Iranian Journal of science and Technology (A: Siences)
Volume:30 Issue: 1, Winter 2006

The effects of drought stress and exogenous abscisic acid on the expression of ribulose-1, 5- bisphosphate carboxyIase/oxygenase activase (Rubisco activase) were examined in wheat (Triticum aestivum L.). In response to water stress and abscisic acid, both the levels of endogenous abscisic acid and Rubisco activase increased in the leaves. Immunoblot analysis showed that both drought stress and abscisic acid, increased the amount of a 51KD activase form of the enzyme. In addition, our results from wheat leaves showed that Rubisco activase up regulated under drought stress by increasing the amount of endogenous abscisic acid. Therefore the level of Rubisco activase was dependent on the abscisic acid level. These results are consistent with previous findings that Rubisco activase increases under high temperature stress. These results indicate that the increased rate of activases synthesis may play a role in coping with the decline in photosynthetic capacity under drought stress. Effects of drought stress and abscisic acid and their interaction were highly significant (p<0.01) for all variables.

Twenty accessions of cultivated grass pea (Lathyrus sativus L.) and wild species of Lathyrus L. collected from western and southern regions of Iran were evaluated for their mitotic metaphase chromosomal characteristics. All populations comprising 16 populations of cultivated L. sativus and 4 wild populations of Lathyrus L. were diploid, 2n=2x=14 chromosomes. There were significant variations among populations in the number of metacentric, submetacentric and subtelocentric chromosomes, the longest and shortest chromosome lengths, total haploid complement, arm ratios and centromeric index. The karyotypic formula of wild Lathyrus spp. populations were quite varied from those in native grass pea cultivars in having either two or three pairs of subtelocentric chromosomes and accordingly containing one or two metacentric chromosomes. In addition, total chromosome length (TCL) in wild Lathyrus L. accessions was less than those for grass pea populations. The mean length of the largest chromosome differed significantly among populations, with populations 5 having the largest chromosome (7.2mm). The mean length of the shortest chromosome did not differ among populations, with wild populations from Ilam (populations 17, 18 and 19) having the lowest value. The arm ratios and centromeric index (CI) data revealed adverse trends, whilst wild populations of Lathyrus L have the highest arm ratios and the lowest CI values. There were only slight differences in the mean of arm ratios among the native grass pea populations considering a range of 1.3 to 1.9 for this morphological trait.

For the first time, a spectrum of morphological abnormalities have been produced in developing mouse embryos (N=50), by injecting (IP) 75 and 100 mg/kg of maternal body weight of a new quinazolinone derivative, 4(3H)quinazolinone-2-propyl-2-phenylethyl(QPPE), on days 9, 10 and 11 of gestation. Measurements of the length of the crown-rump (CR), weight of body of the embryos and placenta on day 17 showed significant growth retardation (P<0.05) with day 9 being the critical day. The severity of the changes was dependent on the concentrations of quinazolinone, as higher doses created more abnormal embryos (syndactily, scaphocephaly, exocephaly, microcephaly, acrocephaly, abnormal polarity in lower and upper limbs, deviation of body axis, growth retardation) and placentas. Apparently QPPE acts on organogenesis on a specific phase of the developmental stage by expressing genes regulating mitosis and cell proliferation.

The individual effects of cadmium concentrations (0, 0.005, 0.05and 0.5 mg. L-1) on the growth (cell number and chlorophyll content) and beta-carotene synthesis of two strains (Iranian and Australian) of green algae D.salina have been studied for a duration of 36 days. The effects of these cadmium concentrations on the amount of cell magnesium and calcium have also been evaluated. An increase in cadmium concentration resulted in a significant reduction in the cell number and chlorophyll content of D. salina. In comparison with control, in both strains, the increase of beta-carotene content of cells was observed in the first few days of the experiment, moreover, the amount of magnesium and calcium in cells decreased. The results indicated that the addition of 0.5 mg. L-1 of cadmium in the medium results in a 50 percent reduction in cell number after 96h. The decrease in growth rate and the increase in beta-carotene content of cells is probably due to the formation of free radicals and deficiency of essential elements such as magnesium and calcium, which is caused by high concentrations of cadmium in the medium.

Viable cell concentration and luminescence activity of P. stutzeri P16 luxAB4 was measured by plate counting and luminometery in sterile and non-sterile soil adjusted to matric potential of -1500, -750 and -30 kPa. Results showed that matric potential had a significant effect on survival and activity of P. stutzeri P16 luxAB4 in soil. P. stutzeri P16 luxAB4 could survive better in Hutner’s minimal medium supplemented with 1mg l-1 phenanthrene than 1 mg ml-1. However changes in viable cell concentration and luminescence activity of lux-marked and wild type strains of P. stutzeri P16 were significantly different in Hutner’s medium, amended with high and low concentrations of phenanthrene. Inoculation of soil with high concentrations of phenanthrene caused an initial decline in the viable cell concentration of P. stutzeri P16 luxAB4 that took a longer time than liquid medium. Changes in viable cell concentration were similar to changes in luminescence indicating the advantage of Bioluminescence-marker systems for monitoring the survival and activity of biodegradative genetically engineered microorganisms (GEMs) in polluted environments. Our results also showed the importance of influence of environmental factors such as matric potential and pollutant concentration on the fate of GEMs.

