Effects of sodium on mineral nutrition in rose plants

Abstract

The effects of sodium (Na + ) ion concentration on shoot elongation, uptake of ammonium (NH 4 + ) and nitrate (NO 3 -) and the activities of nitrate reductase (NR) and glutamine synthetase (GS) were studied in rose plants (Rosa hybrida cv. Lambada).The results showed that shoot elongation was negatively correlated with sodium concentration, although no external symptoms of toxicity were observed. Nitrate uptake decreased at high sodium levels, specifically at 30 meq litre -1 of sodium. As flower development was normal under high saline conditions, this could suggest that nitrogen was being mobilised from shoot and leaf reserves. Ammonium uptake was not affected by any of the salt treatments applied probably because it diffuses through the cell membrane at low concentrations. Nitrate reductase activity was reduced by 50% at 30 meq litre -1 compared with control treatment, probably due to a decrease in the free nitrate related to nitrate uptake pattern. None of the salt treatments used affected total leaf GS activity (both chloroplastic and cytosolic isoforms) or leaf NPK mineral contents. Nitrate reductase activity in leaves increased at 10 meq litre -1 of sodium and GS activity in roots (cytosolic isoform only) followed the same pattern as NR. It is suggested that the activation of both enzymes at low salt level could be attributed to the beneficial effect of increased sulphur in the nutrient solutions.

Evaluation of Genotoxic Risks Due to Temporal Changes in Soil Urea: Using <i>Allium cepa</i> L. Root Tip Bioassay

“…The inhibition of primary root growth by inhibiting cell elongation and division are toxicity symptoms as reported by Qin et al (2011) in Arabidopsis. A high ratio of ammonium to nitrate enhanced the uptake of P (Lorenzo et al 2000a) and N (Lorenzo et al 2000b) during shoot elongation by rose plants. This can be explained by the preferential uptake of NH 4 as compared with NO 3 (Marschner 1995), and also by the reduction of solution pH (Feigin et al 1986).…”

Salinity in rose production

“…Sodium concentration in the medium shows a positive correlation with sodium absorption in roses (LORENZO et al, 2000). Increasing the concentration of NaCl in the in vitro medium led to a higher accumulation of chlorine and sodium in the leaves of Rosa chinensis 'Major', R. rubiginosa, R. hybrida 'Kardinal' and R. hybrida 'Kiss'.…”

“…Also, under higher sodium concentration, the nitrate, potassium and phosphate uptake decreases (LORENZO et al, 2000). Another impact of salt stress is that in presence of higher Cl -levels, the NO 3 -uptake decreases (DEBOUBA et al, 2007).…”

“…However, in many regions where roses are cultivated, the supply of quality water is limited and soil salinization is frequent. The effects of salinity on Rosa species are dependent on the type and concentration of salts, cultivation system (soil or hydroponic), substrate type, irrigation system, rose species/cultivar and rootstock selection (LORENZO, 2000). Therefore, knowing regional environmental conditions and agricultural practices is necessary in order to identify salt-tolerant plants .…”

“…´Lambada`roses are more sensitive to saline conditions in the presence of NH 4 + only. In these plants, the nitrate reductase activity in leaves was reduced and roots presented the highest sodium accumulation (LORENZO et al, 2001). …”