期刊
NEW PHYTOLOGIST
卷 155, 期 2, 页码 285-292出版社
BLACKWELL PUBLISHING LTD
DOI: 10.1046/j.1469-8137.2002.00463.x
关键词
acclimation; floating macrophyte; growth; Lemna minor; nitrogen uptake kinetics; root vs shoot uptake
Both roots and leaves of free-floating plants can potentially take up nutrients. In this study, the ability and relative contribution of roots and fronds for N uptake by the floating macrophyte Lemna minor was investigated. The NH4+ and NO3- uptake kinetics of roots and fronds were measured on plants acclimated to three different NH4NO3 concentrations. Lemna had the capacity to take up NH4+ and NO3- through both roots and fronds; uptake kinetics for the two tissue types were comparable on an area basis. The overall contribution of root and frond to whole-plant uptake, estimated from measured kinetic characteristics, varied depending on plant N status (the root contribution increased from 32 to 73% for N-satiated and N-depleted plants, respectively). The shift in the balance between root and frond contribution to whole-plant uptake resulted from a 1.5-38 times greater increase in the area-specific uptake capacity and affinity of roots relative to fronds, combined with a larger decrease in the minimum concentration for uptake (C-min) for roots than fronds. At the morphological level, root-frond surface area increased with declining N supply, which might be beneficial to the plants since the area return per unit biomass invested was nine times greater for roots than for fronds.
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