Iranian Journal of Plant Physiology
Volume:3 Issue: 4, Summer 2013

Heavy metal pollution is a worldwide problem. This study was conducted in a turquoise mine in Nyshabour (Iran) to find accumulator plant(s). Concentrations of metals were determined both in the soil and the plants growing in the mine. Concentrations of total K, Ca, Na, Mg, Mn, Zn, Fe and Cu in the mine area were higher than the control soil. The results showed that four dominant vegetations namely Vincetoxicum scandens Sommier et Levier., Stachys lavandulifolia Vahl., Phlomis anisodonta Boiss. and Onosma bulbotrichum Dc.prod accumulated heavy metals. Based on the results, it was concluded that Stachys lavandulifolia Vahl. is the best accumulator for Fe, but the best Cu accumulator is Onosma bulbotrichum Dc.prod.

Arsenic is considered as one of the most important environmental contaminant elements. Some plant species can grow in arsenic contaminated soils and they are able to reduce arsenic toxicity. In this study, a hydroponic experiment was conducted on Isatis cappadocica, a newly-discovered As hyperaccumulator. Accordingly, we conducted this experiment to compare the interaction of effect of arsenic and phosphorus on total chlorophyll and antioxidant compounds (carotenoids, anthocyanin and proline) of I. cappadocica for better understanding the mechanisms applied by this species. Therefore, the plants were grown for 6 weeks in a medium, embedded with combinations of 50, 200, 800 and 1200 μmol l−1 arsenic and 5, 50, 200, 800 and 1600 μmol l−1 phosphorus, respectively. The highest concentration of arsenic was obtained in plants treated with 1200 μmol l−1 As and 5 μmol l−1 phosphorus. Increasing arsenic concentration in the medium led to increase in antioxidant compounds. The ability of Isatis to accumulate more than 700 mg kg-1 arsenic in the shoots, illustrates the high resistance of this plant to arsenic and the existence of efficient mechanisms including increase of antioxidant compounds.

Five alfalfa (Medicago sativa L) cultivars from different areas of Iran were evaluated for oxidative markers under salinity conditions. Plants were grown in hydroponic condition by Hoagland nutrient solution containing different amounts of NaCl (control, 50 and 100 mM). Relative growth rate, membrane stability, lipid peroxidation, proline, hydrogen peroxide and relative water contents were determined. Results indicated that salinity decreased membrane stability, relative water content and growth parameters and increased lipid peroxidation, proline and hydrogen peroxide contents. Important variation was observed for all traits by increasing salinity. There were significant differences between cultivars in amounts of decrease or increase in the measured traits. In general, low membrane stability was observed in Sahand ava cultivar. Regarding salt stress, Yazdi cultivar was successful in maintaining membrane stability and relative growth rate.

In order to understand the response of tobacco to salt stress, antioxidant enzyme activities, plant biomass and ion content were analyzed in two oriental tobacco genotypes (Basma 31 and SPT 406). Tobacco plants were exposed to 0, 50, 100, 150 and 200 mM NaCl for 12 days. The fresh and dry weight as well as shoot and root length of Basma 31 were greater than those of SPT 406 under increasing salt stress. On exposure to NaCl, SPT 406 showed a higher Na/K ratio than that of Basma 31. Activity of catalase, ascorbate peroxidase and guaiacol peroxidase enzymes increased with increasing NaCl content in leaves of two genotypes, but activities of three enzymes in leaves of Basma 31 were higher than SPT 406. Activities of catalase and ascorbate peroxidase in roots of Basma 31 and SPT 406 increased with increasing external NaCl concentration up to 150 and 100 mM, respectively. The highest guaiacol peroxidase activity in roots of Basma 31 and SPT 406 was observed in 100 and 50 mM NaCl, respectively. These studies established that Basma 31 was able to tolerate higher salinity in comparison with SPT 406. Our results suggested that catalase, guaiacol peroxidase and ascorbate peroxidase play a major role in estimating the salt stress tolerance of tobacco genotypes.

