فصلنامه زیست شناسی گیاهی ایران
سال هشتم شماره 1 (پیاپی 27، بهار 1395)

Regarding negative effects of Cd on wheat growth, it seems that evaluation of wheat cultivars behaviors in response to Cd existence is necessary. In this regard, six different cultivars of wheat were selected and cultivated by aeroponic system. Then they were treated by 200 mM cadmium chloride for 14 days since they have reached 3 or 4 leaves stage. Finally, plants were sampled and morphological characteristics, parameters subjected to defense mechanisms as well as amount of accumulated Cd in tissues were evaluated. The results showed that cadmium accumulation in tissues significantly decreased root length and dry matter of root, shoot and whole plant. Cd accumulation also increased hydrogen peroxide amount in leaf cells of Kohdasht and Pishtase cultivars. However, lipid peroxidation was noticed in Izengeran cultivar as well as two previously mentioned cultivars. The reduced activities of glutathione
S-transferase, catalase and ascorbate peroxidase enzymes are probably the main reasons of the lipid peroxidation increase in Kohdasht cultivar. However, there was no damage on membranes of Izengran and Pishtase cultivars, which indicates the balance between production and scavenging of damaging factors of these cultivars. Generally, it can be stated that available Cd in medium was adsorbed and accumulated in wheat leaves resulting in reduction in dry matter of different parts and whole seedling of wheat which is due to susebtability of different cultivars to Cd. However, there were no oxidative stresses in leaves of Gaskogen, Agosta and MV17 cultivars due to their better defense mechanisms.

Today, phenolic compounds and plant growth regulator has been proposed, to reduce the negative effects of stress. Salicylic acid is a substance that causes plant resistance to biotic and abiotic stresses. This experiment was conducted in Zabol University during 2013 as factorial randomized complete block design with 3 replications. Factors included 4 levels of lead nitrate; 0 (control), 100, 200 and 300 mg per kg of soil and foliar application of salicylic acid at 3 levels of 0, 50 and 100 ppm. Addition of lead significantly reduced concentrations of potassium, magnesium, calcium, phosphorous and nitrogen and increased concentrations of sodium, polyphenol oxidase, ascorbate peroxidase, superoxide dismutase and peroxidase. In addition, salicylic acid spraying had a significant influence on all traits, and salicylic acid spraying at 100 mL/L increased concentrations of potassium, magnesium, calcium, phosphorus, nitrogen and decreased concentrations of polyphenol oxidase, ascorbate peroxidase, superoxide dismutase and peroxidase. In this study the interaction between salicylic acid and lead on potassium, magnesium, calcium, phosphorus, nitrogen, sodium and catalase, guaiacol peroxidase and polyphenol oxidase were significant, and salicylic acid play moderating role and reducing the negative effects of lead toxicity. The results suggested salicylic acid application in basil can increase uptake of macro and micro nutrients required for plant growth and reduce the negative effects of stress lead-induced oxidative damage.

Zinc is an essential nutrient for plants and has an important role in plant growth and development although small amounts of it are needed. On the other hand, nano fertilizers such as ZnO nanoparticles cause an increase in agricultural products dramatically. The object of this study was to evaluate the effect of different concentrations of ZnO nanoparticles on some properties of the wheat plant. The experiment was performed in a completely randomized design (CRD) with three replications with different concentrations of ZnO nanoparticles (0, 5.1, 3, 6, 9 and 12 µM in the pot cultivation stage). At the end of a 14-day period, vegetative features, elements content, total carbohydrate and photosynthetic pigments were measured. According to the results, growth parameters such as fresh and dry weights, leaf area, root depth, germination percentage, total carbohydrate, iron and phosphorus contents, as well as photosynthetic pigments in the high concentrations of ZnO nanoparticles (6, 9 and 12 µM) showed a decreasing trend. Zinc and potassium contents increased with the enhancement of external concentrations of ZnO nanoparticles. This study showed that the highest growth efficiency and productivity of wheat was observed in 1.5 µM of Zno nanoparticles.

