فصلنامه زیست شناسی گیاهی ایران
سال ششم شماره 2 (پیاپی 20، تابستان 1393)

In order to study effects of salt stress on activities of hydrogen peroxide scavenging enzymes، glutathione S-transferase، some oxidative stress markers and Na+ and K+ distribution patterns in sensitive (Koohdasht) and tolerant (Gaskogen) wheat varieties were selected and grown in aeroponics culture. The seedlings were fed by nutrition solution till 3-4 leaf stage then the medium was added 200 mM NaCl. The plants were hold at this condition for 14 days. The results indicated that Gaskogen had always more shoot dry matter than Koohdasht. Also، dry matter production rate in control condition was higher than salinity. The enzyme activity of catalase، ascorbate peroxidase and glutathione S-transferase، was significantly decreased under salinity condition compared to the control condition in Koohdasht variety. However guaiacol peroxidase activity in this variety did not change significantly compared to the control. The activities of guaiacol peroxidase and glutathione S-transferase in Gaskogen significantly was increased under salinity whereas ascorbate peroxidase and catalase did not have any significant variation. Further results showed that sodium was readily absorbed and transported to the shoot in both varieties. Among various parts of cultivars there was no difference regarding the level of accumulated sodium. As a result، the ratio of potassium and sodium in various parts of the seedlings was decreased. Results obtained from this study showed that activity of scavenging enzyme like hydrogen peroxide together with glutation S-transferase caused controlling of toxic compounds in the Gaskogen variety and suppressed oxidative stress affects in compared to Kouhdasht that could refer to lower rate of hydrogen peroxidase and less lipid peroxidation in Koohdasht. As a final result، it could be stated that H2O2-scavenging enzymes and glutathione S-transferase had special roles in detoxification of toxic compounds leading to keep stable conditions inside the plant cells in salinity conditions. In addition، it is suggested that for better evaluation of salt tolerance in wheat genotypes or varieties and optimum utilization of genetic resources، addition to sodium rate and its allocation in various parts of the plant، defense mechanisms should be considered against oxidative stress induced salinity.

Tea (Camellia sinensis) is one of the most active and important biochemical sources. A number of factors، such as species، season، agronomic condition and age of the leaves، are known to affect the quality of tea. In this study، fresh tea shoots consisting of one apical bud and two adjoining leaves were collected from Tea Research Institute of Iran (Lahijan). Some of the phenolic components of two clones of tea (100 and 451) + in three harvest seasons (spring، summer and autumn) were investigated. The results indicated that harvesting time was crucial in determining the biochemical compounds of tea clones، so that antioxidant activity was increased in both examined colons from 1st harvest (spring) to 3rd harvest (autumn)، showing some of the impact of ecological factors in different seasons on the biochemical compounds of tea and helping to find oppropriate time to obtain tasty tea during three harvesting season.

Seed production in some crops like pistachio is limited by some abnormalities in ovule development stages. In this study، the ovule developmental stages as well as abnormalities of these stages were investigated. Pistacia vera ovule is single، fullynucellate، monotegumental and converse (anatrope) and is set in an ovary with basic placement and the Polygonum type embryo sac is organized in it one week after complete dehiscence. After pollination and fertilization of egg cell، after 6 weeks of complete dehiscence، the pericarpe was grown to final size and even the lignifications of endocarpe started but the zygote cell was in a dormant state and in 6-8 weeks after complete dehiscence the zygote cell division along an increase in endosperm division occured so that cotyledonary embryo was formed in 10-12 weeks after complete dehiscence and the cotyledons attained their final size in 3 weesks after that، namely 15 weeks after complete dehiscence and at this time، the seedless and filled fruits were completely distinguished. During the ovule development stages، some abnormalities were observed such as lack of embryo sac formation، embryo sac degeneration، small and abnormal embryo sac formation، vascular band collapse inside the funicule، presence of zygote without endosperm and presence of endosperm without zygote، and these abnormalities caused lack of enough ovule growth and seedless or semiseedless fruit formation in pistachio.

