modern research physics

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The effects of cadmium and iron interaction on some physiological parameters in rice (Oryza sativa L.cv.fajr) plant were studied. The four days old seedlings were transferred to pots containing sand, irrigated with Hoagland solution in growth chamber. The 15 days old plants were treated with 0, 50 and 100 &muM  CdCl2 supplemented with 5, 10 and 20 ppm Fe as Fe-EDTA. Plants were grown under controlled condition and harvested after 30 days for measurements of some biochemical and physiological parameters. Treatments were conducted with four replications. Under Cd stress, growth of plant decreased. In plants treated with CdCl2, relative growth rate, net assimilation rate and photosynthetic rate were decreased. Addition of Fe-EDTA (10 and 20 ppm) moderated cadmium effects. Under Cd stress without Fe, respiration rate and CO2  compenstation point increased, however, in solutions containing both CdCl2 and Fe-EDTA, respirations rate and CO2  compenstation point decreased. In plants treated with CdCl2, catalase activity increased. However, after increasing Fe in solution containing CdCl2, catalase activity decreased. Therefor, the results indicated that in CdCl2 treated plants with increasing Fe-EDTA, the toxic effects of Cd decreased.

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Oil pollutions as a consequence of increasing consumption of petroleum, have a tremendous effect on water and soil ecosystems and their microflora. In this study the diversity in physiological parameters, including growth rate, photosynthesis, chlorophyll-a and phycobiliproteins content, between cyanobacterial strains flora isolated from oil-polluted and non-polluted areas, were assessed. To this end, strains were isolated and purified. The experiments were carried out on logarithmic phase cultures of the isolates in suitable liquid media. The chlorophyll and phycobiliproteins contents were determined using a colorimetric method. Photosynthesis was measured by Oxyview apparatus. Growth rates were calculated based on dry weights. Under laboratory conditions, the photosynthesis activity and the chlorophyll content of isolates from oil-polluted sites were significantly lower than non-polluted isolates. On the other hand, the growth rate average of strains from oil-polluted sites was significantly higher than non-polluted strains. Also despite the higher phycobiliproteins content in non-polluted isolates, there was no significant difference in any of these pigments between the two groups. Altogether the results showed that in response to petroleum stress, the cyanobacteria restore the decrease in their chlorophyll content and photosynthesis activity by increasing their biomass. In fact the response is the reflects of restructuring cyanobacterial flora from sensitive autotrophic species to oil-pollution resistant mixotrophic species in the polluted ecosystems that in addition to photosynthesis are able to use crude oil as an energy source for their growth requirements, hence overcome the energy loss due to reduction of photosynthesis and even increase growth rate than non-oil-pollution isolates.

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In a green house pot experiment, the effects of salinity and increasing levels of potassium supply on factors determining dry matter production of two barley cultivars(Reyhan and Afzal) were investigated, with regard to yield (Number of tillers and ears, dry weight of ears, straw, roots, thousand grain weight and leaf area). The plants were grown under four levels of potassium (K1= 0,K2=./25, K3 =./5 and K4=1 gr. K/Kg. soil) and 40mM NaCl in a randomized complete blocks design with four replication. The results indicated that by using of NaCl, the number of ears, dry weight of ears, thousand grain weight, biomass and leaf area increased, whereas dry weight of roots ,the number of tillers per plant ,duration of grain filling and maturity period in both cultivars decreased. Increasing of potassium supply significantly increased dry weight of shoots during vegetative growth, but during reproductive- and maturity growth had no marked influence on dry weight production. By increasing the levels of potassium accompanied with salinity no effects on above mentioned parameters were observed. This may be due to a high availability of potassium in the soil , which led to an increase in dry weight of the plant shoots.