فصلنامه زیست شناسی گیاهی ایران
سال پنجم شماره 4 (پیاپی 18، زمستان 1392)

Nitric oxide (NO) is a highly reactive free radical with a wide variety of physiological implications in plants. In this research، we investigated the protective effects of exogenous Sodium Nitroprusside (SNP) as a NO donor، against the toxicity caused by excess arsenic in sweet basil (Ocimum basilicum L.). Seedlings grown in a Hoagland nutrient solution were treated with SNP at 0 (control) and 150 µM and different concentration of arsenate at 0 (control)، 150 and 300 µM. Arsenic treatment (specially in 300 µM) significantly induced accumulation of hydrogen peroxide (H2O2) significantly increase in serious lipid peroxidation، electrolyte leakage (EL) and decreased the growth and the biomass of basil. Application of SNP before arsenic stress resulted in alleviated arsenic-induced electrolyte leakage and malondiadehyde (MDA) content and increased proline and free amino acid contents in shoots and roots of sweet basil، compared with the control. On the whole، our results showed stronger arsenic toxicity in the root than in the shoot and nitric oxide probably، was increased tolerance capacity in basil due to production of osmoprotecting compounds such as proline، sugar and free amino acid. In addition، analysis of ICP-results indicated that، As translocation from root to shoot of O. basilicum was limited by SNP pretreatment which is very important for human health.

In order to evalouate salicylic acid (SA) priming effects on lentil seed germination (Lens culinaris Medik.)، antioxidant enzyme activity and some physiological traites in salt stress condition، a factorial experiment was conducted at the Seed Technology Laboratory of Yasouj University in a completely randomized design with four replications. The first factor was hydropriming by distilled water and two levels of salicylic acid (0. 2 and 0. 5 mM) for 4 hr and the control without priming. The second was five levels of salinities (0، 50، 100، 150 and 200 mM NaCl) equal to (0، 5، 10، 15 and 20 ds. m-1) and the last one three cultivars of lens (Ghachsaran، Kermanshah and Kimiya). After germination، germination persentage، root and shoot length، dry weight، catalas، polyphenoloxidas and peroxidas activity، MDA and proline were measured. The results showed that the salinity decreased seed germination. Influence of SA was signification and increased percent of germination in the stressed and control treatments. Enzymes activity assay showed that enzyme activity was increased under salt stress conditions and SA reduced activity of antioxidant enzyme by decreasing the salinity effects. Kermanshah cultivar had more tolerance than other cultivars with respect to salinity stress.

Ascorbic acid as a water soluble antioxidant molecule، participates in many physiological processes such as resistance to environmental stresses. To evaluate the effects of copper stress (6. 5 μM) and application of ascorbic acid through rooting medium (0. 5 mM) on some physiological characters of onion plants (Allium cepa L. cv. Red Azarshahr)، a completely randomized design with four replications was conducted. Results showed that excess Cu reduced the dry weight of roots and leaves، as well as content of photosynthetic pigments and K+ of seven-week-old plants. Exogenous ascorbic acid significantly improved dry weight of roots and leaves with increasing content of K+ and photosynthetic pigments in both the non-stressed and Cu-stressed plants. Cu stress led to accumulation of free amino acids and soluble sugars in roots and leaves. Treatment with exogenous ascorbic acid considerably reduced the contents of these compounds in both non-stressed and Cu-stressed plants. There was considerable reduction in osmotic potential at full turgor and significant increase in osmotic adjustment in leaves of Cu-stressed plants. Application of exogenous ascorbic acid had no effect on osmotic potential at full turgor، but significantly increased osmotic adjustment. In leaves of Cu-stressed plants K+ was the minor contributor to osmotic potential at full turgor. Also، by adding ascorbic acid، K+ contribution was increased in leaves of non-stressed and Cu-stressed plants. Results of the present study indicated that usage of exogenous ascorbic acid reduced harmful effects of copper stress and increased resistance to copper stress in onion plants.

Drought stress increases the generation of reactive oxygen species and causes membrane lipid peroxidation and damages cell membranes in the plant cells. In this study، we investigated the role of ascorbate pre-treatment in inducing tolerance to oxidative stress and improving resistance to drought stress. Drought stress reduced growth parameters، percent of water content، chlorophyll، carotenoids، protein، phenolics and phenylalanine ammonialyase activity but increased lipid peroxidation، ion leakage، lipoxygenase activity and hydrogen peroxide، total sugars، and proline levels. Pretreatment with ascorbic acid decreased lipid peroxidation، ion leakage، lipoxygenase activity، the amount of hydrogen peroxide and total sugars content but increased the amount of chlorophyll، carotenoids، protein، phenolics and phenylalanine ammonialyase activity all resulting in increased water content and improved growth parameters.

Glycyrrhiza glabra L. (Licorice) is one of the oldest medicinal plants in Iran and secondary metabolites present in the plant root is used in food and pharmaceutical industries. With the use of heavy metals as elicitors، plant secondary metabolite production can be increased. In this study، the effects of the concentrations of 1 and 10 µM of zinc oxide and copper oxide on the contents of reducing sugars (as precursor of secondary metabolites)، proline، glycyrrhizin، total phenolic compounds، flavonoids and anthocyanins in Glycyrrhiza glabra seedlings were investigated. Also، the correlation between the content of these metabolites in the treated seedlings was examined using Pearson''s test. The amount of reducing sugars at concentration of 10 µM zinc oxide was decreased. Whereas، the amounts of proline and glycyrrhizin under treatment 1 and 10 µM copper oxide and 1 µM zinc oxide compared with the control plants was increased. The content of total phenolic compounds was increased with increasing concentrations of copper oxide. The highest amount of flavonoids was observed at concentrations of 1 and 10 µM copper oxide. Anthocyanin content was increased in concentration of 1 µM copper oxide. Also، the tannin content of the Glycyrrhiza glabra seedlings at concentrations of 10 µM zinc oxide was increased. Based on the result it seemed that at concentrations of 1 and 10 µM copper oxide the amount of glycyrrhizin، phenolic compounds، flavonoids، anthocyanins were significantly increased، whereas، zinc oxide had no significant impact on the levels of these metabolites.

