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