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The effect of potassium deficiency on growth and N2-fixation in Trifolium repens

Høgh-Jensen, Dr. Henning (2003) The effect of potassium deficiency on growth and N2-fixation in Trifolium repens. Physiologia Plantarum (119), pp. 440-449. [In Press]

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Summary

The effects of potassium (K) deficiency on growth, N2-fixation and photosynthesis in white clover (Trifolium repens L.) were investigated using natural occurring gas fluxes on the nodules in real time of plants under three contrasting relative addition rates of K causing mild K deficiency, or following abrupt withdrawal of the K supply causing strong K deficiency of less than 0.65% in dry matter. A steady-state below-optimum K supply rate led to an increase in CO2-fixation per unit leaf surface area as well as per plant leaf surface. However, nitrogenase activity per unit root weight and per unit nodule weight was maintained, as was the efficiency with which electrons were allocated to the reduction of N2 in the nodules. Abrupt K removals stimulated without delay nodule growth strongly but as K concentrations decreased in the plant tissue, a significant decline in nitrogenase activity per unit root weight as well as per unit nodule mass occurred. Further, the rate of photosynthesis per unit leaf area was unaffected, while the CO2 acquisition for the plant as a whole increased due to an expansion of total leaf area whereas the leaf area per unit leaf weight was unaffected. The ratio between CO2-fixation and N2-fixation increased, although not statistically significant, under short-term K deprivation as well as under long-term low K supply indicating a down-regulation of nodule activity following morphological and growth adjustments. This down-regulation took place despite a partly substitution of the K by Na. It is concluded that N2-fixation does not limit the growth of K-deprived clover plants. K deprivation induces changes in the relative growth of roots, nodules, and shoots rather than changes in N and/or carbon uptake rates per unit mass or area of these organs.


EPrint Type:Journal paper
Keywords:potassium, potassium deficiency, white clover, N2 fixation
Subjects: Crop husbandry > Production systems > Pasture and forage crops
Research affiliation: Denmark > DARCOF I (1996-2001) > I.2 Nitrogen fixation, recycling and leaching in organic cropping systems
Deposited By: Jensen, Dr Henning Høgh
ID Code:632
Deposited On:19 Apr 2003
Last Modified:12 Apr 2010 07:27
Document Language:English
Status:In Press
Refereed:Peer-reviewed and accepted
Additional Publishing Information:Accepted for publication.

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