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Articles by Homa Mahmoodzadeh
Total Records ( 8 ) for Homa Mahmoodzadeh
  Homa Mahmoodzadeh
  Seed germination and seedling development of Brassica napus cultivars (Okapi and Symbol) under salt stress were evaluated. Germination percentages after treating were variable among different controls and treatments, despite the initial high seed viability for both cultivars. Seeds exposed to high salinity exhibited significantly lower germination than seeds not exposed to NaCl for the same time periods. No significant differences in germination percentages were observed for exposure to 0, 3 and 6 dS m-1 treatments. Seeds of symbol exposed to 12 dS m-1 treatment showed lower germination percentage than the others. Results showed that the percentage and rate of seed germination, seedling growth and distance between the root hairs and root tips were all decreased by salt solutions, especially by 12 dS m-1 treatment. However, these parameters were increased by 3 dS m-1 treatment. Also, being treated with salt solutions, within the range of 12-20 dS m-1, the threshold concentration for germination was determined as 14 dS m-1 for Okapi and 13 ds m-1 for Symbol. Results showed that the effects of salinity stress on the phase of germination is less than the other phases. Under greenhouse condition, the vegetative growth and yield of both cultivars were unaffected by soil salinity of a rate of up to 3 dS m-1. By increasing the salinity levels above the threshold, the ratio of fresh to dry biomass, thickness of leaves, plastochronic period, thickness of pollen exine and 1000-siliqua weight increase. On the other hand, number of leaves, branches, flowers, flower primordia, siliquas and their length, number of seeds per siliqua and 1000-seed weight all decreased. The most inhibitory effect was observed in 12 dS m-1 treatment with more effect on Symbol than on Okapi. The length of siliquas, plastochronic period and number of flowers were more affected by salinity stress than the other parameters.
  Mehrdad Lahouti , Homa Mahmoodzadeh and Samaneh Jamshidi
  In the present research, effect of caffeine on structure and ultrastructure of shoot apical meristem of Phaseolus vulgaris L. was investigated. The present study showed that low concentrations of caffeine (<22.5 ppm) had no pronounced effect on the growth of bean seedlings and structure of shoot apical meristem, but higher concentrations of caffeine (40-60 ppm) had severe inhibitory effects. Electron microscopy (TEM and SEM) studies showed that apical meristem size and number of leaf primordia was decreased under caffeine treatment. Also in some meristem cells, formation of cell wall was incomplete. Present findings show that a lack of division in strategically located cells in primordia and during organogenesis could produce the organ abnormalities described. The observation that cytokinesis defects can be observed in developing primordial and meristems supports this.
  Homa Mahmoodzadeh and Elham Esparham
  The plant hormone abscisic acid (ABA), as a stress signal, plays important roles in the regulation of plant responses to environmental stresses. The relationship among abscisic acid (ABA) accumulation, the generation of Reactive Oxygen Species (ROS) and the activities of several antioxidant enzymes such as Catalase (CAT), Ascorbate Peroxidase (APX) and Glutathione Reductase (GR) was investigated in leaves of detached bean (Phaseolus vulgaris L.) plants exposed to 10,100 and 1000 μM ABA [Detached leaves of bean were cut into leaf segments and floated in solutions containing 0, 10, 100 and 1,000 μM ABA, at 25°C and then used for assay of antioxidant enzymes]. Treatment with 10 and 100 μM ABA significantly increased the levels of O2¯ and H2O2, followed by an increase in activities of CAT, APX and GR in leaves of bean seedlings. Treatment with 1,000 μM ABA led to a more abundant generation of O2¯and H2O2 .The activities of these antioxidative enzymes were reduced when compared with the treatment of 100 μM ABA. These results indicate that treatment with low concentrations of ABA (10 to 100 μM) induced an antioxidative defense response against oxidative damage, but a high concentration of ABA (1,000 μM) induced an excessive generation of ROS and led to an oxidative damage in plant cells.
  Mehrdad Lahouti , Samaneh Jamshidi , Hamid Ejtehadi , Mina Rowshani and Homa Mahmoodzadeh
  Ultrastructural studies of root cortical cells of Raphanus sativus L. seedlings experimentally exposed to 0-7 mg L1 Cr3+ revealed small electron dense granules especially in preplasmic zone. Root cortical cells of control seedlings grown in the absence of Cr3+ additions were void of any granules. X-ray microanalysis of the granules provided evidence that Cr was the predominant element while lower amounts of Fe, Zn and Mn were also measured in the granules. Presence of chromium deposit inclusions in the cells may be regarded as plant detoxifying mechanism to maintain relatively low cytoplasmic concentration of the element.
  Homa Mahmoodzadeh , Ahmad Majd and Mehrdad Lahouti
  In the present research structure and ultrastructure of shoot apical meristem of canola (Brassica napus cv. Symbol) under salinity conditions were investigated. The experiments were conducted in five groups (0, 3, 6, 9, 12 dS m-1) under greenhouse conditions. Sampling of apical meristem and TEM tissue preparation procedure were carried out. Semithin and ultrathin sections were prepared and viewed in light and electron microscopy, respectively. The results included reduction of meristem size, disorders in meristem structure. Also formation of autophagic vacuoles was observed that is probably one of the plant responses to salt stress for more water storage in these vacuoles and decreasing of cell water requirements.
  Homa Mahmoodzadeh
  n the present research, structure and ultrastructure of shoot apical meristem of canola (Brassica napus cv. Symbol) under salinity conditions were investigated. The experiments were conducted in five groups (0, 3, 6, 9, 12 dS m-1) under greenhouse conditions. Sampling of apical meristem and TEM tissue preparation procedure were carried out. Semithin and ultrathin sections were prepared and viewed in light and electron microscopy, respectively. The results included reduction of meristem size, disorders in meristem structure. Also formation of autophagic vacuoles was observed that is probably one of the plant responses to salt stress for more water storage in these vacuoles and decreasing of cell water requirements.
  Homa Mahmoodzadeh and Maasoumeh Bemani
  Effects of salt stress on developmental stages of male gametophyte were investigated, using both light and electron microscopy through the popular cyto-histological methods. The findings were then compared with those obtained from the unstressed plants. It was found out that salt stress could cause significant changes on the general growth of plants as well as a reduction of the number of pollen grains in anthers at the beginning of flowering stage. In spite of the normal appearance of the florets, the growth of anthers was abnormal, appearing to be shriveled, colorless and small. The other effects observed during various stages of development are as follow: pre-time destruction of the anther wall, degeneration and abnormal forms of pollen grains. As a result, such reduction of the number of pollens and their abnormality of the form and structure could ultimately lead to decrease of crops yield.
  Homa Mahmoodzadeh , Forugh Abbasi and Yalda Ghotbzadeh
  To determine the allelopathic potential of root exudate from early developmental stage of rice (Oryza sativa L.), 6-days-old seedlings of two cultivars were grown with 3-days-old Hedgemustard seedlings in petri dishes under controlled condition. There were 4 treatments (2, 4, 8 and 10 days). Also rice leachate was used for germination test of the weed. Rice lichate caused pronounced inhibitory effect on seed germination and germination rate of receptor plants. Root exudates of rice cultivars also inhibited root and shoot growth and fresh weights of seedlings of receiver plants. Effectiveness of cv. kalat was more than cv. shomal. Hence, it could be concluded that the rice root exudates and rice leachate contain water-soluble allelochemicals which could inhibit the seed germination and reduce seedling growth of Hedgemustard.
 
 
 
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