فصلنامه زیست شناسی گیاهی ایران
سال سوم شماره 2 (پیاپی 8، تابستان 1390)

In this study, the effects of salicylic acid on arsenic toxicity in chamomile plants (Matricaria recutita) were studied by investigating the plant growth and some of the biochemical parameters. Treatment by arsenic (0, 10, 45 and 80 µM) of chamomile plants for 14 days caused serious chlorosis and reduction of plant growth. Also, arsenic significantly increased the accumulation of reactive oxygen species, and resulted in the lipid peroxidation, which was confirmed the by increased concentration of membrane aldehyds. Pre-treatment of the plants by salicylic acid (spray with 0.1 and 0.5 mM salicylic acid for 10 days before arsenic stress) increased the rate of plant growth, photosynthesis, anthocyanins and reduced carbohydrates and significantly decreased lipid peroxidation, hydrogen peroxide and accumulation of arsenic in the leaves of arsenic-exposed plants. The results showed that salicylic acid could improve plant growth to some extend and increased chamomile resistance to arsenic stress.

The Effect of salinity (50 mM NaCl) and exogenous putresine and spermidine (0.5 mM) on growth and photosynthesis of tobacco (Nicotiana rustica L) plants were studied in hydroponic medium. Salinity caused reduction of plants growth. Application of putresine increased dry weight of control plants while exogenous spermidine decreased it. Exogenous putresine ameliorated salinity stress only in roots, but spermidine exerted this effect on both shoot and roots. In the absence of polyamines, salinity decreased chlorophyll a significantly and chlorophyll a/b ratio as well but application of polyamines increased these parameters. Salinity caused reduction of net CO2 assimilation rate. Under control conditions, polyamines reduced net CO2 assimilation ratebut the rate was increased in the treated plants. Total leaf phenolics was not influence by salinity, but application of putresine in salinity conditions reduced phenolic contents and of spermidine increased total phenolics of leaves. The activities of leaf phenylalanine ammonia lyase and polyphenol oxidase decreased in salinized plants, while exogenous polyamines increase and decrease in their activity, respectively. Growth impairment due to exogenous spermidine in control plants could be resulted from reduction of photosynthesis and increase of leaf phenolics. In spite of a negative effect of exogenous spermidine on growth of control plants, application of both polyamines ameliorated salinity stress. This effect was likely mediated by the improvement of leaf photochemical parameters and increase of CO2 assimilation. Phenolics metabolism was greatly influenced by exogenous polyamines, however, no correlation was found between ameliorative effect of polyamines and changes in the phenolics metabolism.

Khybus Protected Area has one of the best and the most intact habitats of boxtrees (Buxus hyrcana Pojark.) in Hyrcanian forests. In this area, the lowest and the highest altitudes are 400 and 900 meters and is located in north east of Savadkooh. The floristic-physiognomic investigation which was performed by field-walk procedure showed that Flora of this region included 60 plant species which belonged to 54 genera and 39 families. The important families were Rosaceae, Aspidiaceae, Cyperaceae, Asparginaceae and Poaceae with 10%, 6.7%, 6.7%, 5% and 5% respectively. These families contained 33.4 percent of the total species. Phanerophytes (40%), Hemicryptophytes (28.3%) and Cryptophytes (25%) were the most important structure groups of the local biological spectrum according to Raunkaiaer method. The result of chorological studies showed that the chorotype form Euro_Sibria was the most important phytochorion which make up the chorological structure of Box trees stands in Khybus Protected Area.

Saffron (Crocus sativus L.) is an important economic crop in Khorasan province which is propagated by corms. The traditional culture has various problems such as pathogen attack and a long period of time for proliferation. Application of plant growth regulators and induction of somatic embryogenesis is an efficient method to propagate a large number of intact corms in in vitro condition. In this research, effects of four exogenous hormones during 90 days on maturation of globular embryo, its germination and microcorm induction of saffron by using half strength Murashige and Skoog media were studied. Investigated phytohormones were NAA (0.1, 0.25 and 0.5 mg l-1), IBA (0.5, 1 and 2 mg l-1), BAP (0.25, 0.5 and 1 mg l-1) and ABA (0.5, 1, 2 and 4 mg l-1). All treatments carried out based on completely randomized design in 4 replicates. Results showed that the most number of globular somatic embryos were obtained in ½ MS medium containing 0.1 mg l-1 NAA, but this media in relation to which were contained BAP or IBA was not suitable for maturation. After 60 days, the media supplied with 1 and 2 mg l-1 IBA were the best for induction of embryo maturation and cormlet formation. Although at the end of 90 days, highest number of mature embryos was obtained in the presence of 0.5 mg l-1 BAP, microcorm induction did not occurred by BAP treatments in long term. Different concentration of ABA quickly improved maturation of globular embryos but they had no positive effect on cormlet regeneration.

This study was carried out in order to investigate chromosomal behavior during meiosis, morphological assessments and fibers quantitative and qualitative traits in herbaceum (Iranian endemic), arboreum species, F1 hybrids of two species and BC4 genotypes. In this study, the endemic varieties Aria and Bandarabas and VTDL as arboreum were used. Regarding to the morphological characters, the F1s traits were intermediate and BC4 showed intermediated and resemble somewhat to the endemic parents traits. F1s Cytological investigations showed the adjacent and alternative quadrivalents frequently but In the BC4 offspring population the quadrivalents were appeared in low frequency. Besides, other abnormalities like univalent, trivalents and triple sets of chromosomes in MII and AII were observed which were resulted in the deviation from Tetrads.