TY - JOUR
T1 - Inorganic nitrogen uptake kinetics and whole-plant nitrogen budget in the seagrass Zostera noltii
AU - Alexandre, Ana
AU - Silva, João
AU - Bouma, Tjeerd J.
AU - Santos, Rui
N1 - Funding Information:
We are grateful to P. Feijóo for his assistance in the building of the incubation chambers. We also thank two anonymous reviewers for their valuable comments on the manuscript. A.A. was supported by a PhD grant from Fundação para a Ciência e a Tecnologia ( SFRH/BD/21487/2005 ), co-funded by POCI 2010 and FSE . [SS]
PY - 2011/5/31
Y1 - 2011/5/31
N2 - The uptake rates of ammonium and nitrate through the leaves and roots, the leaf-root interactions in the nitrogen uptake and the internal translocation of incorporated nitrogen were simultaneously investigated in the seagrass Zostera noltii. Leaf and root uptake rates, which were measured using two-compartment polyethylene chambers that physically separated the leaves from below-ground plant parts, were quantified based on tissue incorporation of 15N-labeled ammonium and nitrate. The maximum leaf uptake rates (Vmax) of ammonium were 100 times higher than those of nitrate. Both Vmax and affinity for ammonium were one order of magnitude higher in the leaves (28.3-31.9μmolg-1DWh-1 and 0.93-0.99, respectively) than in the roots (2.3-3.0μmolg-1DWh-1 and 0.06-0.08, respectively). The uptake of ammonium and nitrate by one plant part did not affect the uptake of the other plant part, and no translocation of inorganic nitrogen was detected between plant parts. The 15N enrichment detected in the rhizomes suggests either a direct uptake of inorganic nitrogen or its transference from the roots. The estimated total inorganic nitrogen uptake of Z. noltii (645μmolm-2h-1) in the peak production season (spring) under typical nutrient concentrations, using the rates obtained during the surge uptake phase, exceeded by 3-fold the species estimated nitrogen requirement for growth (236μmolNm-2h-1). However, using the stabilized values of the uptake rates obtained after several hours of incubation, the estimated whole-plant nitrogen budget (215μmolm-2h-1) was slightly lower than the total nitrogen requirement for growth. We conclude that the growth of Z. noltii in Ria Formosa lagoon is not limited, or is only slightly limited, by nitrogen.
AB - The uptake rates of ammonium and nitrate through the leaves and roots, the leaf-root interactions in the nitrogen uptake and the internal translocation of incorporated nitrogen were simultaneously investigated in the seagrass Zostera noltii. Leaf and root uptake rates, which were measured using two-compartment polyethylene chambers that physically separated the leaves from below-ground plant parts, were quantified based on tissue incorporation of 15N-labeled ammonium and nitrate. The maximum leaf uptake rates (Vmax) of ammonium were 100 times higher than those of nitrate. Both Vmax and affinity for ammonium were one order of magnitude higher in the leaves (28.3-31.9μmolg-1DWh-1 and 0.93-0.99, respectively) than in the roots (2.3-3.0μmolg-1DWh-1 and 0.06-0.08, respectively). The uptake of ammonium and nitrate by one plant part did not affect the uptake of the other plant part, and no translocation of inorganic nitrogen was detected between plant parts. The 15N enrichment detected in the rhizomes suggests either a direct uptake of inorganic nitrogen or its transference from the roots. The estimated total inorganic nitrogen uptake of Z. noltii (645μmolm-2h-1) in the peak production season (spring) under typical nutrient concentrations, using the rates obtained during the surge uptake phase, exceeded by 3-fold the species estimated nitrogen requirement for growth (236μmolNm-2h-1). However, using the stabilized values of the uptake rates obtained after several hours of incubation, the estimated whole-plant nitrogen budget (215μmolm-2h-1) was slightly lower than the total nitrogen requirement for growth. We conclude that the growth of Z. noltii in Ria Formosa lagoon is not limited, or is only slightly limited, by nitrogen.
KW - Nitrogen
KW - Seagrass
KW - Translocation
KW - Uptake
KW - Zostera noltii
UR - http://www.scopus.com/inward/record.url?scp=79955133640&partnerID=8YFLogxK
U2 - 10.1016/j.jembe.2011.03.008
DO - 10.1016/j.jembe.2011.03.008
M3 - Article
AN - SCOPUS:79955133640
SN - 0022-0981
VL - 401
SP - 7
EP - 12
JO - Journal of Experimental Marine Biology and Ecology
JF - Journal of Experimental Marine Biology and Ecology
IS - 1-2
ER -