مجله زیست شناسی ایران
سال نوزدهم شماره 2 (تابستان 1385)

This study was designed to determine the effects of drought stress and exogenous abscisic acid on the structure of reproductive meristem, pollen grains, morphological traits, yield and yield components of Brassica napus. Plants were grown in Karaj Seed and Plant Improvement Institute in a randomized blocks design with 3 replications. Treatments included irrigated plants without exogenous abscisic acid, under drought stress without exogenous abscisic acid and under drought stress with 3 concentrations of exogenous abscisic acid. Reproductive meristem and anthers of control and treated plants were fixed in proper fixative for cyto-histological studies. Plants were collected for studying the morphological traits, yield components and seed yield. Results showed that drought stress plus the lowest concentration of exogenous abscisic acid prematured the meristem, increased the number of pollen grains and their viability. More ribosomes and mithochondria were observed in pollen grains. Drought stress plus the lowest concentration of exogenous abscisic acid showed an increase in yield in comparison with other plants under drought stress also showed 2-3 percent increase in oil percentage.

Cadmium is a heavy metal that causes oxidative stress in plants. Cadmium is highly toxic to plants and animals. In this study toxic effect of CdCl2 on (Brassica napus L.cv. Fusia) was investigated. Plants were grown in vermiculite and irrigated with Long Ashton nutrient solution (pH =5.5) containing CdCl2 from (0 to 800 μM). Leaves and roots from 30-day–old plants were taken and used for determination of biochemical and morphological parameters. The maximum accumulation of cadmium occurred in roots followed by leaves. In leaves cadmium treatment significantly decreased fresh weight at 600 and 800 μM CdCl2 but leaves dry weight and leaf area decreased at 400, 600 and 800 μM CdCl2. In roots cadmium treatment significantly decreased fresh and dry weigh at 600 and 800 μM CdCl2. Cadmium significantly lowered total chlorophyll, chlorophyll a/b ratio and carotenoid content at 400, 600 and 800 μM CdCl2. Cadmium at 600 and 800 μM CdCl2 increased content of soluble reducing sugars and malondealdehyde in leaves and roots of treated plants.

Alfalfa contains proteins and other metabolites such as alkaloids, phenolic compounds, and triterpenoid saponins. Alfalfa saponins cause bitterness and decreasing in palatability for animals. The second role is attributed to the formation of protectants against pests, pathogenes and nematodes. This factor is considered as an antibiotic against biostresses. So, it is expected that alfalfa necessarily is a resistant plant. However, specific pests and pathogens have been found to damage alfalfa and reduce yield. In order to study variability and also biological activity of saponins, the behavior of Therioaphis maculata was evaluated after aphids fed on the seedlings of 4 alfalfa cultivars. The neonates were transferred on seedlings. Number of suvivals, nymphs, and the size of aphids were recorded. Crude saponins were extracted using methanol 80% after cutting the tissues following freezing in liquid nitrogen and making powder in a mortar. Crude saponins were then purified with butanol following ether precipitation. TLC was used to analyze pure saponin mixtures. Different spots were expressed in variable colors but in same pattern for cultivars on TLC plate. The measurment of Rf showed no difference in saponin patterns. The usage of spotted alfalfa aphid was highly also useful for evaluation. Statistical analysis showed that survivals and nymphs were nearly the same. Although no difference of aphid sizes as well as survivals and production of nymphs in each growth stage was found between aphids feeding on different cultivars but aphid size in wide was significant when aphids were fed on cultivar Euver. However, saponins had no significant role in resistance to spotted alfalfa aphid. Further research is necessary to find out the factor increasing wide of aphid body.

Plants consumed humans contain thousands of phenolic compoounds. The effects of dietary polyphenols are of great current interest due to their antioxidative and possible anticarcinogenic activities. Liver is one of the organ in body that exposure with many of oxidant and carcinogen agents thus antioxidant compounds are beneficial for liver healt. In this study was investigation protective effects of silybum marianum and caliendula officinalis against thioacetamide-induced hepatotoxicity in rat. After extraction and purification, the extracts were injected at a dosis of 25mg/Kg together with thioacetamide at a dosis of 50mg/Kg (P.C.). After blood collection and separation of serum, activities of aminotrasferases (SGOT and SGPT), alkalin phosphatas, Bilirubin, Na+ and K+were measured in serum. Significant decrease in activity of aminotrasferases, alkalin phosphatas and Bilirubin were observed in groups treated with extracts in compared with thioacetamide treated group. These result show that protective effects of these extracts against the thioacetamide induced hepatotoxicity that may be due to its ability to block the bioactivation of thioacetamide, primarily by inhibitig the activity of Cyt P450 and its free radical scavenging.

Normal and abnormal developmental studies on chicken embryo system are necessart,as the widespread use of chicken embryo model in embryological experiments,from organ to cell and molecule levels.A knowledge of normal embryonic development is important to understanding embryonic events and efficient performing of experimental and teratological tests.The present study was undertaken by double staining on chicken embryo from 1st to 21st day of incubation period by alizarin red – alcian blue double staining method,to investigation of wing and leg skeleton development. In this method, cartilage and bone matrix stain blue and red, respectively.Totaly 13 pieces bone in wing and 22 pieces in leg skeleton were determined.then, the time of cartilage formation and their ossification,were detected.all of those become ossified through bones, become ossified through enchondral ossification pathway,but some part of each bone remains cartilaginous.results show that leg skeleton development is earlier than wing skeleton development.6th day and 11th day of incubation period are first appearance cartilage and bone matrix, respectively.These skeletogenous stages of the chicken embryo wing and leg will be useful as a normal control not only in studies of experimental embryology and teratology, but also in the analysis of mutant embryos with skeletal abnormalities.