The rape (Brassica napus) is an economically valuable plant shose tolerance to stresses has always drown concern. It is well known that، the cold (0-20 °C) and freezing (<0 °C) stresses can influence growth and productivity of the farm plants and the degree of impressionability is dependent on the type of stresses، genetics of the plants and the resistance mechanisms. In this investigation، the varieties of SLMO46 and Quantum were evaluated as resistant and sensitive varieties، respectively، against low temperature stresses. One of the effective factors in plant resistance to the stresses is quantity of the ascorbate peroxidase (APX) and the metallothionein (MTL) in the plant tissues. The ascorbate peroxidase activity in the SLMO46 tissues was more than Quantum and the activity was increased about two times during the cold stress. Quantitave analysis of Apx2 and Mtl genes expression according to 2-ΔΔCt showed that the quantities were 2. 1 and 9. 1 in the SLMO46 and 1. 8 and 5. 2 in the Quantum، respectively. The data indicated that under normal condition، the enzyme activity in the resistant plants was more than the sensitive one and the stress can induce about 60% increment in the enzyme activity.

To find out the role and effects of exogenous nitric oxide (NO) application in reducing oxidative damage induced by salinity stress in purple coneflower (Echinacea purpurea L.) seed germination، a compeletly randomized design in factorial arrangment with three replications was conducted in Plant Physiology Laboratory of the Genetics and Agricultural Biotechnology Institute of Tabarestan، Sari Agricultural Sciences and Natural Resources University in 2012. The crop seeds were pre-soaked in 0. 1 mM of sodium nitroprusside (SNP 0. 1; as nitric oxide donor) solution as well as in distilled water (SNP 0; as control) for 20 hs just before the onset of the experiment. Then، pre-treated seeds were subjected to different levels of salinity (0، 50، 75، 100، 125، 150 mM NaCl solution) to germinate. Results showed that the SNP0. 1 treatment in saline conditions had significant effect on germination percentage. Different levels of salinity significantly reduced germination rate، germination vigor and index. Pretreated with exogenous NO increased the activity of SOD، POD and APX as compared with SNP0. Accordingly، the highest activity of SOD (116. 3 μM g-1 FW)، POD (1. 7 μM g-1 FW. min.) and APX (50. 1 μM g-1 FW. min.) was related to the 125، 50 and 125 Mm NaCl، respectively. Significant and adverse effects of NO were seen on CAT activity. Exogenous NO، as an antioxidant، also reduced peroxidation of membrane lipids (MDA) and delayed the oxidation of proteins. Overall، it could be concluded that sodium nitroprusside as NO donor could improve coneflower seed germination characteristics in saline condition and increase salinity tolerance by means of scavenging of free ROS radicals.

Each region''s flora is as a result of communities'' reactions to the current environmental conditions and plant evolution in the past. This aim of this study is to introduce floristic list، life form and endangered species of Helen region. This region covers about 40231 ha and lies in the west part of Chaharmahal and Bakhtiari province. The results showed that 392 plant species existed in the region belonging to 67 families and 267 genera. The families Compositae، Labiatae and Papilionaceae with 60، 37 and 34 species embraced higher species respectively. The genus Astragalus with 15 species was the largest genus in the region. According to Raunkiaer’s life form، species followed as: 43. 88% hemicryptophytes (172 species)، 22. 96% therophytes (90 species)، 14. 03% cryptophytes (55 species)، 7. 44% phanerophytes (37 species) and 8. 93% chamephytes (35 species). The chorology of species showed that 64. 80 percent of species belonged to Irano-Turanian، 6. 12 percent Polyregional، 3. 32 percent Cosmopolitan and the rest to the others. Threatened species included 70 totally belonging to Irano-Turanian. Among which them the endangered class، vulnerable، lower risk and data deficient were 3، 3، 55 and 9 species respectively.

Seeds gradually lose their viability during storage. The damage that occurs at the biochemical level can alter the seed physiological status and is affected by the storage conditions of the seed. The lipid peroxidation through the production of free radical plays an important role in the loss of seed viability during seed storage. In the present study، we examined the relationship between the activity of free radical detoxifying enzymes، lipid peroxidation and seed deterioration in medicinal pumpkin (Cucurbita pepo subsp. Pepo. Convar. Pepo var. styriaca Greb) during storage. The seeds were incubated at different storage temperatures (35 and 5oC) and seed moisture content (5، 8 and 14%) for 2 and 4 days. Malondialdehyde content in seed was increased during storage with increasing moisture content and temperature، suggesting that seed deterioration was associated with lipid peroxidation. The increase in lipid peroxidation was related with increased electrical conductivity، which suggested membrane damage during deterioration. The decrease in germination was also associated with a decrease in catalase and peroxidase activity and as a result، the antioxidant system was not sufficient to protect seeds against free radical damage. Thus، medicinal pumpkin seed deterioration was closely related to decrease in the activities of free radical detoxifying enzymes and increased lipid peroxidation.

