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1

Potassium deficiency in plants: effects and signaling cascades

100%
Hafsi C., Debez A., Abdelly C.
Acta Physiologiae Plantarum
|
2014
|
tom 36
|
nr 05
Potassium (K⁺) is an important macronutrient for plant growth and productivity. It fulfills important functions and it is widely included in fertilization management strategies to increase crop production. Although K⁺ is one of the most abundant elements of the earth crust, its availability to plants is usually limited leading to severe reduction in plant growth and yield. In plants, K⁺ shortage induces several responses at different levels: morphological, physiological, biochemical, and molecular. Activation of signaling cascades including reactive oxygen species, phytohormones (ethylene, auxin, and jasmonic acid), Ca²⁺, and phosphatidic acid is also triggered. In this review, we summarize the main of these adaptive responses evolved by plants to cope with K⁺ deficiency in the rhizosphere.
2

Photosynthetic activity and leaf antioxidative responses of Atriplex portulacoides subjected to extreme salinity

88%
Benzarti M., Ben Rejeb K., Debez A., Messedi D., Abdelly C.
Acta Physiologiae Plantarum
|
2012
|
tom 34
|
nr 5
Responses of Atriplex portulacoides upon 40-day-long exposure to salinity (0–1,000 mM NaCl) were investigated. Mother plants originated from a sabkha located in a semi-arid region of Tunisia. The plant relative growth rate and leaf expansion increased significantly at 200 mM NaCl but decreased at higher salinities. Interestingly, the plants survived salinity as high as 1,000 mM NaCl without displaying salt-induced toxicity symptoms. Despite significant increase in leaf Na⁺ and Cl⁻ concentrations upon salt treatment, no significant effect on leaf relative water content was registered. Chlorophyll contents and the gas exchange parameters showed a significant stimulation at the optimal salinity (200 mM NaCl) followed by a decline at higher salinities. Extreme salinity hardly impacted the maximal efficiency of photosystem II photochemistry (Fv/Fm), but a marked decrease in the relative quantum yield of photosystem II (ΦPSII) was observed, along with a significant increase in non-photochemical quenching (NPQ). Leaf malondialdehyde and carotenoid contents were generally unaffected following salt exposure, whereas those of anthocyanins, polyphenols, and proline increased significantly, being maximal at 1,000 mM NaCl. Leaf superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11), and glutathione reductase (EC 1.6.4.2) activities were significantly stimulated by salinity, whereas catalase (EC 1.11.1.6) activity was maximal in the 0–400 mM NaCl range. As a whole, protecting the photosynthetic machinery from salt-induced photodamage together with the sustained antioxidant activity may account for the performance of A. portulacoides under high salinity.
3

Salt tolerance of the annual halophyte Cakile maritima as affected by the provenance and the development stage

76%
Megdiche W., Amor N. B., Debez A., Hessini K., Ksouri R., Zuily-Fodil Y., Abdelly C.
Acta Physiologiae Plantarum
|
2007
|
tom 29
|
nr 4
Though halophytes are naturally adapted to salinity, their salt-tolerance limits are greatly influenced by their provenance and developmental stage. In the present study, physio-biochemical responses of two Tunisian ecotypes of the oilseed coastal halophyte Cakile maritima (Brassicaceae) to salinity (0–400 mM NaCl) were monitored during germination and vegetative growth stages. Tabarka and Jerba seeds were collected from humid or arid climatic areas, respectively. Plant response to salinity appeared to depend on the ecotype and salinity levels. Increasing salinity inhibited germination process. Jerba seeds were found to be more salt tolerant than the Tabarka ones. At the autotrophic stage of growth and under salt-free conditions, Jerba was less productive than Tabarka (in terms of dry matter accumulation), but plant biomass production and leaf expansion (area and number) of the former ecotype were progressively improved by 100 mM NaCl, as compared to the control. In contrast, at the same salt concentration, these parameters decreased under increasing salinity in Tabarka (salt sensitive). Leaf chlorophyll content was reduced at severe salinity, but this effect was more conspicuous in the sensitive Tabarka plants. Na⁺ contents in the Jerba and Tabarka leaves collected from the 400 mM NaCl-treated plants were 17- and 12-fold higher than in the respective controls. This effect was accompanied by a significant reduction in the leaf K⁺, Mg²⁺ and Ca²⁺ contents, especially in the salt-treated Tabarka. A significant accumulation of proline and soluble carbohydrates in leaves was found during the period of intensive leaf growth. These organic compounds likely play a role in leaf osmotic adjustment and in protection of membrane stability at severe salinity.
4

Risk of municipal solid waste compost and sewage sludge use on photosynthetic performance in common crop (Triticum durum)

64%
Lakhdar A., Slatni T., Iannelli M. A., Debez A., Petrini F., Jedidi N., Massacci A., Abdelly C.
Acta Physiologiae Plantarum
|
2012
|
tom 34
|
nr 3
The effect of composted municipal solid waste (MSW) and sewage sludge (SS) on photosynthetic activity of wheat (Triticum durum L.) was investigated. Chlorophyll fluorescence and gas exchange parameters were assessed following application of up to 300 t ha-1 of MSW compost or SS. 100 t ha⁻¹ MSW compost was optimal for the plant growth, which showed 78% stimulation as compared to the control. This was associated with higher maximum quantum efficiency (Fv/Fm) of photosystem II (PSII) and the actual quantum efficiency of PSII open centers at light adapted state (ΔF/F'm ). Maximal values of net photosynthetic rate and stomatal conductance were recorded at 100 t ha⁻¹ MSW compost (+40 and +116%, respectively). Ribulose bisphosphate carboxylase/oxygenase (RubisCO) activity was also significantly stimulated at 100 t ha⁻¹, while less significant impact was found in SS treatment. A marked accumulation of Ni, Pb, Cu, and Zn in concomitance with membrane lipid peroxidation were observed at 200–300 t ha⁻¹ MSW compost and SS, resulting in lower photosynthetic activity and altered PSII functional integrity. Altogether, these results suggest that the MSW compost at 100 t ha⁻¹ would be suitable for wheat cultivation, within the critical limits of heavy metal accumulation. However, long-term field experiments seem necessary to more accurately evaluate the safety of MSW application.
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