Effet de l’interaction lumiere-salinite sur l’activite du photosysteme ii des feuilles excisees de maïs

La diminution de la croissance vegetative observée chez nombreuses plantes, soumises au stress salin et exposées à des conditions naturelles d’ensoleillement, est souvent associée à une baisse de leur activité photosynthétique. Cependant les mécanismes de l’inhibition photosynthétique sont encore peu étudiés. Le photosystème II (PS II) est considéré un des facteurs clé dans la réponse de la photosynthèse des feuilles aux stress environnementaux. L’association de la lumière et du stress salin parait avoir des effets synergétiques sur l’activité photochimique du PSII conduisant, ainsi à la photoinhibition. L’objectif de cette etude est de diagnostiquer l’effet de l’interaction lumière- salinité sur l’activité photochimique du photosystème II au cours de la photosynthèse. Le materiel vegetal est constitué de deux variétés de maïs (Zea mays L.) fourrager: Aristo et Arper. Des feuilles détachées de plantes cultivées sur milieu témoin (eau distilée), sont incubées pendant 6 heures dans des solutions salines à différentes concentrations (0, 100, 200 et 300 mM NaCl), soit en absence ou en présence de lumière (1000 μmol m-2 s-1). Puis, leurs teneurs en sodium ont été déterminées. Pour vérifiers’il y’aura récupération de leur activité photochimique, d’autres feuilles qui ont été mises à absorber du NaCl dans une solution de 300 mM à la lumière pendant 4 heures, sont transferees dans de l’eau distillée en obscurité ou en lumière. Les resultants montrent une stabilité du rendement quantique maximal (Fv/Fm) pour les feuilles mises à absorber du NaCl à l’obscurité.Par contre l’éclairement associé avec la salinité engender une photoinhibition qui se manifeste par une diminution du rendement quantique maximal du PSII. Cette photoinhibition, due à une accumulation excessive des ions Na+dans les tissus foliaires, est réversible. En effet, en absence d’un seul des facteurs de l’association lumière-salinité le PSII récupère son activité photochimique.Mots Clés: fluorescence chlorophyllienne, feuillesexcisées, stress lumineux, chlorure de sodium, Zea maysEnglish AbstractThe decline in growth observed in many plants, subjected to salt stress and exposed to sunlight conditions, is often associated with a decrease in their photosynthetic activity. No clear mechanisms of the inhibited photosynthesis have emerged since photosystem II (PS II) is considered to play a key role in the response of leaf photosynthesis to environmental  perturbations. The combination of light and salt stress appears to have synergistic effects on the photochemical activity of PSII driving, and to photoinhibition. The objective of this study was to evaluate the reversible effect of salinity and light interaction on maximal quantum efficiency of photosystem II (Fv/Fm.). In this experiment, detached leaves of two forage maize (Zea mays L.) varieties, Aristo and Arper were placed during 6 hours in solutions of different concentrations of NaCl (0, 100, 200 and 300 mM) and subjected to light (1000 μmol m-2 s-1) or obscurity. Then, their contents of sodium were determined. In order to verify the photo-inhibition reversibility, other leaves which were incubated in a solution of 300 Mm NaCl, during 4 hours were transferred in distilled water and also subjected to light or to obscurity. Results indicate that leaves which had been put to absorb NaCl in obscurity showed no change in maximal efficiency of PSII (Fv/Fm). Nevertheless, light treatment associated with salinity generates a photo-inhibition of PSII manifested by a significant decrease in maximal efficiency of PSII. This photo-inhibition, due to an excessive accumulation of sodium in leaves, is reversible. It is quite sufficient to eliminate only one factor of the association light-salinity for the PSII activity resume.Keywords: Light stress, sodium chloride, Zea may

Effects of electromagnetic treated saline water on potatoes (Solanum tuberosum L.) physiological and nutritional characteristics

