Growth and nitrate assimilation in tomato (Solanum lycopersicon)grown with different nitrogen source and treated with cadmium

Abstract

Abstract.-In tomato seedlings, the effects of Cd on growth and activity of enzymes involved in nitrate assimilation were studied on different nitrogen sources. After one week on basal growth medium, seedlings were transferred and grown for 14 days on a medium containing 5 mM nitrate, 5 mM ammonium or varying ratios of nitrate to ammonium. In each nitrogen medium, plants were divided into control and Cd treated. In nitrate-rich medium, plant dry weigh was improved while growth was more inhibited by Cd stress than in ammonium-rich medium. Regardless of nitrogen source, Cd treatments decreased nitrate contents in leaves and roots. Nitrate reductase and nitrite reductase activities were decreased by presence of ammonium in culture medium. Cd treatments inhibited NR and NiR activities independently of nitrogen form and plant organ. It could be concluded that tomato plants preferred nitrate as a nitrogen source where as external ammonium was found to inhibit growth. The addition of ammonium in nutrient solution slows down Cd absorption. Endogenous nitrate accumulation may mirror an important role of this metabolite in nitrate and nitrite reductase induction.Key words : tomato -cadmium -nitrate -ammonium -nitrate reductase -nitrite reductase.Résumé.-Chez des jeunes plantes de tomate, les effets de cadmium sur la croissance et l'activité des enzymes impliquées dans l'assimilation du nitrate ont été étu-diés en présence de différentes sources d'azote. Après une semaine sur milieu nutritif de base, les plants ont été transférés et cultivés pendant 14 jours sur un milieu contenant 5 mM de nitrate, 5 mM d'ammonium ou différentes proportions de nitrate et d'ammonium. Dans chaque milieu, les plantes ont été divisées en deux lots : témoins et traitées par Cd. Sur milieu riche en nitrate, la matière sèche des plantes a été plus importante, tandis que la croissance a été plus inhibée par le stress de Cd que sur milieu riche en ammonium. Indépendamment de la source d'azote, le traitement par Cd a diminué le contenu de nitrate dans les feuilles et les racines. Les activités nitrate réductase et nitrite réductase sont diminuées par la présence de l'ammonium dans le milieu de culture. Indépendamment de le forme d'azote et l'organe de la plante étudié, Cd inhibe les activités NR et NiR. On pourrait conclure que les plantes de tomate préfèrent le nitrate comme source d'azote, alors que l'ammonium exogène inhibe la croissance. L'accumulation endogène du nitrate peut reflé-ter le rôle important de ce métabolite dans l'induction de la nitrate et nitrite réductases.Mots clés : tomate -cadmium -nitrate -ammonium -nitrate réductase -nitrite réductase.

Metabolism biochemical of young plants of Ucuúba (Virola surinamensis) in the presence of cadmium

“…Cd have a reduced NRA, leading to a decreased NO 3 − assimilation because the metal causes a lower NO 3 − absorption by plant roots (Nasraoui-Hajaji et al 2011, Nikolić et al 2017. In this study, the marked reduction of NRA with the increasing Cd concentration (Fig.…”

“…High levels of Cd in the soil commonly causes many stress symptoms in plants such as the reduction of the photosynthetic rate, which may result in alterations in the concentration of starch and soluble carbohydrates in plants tissues (He et al 2013;Elloumi et al 2014), and nutritional imbalance between carbon and nitrogen metabolism (Ci et al 2009), thus reducing biomass production and total plant growth. The lower nitrate absorption (NO 3 − ) (Nasraoui-Hajaji et al 2011;Nikolić et al 2017), changes in nitrate reductase (NR) activity (Song et al 2016), proline (Wang et al 2016;Nikolić et al 2017), total soluble proteins (PST) and total soluble amino acids (TSA) (Rahoui et al 2015) in plants under the effect of Cd have also been observed.…”

Vegetable Crops Prefer Different Ratios of Ammonium-N and Nitrate-N in the Growth Media

“…The dry matter yield of roots and shoots, nutrient accumulation and tissue nutrient concentration in studied crops were significantly affected by the NH4 + -N:NO3 --N ratio in the growth medium (Table 1). Changes in dry matter yield and uptake of N and K with the ratio of NH4 + -N:NO3 --N in the growth medium has been reported previously for vegetable crops (Ikeda and Osawa, 1981;Marti and Mills, 1991;Song et al, 2000;Tian et al, 2003;Zhang et al, 2010;Nasraoui et al, 2011). According to previous studies, preference of a crop for NH4 + and NO3 -could change with crop growth stage (Ganmore-Neumann and Kafkari, 1985;Marti and Mills, 1991;Cui et al, 2017).…”

“…In the present study, dry matter yield of knolkhol and tomato were high under high NO3 --N (NH4 + -N:NO3 --N, 0:100) in the growth medium, whereas cabbage had the highest dry matter yield at 50:50, NH4 + -N to NO3 --N ratio. Nasraoui et al, (2011) observed that tomato plants preferred NO3 -while NH4 + inhibited its growth. Song et al, (2001) reported that supplying N with 25% NH4 + in a nutrient solution increased plant height, stem diameter and dry matter of Chinese cabbage (Brassica rapa) when compared to supplying NO3 -as the primary N source (100% NO3 --N).…”

Carbon And Nitrogen Metabolism of Young Plants of Ucuúba (Virola surinamensis) in the Presence Of Cadmium

“…The lower nitrate absorption (NO 3 − ) (Nasraoui-Hajaji et al 2011;Nikolić et al 2017), changes in nitrate reductase (NR) activity (Song et al 2016), proline (Wang et al 2016;Nikolić et al 2017), total soluble proteins (PST) and total soluble amino acids (TSA) (Rahoui et al 2015) in plants under the effect of Cd have also been observed.…”