15NO3 assimilation by the field Pea Pisum sativum L.

Abstract

The objectives of this study were to determine the effect of low mineral supply on plant growth and the uptake and redistribution of mineral N by different plant organs according to the period of uptake. A glasshouse study was conducted on two pea genotypes, L833 and cv. Frisson, fed without or with 4 mM NO 3. Plants fed with 4 mM N were labelled for 5 days with 15 N at three stages: 7 leaf stage, beginning of flowering, and beginning of seed filling. Plants were harvested at day 6 and at later stages. The results indicated for the two genotypes that supplying 4 mM N to the plants significantly increased their total dry weight up to the beginning of seed filling, whereas nodule dry weight was reduced. Genotype differences in N uptake and redistribution among plant organs were minor. When plants were labelled with 15 N at early stages of growth, about 60% of total plant 15 N was located in leaves. At maturity the proportion of 15 N recovered in seeds was about 60% for both genotypes. When plants were labelled at the beginning of seed filling, 15 N was mainly located in young organs such as upper leaves, pods and seeds. During seed fill the remobilisation of 15 N to seeds occurred from all organs of the plant. At physiological maturity about 70% of 15 N was located in seeds.

Determination of the uptake and translocation of nitrogen applied at different growth stages of a melon crop (Cucumis melo L.) using 15N isotope

“…In agreement with the findings of Atta et al (2004), when our melon plants had vegetative but not reproductive growth, the N accumulated mainly in the leaves. As the fruits started to develop and grow, their higher N demand, relative to the vegetative organs, caused a continuous translocation of N from the stems and, particularly, the leaves.…”

“…The dynamics of N accumulation and translocation within the plant can be gauged from the changing pattern of source and sink interactions (Atta et al, 2004). In agreement with the findings of Atta et al (2004), when our melon plants had vegetative but not reproductive growth, the N accumulated mainly in the leaves.…”

“…This is due to the sink effect of the fruits, so that the more fruits there are, the greater is the amount of N directed to them. This effect has been observed also by Atta et al (2004) in pea (Pisum sativum L.), Darawsheh and Bouranis (2006) in tomato (Lycopersicon esculentum Mill) and Mohammad (2004) in squash (Cucúrbita pepo L.).…”

“…It could be due to a higher soil mineral N content before transplanting in the first year (67 kgN ha -1 ) than in the second (34kgNha _1 ) (Castellanos et al, 2010), because the amount of nitrate in soil regulates the uptake of N by crops (Gastal and Lemaire, 2002). On the other hand, the fact that the fruit N uptake in all experiments was similar, and both leaf and stem N uptake were lower, suggests that when the plant takes up less N, this reduction is first observed in the leaves and stem because the fruits are a strong sink and there is translocation to them from vegetative parts, mainly from the leaves (Atta et al, 2004). The patterns of N accumulation during the growing period for the whole plant and individual plant parts essentially followed the time course of the DM production, as shown also by Latus et al (1995) in cucumber.…”

“…Therefore, it is necessary to study the N uptake dynamic and its translocation in the plant in order to optimise the fertilisation, because differences in soil characteristics, climate and crop management may significantly influence the results. Isotopic techniques based on 15 N labelling have proved to be the most-effective means of measuring N fluxes between different tissues or organs, and for evaluating the respective contributions of N remobilised from storage tissues or recently acquired by uptake and fixation from the environment (Atta et al, 2004;Tanemura et al, 2008). Also, 15 N studies can be used to quantify the percentage of N uptake by the plant that originates from fertiliser and how much comes from soil mineral N (Janat, 2007;Kotur et al, 2007;Latus et al, 1995;Lopez-Bellido et al, 2006).…”