Purpose: This work was designed to assess the physiological response of three potatoes cultivars to saline water irrigation, and the role of the electromagnetic treatment on alleviating salinity impacts on potatoes crops. Research Method: The experiment was conducted under factorial RCBD with potato varieties Spunta, Bellini and Alaska under three irrigation treatments; ground water (C), saline water (SW) and electromagnetic saline water (EMSW). We analyzed soil proprieties, minerals and water usage efficiency, plant water status, chlorophyll pigments, absiscic acid (ABA) content, and expression of StNCED gene. Findings: Data showed that EMSW promote salt leaching from soil, decrease soil salinity and improve the efficiency of water and minerals use. Leaf area, leaf dry weight, stem thickness, tuber weight, water potential, water content and water use efficiency were more disturbed under SW. The ABA content in Alaska leaves was associated with StNCED expression level. The cultivar Alaska displayed highest leaf size, SPAD and minerals use efficiency. Spunta had upmost correlation between LA and WCap and highest water use efficiency. Contrarily, Bellini manifested less water potential and ABA content. Research limitations: No limitations were found. Originality/value: Thus, Spunta and Alaska revealed better physiological and metabolic capacity to tackle salinity. The results advance knowledge on potatoes response to salinity and could improve management of saline water

Improvement of Circularly Polarized Slot-Patch Antenna Parameters by Using Electromagnetic Band Gap Structures

Abstract This paper is devoted to the design of a novel Electromagnetic Band Gap (EBG) circularly polarized slot-patch antenna in multilayered configuration. The operating frequency band can be controlled via the disk radius and adjusting the slit lengths. An arrangement combining the circular slot-patch antenna design and feeding sources included are considered is necessary. Due to the exisiting of two feeding points, Position of both feeding points will permit Right-hand and Left-hand circular polarization operations. Thickness of substrate is chosen to reduce the spurious surface wave and width. The same technique will be used for the EBG cirlcularly polarized circular slot-patch antenna network and carry two benefits (such as improvement of bandwidth, beamforming, creating zero radiation beams) and filtering characteristics of the resonator (spatial filtering, increased directivity, misalignment) due to the resonant structure itself. The analysis provided will confirm successfully the various proposed structures and interest occupied by these types of antenna. Two approaches, one introduced by one layered Circularly-Polarized Patch-Slot antenna design with some changes in material configuration and the other produced by multilayered structures with different dielectric constants in the EBG resonator, are simultaneously used as key controllers of directivity enhancement

Foliar Fertilization of Potassium Silicon Improved Postharvest Fruit Quality of Peach and Nectarine [<i>Prunus persica</i> (L.) Batsch] Cultivars

Peach fruit quality is dependent on preharvest treatments and orchard practices. The aim of this study is to evaluate the effects of preharvest potassium silicon fertilization on fruit postharvest quality. Two peach cultivars (“Early Bomba” and “Plagold 17”) were sprayed with three concentrations of potassium silicon (K-Si) at fruit set, stone hardening, and physiological maturity stages. The applied treatments corresponded to control (T0 = 0% K-Si) pulverized with distilled water and two K-Si treatments (T1 = 3% K-Si and T2 = 4.5% K-Si). The blooming and harvesting dates, vegetative growth and agronomical parameters were analyzed over two growing seasons (2021–2022). Peach fruits were stored at 5 °C and 95% RH during two cold storage periods (2 and 4 weeks) followed by 2 days at room temperatures. The fruit weights (FW), color, firmness, soluble solids content (SSC), titratable acidity (TA), pulp stone ratio (P/S) and fruit weight loss (FWL) were evaluated. The anthocyanins, flavonoids, total phenolics, carotenoids and antioxidant capacity (DPPH) were determined. Vitamin B5 and vitamin C were analyzed by HPLC. The ethylene rate and the chilling injury symptoms (CI) were analyzed after two cold storage periods (2 and 4 weeks). Results showed that the applied potassium silicon treatments (3% K-Si and 4.5% K-Si) enhanced the FW, SSC, TA, FWL, fruit composition and CI. Anthocyanins and total phenolics increased after cold storage period under K-Si treatments. The nectarine cultivar (cv) Early Bomba showed low sensibility to chilling injury symptoms as compared to the cv Plagold 17

