caa a22 4500 477111645 CHVBK 20180405111610.0 cr unu---uuuuu 170330e19960301xx s 000 0 eng 10.1007/BF00015312 doi (NATIONALLICENCE)springer-10.1007/BF00015312 Inhibition of N2 fixation by white clover ( Trifolium repens L.) at low concentrations of NOinf3sup− in flowing solution culture [Elektronische Daten] [J. Macduff, S. Jarvis, I. Davidson] The impact of sustained low external concentrations of NO 3 − (0, 10, 100 and 1000 mmol m−3) on plant growth and the relative acquisition of N through N2 fixation and NO 3 − uptake by established, nodulated white clover (Trifolium repens L. cv. Blanca) was studied over 28 days in flowing solution culture. Nitrogen fixation was measured by N difference and 15N dilution methods. Plants supplied with NO 3 − achieved higher relative growth rates (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmiEayaara% aaaa!3702!\[\bar x\]=0.091 d−1) compared with ‘control' plants dependent on N2 fixation (0.073 d−1). Nitrate plants showed progressive increases in shoot: root d.w. ratios from 4 to 6.5-7.6 between days 0-28, compared with 5.1 on day 28 for control plants. Increases in both nodule d.w. and numbers per plant were inhibited after day seven at all concentrations of NO 3 − . The severity of inhibition of N2 fixation increased with increasing NO 3 − concentration and with time. The total amounts of N2 fixed per plant between days 0-7 after supplying 10, 100 and 1000 mmol m−3 NO 3 − , respectively, were 37-39, 28-30 and 0-13%, of the total N acquired. Between days 7-28 the proportional contributions of N2 fixation to total N acquisition declined to 3, 0.5 and 0%, respectively, in these treatments. The corresponding mean specific rates of N2 fixation between days 0-7 were, respectively, 5.4, 3.2, and 2.0 mmol N d−1 g−1 nodule d.w., compared with 7.9 mmol N d−1 g−1 nodule d.w. for zero NO 3 − plants. There was no evidence of a transitory increase in N2 fixation following the addition of NO 3 − , even at the lowest supply concentration. Kluwer Academic Publishers, 1996 inhibition nationallicence 15N nationallicence nitrate nationallicence nitrogen fixation nationallicence Trifolium repens nationallicence uptake nationallicence white clover nationallicence Macduff J. Institute of Grassland and Environmental Research, SY23 3EB, Aberystwyth, Dyfed, UK aut Jarvis S. North Wyke Research Station, Institute of Grassland and Environmental Research, EX2O 2SB, Okehampton, Devon, UK aut Davidson I. Institute of Grassland and Environmental Research, SY23 3EB, Aberystwyth, Dyfed, UK aut Plant and Soil Kluwer Academic Publishers; gopher://gopher.wkap.nl 180/2(1996-03-01), 287-295 0032-079X 180:2<287 1996 180 11104 https://doi.org/10.1007/BF00015312 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00015312 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Macduff J. Institute of Grassland and Environmental Research, SY23 3EB, Aberystwyth, Dyfed, UK aut NATIONALLICENCE 700 1- Jarvis S. North Wyke Research Station, Institute of Grassland and Environmental Research, EX2O 2SB, Okehampton, Devon, UK aut NATIONALLICENCE 700 1- Davidson I. Institute of Grassland and Environmental Research, SY23 3EB, Aberystwyth, Dyfed, UK aut NATIONALLICENCE 773 0- Plant and Soil Kluwer Academic Publishers; gopher://gopher.wkap.nl/ 180/2(1996-03-01), 287-295 0032-079X 180:2<287 1996 180 11104 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer