فصلنامه فرآیند و کارکرد گیاهی
سال دوم شماره 4 (پیاپی 6، زمستان 1392)

In order to investigate two different strains of Pseudomonas putida on forage quantity and quality of three sorghum cultivars، an experiment was carried out at Agricultural and Natural Resource Research Center of Tehran Province (Varamin) during 2009-2010. The experiment design consisted of three randomized complete blocks in a factorial arrangement. Seed inoculation with Pseudomonas putida strain 168 had the highest wet and dried forage، percent of dry matter digestibility and percent of crude protein and seed inoculation with Pseudomonas putida strain 41 had the highest percentage of Water Soluble Carbohydrates. Seed inoculation with Pseudomonas putida strain 168 had the highest amount in the most of investigated characteristics seed co-inoculation with two bacterial strains had the lowest amount. The results showed that two strains of phosphate solubilizing bacteria had antagonistic effect on، however seed inoculation with bacterial strains alone (especially strain 168) caused nutrient uptake and plant growth promotion consequently، exuding of second metabolites could lead to plant yield promotion.

In this research, the effects of cysteine on alleviation of heavy metal stress in purple basil plants were studied and some parameters such as fresh weight of shoot and root, chlorophyll a and b content, carotenoids, anthocyanin, and total phenolic compounds and reducing sugar was measured. Research was conducted in two separate trials for the two group pre-treated cysteine and cysteine -cobalt combined treatments. The treatments containing of 0, 500 and 2500 mM cysteine and 0, 100 and 500 mM cobalt was used. Higher concentrations of cobalt decreased photosynthetic pigments, leaf, root and shoot length, fresh weight of roots and shoots while cobalt stress increased, caused reducing sugars, anthocyanins and total phenolics content. Cysteine reduced the fresh weight of roots, reduction sugar, anthocyanins, and total phenolics of plants compared to plant treated with cobalt treatments without cysteine. Thus, this amino acid improved leaf area, root and shoot length, shoot fresh weight and photosynthetic pigments in stress conditions. Generally, the results showed that pre-treatment of cysteine could alleviate low concentrations of cobalt stress effects than higher amounts application of this heavy metal, while combined treatments containing cysteine was more effective at higher concentrations of cobalt.

Soil pollution with heavy metals is an important environmental problem which affects human and food health. Neotyphodium endophytes are a group of fungi which spend their entire life cycle within the aerial portion of many grass species without any symptoms, and increase host tolerance to biotic and abiotic stresses. In this study, two genotypes of tall fescue (75 B and 75 C) in two types (infected (E+) and non-infected (E-) by endophyte) were cultivated in a Ni contaminated soil at 0, 30, 90 and 180 mg Ni per kg with 3 replicates. After 2 months, Ni uptake of the root and shoot as well as chlorophyll and carotenoid content of the shoot were measured. Growth parameters including root and shoot wet weight and root to shoot weight ratio of plants were also measured at the end of the experiment. The results showed that endophytic fungi caused an increase in chlorophyll contents of the shoots in the both genotypes and an increase in Ni uptake only in genotype 75 B. Results also demonstrated that endophyte infection led to improvement in the growth and Ni tolerance within genotype 75 B of tall fescue under Ni stress. But in the genotype 75 C, in contrast, the E- plants showed more tolerance to Ni stress compared to E+ plants. It revealed that how the effects of endophyte infection in Festuca plants as the host were dependent on the host genotype.

Nowadays medicinal plants are considered as important economical plants. Recently, due to the extension of saline lands, shortage of appropriate agricultural farms and economical value of medicinal plants. There is a growing interes of identifying salt tolerant medicinal plants. A cheap time saving and reliable way for selecting proper salt tolerant plants can be achieved by culturing these plants in hydroponic condition. On the other hand, silicon which is the second most abundant element of soil has good effects on increasing the plant's ability in enduring biotic and abiotic stresses. This experiment was arranged as a factorial scheme based on randomized complete block design with four replications. Six levels of silicon (0, 0.5, 1, 1.5, 2, 2.5 mM) and two levels of NaCl (0 and 120 mM) were added to nutrient solution in order to analyze the reaction of salt and silicon on physiological and anatomical properties of Borago officinalis L. In this study, the effects of salinity and silicon on shoot apical meristem and contents of chlorophyll, carotenoids, antocyanin, phenols and reducing sugars were assessed. The results showed that salinity decreased the chlorophyll, carotenoids, phenols and reducing sugars but increases the anthocyanin content. Although in comparison with the plants which was just treated by salt, silicon treatment, especially with 1.5 mM, made an improvement in the studied physiological and biochemical parameters. Also silicon could moderate negative effects of salt treatment on shoot apical meristem.