EFFET DE L\u2019INTERACTION LUMIERE-SALINITE SUR L\u2019ACTIVITE DU PHOTOSYSTEME II DES FEUILLES EXCISEES DE MA\ucfS

The decline in growth observed in many plants, subjected to salt stress and exposed to sunlight conditions, is often associated with a decrease in their photosynthetic activity. No clear mechanisms of the inhibited photosynthesis have emerged since photosystem II (PS II) is considered to play a key role in the response of leaf photosynthesis to environmental perturbations. The combination of light and salt stress appears to have synergistic effects on the photochemical activity of PSII driving, and to photoinhibition. The objective of this study was to evaluate the reversible effect of salinity and light interaction on maximal quantum efficiency of photosystem II (Fv/Fm.). In this experiment, detached leaves of two forage maize ( Zea mays L. ) varieties, Aristo and Arper were placed during 6 hours in solutions of different concentrations of NaCl (0, 100, 200 and 300 mM) and subjected to light (1000 \ub5mol m-2 s-1) or obscurity. Then, their contents of sodium were determined. In order to verify the photo-inhibition reversibility, other leaves which were incubated in a solution of 300 Mm NaCl, during 4 hours were transferred in distilled water and also subjected to light or to obscurity. Results indicate that leaves which had been put to absorb NaCl in obscurity showed no change in maximal efficiency of PSII (Fv/Fm). Nevertheless, light treatment associated with salinity generates a photo-inhibition of PSII manifested by a significant decrease in maximal efficiency of PSII. This photo-inhibition, due to an excessive accumulation of sodium in leaves, is reversible. It is quite sufficient to eliminate only one factor of the association light-salinity for the PSII activity resume.La diminution de la croissance vegetative observ\ue9e chez nombreuses plantes, soumises au stress salin et expos\ue9es \ue0 des conditions naturelles d\u2019ensoleillement, est souvent associ\ue9e \ue0 une baisse de leur activit\ue9 photosynth\ue9tique. Cependant les m\ue9canismes de l\u2019inhibition photosynth\ue9tique sont encore peu \ue9tudi\ue9s. Le photosyst\ue8me II (PS II) est consid\ue9r\ue9 un des facteurs cl\ue9 dans la r\ue9ponse de la photosynth\ue8se des feuilles aux stress environnementaux. L\u2019association de la lumi\ue8re et du stress salin parait avoir des effets synerg\ue9tiques sur l\u2019activit\ue9 photochimique du PSII conduisant, ainsi \ue0 la photoinhibition. L\u2019objectif de cette etude est de diagnostiquer l\u2019effet de l\u2019interaction lumi\ue8re- salinit\ue9 sur l\u2019activit\ue9 photochimique du photosyst\ue8me II au cours de la photosynth\ue8se. Le materiel vegetal est constitu\ue9 de deux vari\ue9t\ue9s de ma\uefs ( Zea mays L. ) fourrager: Aristo et Arper. Des feuilles d\ue9tach\ue9es de plantes cultiv\ue9es sur milieu t\ue9moin (eau distil\ue9e), sont incub\ue9es pendant 6 heures dans des solutions salines \ue0 diff\ue9rentes concentrations (0, 100, 200 et 300 mM NaCl), soit en absence ou en pr\ue9sence de lumi\ue8re (1000 \ub5mol m-2 s-1). Puis, leurs teneurs en sodium ont \ue9t\ue9 d\ue9termin\ue9es. Pour v\ue9rifiers\u2019il y\u2019aura r\ue9cup\ue9ration de leur activit\ue9 photochimique, d\u2019autres feuilles qui ont \ue9t\ue9 mises \ue0 absorber du NaCl dans une solution de 300 mM \ue0 la lumi\ue8re pendant 4 heures, sont transferees dans de l\u2019eau distill\ue9e en obscurit\ue9 ou en lumi\ue8re. Les resultants montrent une stabilit\ue9 du rendement quantique maximal (Fv/Fm) pour les feuilles mises \ue0 absorber du NaCl \ue0 l\u2019obscurit\ue9.Par contre l\u2019\ue9clairement associ\ue9 avec la salinit\ue9 engender une photoinhibition qui se manifeste par une diminution du rendement quantique maximal du PSII. Cette photoinhibition, due \ue0 une accumulation excessive des ions Na+dans les tissus foliaires, est r\ue9versible. En effet, en absence d\u2019un seul des facteurs de l\u2019association lumi\ue8re-salinit\ue9 le PSII r\ue9cup\ue8re son activit\ue9 photochimique

