Salt effect on physiological, biochemical and anatomical structures of two Origanum majorana varieties (Tunisian and Canadian)

In this study, we evaluated the salt concentration effect on plant growth, mineral composition, antioxidant responses and anatomical structure of two varieties of Origanum majorana after exposure to NaCl treatment. Our results show an inclusive behaviour of the two varieties, since the majority of sodium was exported and accumulated in their aerial parts. The Canadian variety (CV) appeared relatively more tolerant to salt than the Tunisian one (TV). Transversal section of leaves showed a thickening of dorsal and ventral cuticle, more importantly in CV than in TV, in the presence and in absence of salt. This was accompanied by an increase in the length of palisade cells, and the width of spongy collenchyma lacuna. The stem had a subquadrangular shape in TV and quadrangular in the Canadian variety. At mature stage, the stem pit was reabsorbed in the TV and replaced by a large cavity, whereas it remained unchanged in CV. The relative salt tolerance of the CV was related to: (1) a good selectivity in favour of K+: (2) a strong peroxidase activity and (3) an increase in the lengthening of palisade cell accompanied with an increase of lacunae in spongy parenchyma in CV.Key words: Origanum majorana, salinity, growth, mineral nutrition, leaves, stems, anatomical, antioxidant

Effect of growth stages on phenolics content and antioxidant activities of shoots in sweet marjoram (Origanum majorana L.) varieties under salt stress

We investigated the contributions of salinity and development stage on total polyphenols, flavonoids,  condensed tannins contents, phenolic content, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide  scavenging activities at three phenolic stages: early vegetative stage (EVS), late or prefloral vegetative (LVS) stage and flowering stage (FS). The total phenolic, flavonoids and condensed tannins contents were more  important in the presence and absence of salt at prefloral or building stage than at EVS and FS. In addition, salt stress increased total polyphenol and individual phenolic contents in shoots of Origanum majorana. This  increase was more important in LVS than in EVS and FS. Moreover, the antiradical activity of the shoots (DPPH) decreased with the addition of NaCl. In fact, LVS extracts showed the highest antioxidant properties.  Furthermore, at LVS, marjoram grown at 75 mM showed a higher antiradical ability against DPPH radical and antioxidant activity, compared to EVS and LVS. Data reported here revealed the variation of phenolic  compound contents at different stages of growth of O. majorana, and the possible role of these changes in the response of the plant to salt was also discussed.Key words: Antiradical activity, Origanum majorana, early vegetative stage (EVS), late or prefloral vegetative (LVS) stage and flowering stage (FS), phenolic content

Utjecaj uvjeta uzgoja i dodatka soli na sastav eteričnog ulja slatkog mažurana (Origanum majorana) iz Tunisa

O. majorana shoots were investigated for their essential oil (EO) composition. Two experiments were carried out; the first on hydroponic medium in a culture chamber and the second on inert sand in a greenhouse for 20 days. Plants were cultivated for 17 days in hydroponic medium supplemented with NaCl 100 mmol L1. The results showed that the O. majorana hydroponic medium offered higher essential oil yield than that from the greenhouse. The latter increased significantly in yield (by 50 %) under saline constraint while it did not change in the culture chamber. Under greenhouse conditions and in the absence of salt treatment, the major constituents were terpinene-4-ol and trans-sabinene hydrate. However, in the culture chamber, the major volatile components were cis-sabinene hydrate and terpinene-4-ol. In the presence of NaCl, new compounds appeared, such as eicosane, spathulenol, eugenol, and phenol. In addition, in the greenhouse, with or without salt, a very important change of trans-sabinene hydrate concentration in EO occurred, whereas in the culture chamber change appeared in cis-sabinene hydrate content.U radu je opisano ispitivanje sastava eteričnog ulja izdanaka biljke O. majorana. Provedena su dva eksperimenta: prvi na hidroponom mediju u komorama za uzgoj, a drugi na inertnom pijesku u stakleniku tijekom 20 dana. Biljke su uzgajane 17 dana u hidroponom mediju u koji je dodan NaCl 100 mmol L1. Rezultati ukazuju na to da hidroponi medij O. majorana osigurava veće prinose eteričnog ulja nego staklenik. U stakleniku se prinos ulja značajno povećao dodavanjem 50 % soli dok u uzgoju u uzgojnoj komori nije bilo promjene. U uvjetima u stakleniku i u odsutnosti soli, najvažniji sastojci ulja bili su terpinen-4-ol i trans-sabinen hidrat, dok su u uvjetima uzgojne komore najvažnije hlapljive komponente bile cis-sabinen hidrat i terpinen-4-ol. U prisutnosti NaCl-a, pojavili su se novi sastojci, kao što su eikozan, spatulenol, eugenol i fenol. Dodatno je uz stakleničke uvjete, sa i bez soli, došlo do važne promjene u količini trans-sabinen hidrata u eteričnom ulju, dok se u komorama promijenio sadržaj cis-sabinen hidrata

