Iranian Journal of Plant Physiology
Volume:3 Issue: 1, Autumn 2012

The technology of phytoremediation is cost effective and ecologically friendly in which plant utilizes its natural abilities to restore environment. In nature there are a number of plants existing with innate mechanisms for removing heavy metals from soil, air and water as a survival strategy. Among several subsets of phytoremediation, the widely studied strategies are (a) phytoextraction (b) phytofiltration (c) phytovolatilization and (d) phytostabilization. Application of organic / inorganic chelants in soil directly affects the solubility of heavy metals and consequently increases their accumulation in plants that enhances phytoextraction. In the present review current knowledge about the phytoremediation and its techniques are discussed.

Satureja hortensis L., (summer savory) is an annual, herbaceous aromatic and well-known medicinal plant. S. hortensis essential oil has a high percentage of carvacrol which is responsible mainly for its biological activity. The biomass production, essential oil composition and mineral content of Satureja hortensis are known to be dependent on its growth and development conditions. The aim of this work was, therefore, to evaluate the essential oil composition as well as minerals content at different stages of growth of Satureja hortensis. The growth media was 10 cm diameter pots containing perlite watered using Hoagland nutrient solution. Plants were harvested at different stages of growth (before flowering and after flowering period) and dry weights were measured. The essential oils were analyzed by GC-MS. Before flowering stage and in full flowering stage, 29 compounds were characterized. In both stages, carvacrol showed the highest rates of the compounds an increasing trend from before flowing to flowering so that it changed from 47.77% to 49.96% whereas α-terpinene and cymene had a decreasing trend from before flowing to flowering stage. There was a rapid uptake of minerals during early growth and gradual dilution as the plant matured. Phosphorus and magnesium concentrations increased with expansion of growth and development in shoots and roots.

Lisianthus (Eustoma grandiflorum L.) is a very popular, ornamental plant. Due to low germination of its seeds, usual techniques for its propagation are not efficient. The present study was aimed to establish callus from explants of different plant parts of Eustoma grandiflorum L. Raf Shinners in B5, LS and MS media with modifications. The results showed that among different plant parts, leaf explants were pioneer to produce callus. Basal LS medium containing 3 mg/L IAA, 3 mg/L NAA, 0.1 mg/L kinetin, and B5 medium containing 0.225 mg/L BA and 1.86 mg/L NAA were the best media for induction of callus. The calluses in LS media started for organogenesis (rhizogenesis) earlier than those in B5, and MS medium containing 3 mg/L IAA, 3 mg/L NAA, and 2 mg/L Glycin. All calluses from aforesaid media were able to regenerate new plants. Flowering onset occurred after 84 days growing under 16/8 h photoperiod, 25±2 ºC.

Mycorrhizal association in seven plants grown in Arasbaran forest located in the north west of Iran was investigated. The soil samples were collected from the plants rhizosphere. Physico-chemical properties of rhizosphere soils like soil texture, pH, EC and some extractable nutrients such as N, P and K were recorded. The number of spores in rhizosphere and percentage of root mycorrhizal colonization were found. Soil physico-chemical analyses were done on August while spore number and root colonization were studied in May and August. All the data collected in this research were analyzed by the statistical software, SPSS. Results showed that different plant species colonized differently by VAM fungi, and spore number and root mycorrhizal colonization increased through the time from May to August. Among the physico-chemical factors, soil N content had high correlation with root colonization and soil extractable P had high correlation with soil spore number. pH had a high negative correlation with spore number. Among the plant species, Stachys pubescens showed the most VAM fungi root colonization and Cruciata laevipes rhizosphere soil showed the highest spore number.

The negative and positive effects of alumina nanoparticles have been reported for various plant species, while the mechanism that brings about these effects has not yet been clearly understood. Here, the effects of different concentrations of nano-scale alumina on growth and enzymatic antioxidant system of wheat seedlings are investigated. The results show while root growth is affected by the nanoparticles (NPs), other morphological properties including seed germination, shoot length, and dry biomass were the same as the control plants’ properties. This can be attributed to selective permeability of seed coats which confronts roots with excess in the NPs and low rate in transportation of this material to the shoot. Interestingly, while root elongation was significantly improved in both treatments of 50 and 1000 mg/L nano-scale alumina, length of the roots were measured slightly lower than control in cases of 200 and 500 mg/L treatments. Additionally, the activity of superoxidase dismutase and catalase were elevated for treatments of 200 and 500 mg/L while growth of the roots was apparently decreased and the uptake of aluminum by the roots was more than the uptake for other concentrations. However, due to the potential retarding of alumina nanoparticles on root growth for some plant species, it seems that the activity of antioxidant enzymes which reduces the level of free radicals (O˙-, H2O2) is responsible for reducing phytotoxicity effects of these particles on seedlings. In conclusion, it is proposed that oxidative damage can be introduced as a way of inducing toxicity in plants through the uptake of nanoparticles.

In this study, the interaction between iron and copper on growth parameters (plant height, fresh weight of roots, stem’s length, fresh weight of shoots, fresh and dry weight of seeds), total proteins and the antioxidant enzymes activity in Cuminum cyminum L. were investigated. This experiment was carried out in completely randomized blocks with 9 treatments in 3 repetitions. Plants were treated with Fe fertilizer (0, 3, 6 kgh-1) together with CuSO4, 5H2O (0, 100, 200 μM). Maximum level of stem length and shoot fresh weight was observed in Fe3Cu100. In the treatment of Fe6Cu100, root weight was significantly increased. Fresh and dry weights of seeds were significantly increased under Fe3 treatment. High concentration of Fe fertilizer with low concentration of CuSO4 decreased catalase and peroxidase enzymes activities. However, by increasing concentration of Cu in both Fe levels, the activity of ascorbate peroxidase was decreased.

Accumulation of γ -aminobutyric acid (GABA) is associated with stress factors in plant systems. The objective of the current study was to compare GABA concentration in wheat plants under chilling stress. After 48 h treatments of seedlings under chilling stress combined stresses with and without GABA, morphological and biochemical assays were conducted. It was observed that the inhibition of seedling roots elongation caused by chilling stress was significantly mitigated by GABA. The activities of antioxidant enzymes were changed; the content of malondialdehyde was increased in chilling stress but reduced in GABA treated seedlings. GABA can alleviate oxidative damage caused by chilling stress in wheat seedlings by activating antioxidant defense responses.

In order to investigate the effect of different levels of nitrogen and bio-fertilizers on yield of canola plants in Qazvin, Iran, a split-plot design was conducted on the base of randomized complete block design with four replications. Treatments included 3 levels of nitrogen (0, 75 and 150 kg ha-1) and bio-fertilizers on four levels (no inoculation, Azotobacter, Azospirillum and a combination of Azotobacter and Azospirillum). Results showed that nitrogen treatment had a significant effect on yield and yield components. Significant increase was observed in all characters with applying bio-fertilizers. Interaction of effect of nitrogen and bio-fertilizers treatments on seed yield showed when no nitrogen fertilizer was used, the highest seed yield was obtained from the combined use of bio-fertilizers. But with application of 150 N (kg ha-1), the highest seed yield was obtained when no bio-fertilizers were applied. The oil yield was also influenced by experimental treatments so that the highest oil yield was obtained from 75 and 150 kg ha-1 N treatments. The combined use of bio-fertilizers also was statistically superior to other treatments. According to findings of the present study, it can be concluded that farmers can obtain the same canola yield if they apply half the conventional allocation of nitrogen with bio-fertilizers.