The aim of this research was to identify the plant species, introducing the flora, determination of life forms, and geographical distribution of Shahbaz Mountain. Shahbaz Mountain, with 3420 m altitude (above sea level), is covers an area of 2255 hectares situated in Shazand city where the amount of annual precipitation is 380 mm and means annual temperature is 10.5 °C. Plant samples were collected from different parts of the area between 2700-3400 m during two growing seasons 2008-2009. The biological spectrum of the area was plotted by means of life forms results. The position of the area within Iran’s phytogeography classification was studied based on geographical distribution data and references. From 113 identified species, 90 dicotyledons and 23 monocotyledons were identified. These species belong to 23 families and 82 genera. The important families are Lamiaceae, Liliaceae, Asteraceae and Brassicaceae with 13.27%, 10.61%, 10.61% and 9.73%, respectively. Hemicryptophytes with 61 species (53.99%) were the most frequent life form. 92 species (81.42%) were endemics of Irano-Turanian region; 17 species of them were endemics of Iran.

The inhibitory or stimulatory effect of one plant on other plant species through the released chemical compounds into the environment, known as allelochemicals, is called allelopathy. In the present study, effect of aqueous extracts of lavender (Lavandula angustifolia) leaves on growth pattern and ability of β-carotene production in unicellular green alga, Dunaliella salina was investigated. Based on these results, phenolics content and antioxidant capacity of the extracts was relatively low. Treated cultures with extract concentrations of 1, 2, 3 and 4 % showed that the process of cell division was ceased because of extracts phytotoxicity. However, the chlorophyll and β-carotene concentration pronouncedly increased in phytotoxin-treated cells, so that the highest of these values were detected in 3 % extracts-exposed cells. Percentage change of all three fresh weight, total sugar and protein between 0 and 48 h of phytotoxins treatment was significantly increased concurrently with increasing dose of extracts. These results suggest that D. salina tolerate allelochemicals-induced stress by metabolic modifications. Therefore, phytotoxins-tolerance mechanisms in D. salina are associated with physiological and metabolic adjustments by allocating the carbon flux to the synthesis of the sugars, chlorophyll and β-carotene, which induce phytotoxins stress tolerance in this alga.

The most important abiotic stresses is salinity, the high levels of sodium which is toxic to most varieties of plants species, and more importantly affect plant growth and limit the plants yield capacity. Hyssopus officinalis L. has been known as a culinary and medicinal herb for hundreds of years, it is cultivated globally. Although Hyssopus officinalis L. is one of valuable medicinal plants and its cultivation is continuously being extended in the world, no information is available on the responses of this plant to salinity. Since the growth stages are very sensitive to stress, in this research the effects of salinity on growth parameters of Hyssopus officinalis L. in seedling stage were studied. The treatments were six levels (0, 2, 4, 6, 8 and 10 dS m-1 of saline water). The results showed that with increasing the salinity stress, protein, cartenoids, oligosaccharides and reducing sugar, MDA and H2O2 contents significantly increased however total chlorophylls, chl a and chl b contents and total sugar and polysaccharides significantly decreased. It seems that increasing the amount of protein, cartenoids and carbohydrates are important risk factors for resistance to salt Hyssopus officinalis L.

The use of nano-chelates, in lieu of conventional fertilizers, result in the controlled and gradual release of the nutrients throughout the growth seasons. Drought stress is one of the stresses that lead to reduced tobacco farming yields. Potassium-containing fertilisers play an important role in improving the quality of tobacco and under draught conditions, higher levels of potassium reduce the damaging effects of the draught stress. In this study, we initially subjected tobacco plants to a drought stress induced by 20% polyethylene glycol, 48 hours after which the plants were treated with three concentrations of potassium nano-chelate over 9 days. .The amounts of proline, total proteins, photosynthetic pigments, malondialdehyde, phenol and potassium in the leaf were determined and the results were statistically analyzed by SPSS software. The results showed that increase in the duration of treatments and higher concentrations of potassium nano-chelates decrease the drought-induced deleterious effects in tobacco leaves, as revealed by lower amounts of proline, malondialdehyde and phenol, whose concentrations are generally elevated in drought-stressed plants. Further biochemical analyses revealed that increase in the synthesis of proteins, chlorophylls and carotenoids. In conclusion, the results of this study suggest that, in a shorter time nano-chelates of potassium reduce the destructive effects of the draught stress.