Phenolic acids and total antioxidant activity in Ocimum basilicum L. grown under Na2SO4 medium

The antioxidant activity of two basil cvs (Ocimum basilicum L. cvs. Genovese and Fine), grown for 15 and 30 days in the absence or in the presence of 25 mM sodium sulphate (Na2SO4), was measured. At the same time, phenolic acid contents of the same plant materials were determined to evaluate their probable contribution to the total antioxidant capacity. The results showed that Genovese cultivar was a better source of antioxidant compounds than Fine one, irrespective of the salt and the period of treatment, even if Na2SO4 salinity was less stressful for Fine cultivar that after 15 days of treatment was able to increase its antioxidant power in comparison to Genovese one. In addition,although major phenolic acids in Genovese and Fine basil remained constant or decreased with salinity, we observed an increase in hydrophilic antioxidant power either after 15 or 30 days of treatment. The lack of correlation between phenolic acids present in basil and antioxidant activity could be explained by the fact that other antioxidant hydrophilic molecules are synthesised under stress conditions

Physiological and molecular responses of two Arabidopsis< accessions to calcium amendment and salt constraint

International audienceThe Arabidopsis thaliana NOK2 accession displays salt tolerance compared to more commonly known A. thaliana accessions, such as Col-0, but the basis of this phenotypic feature is unknown. This work was focused on determining whether salt tolerance in NOK2 plants is affected by calcium supplementation to the growth medium. A. thaliana seedlings were grown in pots containing a mixture of sand and peat under controlled conditions in a low-level Ca(NO3)2 medium supplemented with 0 or 50 mM NaCl with and without amendment with two higher levels of Ca(NO3)2. Calcium amendment was beneficial for salt-treated NOK2 plants, as shown by the increase in dry weight of NOK2 plants with and without NaCl, but had no impact on Col-0 biomass. Sodium accumulation decreased as a function of calcium amendment in NOK2, while Col-0 maintained its high Na levels under these conditions. Leaf K+ content, K+ uptake, and Ca content decreased in NOK2 and Col-0 plants growing in the low-level Ca medium when NaCl was added, but rose in leaves of both accessions with calcium amendment, although K remained low in both accessions in the absence of NaCl. K+/Na+ selectivity increased preferentially in NOK2 with increasing calcium in the presence of NaCl, but when Na was restricted and not under any conditions in Col-0. Preferential effects of calcium were not observed on the transcript accumulation of seven Na+, K+ or Ca2? transport genes for either of the accessions, except for increased transcription of the CAX4 gene in NOK2 leaves at the highest calcium concentration used (5 mM). Leaf membrane leakage, which increased two-fold higher in Col-0 under salt application compared with the increase in NOK2, declined for both accessions in response to calcium supplementation, and in NOK2 this decline reached no salt levels when Ca2+ amendments were highest. Chlorophyll and carotenoid content dropped two-fold in Col-0 in response to salt, but were unchanged in NOK2 under these conditions. In contrast, leaf anthocyanins, which were normally tenfold higher in Col-0 than in NOK2 in the lowlevel Ca2+ medium, declined in Col-0 plants as a function of Ca2+ supplementation, but were maintained at low levels in NOK2 leaves regardless of salinity and calcium. In conclusion, NOK2 plants responded positively to calcium supplementation by improving biomass yield during salinity treatment, whereas this amendment only affected Col-0 by reducing its permeability and anthocyanin titre. K+/Na+ selectivity appeared to be an important characteristic of NOK2 response to calcium. The regulation of this response may involve the CAX4 Ca2+/H+ vacuolar transport gene, but does not appear to involve six other common ion transporters