In this project، the vegetation of the Noujian Watershed located in Lorestan province was identified. Noujian Watershed with the area of 34000 hectares is situated between the eastern latitude of 48° 23̕ to 48° 40̕ and its northern longitude ranging from 33° 17̕ to 33° 60̕ at Lorestan province in the watershed of Dez dam. Minimum altitude of the region is 770 meters and its maximum reaches to 3012 meters. The method of plant collection in this region was classical method of regional floristic studies. Collected plants were recognized and determined as families، genera and species by using taxonomic method and required references. The plants of this region included 421 species which belonged to 241 genera and 56 families. The largest families respectively، were: Asteraceae (56 species)، Fabaceae (39 species)، Brassicaceae (34 species)، Lamiaceae (29 species)، Caryophylaceae (24 species)، Poaceae (23 species)، Lilaceae (22 species)، Ranunculuaceae (20 species)، Apiaceae (19 species)، Boraginaceae (17 species) and Rosaceae (15 species). The analyses of the geographical distribution of the plants wwas carried out according to Takhtajan and Zohary methods، showed that the Irano-Turanian elements، with 47% growth، were the dominant species of Noujian watershed and about 15% of these species were native of Iran. The species like Onosma Kotschyi، Cousinia Khorramabadensis، Echinops endotrichus، Morrina persica، Dionysia hausskenechtii and Bunium Lurestanicum exclusively grow in Zagros Mountains. Therophyts (36%) and geophytes (21%) were the dominant life-forms of Noujian watershed.

Soorkesh protected area is one of the main habitat of important Tertiary relict species Platycladus orientalis in Golestan province. The altitude of this area ranges from 820 to 1680 m a. s. l. with an area of 223 ha. In a floristic survey of the area، 284 species from 212 genera and 63 families were identified. Asteraceae (42 spp.)، Poaceae (34 spp.) and Papilionaceae (24 spp.) were the largest families in terms of number of species. In the assessment of life form spectrum، the dominant life forms were hemicryptophytes (47. 5%)، followed by the therophytes (29. 2%)، phanerophytes (10. 9%)، cryptophytes (7. 4%) and chamaephytes (4. 9%). The flora was composed mostly of Euro-Siberian، Irano-Turanian، Mediterranean elements (24. 8%). A combined analyses of DCA indirect gradient analysis and Pearson correlation analysis of vegetation data and topographical data of 20 relevés of 100 m2 indicated that altitude، slope inclination and heat index affect floristic composition of the area.

Increasing the activity of antioxidant defense system against harmful agents such as reactive oxygen species، resulting from drought، is a common response in plants. In order to study these responses، the effects of two withholding irrigation in treatments (10 and 20 days) on the progress of the phenolic and flavonoid compounds activity malondialdehyde rate and also the amounts of chlorophyll a، total and carotenoids in three clone of tea (DN، 100 and 258) were investigated. Results showed that the amounts of phenol had the most increase in clones DN and 100 in 20 and 10 day-treatments respectively. However، changes in neither of the treatments had no significant effect in clone 258. The amounts of flavonoid and antioxidant capacity increased in clone DN with 20 day-treatment however; it decreased in clone 258 and stayed constant in clone 100. The most values of proline appeared in 20 day-treatments in all clones. Results of malondialdehyde contents were increased in clones 258 and 100، but it did not change in clone DN. Decreasing in amount of chlorophyll a and total chlorophyll were observed in clones DN and 100 with 20 day-treatments and remained unchanged in clone 258. Carotenoids remained constant in clones and treatments. On the basis of obtained data it seemed that clone DN had more ability against drought and consequently its defense mechanism was excited more than others.

In this study، in order to reduce the pathogenesis of potato virus Y in two potato (Solanum tuberosum L.) cultivars (Marfona and Agria)، the effects of salicylic acid on chlorophyll content and leaf area were investigated under greenhouse conditions. The healthy potato plantlets were propagated and transferred to pots containing suitable and sterilized soil. The plantlets were sprayed with different concentrations (0، 0. 2، 0. 5، 1 and 2 mM) of salicylic acid. The leaves were inoculated by potato virus Y، extracted from infected tobacco leaves. Although viral infection symptoms on tobacco were manifested by leaf rippling، no such symptoms were visible on infected potato leaves. Also، results showed that treatments with 0. 5 and 1. 0 mM of salicylic acid resulted in 26% reduction in potato damages. Moreover، our study revealed that Marfona cultivar was more resistant to potato virus Y than Agria cultivar.