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The maintenance of rapid growth under conditions of CO_2 enrichment is directly related to the capacity of new leaves to use or store the additional assimilated carbon(C) and nitrogen(N). Under drought conditions, however, less is known about C and N transport in C_4 plants and the contributions of these processes to new foliar growth. We measured the patterns of C and N accumulation in maize(Zea mays L.) seedlings using 13 C and 15 N as tracers in CO_2 climate chambers(380 or 750 μmol mol~(–1)) under a mild drought stress induced with 10% PEG-6000. The drought stress under ambient conditions decreased the biomass production of the maize plants; however, this effect was reduced under elevated CO_2. Compared with the water-stressed maize plants under atmospheric CO_2, the treatment that combined elevated CO_2 with water stress increased the accumulation of biomass, partitioned more C and N to new leaves as well as enhanced the carbon resource in ageing leaves and the carbon pool in new leaves. However, the C counterflow capability of the roots decreased. The elevated CO_2 increased the time needed for newly acquired N to be present in the roots and increased the proportion of new N in the leaves. The maize plants supported the development of new leaves at elevated CO_2 by altering the transport and remobilization of C and N. Under drought conditions, the increased activity of new leaves in relation to the storage of C and N sustained the enhanced growth of these plants under elevated CO_2.
The maintenance of rapid growth under conditions of CO 2 enrichment is directly related to the capacity of new leaves to use or store the additional assimilated carbon (C) and nitrogen (N). Under drought conditions, however, less is known about C and N transport in C_4 plants and the contributions of these processes to new foliar growth. We measured the patterns of C and N accumulation in maize (Zea mays L.) seedlings using 13 C and 15 N as tracers in CO_2 climate chambers (380 or 750 μmol mol ~ (-1)) under a mild drought stress induced with 10% PEG-6000. The drought stress under ambient conditions decreased the biomass production of the maize plants; however, this effect was reduced under elevated CO_2. Compared with the water-stressed maize plants under atmospheric CO_2, the treatment that combined elevated CO_2 with water stress increased the accumulation of biomass, partitioned more C and N to new leaves as well as enhanced the carbon resource in aging leaves and the carbon pool in n The elevated CO_2 increased the time needed for newly acquired N to be present in the roots and increased the proportion of new N in the leaves. The maize plants supported the development of new leaves at elevated CO_2 by altering the transport and remobilization of C and N. Under drought conditions, the increased activity of new leaves in relation to the storage of C and N sustained the enhanced growth of these plants under elevated CO_2.