نشریه یافته های نوین در علوم زیستی
پیاپی 1 (پاییز 1393)

To assess nickel-induced toxicity in plants, Zea mays seeds were germinated and cultured on nutrient solution with nickel concentrations of 0, 50, 100 and 200 μM for a period of two weeks. Its effects on the growth, Hill reaction and photosynthetic pigments content were then investigated. The fresh and dry weight of leaves and roots increased in 50 μM nickel, but decreased in 100 and 200 μM. The decline in length of root and shoot were observed by increasing nickel concentration. According to the results, root and shoot showed differential growth response to various nickel concentrations. Nickel concentrations up to 100 μM caused increase in the content of chlorophyll a, but resulted in decrease at 200 μM nickel. No significant changes in chlorophyll b and carotenoids contents were observed. The rate of Hill reaction, as the ability of chlorophyll a in the reaction center of PSII680 to split water, decreased by increase in nickel concentration.

Induced pluripotent cells have been considered as one of the most recent and best cell sources for the cell therapy. In this study, the differentiation potency of human iPS cells, cultured on scaffolds, which can differentiate into definitive endodermal cells as precursor for hepatocytes, pancreatic and lung cells, was studied. Embryoid bodies composed of pluripotent cells, were seeded on electrospinning nanofiber scaffold. The cells were differentiated into definitive endoderm using IDE1. Expression of definitive endoderm markers including Sox17, FoxA2 and GSC were confirmed by immunocytochemistry staining and qRT-PCR analysis. In the present study, morphology and viability of cells were evaluated by utilizing a scanning electron microscopy and MTT assay, respectively. The results demonstrated the positive effect of 3D cultures, using suitable factors, on definitive endoderm differentiation.

Mesquite is an invasive and problematic weed in warm and dry areas and so its management is very important. In order to study the effective factors on mesquite seed germination, the following studies were conducted to investigate: 1- seed viability; 2- the effect of constant temperatures on seed germination including 5, 10, 15, 20, 25, 30, 35 and 40°C independent dark and independent light conditions; 3- Effect of temperature fluctuations on seed germination including 10/0, 20/10 and 30/20°C; 4- the effect of scarification with concentrated sulphuric acid and physiacal scarification on seed germination; 5- the effect of planting depth seed on seedling emergence; 6- the effect of drought stress including 0, 100, 200, 300, 400, 500, and 600 Mm PEG on seed germination; and finally 7- the effect of salt stress including 0, 100, 200, 300, 400, 500, 600, and 700 mM NaCl on seed germination. All experiments were performed as completely randomized designs with 4 replications. The results showed that seed viability of mesquite was 81%. The optimum temperature for seed germination was a constant temperature- 30°C. In general, constant temperature was more suitable than temperature fluctuations for seed germination. The best seed planting depth for seedling emergence was 2 cm. The most seed germination was observed under the effect of 20 min scarification with concentrated sulphuric acid. Physical scarification had no significant effect on seed germination. While the study of salt and drought stresses effect showed that the most seed germination (after control without NaCl and PEG), was due to concentrations of 100 and 200 mM, seed germination decreased with the increase of NaCl and PEG concentrations. Based on the present results, light did not play a crucial role on seed germination. Therefore, mesquite seeds were not photoblastic. These characteristics are very important in making mesquite an invasive weed. Having precise information of these traits, enables us to have a better control over the management of this troublesome weed.

Kasf forest, with an area of over 12 ha, running in the east-west direction and located at a distance of 20 kilometers in the north of the city of Bardaskan in a mountainous arid region. The minimum and maximum temperature of the area ranges between -10° C and +45° C. The average annual precipitation of the region is 155 mm. The altitude of the forest is about 1600 m above sea level with a 15% slope. The vegetation of this forest was studied using floristic methods 2 years after a devastative fire and life forms and geographical distributions of plant species were determined. Sixty nine plant species belonged to 29 families (25 Dicots, 3 monocots and one gymnosperm). The largest families were the Lamiaceae with 11, Asteraceae with 9 and Caryophyllaceae with 5 species. The percentages of life forms were determined as follows: Therophytes with 36% (25 species), Hemicryptophytes with 29% (20 species), Chamaephytes with 16% (11 species), Phanerophytes with 13% (9 species) and Cryptophytes with 6% (4 species) of total investigated species. The high percentage of Hemicryptophytes indicated the dominance of cold mountainous climate and the presence of Asteraceae species such as harmala (Peganum harmala) showed that a severe disturbance had taken place in the region, which indicated a poor ecological administration in the studied region.

Methods of physical and chemical adsorption of heavy metals have disadvantages in some ways- such as high cost and ineffectiveness at low concentrations. In recent decades methods of biological uptake of heavy metals have been investigated. The biological adsorbents include bacteria, fungi and alga, among which algae have the highest efficiency of metal uptake. This study indicated that Alginic acid is most responsible for the uptake of metals, such as nickel (II) and cadmium (II). Fucus serratus, brown alga, used as a cost-effective adsorbent for the biological uptake of cadmium and nickel ions simultaneously in a batch reactor in this study. Surface structure of algae has also been investigated. Adsorption kinetics have been measured and the results have indicated that the equilibrium time is about 300 minutes. The adsorption isotherm was interpreted by means of the Langmuir equation. The maximum adsorption rate for cadmium (II) and nickel (II) turned out to be about 0.85 and 0.95 mmol/g, respectively.

Formations of feather and hair follicles during embryonic stage are nearly similar. The aim of the present research is to study the similarities and differences between these two follicles in adult pigeons and rats. To fulfill this task, feather and hair follicles were dissected and processed for light and electron microscopy. The results demonstrated that these two follicles were similar in having dermal papilla and epidermal matrix. Moreover, the production of feather fibers and hair in them, respectively, is almost similar. However, unlike the hair follicle, the feather follicle has a distinct compartment, called the pulp at the top of the papilla. At the center of this pulp and dermal papilla a blood vessel exists, a character never observed in the hair follicle. Another difference between the two related to the thickness of the basement membrane exists at the interface between the papilla and epidermal matrix which in feather follicle is much thicker than its hair equivalent. In addition, at the base of feather follicle there is a distinct population of stem-like cells which could not be distinguished in the hair follicle. Based on the results obtained in this study, it seems that the feathers in birds and the hairs in mammals have been adapted for different biological tasks.

Acid rain, which is a wet form of gaseous air pollutants, is formed when air pollutants such as SO2, NO2, CO2 in the atmosphere combine with water vapor of clouds. With the increase of concentration of these pollutants, the amount of acid rain increases. Acid rain, which is the mixture of sulphuric, nitric and carbonic acids, results in some changes in the soil such as decrease in pH, uncommon nutrient liberation, increase of release of toxic metals and the decline in the fertility of soil. These impacts have negative effects on plants. In the present work wheat plants were irrigated and leaf sprayed with four treatments of acid rain which contain sulphuric and nitrics acids with the pH of 2.5, 3.5, 4.5, 5.6 for a period of 32 days, whereas, control plants were irrigated and leaf sprayed by normal water with a pH of 7.4. According to the results we have obtained, control plants in whole growth and physiological indexes were better than those plants treated by acid rains with the pH of 2.5 and 3.5. Moreover, the plants treated by acid rain with the pH of 4.5 and 5.6, were lower in other factors except photosynthetic rate, pigment content and carbohydrate content than control plants. Also acid rains with the pH of 2.5 and 3.5 caused white spots in both surfaces of leaf and tip and border atrophy.