Journal of Plant Process and Function

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The effect of concentrations 0(control), 250, 500, 1000, 2000 and 4000 µM of aluminum on the growth rate and content total chlorophyll of Dunaliella salina strain UTEX-200 has been studied for duration of 27 days. The results indicated that an increase in aluminum concentration resulted in a decrease in the growth rate and chlorophyll content. It seems that these effects are probably due to destruction of cell membrane and suppression of essential elements uptake, such of Ca2+ and Mg2+, respectively. The treatment of algal suspension by different concentrations 0(control), 500, 1000, 2000, 3000 and 4000 µM of aluminum resulted in algal cells-Al3+ ions binding, cell agglutination and sedimentation, reduction of the algal cell number in supernatant of cell suspension and consequently removal of aluminum. The results of adding EDTA to algal suspension for binding of aluminum and preventing of cell sedimentation confirmed algal cells-Al3+ ions binding. Also, this study indicated that not only each cell of algal suspension has defined capacity for sedimentation of aluminum, but just intact cells can bind to Al3+ ions and aluminum bioremediation. In adding, the results of this study indicates that strong binding of algal cells-Al3+ ions resulted in reduction of growth rate and cell division, cell agglutination and sedimentation and aluminum bioremediation.

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Surveying the inhibition of mevanolate / acetate (MVA) pathway in lipid production in green algae of Dunaliella salina and Dunaliella bardawil by using Lovastatin

Z and  *

Department of Biology, Faculty of Science, University of Isfahan

 
Abstract
 
Many of microalgae are rich in lipid and are very much considered due to the limitations of nutritional needs and rapid growth. Since the lovastatin inhibits the pathway of mevanolate (the pathway of beta-carotene biosynthesis) and the beta-carotene is a terpenic compound and is a simple lipid types, in this study, the inhibitory effect of lovastatin on two microalgae Dunaliella salina and Dunaliella bardawil was studied in lipid production. Algal cells were cultured in autotrophic conditions under different concentrations of lovastatin. The results showed that the prevention of mevanolate pathway leading to decrease of cell growth, chlorophyll and beta-carotene concentrations, and  as well as  an increase in lipid production in D. salina, whereas in D. bardawil caused a decrease in the concentration of chlorophyll and beta-carotene, as well as an increase in lipid production with no affect on cell growth. The results showed, twice amount of chlorophyll and beta-carotene content in D. bardawil compared to D. salina and double growth of D. salina than D. bardawil. An increase of 1.5 times the lipid production in the shortest time (one week) in D. bardawil compared to D. salina showed that D. bardawil algae is more appropriate species for the production of lipid by inhibiting the mevanolate pathway. The results suggest that the mevanolate pathway is the required route for D. salina and D. bardawil algae, and preventing it, leading to change the pathway of acetyl coenzyme A from beta-carotene synthesis to increase of lipid production in the cell. 

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Heat shock proteins (HSPs) as stress proteins have vital roles in plant adaptation to biotic and abiotic stresses. These proteins expressed in almost all kinds of stresses and are well known to be contribute in protection of cells. Among them the HSP90, HSP70 and smHSPs have significant roles in cell. In this study, the gene fragments of smHSP, HSP70 and HSP90 from Capparis spinosa L. plant were cloned into the tobacco rattle virus vector, pTRV2 to heterologously suppress the corresponding endogenes of N. benthamiana. Silenced plants were exposed to salt stress (100 mM NaCl) for 3 weeks and Chl a fluorescence induction kinetics was analyzed. Compare to smHSP and HSP90, silencing of HSP70 was found to have stronger negative effect especially after salinity on some parameters related to the donor site of electron in PSII [F_v/F_o] and, the parameters dependent on the acceptor site of the electron such as φ_Eo, φ_Ro, ψ_o and ψ_o/(1-ψ_o.) It was also represented that simultaneous silencing of the HSP70 gene and salinity treatment resulted in a significant decrease of Sm/t _Fm and the Performance Index (PI_ABS) and an increase of dissipation per active reaction center (DI_o/RC). So these results reflecting among the HSPs tested in the present study, HSP70 silencing cause severe injuries in reaction centers of PSII especially after salt stress.

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The ornamental plant industry faces many environmental constraints, such as drought due to climate change. Therefore, the use of materials that mitigate these stresses is essential. A pot experiment was conducted to investigate the effect of potassium silicate on the physiological and biochemical responses of marigolds under water stress. Four water deficit treatments were applied, including 90, 80, 70, and 60% of field capacity and potassium silicate at three concentrations (0, 1, and 3 mM). Results showed that the water deficit at 60% FC significantly reduced leaf relative water content (10.6%) and plant vegetative characteristics (height, leaf area, dry weight) compared to 90% of crop capacity in the no foliar spray condition. Increased ion leakage was observed in plants under water stress as an indicator of oxidative damage. In response to oxidative stress caused by a water deficit, the amount of chlorophyll, carbohydrate, and proline increased compared to the control. Foliar spraying of potassium silicate at a dosage of 3 mM increased the amount of chlorophyll a (92%), chlorophyll b (74%), and total chlorophyll (73%) under 60% FC stress compared to the control. The number and diameter of flowers increased by 39% and 16%, respectively, in the 3 mM treatment compared to the plants without foliar spraying. According to the results, foliar spraying with potassium silicate at a concentration of 3 mM reduced the negative effects of drought stress on the growth characteristics of marigold, such as leaf area and dry weight, and increased the amount of essential oil in the plant. In this way, the use of 3 mM potassium silicate before transplanting plants into environmental conditions can prevent damage caused by a water deficit.