esculentum）幼苗根系同化碳对碳预算的贡献。
• 在供应硝酸盐和铵盐的植株中，根际二氧化碳浓度为0.5%和1%（体积/体积）时的生物量积累大于根际二氧化碳浓度为0%时。植物的δ¹³C值在二氧化碳浓度为1%（δ¹³C = -29.00‰）时未改变，但在二氧化碳浓度为1%（δ¹³C = -10.91‰）时升高。供应硝酸盐的植株的δ¹⁵N值不受根际二氧化碳浓度变化的影响。在供应铵盐的植株中，二氧化碳浓度为1%时的δ¹⁵N值约高1.5‰。
• 随着二氧化碳浓度升高（δ¹³C = -10.91‰），δ¹³C值的变化归因于根系对二氧化碳的固定。少于5%的碳来自根系暗固定，因此无法解释基于质量的生长增加。在二氧化碳浓度为1%时，铵盐营养条件下的分馏降低可能与铵盐和有机氮渗出增加以及吸收减少有关。