The aim of this study was to investigate the effects of foliar application of Ni in the form of NiCl2 or urea-Ni complex on growth, yield, and nitrogen metabolism of two commercial lettuce cultivars (Lactuca sativa L. cvs. Conco Istador and Grizzly) in nutrient solution culture containing urea. A group of lettuce plants was received only urea as foliar spray. Another group of plants did not received urea and Ni as foliar spray application. Results showed that foliar application of Ni, regardless of applied source, significantly increased fresh and dry biomass of the lettuce shoots. Foliar application of Ni resulted in significant increase of shoot Ni concentration; although this increase was, in general greater by urea-Ni than by NiCl2. Floiar spray of Ni significantly increased activity of urease and reduced shoot concentration of urea in both lettuce cultivars. Application of Ni reduction of tissue concentration of ammonium (NH4+) by enhancing activity of glumine synthetase (GS). Foliar spray of Ni resulted in reduced concentration of nitrate (NO3-) and ammonium (NH4+) in lettuce shoots. A significant increase in activity of GS was also observed by foliar spray of Ni. According to the results, foliar spray of Ni particularly in the form of urea-Ni complex was effective in improving yield and nitrogen metabolism of urea-fed lettuce.

The effects of different concentrations of walnut leaf extract on physiological and biochemical characteristics of parsley plants inoculated with mycorrhizal fungus Glomus versiforme and non-mycorrhizal plants were studied under greenhouse conditions. In the present study, three different concentrations of walnut extract (full extract, half and quarter concentration levels) were used. The results of the 45 day-old plants showed that the increasing of the concentration of walnut extract decreased amounts of chlorophyll a and b but increased the carotenoids content. This increase was more pronounced in mycorrhizal plants than non-mycorrhizal ones. When ¼ concentration of extract was applied the total protein content in mycorrhizal and non-mycorrhizal plant shoots was increased and then decreased at higher concentrations with increasing in concentrations of aqueous extract of walnut leaves. The free amino acids and proline content in plants were increased but such effects in non-mycorrhizal plants were greater than in mycorrhizal ones. Ascorbate peroxidase (APX) and Guaiacol peroxidase (GPX) activities in mycorrhizal and non-mycorrhizal plants also increased due to walnut extract, but the increased activity of these enzymes was higher in the inoculated plants. Results of this study indicated that by inoculating mycorrhizal fungi with root of parsley adverse potential effects of allelopathic extract on the physiological and biochemical characteristics of these plants.

Water deficit is one of the major abiotic stresses, which adversely affects crop growth and development. These changes are mainly related to the alternation of some metabolic functions. This alteration can resist plant under stresses. Certain plants have devised mechanisms to survive under low water conditions. Usually, water deficit has a positive effect in the biosynthesis of secondary metabolites such that these constraint decrease oxidative stress. In this study to evaluate the effect of Water stress on active substance of Silybum marianum two experiments under pot and field conditions were carried out. In the first experiments, a completely randomized design (CRD) was conducted with four levels of water stress inducing soil water potential of -0.33, -4, -8 and -12 bar. In the second experiment, five treatments inducing soil water potential of –0.33, -4, -8, -12 and –15 bar were applied treatments was applied using a randomized complete block design with four replications. The highest content of Silibin a, b and total amount were measured to be -4 and -12 bar in pot and field experiments respectively. The highest content of Silymarin and oil percentage were accumulated under water potential of -4 bars in both experiments. Thus, the result showed that soil water potential of -4 bar was the best treatment to increase of milk thistle secondry metabolites.

Accumulation of phenolic compounds is considered as an important tool for environmental stress protection of plants. In this investigation, garden cress seedlings were in control conditions and were irrigated with Hoagland nutrient solution and were treated with methyl jasmonate (MeJ) at 0 (Control),5, 10 and 20 µM and different concentrations of copper 0 (Control), 50, 100 and 200 µM. Then shoot fresh weight, phenolic compounds content, anthocyanin content and PAL activity in response to treatments were measured. According to the results, shoot dry weight and PAL activity in treatment (5 μM) MeJ with (50 and 100 μM) copper, were significantly increased compared to control condition. Concentrations of MeJ (5 and 10μM) treated with 50 μM copper significantly increased the chlorophyll a, b, total chlorophyll and phenolic compound contents control conditions were compared. The results indicated that MeJ may act as a signaling molecule to enhance antioxidant pool and protected plants against injuries caused by Cu toxicity. Based on the results, determined that medium concentrations of MeJ (5 and 10 µM) had good effects on improvement of physiological effects in plants under cu toxicity.