Physiological responses of native Tunisian grapevines and some rootstocks to direct iron deficiency

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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

Variation de la sensibilité au sel en fonction du stade de développement chez la lentille (Lens culinaris L)

Dans le but de comparer la sensibilité au sel de la lentille, Lens culinaris L, à deux stades de développement (premier mois de développement végétatif, et stade floraison), deux séries d'expériences sont réalisées sur quatre populations locales provenant de diverses régions de la Tunisie. Dans la première expérience, les plantes sont cultivées sous plafond lumineux, sur milieu liquide dépourvu de NaCl pendant 3 semaines. Le milieu est ensuite additionné de NaCl 50, 100 ou 150 mM, et les plantes sont récoltées 9 jours plus tard. Dans la seconde expérience, les cultures sont conduites sur sable inerte en pots. Pendant les 3 premières semaines, toutes les plantes sont irriguées avec une solution nutritive contenant NaCl 10 mM (concentration dans l'eau de ville). La concentration de NaCl est ensuite portée à 36 mM pour la moitié des plantes. La récolte est faite 2 mois plus tard, les plantes étant alors âgées de 11 semaines, et ayant atteint le stade floraison depuis 2 semaines. Les plantes aux stades juvéniles (1 mois) mises en présence de NaCl 50 mM ne présentent aucun ralentissement de croissance (première expérience). Des inhibitions de croissance, différentes entre les populations, apparaissent aux stades plus tardifs, quand les plantes sont traitées par NaCl 36 mM (deuxième expérience). À ces stades, un dessèchement d'une partie des feuilles intervient, qui paraît lié à une accumulation excessive de Na+ et Cl-. Les différences de sensibilité au sel des populations sont liées à des différences de vitesse de production des feuilles. Les populations à croissance rapide, qui mettent en place de nouvelles feuilles plus vite que l'accumulation de Na+ et Cl- n'élimine les anciennes, sont les plus résistantes au sel.Variation in salt sensitivity during development of lentils. The sensitivity of Lens culinaris L to NaCl was compared at two developmental stages. Four local populations of lentil taken from various regions of Tunisia were used. Seedlings were grown for 3 weeks on liquid medium, under artificial light. The medium was then supplemented with NaCl (50, 100 and 150 mM). The plants were harvested 9 days later. In a second experiment, the plants were grown for 3 weeks on sand irrigated with a medium containing 10 mM NaCl. For half of them, the NaCl concentration was then increased to 36 mM. The experiment ended when the plants were 11 week old (2 weeks after the beginning of flowering). In young plants (1-month-old) treated with 50 mM NaCl, no growth inhibition was observed. Growth inhibitions, variable according to populations, appeared at late developmental stages in plants treated with 36 mM NaCl. Excess accumulation of Na+ and Cl-, associated with leaf dehydratation, occurred in leaves. The differential effect of NaCl on growth between populations was related to differences in the rate of leaf production. In populations with high growth rate, the production of new leaves was more rapid than the elimination of old leaves by Na+ and Cl- excess accumulation. These populations were more tolerant to NaCl

Physiological responses of Arabidopsis thaliana to the interaction of iron deficiency and nitrogen form

Physiological responses of Arabidopsis thaliana to the interaction of iron deficiency and nitrogen form were studied using plants grown in hydroponics. Thirty-three-day-old seedlings were submitted to four treatments for 7 days : NO3 + 5 µM Fe; NO3 + 0.1 µM Fe; NH4 + 5 µM Fe and NH4 + 0.1 µM Fe. Leaf growth and chlorophyll content were highest in NO3-fed, Fe sufficient plants, but were strongly diminished by Fe deficiency under nitric nutrition, and by ammoniacal nutrition independently of Fe regime. However, the leaves of NH4-fed plants presented a higher Fe content than those of Fe sufficient, NO3-fed plants. Thus, leaf chlorosis of NH4-fed in plant did not depend on Fe availability, and seemed to be due to another factor. Root acidification capacity and Fe-chelate reductase (FCR) activity were also dependent on N form. The medium was acidified under ammoniacal regime and alkalinized under nitric regime regardless of Fe level. FCR activity stimulation in response to Fe deficiency was observed only in NO3- fed plants. In addition, both N form and Fe level induced antioxidant responses in rosette leaves. Ammoniacal regime increased both peroxidase expression and anthocyanin accumulation, whereas Fe deficiency enhanced superoxide dismutase expression

Effects of NaCl on the growth, ion accumulation and photosynthetic parameters of Thellungiella halophila

Thellungiella halophila seedlings grown on a solid substrate for 25 days on standard medium were challenged with NaCl. Growth, tissue hydration, ion accumulation, photosynthesis, lipid peroxidation and antioxidant enzymatic activities were studied on rosette leaves. Three accessions of Arabidopsis thaliana were cultivated under the same conditions. During the first two weeks of salt treatment, the growth of T. halophila leaves was restricted by NaCl. No significant difference appeared between T. halophila and A. thaliana concerning biomass deposition, or hydric and ionic parameters. However, all A. thaliana plants displayed foliar damage, and died during the third week of salt (50mM NaCl) treatment. Almost all (94%) T. halophila plants remained alive, but did not display any sign of altered physiological condition. Tissue hydration, chlorophyll content, stomatal conductance, photosynthetic quantum yield, and photosynthetic rate were very similar to those of control plants. Lipid peroxidation, estimated from thermoluminescence, was very low and insensitive to salt treatment. Only slight changes occurred in antioxidant enzymatic activities (SOD, several peroxidases, and catalase). From the absence of physiological disorder symptoms, we infer that salt was efficiently compartmentalized in leaf vacuoles. In salt-treated A. thaliana, the photosynthetic quantum yield was diminished, and lipi