Caspian Sea sand goby, Neogobius fluviatilis pallasi (Berg, 1916), due to lack of commercial exploitation and richness of their population, have an important role in food chain of Caspian Sea.This study carried out during July 2004 to June 2005 and documents their diet in shallow coastal waters of Noor at southern part of Caspian Sea. In this regard, diet regim of 240 specimens were analyzed. According to results of present study, the relative length of gut was 0.576 ± 0.099, Vacuity Index for all of specimens was 39.58, so this subspecies classified in relatively gluttonous group. While matured males show increased value of this index during reproduction season, so they can be categorised as medium feeders group. In April, May and June Gastrosomatic Indices were higher than other months. Also study on composition of digestive system, shows that Caspian sand goby was fed on nine different kind of food with Preferences following food: 1- Amphipods from order Amphipoda, 2 - fish larvae, 3- Barnacels from family Balanidae, 4 - Shrimps from family Plaemonidae, 5 - Bivalves from family Mytilidae, 6 - Round crabs from family Xanthidae, 7 - Bivalves from family Cardidae, 8 - Fish eggs, 9- Wormes from order Oligochaeta. In the basis of food prefrence indices, non of mentioned organism were considered as main food item during the study period. It seems that Caspian sand goby diet has been changed during different seasons,according to adaptation with environmental changes.

According to many literatures Rana ridibunda probably has the potential to become a commercial species which was exploited at least once about 30 years ago in Anzali wetland region. In this study, the larval growth was surveyed at 5 stations in Anzali wetland and the sampling was performed by sieve every 10 days and 2200 larvae were measured and grouped in length frequency classes. The population estimation was done at 20 stations by Jolly-Seber and Leslie methods. The results showed that the maximum length and weight of larvae were 87.7 mm and 5.1 gr respectively. Frequency of total length classes higher than 56 mm and body length more than 26 mm were very little. The findings showed that total frequency of larvae decreased as time proceed. Mortality rate of larva was very high about 97 % and first metamorphosed specimen was observed at early June after about 43 days. According to this study the average survival rate of Rana ridibunda in all studied stations was 0.64 ± 0.16 percent and the average population density was 1.033 N/m2. Maximum sustainable yield was estimated to be about 0.304 individual/m2.

Chitinases are widely distributed in nature and play important roles in degradation of chitin. Chitin, a linear polymer of N-acetylglucosamine residues, has been the most abundant polymer in nature after cellulose. It plays a major role in fungal cell walls. Chitinase enzymes degrade the chitin polymer into its component residues by breaking the β-1,4 glycosidic bonds. As a producer of a variety of chitinase enzymes, the filamentous fungus, Trichoderma sp., has become an important means of biological control for fungal diseases. The aim of this study was to identify a Trichoderma sp. isolate with over production of chitinase. Trichoderma atroviride PTCC5220 was selected as over producer of chitinase enzyme among 31 different isolates of Trichoderma sp. Also chitinase 42 kDa (Chit42) was purified from supernatants of T. atroviride grown in medium supplemented with colloidal chitin as the sole carbon source. Enzyme purification was achived in two steps ion exchange chromatography using CM-Sepharose and DEAESepharose. Elution of the column was carried out with 1 M NaCl gradient. The purity of chit42 was investigated by SDS-PAGE. The results showed one band about 42 kDa after the second step of chromatography. The purified protein showed chitinase activity in enzyme assay technique.

Nonhistone chromosomal proteins are a set of heterogenous chromatin proteins which play different functions dependent on the cell type. A group of these proteins with a high molecular weight and low mobility on the gel electrophoresis, called LMG proteins, has been the subject of many workers. We have recently isolated a fraction of these proteins from rat liver nuclei, with a molecular weight of 160 KDa and named HMG160. In this study the position of this purified protein in different fractions of chromatin has been studied. After brief digestion of rat liver chromatin with MNase, chromatin fractions S1 and S2 were prepared and analyzed by gel electrophoresis and imminobloting techniques. The results show that the protein LMG160 has higher affinity to di- and oligonucleosomes rather than to mononucleosomes. This implies that LMG160 preferentially binds to bulk chromatin and may have a role in chromatin inactivation which demands further investigation.

The primary causal agent of FHB (F. graminearum) can produce deoxynivalenol (DON), a trichothecene mycotoxin that enhances disease severity and poses a health hazard to human and monogastric animals. To study the possible ways for reducing the effect of DON, an acetyltransferase (AYT1) gene from yeast was cloned and transformed into tobacco as a model plant. AYT1 encodes an enzyme that transfers an acetyl moiety to the C3 hydroxil group of trichothecene. The results of in vitro culture resistance tests suggested detoxification and partial protection against DON mycotoxin in transgenic plants.