Kleiner Karl W, Raffa Kenneth F, Dickson Richard E
Department of Entomology, University of Wisconsin, Madison, WI 53706, USA, , , , , , US.
USDA Forest Service, North Central Forest Research Station, Forestry Sciences Laboratory, 5985 Highway K, Rhinelander, WI 54501, USA, , , , , , US.
Oecologia. 1999 May;119(3):408-418. doi: 10.1007/s004420050802.
Theories on allelochemical concentrations in plants are often based upon the relative carbon costs and benefits of multiple metabolic fractions. Tests of these theories often rely on measuring metabolite concentrations, but frequently overlook priorities in carbon partitioning. We conducted a pulse-labeling experiment to follow the partitioning of CO-labeled photosynthate into ten metabolic pools representing growth and maintenance (amino acids, organic acids, lipids plus pigments, protein, residue), defense (phenolic glycosides, methanol:water and acetone-soluble tannins/phenolics), and transport and storage (sugars and starch) in source and importing sink leaves of quaking aspen (Populus tremuloides). The peak period of C incorporation into sink leaves occurred at 24 h. Within 48 h of labeling, the specific radioactivity (dpm/mg dry leaf weight) of phenolic glycosides declined by over one-third in source and sink leaves. In addition, the specific radioactivity in the tannin/phenolic fraction decreased by 53% and 28% in source and sink leaves, respectively. On a percent recovery basis, sink leaves partitioned 1.7 times as much labeled photosynthate into phenolic glycosides as source leaves at peak C incorporation. In contrast, source leaves partitioned 1.8 times as much C-labeled photosynthate into tannins/phenolics as importing sink leaves. At the end of the 7-day chase period, sink leaves retained 18%, 52%, and 30% of imported C photosynthate, and labeled source leaves retained 15%, 66%, and 19% of in situ photosynthate in metabolic fractions representing transport and storage, growth and maintenance, and defense, respectively. Analyses of the phenolic fractions showed that total phenolics were twice as great and condensed tannins were 1.7 times greater in sink than in source leaves. The concentration of total phenolics and condensed tannins did not change in source and sink leaves during the 7-day chase period.
关于植物中化感物质浓度的理论通常基于多种代谢组分的相对碳成本和收益。这些理论的验证往往依赖于测量代谢物浓度，但常常忽略了碳分配的优先级。我们进行了一项脉冲标记实验，以追踪CO标记的光合产物在颤杨（Populus tremuloides）的源叶和输入库叶中分配到代表生长和维持（氨基酸、有机酸、脂质加色素、蛋白质、残渣）、防御（酚糖苷、甲醇：水和丙酮可溶性单宁/酚类）以及运输和储存（糖和淀粉）的十个代谢库中的情况。光合产物进入库叶的高峰期出现在24小时。在标记后的48小时内，酚糖苷的比放射性（dpm/毫克干叶重）在源叶和库叶中均下降了三分之一以上。此外，单宁/酚类组分中的比放射性在源叶和库叶中分别下降了53%和28%。在光合产物掺入高峰期，以回收百分比计算，库叶分配到酚糖苷中的标记光合产物是源叶的1.7倍。相反，源叶分配到单宁/酚类中的C标记光合产物是输入库叶的1.8倍。在7天的追踪期结束时，库叶分别保留了18%、52%和30%的输入C光合产物，而标记的源叶在代表运输和储存、生长和维持以及防御的代谢组分中分别保留了15%、66%和19%的原位光合产物。对酚类组分的分析表明，库叶中的总酚含量是源叶的两倍，缩合单宁含量是源叶的1.7倍。在7天的追踪期内，源叶和库叶中的总酚和缩合单宁浓度没有变化。
