JOURNAL OF PLANT PROCESS AND FUNCTION
Year:2017 | Volume:5 | Issue:18|Papers Count:8

Silicon(Si) is the second most abundant element in the earth’s crust and is regarded as a beneficial element for higher plants.In this study, the effect of Si supplementation (1 and 4 mM) was studied on wheat (Triticum aestivum cv. Homa) plants grown hydroponically under salinity stress (50 and 150 mM NaCl) for two weeks under controlled environmental conditions. Plant biomass was found to decrease at both salinity levels. Contrary to our expectation, Si supplementation failed to mitigate the salt stress effects on dry matter production. However, the majority of biochemical parameters related to salt tolerance showed improvements as a result of Si application, particularly at 1 mM. Under both control and salinity conditions, Si treatment resulted in higher leaf contents of chlorophyll and carotenoids, soluble sugars, proteins, and free amino acids, particularly proline. Osmotic potential, however, declined in the roots, suggesting that Si supplementation might contribute to plant’s higher water uptake capacity. Sitreatment diminished leaf concentration of Na+ in the cell sap but increased it in the cell wall-bound fraction, indicating a Na+ detoxification mechanism mediated by Si. Our results suggest that a short-term Si treatment affects biochemical indicators of salt tolerance but that long-term exposure to Si is needed for a significantly alleviating effect on plant biomass.

Drought is the cause of adverse environmental impacts on plant growth and crop yield. In this study, the effects of water deficit on plant molecular and physiological responses were investigated using two cultivars (namely, Sardari and Zarin) of bread wheat selected based on the results of a three-year research. For the purposes of this study, they were grown in plastic pots containing field soil and maintained in growth chambers (30.20oC, 14.10 h day/night, 60% R.H). The cultivars had been The experiment was conducted in a completely randomized design with three replications. Plant response to water stress was evaluated at the physiological level by determining the relative water content (RWC) as well as chlorophyll, free proline, and total protein contents following the drought treatment with subsequent re-irrigation. All the physiological parameters were found to be affected by drought stress. The Zarin cultivar exhibited a significant decrease in its RWC. Chlorophyll a and total chlorophyll in both the cultivars showed significant decreases but chlorophyll b did not exhibit any significant variation in either cultivar. The free proline content increased significantly in both cultivars such that they were both restored thei r normal proline contents life when irrigation was resumed after a short-term experimental drought stress. SDS-PAGE electrophoresis of leaf proteins in both control and experimental samples revealed regulating adjustments in protein contents.Modification in the expression level of the dehydrin (DHN) gene (that is, Rab17) was also analyzed by reverse transcription–polymerase chain reaction (RT-PCR). This gene was expressed slightly in the well watered plants of the two cultivars, but the gene expression in the Sardari cultivar increased significantly after the long-term experimental drought.

Heavy metals are the cause of major abiotic stresses in plants and a principal contributor to environmental pollution in recent decades. This study investigated the effects of exogenous hydrogen sulfide on the ascorbate-glutathione cycle in the leaves of coriander seedlings under copper stress. Results showed that copper stress not only reduced APX and GR activities but also decreased leaf As A, DHA, and GSH contents. Pretreatment with sodium hydrosulfide (NaHS), a hydrogen sulfide (H2S) donor, was observed to enhance both GR activity and AsA, GSH, and DHA contents under copper stress. Moreover, the pretreatment decreased the malondialdehyde content and electrolyte leakage induced by copper stress in plants. Based on the results obtained, it was hypothesized that exogenous hydrogen sulfide alleviates oxidative damage under copper stress by regulating the ascorbate-glutathione cycle and, further, that H2S plays an important role in the acquisition of copper stress tolerance in coriander seedlings. Exogenous hydrogen sulfide is, therefore, identified as an agent with the potential to be used as a regulator to improve crop tolerance under copper stress.

To study the effects of both drought stress and seed zinc and iron concentrations on the photosynthesis, chlorophyll fluorescence, and proline and carbohydrate accumulations in soybean (Glycine max (L.) Merr. cv. M9) leaf, a split plot experiment was carried out in 2012 based on a randomized complete block design with three replications in greenhouse conditions at Yasouj University. Drought stress, based on 70% depletion of the available soil water, was designated as the main-plot that included drought stress at the flowering, pod filling, and seed filling stages. Zinc and iron concentrations were designated as sub-plot factors that included high zinc, iron and zinc+iron contents of the seed, and control as well as seed soaking in distilled water, 3% zinc sulfate, 3% iron sulfate, and 3% zinc+3% iron sulfate solutions. Results showed that photosynthesis characteristics, net photosynthesis rates, stomatal conductance, and transpiration rates decreased under the drought stress conditions. Drought stress also led to decreased water use efficiency (WUEi). Moreover, leaf proline and soluble carbohydrate contents increased in response to drought stress. While PSII quantum yield reduced under drought stress, it increased under high seed zinc and iron concentrations. It was concluded that enhanced seed zinc and iron concentration was capable of ameliorating the impacts of drought stress on leaf proline and carbohydrate concentrations.