A split plot factorial experiment in RCBD with 3 replications was performed in 2012-2013. Three sesame cultivars namely Biarjomand native, Dashtestan 2, and Darab 1 in the main plot were subjected to drought stress at different growth stages, i.e., control (full irrigation), withdrawing irrigation at 69 BBCH (end of flowering stage) and withdrawing irrigation at 79 BBCH (fully grown fruits). Two levels of the foliar application of salicylic acid (0, 0.6 mM) were considered as sub plot. Results indicated that the highest level of carotenoid rate was 0.265 mg/g FW measured at 69 BBCH stage 69 cut of irrigation. The maximum of height, oil percentage, harvest index and grain yield under control treatment were 99.67 cm, 48.26%, 18.2%, and 1147.33 kg, respectively. The results showed that withdrawing irrigation at 69 BBCH caused a significant increase in carotenoid concentration and best results under control conditions were obtained in Darab 1.

The effect of leachates of different phenological stages of Cassia occidentalis L. on Parthenium hysterophorus L. was studied. Seed germination, radicle length, plumule length and fresh and dry weight of Parthenium were recorded. Pigments and protein contents were also measured to evaluate relation between biochemical and biophysical parameters of Parthenium under stress. The leaf leachate of Cassia in different developmental stages and pod and seed leachates exhibited varying effect. The Cassia leachate obtained from the leaves of vegetative and flowering stages was more phytotoxic. It caused maximum inhibition of germination and seedling growth of Parthenium. Biochemical parameters, viz. protein and chlorophyll were also influenced. Root and shoot growth and fresh and dry weight decreased in almost all the treatments. The inhibition of germination was in order of vegetative > flowering > fruiting > fruit ripening > pod > seed while 25 and 50% concentrations of seed leachate stimulated the germination. The 100% concentration of leaf leachate from vegetative stage completely inhibited the germination while highest concentration of leaf leachate from vegetative, flowering, fruiting and fruit ripening stages caused the death of the plants. The average inhibition of parameters of seedlings in pot culture was in order of fruiting > vegetative > fruit ripening > flowering > pod > seed.

In order to study the effect of Pseudomonas fluorescens on growth, morphological characteristics and phosphate uptake by rapeseed (Brassica napus L. Hyola 401), an experiment was performed in 2010. The study was carried out as a randomized complete blocks design with three replications. The treatments included plants inoculation by Pseudomonas fluorescence strain 11, strain 4, strain 169, the dual combinations of strains 11+4, 11+169, 4+169, combination of all three strains studied (11+169+4) and treatment without inoculation (control plant). The findings suggested that application of strain 169 increased plants height, number of leaves and pod; however, it was ineffective on dry and wet weight of root and shoot compared to control and other treatments. It also increased phosphate concentration of roots and shoots compared to the control plant. Results showed strain 169 had successful and important function on improving growth of rapeseed (Brassica napus L. Var Hyola 401). On the other hand, these bacteria caused an increase in phosphate uptake.

To determine seed storage protein banding patterns in some bread wheat cultivars and the similarity of banding patterns among different cultivars, an experiment based on seed storage protein electrophoresis (albumin and globulin) was performed. Water and salt soluble proteins were extracted in sixteen wheat cultivars using polyacrylamide gel electrophoresis and banding pattern was obtained. Studied cultivars were Karaj 3, Atila 50, N-8019, Khazar 1, Shahriar, Darya, Chenab, Kouhdasht, Augusta, Toos, Cros shahi, C-845512, Saysons, Ghermezak, Sardari and Tajan. Based on dendrogram, sixteen wheat cultivars were placed in four groups. Cultivars that were placed together in a group were more similar than the others considering morphological characteristics and growth habits. Electrophoretic patterns of seed albumin and globulin proteins in sixteen wheat cultivars showed that these sixteen cultivars are different in terms of protein banding patterns. It means that the albumin and globulin can be used in genetic evaluation to evaluate genetic distances and identify the cultivars. It can also be used for genetic evaluation of seed storage proteins, including investigation of genetic distances and proximity between species and cultivars.