مجله پژوهشهای گیاهی (زیست شناسی ایران)
سال بیست و ششم شماره 2 (تابستان 1392)

The Hyoscyamus genus has always been regarded as an important medical plant and its therapeutic effects are attributed to its contained different tropan alkaloids. Utilizing genetic engineering for production of plants belonging to this genus with more valuable pharmaceutical properties without consuming much time and cost is one of the most regarded points in this issue. Somatic embryogenesis and gathering knowledge about it is a great help. For this perpose we attempted to perform successful somatic embryogenesis، and to get more knowledge about its mechanism via assessing enzymes in different stages of embryo formation. In this study، leaves were cultured on MS medium containing BAP (1. 5 mgL-1) and IAA (0. 2mgL-1) lead to a successful embryogenesis. The results show that highest activity of superoxide dismutase and peroxidase had the highest activity in primary embryo-holding callus، catalase and ascorbate peroxidase had the highest activity in embryogenic callus but polyphenol oxidase had the highest activity in callus. In different stages of embryo formation from leaf explants of H. niger showed that changes of activities of these enzymes in various stages of embryo formation. The electrophoresis patterns of iso-enzymes of superoxide dismutase، peroxidase، catalase، ascorbate peroxidase، polyphenol oxidase and auxin oxidase showed the presence of 7، 6، 1، 5، 6، 7، and 2 isosymes in these enzymes respectively. The molecular mass of the isozymes were determined and up-regulation، down-regulation، and modulation of the isosymal bands were assessed. The main as well as concervative isozymes involved in embryogenesis were also identified.

In this study the effect of different concentrations of sucrose was examined on the anthocyanins stability that was extracted from sour cherry (Prunuscerasus L.) at low pH (2،3) under high temperature (90°C) and during time. Degradation index of anthocyanin (DI) was evaluated according to absorbance at 520 nm. According to the results، samples with sucrose havehighest content of degradation of anthocyanins at 90°C، which indicated browning occurred during this period. Furfural measurement an indication of anthocyanin degradation، were higher after 20 hr heating in the samples with anthocyanin + sucrose than samples with and without sucrose. Results indicated that browning is depends on the pH and sucrose concentration.

Callogenesis and anthocyanin content of vegetative explants such as leaf، stem، petiole and floral ones (petal، pistil، anther) from Rosa gallica were investigated under physical (light and dark) and chemical (different combinations of 2، 4-D، BAP and GA3) factors at different periods. The explants were cultured on the modified MS medium supplemented with vitamins and growth regulators. Cultures were exposed to dark and a 16/8 h (light dark) photoperiod at 1000 and 2000 lux light intensities. The calli (with the original explant) were then routinely subcultured onto fresh medium of the same composition at two weeks intervals. Combinations of 1mg l-1 BAP and 2- 3 mg l-1 2، 4-D were the most suitable treatment for callus induction in various explants. GA3 was resulted in callogenesis reduction. Callogenesis was started after 4 days in stem explants and after 8 days in the other explants. Calli grew and became massive and enlarged in the next weeks. Dark and 1000 and 2000 lux light intensities showed no significant different on callus induction although 2000 lux light intensity somewhat reduced callogenesis in anther and vegetative explants. Calli produced in light were red like and accumulated anthocynin. Anthocynin content was the higher in calli obtained from explants exposed to 2000 lux light intensity. Calli grown in dark were white to cremish، soft، fraible and contained a bit of anthocyanin.

Callogenesis and anthocyanin content of vegetative explants such as leaf، stem، petiole and floral ones (petal، pistil، anther) from Rosa gallica were investigated under physical (light and dark) and chemical (different combinations of 2، 4-D، BAP and GA3) factors at different periods. The explants were cultured on the modified MS medium supplemented with vitamins and growth regulators. Cultures were exposed to dark and a 16/8 h (light dark) photoperiod at 1000 and 2000 lux light intensities. The calli (with the original explant) were then routinely subcultured onto fresh medium of the same composition at two weeks intervals. Combinations of 1mg l-1 BAP and 2- 3 mg l-1 2، 4-D were the most suitable treatment for callus induction in various explants. GA3 was resulted in callogenesis reduction. Callogenesis was started after 4 days in stem explants and after 8 days in the other explants. Calli grew and became massive and enlarged in the next weeks. Dark and 1000 and 2000 lux light intensities showed no significant different on callus induction although 2000 lux light intensity somewhat reduced callogenesis in anther and vegetative explants. Calli produced in light were red like and accumulated anthocynin. Anthocynin content was the higher in calli obtained from explants exposed to 2000 lux light intensity. Calli grown in dark were white to cremish، soft، fraible and contained a bit of anthocyanin.

