فصلنامه زیست شناسی گیاهی ایران
سال هفتم شماره 4 (پیاپی 26، زمستان 1394)

Salt stress is one of the most important factors that endanger plant growth and production all around the world. Application of compounds which increase plant resistance to salt stress obviously has significant importance in reduction of economic losses. One of these compounds is the biological alcohol called ethanolamine, and the present study aimed to understand the way by which ethanolamine exerts its protecting effect against salt stress. For this purpose, 4-week-old Nicotiana rustica plants which had been kept in MS medium were pretreated with ethanolamine and 2 days later they were transferred to MS medium supplemented with 200 mM NaCl for 3 weeks. The our results revealed that Nicotiana rustica plants pretreated with exogenous ethanolamine showed elevated level of TAL activity and anthocyanin content whereas PAL activity was decreased, and reduced level of MDA, total flavonoid and phenol content in plants under salt stress condition. According to these results, it can be suggested that ethanolamine exerts its protective effect by anthocyanin content increase.

Evolutionary trend of morphological characters of Astragalus dictyolobus, A. tawilicus (previously classified in section Laxiflori) and A. victoriae (previously classified in section Chrstianophysa) with other species of section Alopecuroidei based on phylogeny of cpDNA matK sequences is presented. 25 taxa belonging to section Alopecuroidei as well as A. bassineri and A. sieversianus belonging to section Astragalus as outgroups were analysed. 12 vegetative and generative characters were selected and different states of them based on phylogeny of cpDNA matK sequences were analyzed. The present analysis revealed that state of pod in calyx, density and shape of inflorescence were not in agreement with results of molecular data and indicated the artificial nature of these characters in previous classification of section Alopecuroidei. Presence of bracteole and shape of ovary were consistent with phylogeny of cpDNA matK sequences. Presence of peduncle in A. dictyolobus and A. tawilicus demonstrated that they are well allied with other species of section Alopecuroidei. Lax inflorescence makes A. victoriae relative to A. dictyolobus and A. tawilicus. Other mentioned characters except lax inflorescence make it relative to section Alopecuroidei.

Ultrasound (US) with low intensity is considered as a physical tool to stimulate living systems in medicine and biotechnology. This study aim to survey the US effects on some physiological parameters and podophyllotoxin production in Linum album cell culture. The cell cultures were treated with US waves with a frequency of 40 kHz and the power 5 Wcm-3, in a time dependent experiment with 3 replicates and the cells were collected at 24, 48 and 72 h after the treatment. Evaluated parameters were cell growth, contents of total protein, MDA, hydrogen peroxide, phenolics, flavonoids, activity of peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase and podophyllotoxin. The results showed that cell growth was significantly decreased by the US, but there was no significant change in protein content. The amount of hydrogen peroxide, membrane lipid peroxidation and activity of peroxidase, polyphenol oxidase and phenylalanine ammonia-lyase enzymes were increased in cells under the effect of US, compared to control. Also US increased the production of phenolic compounds, flavonoids and podophyllotoxin in treated cells. Maximum amount of podophyllotoxin was obtained in treated cultures after 72 hours which was the 268.9 µg/g DW (2.7 times that of the control). It seems that US by stimulating cells and induction of defensive responses and secondary metabolism increased the amount of podophyllotoxin in cells of Linum album plant.

Salinity is one of the major factors limiting the growth of plants that threaten the sustainability of agriculture in vast areas of the world. It seems that the evaluation of medicinal plants such as thyme due to food, pharmaceutical and health is essential under salinity stress to discover its benefits of economic and health. This study was designed to investigate the effect of salinity on physiological parameters, biochemical and secondary metabolites in thyme (Thymus vulgaris) under in vitro culture conditions. Thyme seedlings grown from the seeds, 4 weeks after growth at 16 hours of light and 8 hours of dark and at temperature of 25±1 ºC in the growth chamber, were transferred to MS (Murashige and skoog) medium containing different concentrations of NaCl (0, 80, 100, 120 and 150 mM) and 25 days after the subculture, physiological parameters such as antioxidant enzymes activities and active pharmaceutical ingredients were measured. 25 days after salt treatment, the chlorophyll a, b, total chlorophyll, carotenoids, and total soluble protein content were significantly decreased with increasing NaCl concentration, whereas increasing the salt concentration increased carbohydrates, proline and phenolics in thyme seedlings. Also salinity led to a significant increase in the activity of antioxidant enzymes. GC-Mass analysis showed that the productions of secondary metabolites were greatly affected by salinity. By increasing salinity level of P-cymene and Gama Terpinene increased and Thymol decreased. In general, it was observed that salinity with changes the physiological and biochemical parameters and the amount of active ingredients of Thyme can change the value of its medicinal properties.

Salinity reduced the efficiency of agricultural production like maize as one of the most important cereals for food and oil for humans. Silicon is the second most abundant element in the soil and alleviates the biotic and abiotic stresses in plants. The aim of this study is evaluate the effect of silicon and nanosilicon on improvement of salt stress in maize (Zea mays). For this propose, the interaction between the effects of different levels of salinity (0 and 100 mM), silicon and nanosilicon (50, 100 and 150 mg /mL) was studied in completely randomized block design with factorial experiments and with three replications. The results showed that salinity significantly decreased root and shoot growth, amount of chlorophyll and carotenoid pigments, protein and potassium contents, compared to control. Treating plants with silicon and nanosilicon caused reduction of salinity effects and increase above indices. Salinity stress also caused a significant increase in proline, anthocyanin and soluble carbohydrate contents, lipid peroxidation, and catalase activity and treatment with silicon and nanosilicon alleviates effects of salt stress and reduced the amount of above indices. 150 mg/mL of nanosilicon showed the maximum effect on diminishing negative effects of salt stress on all examined parameters. So, the use of this element is proposed as alleviator of salt stress on maize.

Opposition to destructive and side effects of salt stress, have limited suitable water and soil sources for plant culturing, is possible by increasing the tolerance level of seeds and seedlings. In present research, the effect of priming technique was studied with Na2SiO3 or KNO3 in 3, 6, 9 and 12 hours on Medicago sativa cv. Hamadani in response to 200 mM salt stress. Salinity caused a decrease of most of germination and growth indices from seeds and seedlings, whereas 3h-Na2SiO3 priming increased final germination percentage (FGP) and (3/6/9h)-KNO3 increased FGP, coefficient velocity of germination (CVG), compared to control. An improvement in mean germination rate (MGR) and mean germination time (MGT) was shown by 6h-Na2SiO3 and all KNO3 treatment times and increase of Vigor index (I) was observed at 3h-KNO3. Pretreatment with (3/6/9h)-Na2SiO3 and all h-KNO3 decreased T50 at stress and in non stress conditions, 9h-Na2SiO3 and 9h-KNO3 caused a decrease in mean daily germination (MDG) and an increase in Timson index and improvement of coefficient uniformity of germination (CUG). 12 hour treatments from both substances exacerbated the conditions and decreased the FGP, Vig (I) and (II) and decreased CVG. All-Na2SiO3 and (9/12)-KNO3 decreased the dry weight of shoots at stress. Proline was raised only with KNO3 and salt affected pigments negatively and priming increased them. In conclusion, priming elevated tolerance to salt stress and treatment compositions with the lower times were more efficient.