In this study، total phenolic compounds and essential oils content of six mint genotypes (Bojnoord، Esfahan، Kashan، Kermanshah، Mybod and Yazd) were investigated following inoculation with two arbuscular mycorrhizal fungi (AMF) strains (Glomus etunicatum and G. mosseae). Moreover، phenylalanine ammonia-lyase (PAL) enzyme activity and trichome (main sites of essential oil synthesis) number of fresh leaves were studied. The results revealed that mint plants inoculated with AMF (Glomus sp.) made higher phenolic and essential oils content than nonmycorrhizal mint plants. However، the response was found to be dependent on the genotype. Also، it was found that there was a positive correlation between total phenolic accumulation and PAL enzyme activity in leaves of inoculated plants with AMF. Increased oil yield was associated with significant biomass content and the number of glandular trichome. Result of this study showed that inducing biosynthesis pathway of essential oils and phenolic compound was possible through infection by mycorrhizal fungi، and that the different genotypes of mint showed different potentials in responding to this induction.

The aim of this study was to obtain a suitable combination of hormones including naphthalene acetic acid (NAA) with benzyl aminopurin (BAP) or kinetin (KIN) to lower seed dormancy of Peroveskia abrotanoides، studying in vitro organogenesis and evaluation of antioxidant activity of shoots and roots. The seeds were sterilized and cultured on Murashige and Skoog medium (MS) containing BAP or KIN (at 0، 1، 2. 5 and 5 mg/L concentrations) and NAA (at 0، 0. 1، 0. 25 and 0. 5 mg/L concentrations). All experiments were done based on factorial design in a randomized block design with at least five replicas. Germination percent was estimated after 30 days and number of shoots and leave، leaf area، root and shoot length were determined after 80 days. The highest germination percent (93%) was obtained by 5 mg/L KIN and 2. 5 mg/L KIN + 0. 1 mg/L NAA treatments which was indicative of the role of the cytokinin on the seed dormancy breaking. Effect of BAP on rising shoot number was greater than KIN (30 shoots after 2. 5 mg/L BAP treatment). In contrast to NAA that was inhibitor of shoot induction in P. abrotanoides، number of the shoots was reduced to half by addition of it to the media. The highest value of leaf area (15 mm2) was obtained by treated seeds in the media supported with NAA alone. The highest percentage of callus induction (80%) was obverved on media containing 0. 25 or 0. 5 mg/L NAA in combination with 2. 5 mg/L BAP or KIN. Intermediate concentration of the studied cytokinins alone or with intermediate concentration of NAA، such as 2. 5 mg/L KIN + 0. 25 mg/L NAA، had the highest effect on rosmarinic acid storage in de novo organs (75. 21 mg/g DW). While، the induced organs was grown on the media that supplemented just with NAA had less antioxidant activity and rosmarinic acid content.

To evaluate the effects of foliar application of methanol on photosynthetic characteristics، chlorophyll fluorescence and chlorophyll content of chickpea under drought stress، a factorial experiment was conducted based on completely randomized design with three replications in 2011 at the Recearch Center for Sciences of Ferdowsi University of Mashhad. In this experiments، different levels of methanol including، 0 (control)، 20، 25، 30 and 35 volumetric percentage (v/v) were used as foliar applications at three times during growth season of chickpea، with 10 days intervals. Moisture regimes were at two levels، 25 and 100 percent of field capacity. Results showed that there was significant difference (P≤0. 01) between methanol concentrations after each spraying، regarding to chlorophyll content، CO2 assimilation، stomatal conductance، transpiration، CO2 concentration in stomatal chamber and Fv/Fm. Spraying with 30% volume level than the other treatments were effective on the physiological components، while was observed significant increase in chlorophyll content، stomatal conductance and assimilation CO2 compared to the control. Results indicated that interactions between drought and methanol after each spraying had significant differences (P≤0. 05) in traits such as content، assimilation CO2، stomatal conductance، transpiration، CO2 concentration in stomatal chamber، Fv/Fm. It could be concluded that spraying methanol improve photosynthetic characteristics، (Fv/Fm) and chlorophyll content in drought conditions.

In this study، the relationships between some quantitative traits and enzyme markers in 12 half-sib families of alfalfa resulted from polycross nursery، were investigated in the Agricultural Research Station of University of Tabriz. First، thirty five individuals of each family were grown in separate pots in the from of completely randomized design at field conditions and then، they were analyzed for two enzymatic system by slab acrylamide gels. Statistical analysis of different data based on isozyme interpretation showed that there were a significant relationships between peroxidase and seedling traits. In addition، the presence of a band increased the mean values of related traits. Furthermore، POX-4 isozyme showed a significant relationship with respect to leaf weight. Statistical analysis of the studied traits based on allozyme interpretation showed that EST-b1 and POX-b2 had a positive correlation with both yield and number of internodes. Thus، it might be possible to use these enzymes as markers to select alfalfa genotypes in the early breeding stages after the stability of markers were verified in other experiments.