In order to investigate the effects of nitrogen levels on grain yield، phyllochron and leaf emergence rate of maize cultivars، a split plot experiment based on randomized complete block design with three replications was conducted at the Research Farm of Islamic Azad University of Ardabil during 2007 cropping. Factors were: nitrogen levels in main plots (0، 80، 160 and 240 Kg N ha-1) and maize cultivars in three levels (SC-301، DC-370 and SC-404) in sub plots. The results showed that phyllochron، time between the appearance of successive leaves on a shoot، was significantly affected by corn، nitrogen levels and interaction of nitrogen levels × maize cultivars. With increased nitrogen levels، the phyllochron was decreased but rate of leaf appearance was increased. Response of maize cultivars was different to these characteristics. Leaf appearance rate in SC-301 was more than SC-404 and DC-370. The highest leaf appearance rate and the least of time for phyllochron was obtained in treatment compounds of SC-301 with application of 240 kg N/ha. Grain yield was significantly as affected by nitrogen levels، cultivar and interaction of cultivar × nitrogen levels. Maximum grain yield was in SC-404 cultivar and minimum of it was in SC-301 cultivar. Means comparisons showed that maximum grain yield was obtained in SC-404 with application of 240 kg N/ ha. However، no significant different was between application of 160 and 240 kg n/ha. Minimum grain yield belonged to SC-301 without application of nitrogen fertilizer. If growth period was limited، it seems that SC-301 with 240 kg N/ha was applied in order to increasing leaf appearance rate and decreasing of phyllochron. However، if growth period wasn’t limited، it would be better to use of SC-404 with application of 240 kg N/ha.

Plants deal with different stresses including biotic and abiotic stresses during their life. The stresses affect germination and growth of plants. Heavy metals such as cadmium in soil could decrease seed germination and growth of plants. It has been found that salicylic acid is able to reduce negative effects of the heavy metals on different aspects of plant life. The current research was carried out to evaluate probable positive effects of salicylic acid on germination and initial growth properties of B. tomentellus when facing with cadmium stress. For this purpose، an experiment including B. tomentellus seeds pretreatment with 0، 100، 200 and 300 mg/L levels of salicylic acid for 10 hours was conducted. Also، stress condition was prepared using cadmium levels of 0، 10، 20 and 30 mg/L. Results indicated that cadmium decrease germination percentage، rate of germination، radicle and plumule length while using salicylic acid inhibit negative effects of cadmium. Germination percentage and radicle length showed the highest one when 200 and 300 mg/L of salicylic acid was used، respectively.

Arctium lappa is a medicinal plant of Asteraceae. To break dormancy and increase the germination of its seeds، various methods was tested including KNO3 (0. 2% for 48 h.)، H2SO4 (75% for 5 and 10 min.)، hot water (70 and 90 °C، each for 15 min.)، and tap water (for 24 and 48 h.). Results revealed that the treatment with KNO3 was more effective، yielding 85% germination. On the other hand، treatments with H2SO4، hot (70°C) and tap water also exhibited considerable effects on the germination rate and percentage (in turn- 66%، 65% and 24%). Overall، according to the obtained results and with regard to the negative effect of H2SO4 on the consequential growth of seedlings، KNO3 (0. 2% for 48 h.) and hot water (70°C) would be suggested as the most efficient treatments to break seed dormancy of Arctium lappa.

The unsuitable climatic conditions such as suboptimal temperatures inhibit seed germination and plant growth and their yield may be reduced. The priming is considered as a promising technique for increasing of seed germination percentage and improvement of germination rate of many plants in stress condition. In this research effect of priming was investigated on seed germination of two tomato cultivars (Cherry and Falcato) under suboptimal temperatures. Priming was accomplished by soaking seeds in a polyethylene glycol 6000 (PEG 6000) aerated solution (osmopriming) and in moist vermiculite (hydration) for 24 h at 250C. Seeds were laid in Petri dishes with two filter papers and were incubated in growth chambers at 10، 15، 20 and 250C and calculated the germination mean، mean germination time، germination velocity and T50. Result showed that both priming treatments improved germination percentage and rate of tomato seeds، even under suboptimal temperatures.