Jonasson Sven, Stuart Chapin F
Institute of Plant Ecology, University of Copenhagen, Øster Farimagsgade 2D, DK-1353 Copenhagen K. Denmark.
Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
New Phytol. 1991 Jun;118(2):349-357. doi: 10.1111/j.1469-8137.1991.tb00987.x.
Seasonal measurements of phosphorus (P) pools in the tussock-forming sedge Eriophorum vaginatum L. indicated low annual P uptake, but pronounced fluxes of P to growing biomass from below-ground stores in spring, and a return in autumn. Additions of P to tussocks in early spring and mid summer confirmed this deduction. Addition of P caused a rapid incorporation of about 10% of the labelled P in the tillers within a few days. Subsequent uptake was negligible, presumably because the P not immediately absorbed was fixed in the soil and unavailable to plants. This demonstrates that nutrient pulses were more important than steady-state mineralization in supporting P uptake by Eriophorum vaginatum. After the P additions, roots initially retained 60% of the total P taken up. During the following weeks, part of the P was transported slowly to stem bases and leaf sheaths, the principal storage organs. A lower proportion was transported to the leaf blades. We suggest that storage and recirculation of nutrients are the main sources of the annual nutrient supply to growth of E. vaginatum under normal field conditions, where P fixation in the soil and low rate of P diffusion towards the roots limit P uptake from soil except during periods of pulsed release.
对丛生莎草毛果苔草磷（P）库的季节性测量表明，其年磷吸收量较低，但春季地下储存的磷向生长生物量的通量显著，秋季又会回流。早春和仲夏向草丘添加磷证实了这一推断。添加磷后，几天内约10%的标记磷迅速被分蘖吸收。随后的吸收量可忽略不计，可能是因为未立即吸收的磷固定在土壤中，植物无法利用。这表明养分脉冲在支持毛果苔草吸收磷方面比稳态矿化更重要。添加磷后，根系最初保留了吸收的总磷的60%。在接下来的几周内，部分磷缓慢运输到茎基部和叶鞘，这是主要的储存器官。运输到叶片的比例较低。我们认为，在正常田间条件下，养分的储存和再循环是毛果苔草生长的年度养分供应的主要来源，在这种条件下，土壤中的磷固定和磷向根的低扩散速率限制了除脉冲释放期外从土壤中吸收磷。