Meiotic study was performed in 11 Brassica napus cultivars considering chiasma frequency and distribution, chromosome pairing, as well as the occurrence of B-chromosomes and their effects on chiasma frequency. Such cytogenetic pairing, along with agronomic characteristics, may be used in planning hybridization among the B. napus cultivars. All the cultivars studied possessed n=19 chromosome number (4x) and showed a deviant course of prophase-I meiosis with a synezetic knot and post pachytene diffuse stage. Chromosome stickiness occurred in most of the cultivars from early prophase to late telophase-II leading to the formation of laggard chromosomes and micronuclei. The cultivars studied differed significantly in chiasma frequency and distribution as well as bivalent formation, indicating their genomic differences. Cluster analysis and ordination based on principal components analysis grouped those cultivars showing meiotic similarities. Some of the cultivars showed the occurrence of B-chromosomes.

The genus Fusarium is a species rich genus. Different media are required to study the morphological characters and classify different species, a time consuming technique. In this study pectic zymograms were used to identify species and form species of Fusarium isolates. Fusarium isolates (318) were obtained from different areas and hosts in Isfahan Province, Iran. Isolates were identified to species based on morphological characters. A pectic enzyme solution was prepared for each isolate using liquid media containing citrus pectin as the sole carbon source. Electrophoresis was performed using acrylamide gel containing 0.2% citrus pectin as the enzyme substrate. The gels were incubated in 0.1M malic acid before staining overnight in 0.02% ruthenium red, to visualize enzyme electrophoretic patterns. Several zymogram phenotypes were obtained for polygalacturonase and pectin esterase. In total, 12 zymogram patterns were determined for the 318 isolates tested. The results showed that there is considerable intraspecific variation in Fusarium species. There were 3, 5 and 2 zymogram electrophoretic patterns for Fusarium oxysporum, F. solani and F. culmorum respectively. However, there was only one zymogram pattern for F. subglutinans and also one for F. equiseti. Although the intraspecific variation based on pectic zymograms was not correlated to the form species of Fusarium, species of Fusarium could be distinguished using this technique as there was no common zymogram pattern among species.

A cytogenetic study was performed on 11 tetraploid cotton cultivars (Gossypium hirsutum L.) including the Oltan cultivar and its crossing progenies. The chromosome pairing and chiasma frequency, as well as meiotic abnormalities were compared among the genotypes studied. Heterozygote translocations with alternate orientation were observed between some of the chromosomes of the A genome and those of D genome in some of the cultivars, which may bring about new genetic rearrangement to be used in breeding programs. Meiotic abnormalities including formation of laggard chromosome, stickiness, as well as disorganized chromosomes occurred in some of the cultivars, which may cause pollen sterility. B-chromosomes were observed in some of the cultivars. The cultivars studied differed significantly in their cytogenetic characteristics, partly indicating their genomic differences, which may be used in cotton breeding.

The late Eocene-early Oligocene Sarnowsar granitic rocks and many dacitic to rhyolitic dykes intruded in metamorphosed and metasomatized shale, sandstone, calcite and dolomite marbles and volcaniclastic and pyroclastic rocks. As a result several million tons of iron ores formed within carbonate rocks in the Sangan area. The Sarnowsar granitic rocks are mainly granite to granodiorite, metaluminous, I type and high calc-alkaline.Fluorine contents in the biotite range from 0.37 to 4.4 wt. % and Cl contents range from 0.1 to 0.30 wt. %. Fluorine contents in the biotite are negatively correlated with XTi, while Cl contents positively correlated with XMg and XSi. Values of the calculated log (ƒH2O/ƒHF) and log (ƒH2O/ƒHCl) of fluid in equilibrium with the chemical composition of biotite range from 3.38 to 4.43 and 0.57 to 1.2, respectively. The contour lines representing log (ƒH2O/ƒHF) and log (ƒH2O/ƒHCl) values are different with the slope of the trend of biotite composition suggesting that, in addition to chemical structure of biotite, the fluid composition also plays some role in the incorporation of F, and especially Cl in biotite. The F intercept values for biotite in the Sarnowsar granitic rocks are similar to those of igneous rocks and porphyry Cu ore deposits. The Cl intercept values of biotite in the Sarnowsar granitic rocks are similar to those of hydrothermal and ore forming systems. The data suggest that chlorine intercept values for biotite from the Sangan deposit tend to be more Cl rich than comparable values from biotites in common igneous rocks. F-rich biotites and F-poor biotites from the Sangan deposit show similar and narrow ranges of F/Cl intercept values corresponding to Cl-rich and ore-forming systems such as porphyry copper deposits. Therefore, the chemical composition of biotite from the Sarnowsar granitic rocks interacted with hydrothermal solutions.

The formation of atoll garnet in hornblende schists from the contact aureole of Mashhad granite, NE Iran, is discussed using textural and chemical data. These data suggest the possibility of incipient replacement of pre-existing idioblastic garnet from the core. In addition, the presence of chlorite and calcite in the core of atoll garnet reveal the retrograde nature of atoll formation.

While our knowledge of anuran embryonic and larval surface ciliation and their diversity of ciliation patterns are significant, very few references were noticed on embryonic ciliation in direct-developing anurans, such as species in the genus Eleutherodactylus. Eleutherodactylus urichi embryos were found to have surface ciliated cells during much of their development until a few days before hatching. Ciliation was most prominent on the pharyngeal region and on the tail fins, both regions believed to have a respiratory role, and supporting the hypothesis that embryonic ciliation in amphibians serves principally to aid respiration by moving intracapsular fluid. The limb-buds were also well ciliated, an evolutionary novelty since in most anurans with a tadpole stage, surface ciliation regresses before limbs show significant development.