Electromagnetic Saline Water for Potato Growth and Water Relations

Under water insecurity conditions, electromagnetic saline water may be experienced in irrigation. This study examined the impact of electromagnetic saline water on three potato varieties (Spunta, Bellini and Alaska). The trial includes three treatments; ground water (T1: 2.2 ms cm&minus;1 EC), saline water (T2: 8.5 ms cm&minus;1 EC) and saline water having undergone electromagnetic treatment (T3: 8.5 ms cm&minus;1 EC) with Aqua-4D. The results revealed an improvement in yield with T3 compared to T2. Spunta and Alaska were more responsive to T3 than Bellini. The approving response of Alaska was associated with effective adjustment with proline, while Spunta was more efficient in water use

Priming with EDTA, IAA and Fe Alleviates Pb Toxicity in Trigonella Foneum graecum L. growth: Phytochemicals and secondary metabolites

This study evaluated the effects of the exogenous application of ethylenediaminetetraacetic acid (EDTA), indole-3-acetic acid (IAA) and iron sulfate (FeSO4) upon the phytochemical mechanisms of fenugreek grown under Pb-excess (2000 mg L-1 PbCl2). The results showed that chemical additives of EDTA and IAA as well as FeSO4 improved fenugreek germination parameters. The radicle length and the amylase activity were significantly improved under IAA treatment compared to EDTA and FeSO4. Exogenous FeSO4 was more effective to improving growth parameters. Moreover, the decrease in hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels was noted under all chemical additives especially under IAA application. In addition, it was more effective than EDTA and Fe in increasing catalase, glutathione (GSH), ascorbate peroxidase (APX), flavonoids and phenols while the increment superoxide dismutase (SOD) production was more pronounced under EDTA addition to Pb than other chelators. HPLC analysis revealed that the gallic was the major phenol produced under all chelators addition especially with IAA. In addition, the syringic acid was only produced with exogenous IAA while the quercetin was only detected under EDTA addition. Our results exhibited a higher IAA efficiency than EDTA and FeSO4 in mitigating Pb stress in fenugreek through up-regulated mechanisms of the antioxidant system for reducing reactive oxygen species (ROS) activities and enhancing special phenols

Changes in biochemical compounds in flesh and peel from Prunus persica fruits grown in Tunisia during two maturation stages.

Plants can synthesize tens to hundreds of thousands of primary and secondary metabolites with diverse biological properties and functions. Fatty acids (FA), phenolic compounds (PC) and volatile compounds (VC) of flesh and peel from three Prunus persica cultivars were evaluated at the Regional Centre of Agricultural Research - Experimental Farm (Sidi Bouzid, Tunisia) during two maturation stages. Palmitic, oleic and linoleic acids are the most abundant FA in Prunus persica cultivars. A genetic effect on FA composition was observed throughout the two sampling periods. Peel was rich in oleic acid with the highest content (31.3% on total FA) in 'O'Henry' cultivar at the commercial ripening date; flesh was rich in linoleic acid with the highest content (44.7% on total FA) in 'Sweet Cap' cultivar at the full ripening date. The monounsaturated/polyunsaturated fatty acids ratios were higher in the commercial ripe than in the full ripe fruits. The analysis of the composition of the VC led to the characterization of 98 different compounds, showing a very high variability among the cultivars. The full ripe fruit (peel and flesh) exhibited the highest total number of terpenoids. Commercial ripe peels were richest in the percentage of hydrocarbons. Comparing cultivars, 'Sweet Cap' cultivar showed the lowest contents of alcohols in peel and flesh of full ripe fruit but highest in peel of commercial ripe fruit, and lowest content of aldehydes in peel and flesh of commercial ripe fruit but highest in peel of ripe ones and the highest ones of lactones. Among PC, the highest contents were observed for o-diphenols and the values showed varietal influence. Total phenols contents decreased during ripening process (p < 0.05) in both peel and flesh tissues, except found for 'Sweet Cap' cultivar. In conclusion, to achieve better FA composition and greater VC and PC production of the peach fruit, P. persica cultivars should be harvested at the commercial ripening date