فصلنامه فرآیند و کارکرد گیاهی
سال پنجم شماره 4 (پیاپی 18، زمستان 1395)

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 AsA, 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誺 contents of the seed, and control as well as seed soaking in distilled water, 3% zinc sulfate, 3% iron sulfate, and 3% zinc% 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 different levels (0, 3, and 6%) of either sorbitol or mannitol. Both sorbitol and mannitol were found to reduce the photosynthetic pigments 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 culture media, 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 oil compounds of both the seedlings and the calli of C. copticum. Analysis of the essential oil constituents by Gas chromatography–Mass Spectrometry (GC–MS) showed thymol, gamatherpinen, and parasimen to be the main essential oil components which increased in quantity under high stress conditions. These bioactive compounds have many industrial and medicinal applications.

Drought is one of the most adverse environmental constraints that impact on plant growth and reduce crop yields.To discus effect of water deficit on molecular and physiological responses, two cultivars of bread wheat (Sardari and Zarin) were selected (based on results accumulated during three years of research described in Heidari et al (1381). The plantswere cultivated in a completely randomized design with three replication in plastic pots containing field soil in growth chambers (30/ 20 °C, 14 h day/ 10 night, 60% R.H).Their response to water stress was performed at the physiological level by determination of relative water content (RWC), chlorophyll, free proline and total proteins content for duration of the drought treatment and subsequent re-watering.All physiological parameters were affected by drought stress. Relative water content of zarin cultivar reduced significantly. The content of chlorophyll a and total chlorophyll in the both cultivars decrease significantly but the change of the content of chlorophyll b in two cultivars wasnt significant. The free proline contents of two cultivars increased significantly and both cultivars could recover to normal condition by re-watering after short term drought. SDS-PAGE electrophoresis of leaf proteins under control and drought treatments showed some up and down regulated proteins.Modification in the expression level of dehydrin (DHN) gene (Rab17) was also analyzed by reverse transcription–polymerase chain reaction (RT-PCR). This gene was expressed slightly in the well water plants of two cultivars, but the gene expression of sardari cultivar increased significantly after long term drought.

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.

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 AsA, 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.

A modern biotechnological technique to obtain useful natural products from plants is to isolate them from their callus cultures. Lallemantia iberica is an annual herb of the Lamiaceae family known for its stimulant, diuretic, and expectorant effects in Iranian folk medicine. The present study investigated the induction of plant callus tissue and identification of its volatile compounds. For this purpose, plant seeds of Lallemantia iberica were sterilized and cultured in petri dishes lined with an 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 at 25 °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 to analysis by gas chromatography-mass spectrometry (GC-MS). Results showed that callus induction from the cotyledon segments of the seedlings was better accomplished in the MS medium containing phytohormones and in a dose-dependent manner. 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%).