Carum copticum L. is a medicinal plant of the Apiaceae family with medicinal properties. In this study, the effects of drought stress on the photosynthetic pigments and essential oils as well as the enzymatic and non-enzymatic mechanisms of the seedlings and callus of C. copticum were investigated within the framework of a controlled experiment under in vitro conditions. For this purpose, the seedlings of C. copticum were cultured in the Murashige and Skoog medium containing three levels (0, 3, and 6%) of either sorbitol or mannitol. Furthermore, its calli were independently cultured in the Murashige and Skoog (MS) medium containing 0.25 mg.L-1 2, 4-dichlorophenoxyacetic acid, 1 mg.L-1 benzyl amino purine, and differentl evels (0, 3, and 6%) of either sorbitol or mannitol. Both sorbitol and mannitol were found to reduce the photosyntheticpigments and carotenoid contents but increased the anthocyanin and flavonoid contents significantly. However, these effects were significantly more severe in plants submitted to mannitol, as compared to the sorbitol-treated ones. With the exception of the mannitol-treated leaf samples whose phenolic contents decreased with increasing drought concentration in the culturemedia, the phenolic contents in the other samples increased relative to those in the control samples. The ascorbate peroxidase activity was found to decrease in all the treated samples while the catalase activity greatly increased, particularly in the mannitol-stressed plants. Compared to the control, drought led to a significant increase in superoxide dismutase activity in all the samples treated with 6% sorbitol and in the calli samples treated with 3% mannitol, whereas the seedlings grown under mannitol treatment showed almost no difference with the control plants. In addition, drought stress changed the essential oilcompounds of both the seedlings and the calli of C. copticum. Analysis of the essential oil constituents by Gaschromatography–Mass Spectrometry (GC–MS) showed thymol, gamatherpinen, and parasimen to be the main essential oilcomponents which increased in quantity under high stress conditions. These bioactive compounds have many industrial andmedicinal applications.

It is essential to identify and determine the properties of native plants as natural genetic resources. The present study was performed to identify the Mindium (Michauxi) laevigata species using molecular and biochemical procedures such as genomic DNA extraction, sequencing, and antioxidant capacity and protein content determination at both vegetative and generative phases in various parts of the plant. For this purpose, Mindium laevigata plants were collected from natural habitats and their genomic DNAs were extracted and purified. This was followed by the extraction of 18S ribosomal DNA sequence from the genomic DNA by PCR and its analysis to determine the antioxidant enzymes (peroxidase, ascorbate peroxidase, and catalase). Accordingly, the proteins were quantitatively and qualitatively assayed at both vegetative and reproductive stages in the different plant organs of roots, stems, and leaves. Ascorbate peroxidase and catalase activities were detected in the stem samples at the vegetative and generative phases, respectively. Gel electrophoresis bands of the total protein were found to be different in various parts and at different developmental stages of the plant. Another aspect of the study involved the use of the phylogenetic tree for the biosystematic investigations of Mindium laevigata. Molecular analyses resulted in the inscription of a new gene in GenBank under the accession number KC294445.1.Mindium laevigata seems to be a rich source of antioxidant enzymes and proteins and as such it is recommended for further research.

The present investigation was undertaken to determine the biochemical changes associated with flower development during the flowering season in the potted carnation cultivars of ‘Lilac on purple’ and ‘Pink’. Ethylene production and the 1-aminocyclopropane-1-carboxylic acid (ACC) content of the flowers were observed to increase up to stage 5 (during the five stage of flowering) in both cultivars. Peroxidase (POD) and superoxide dismutase (SOD) showed three distinct phases: a low activity during the initial stages of flowering, a sustained activity during the mid-developmental stages, and accelerated activity at the full bloom. A significantly high activity of POD was observed in both cultivars during the fully open flower stage. The catalase (CAT) activity in ‘Lilac on purple’ was high during the 4th or 5th stages. However, no significant differences in CAT were observed in ‘Pink’. H2O2 content increased with age, with the highest observed at the last stage.Finally, the sugar (Sucrose, Glucose, and Fructose) content in the tissues of the petals increased during the flower opening stage. The findings suggest that the regulation of flower development in mini-potted carnation may be linked to the antioxidant metabolism and the sugar status of the petal tissues.

A modern biotechnological technique to obtain useful natural products from plants is to isolate them from their calluscultures. Lallemantia iberica is an annual herb of the Lamiaceae family known for its stimulant, diuretic, and expectoranteffects in Iranian folk medicine. The present study investigated the induction of plant callus tissue and identification of i tsvolatile compounds. For this purpose, plant seeds of Lallemantia iberica were sterilized and cultured in petri dishes lined withan MS medium. After the emergence of seedlings, cotyledon segments were transferred to another MS medium supplemented with different combinations of the plant hormones BAP and 2, 4-D. The petri dishes were incubated in a growth chamber at25 °C for a given photoperiod. The fresh weights of the calli thus produced in the hormonal treatments were measured. In a second stage of the study, the essential oil of the fresh calli was obtained using a Clevenger type apparatus and subjected toanalysis by gas chromatography-mass spectrometry (GC-MS). Results showed that callus induction from the cotyledonsegments of the seedlings was better accomplished in the MS medium containing phytohormones and in a dose-dependentmanner. Maximum callus production was induced in the MS medium supplemented with 2, 4-D (4 mg/L) and BAP (1.5 mg/L) as 3.5g. GC/MS analysis showed that the dominant compounds in the essential oil were Thymol (53.03%), Octane (19.90%), Decane (5.73%), Carvacrol (5.63%), and Octadecane (3.73%).