فصلنامه فرآیند و کارکرد گیاهی
پیاپی 1 (بهار و تابستان 1391)

In this experiment, the response of canola cultivars to salnity stress in germination stage was evaluated using a factorial experiment with four replications in completely randomized design. Six canola cultivars (Fornex, Alice, Orient, Consoul, Okamer and Okapi) were subjected to four salinity levels (0, 40, 80 and 120 mMol NaCl) under room, greenhouse, field? Salinity reduced the percentage of seed germination, seedling vigor index, α-amylase activity and seedling fresh weight, but it increased the mean germination time, malondialdehyde concentration, and cell membrane leakage. At the highest salinity level, Orient and Fornex cultivars had the highest germination percentage (84% and 80%), α-amylase activity (9.3 nmol seed-1 min-2 and 9.4 nmol seed-1 min-2) and seedling fresh weight (0.95 mg and 0.70 gr) compared to other cultivars. The electrical leakage of the seedling was lowest in the latter cultivars. Results showed a positive correlation of canola seedling weight with α amylase activity but negative correlations with the malondialdehyde concentration and cell membrane leakage. Salinity stress increased cell membrane damage and decreased α amylase activity, canola seed germination and seedling growth. Results indicated that under salt stress condition, Okamer and Okapi was sensitive canola cultivars compare with other cultivars.

Jasmonic acid and its methyl ester, methyl jasmonate (MeJA), are naturally occurring plant growth regulators, which can affect many physiological and biochemical processes in plants. In present investigation, the effects of methyl jasmonate (0, 1, 10, 100 and 500µM) on some physiological and antioxidative responses in soybean (Glycine max L.) plants were studied. Under MeJA (1 and 10 µM) treatments, shoot dry weight and chlorophyll content increased and lipid peroxidation decreased. Treatment of plants with methyl jasmonate, especially at 100 and 500 µM concentrations reduced shoot dry weight and total chlorophyll content and increased lipid peroxidation. All concentrations of MeJA increased the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POD) and also increased the content of ascorbate pool, phenolic compound and anthocyanins as well. Based on our results, it seemed that the application of methyl assonate at low concentrations enhanced the antioxidant defence system, at the same time, decreased lipid peroxidation and improved growth parameter. The higher concentrations of methyl jasmonate increased lipid peroxidation and reduced plants growth, so that increasing the antioxidant capacity of plants did not decrease the oxidative stress and did not improve plants growth.

Wheat grain yield is reduced by post-anthesis drought stress conditions in most wheat growing farmlands of Iran. To evaluate the effect of post-anthesis-withholding irrigation on yield, yield components and canopy temperature of wheat cultivars, a field experiment was conducted as split plot in a completely randomized block design with four replications at experimental farm of college of Agriculture, Shiraz University during 2009-2010 and 2010-2011 growing seasons. Irrigation regimes (normal and cut off after anthesis) and bread wheat cultivars (40 cultivars) were assigned in main plots and subplots, respectively. The results showed that post-anthesis withholding irrigation significantly reduced grain yield, grain number per unit area, 1000 grain weight, biological yield, harvest index, canopy temperature depression (CTD) index, rate of biological yield accumulation, grain yield production rate and grain filling rate. Maximum grain yield under normal irrigation conditions belonged to Shiroudi (8864 kg.ha-1), Navid (8440kg.ha-1) and Karaj-2 (8403 kg.ha-1) cultivars, whereas in the late season drought stress conditions, Moghan-2 (4445 kg.ha-1) and Adl (4179 kg.ha-1) had maximum grain yield. Positive and significant correlation between grain yield and CTD under two irrigation regimes suggested that CTD might be a good indicator for selecting of drought resistant cultivars for late season water deficit, as well as high grain yield under normal irrigation conditions.

Two experiments were conducted to study the impact of salt stress and salicylic acid (SA) on seed germination and plant growth of maize (SC704) under field conditions in the city of Kerman in 2010. For germination experiment, SA seed pretreatments included; control, water soaked, SA soaked in 0.1 and 0.2 mM for 24 hours and salt treatment included; control, 40 and 80 mM NaCl. All seed germination parameters including germination percentage, mean germination time, germination uniformity, radicle and root length and seedling dry weight were adversely affected by salt stress. SA especially at 0.1 mM improved all parameters significantly, especially under salt treatment. Under field conditions (40 mM salinity), 0.1 mM SA improved chlorophyll, relative water content, membrane permeability, fresh and dry weight of forage, comb length, grain yield, 1000 seed weight, water use efficiency and K+ in leaf. However, leaf Na+ content was significantly lower when SA was used. Thus, it was concluded that seed pretreatment with SA could be used commercially to improve plant performance and yield in maize under salt stress conditions.

In this study, a greenhouse study was conducted to investigate the growth of Aloe vera with different content of nitrogen fertilizers. Treatments consisted of 0, 0.15, 0.29, 0.43, 0.57 and 0.71 g/pot ammonium nitrate and 0, 0.11, 0.22, 0.33, 0.43, 0.53 g/pot urea. Then the effects of nitrogen fertilizers on fresh weight, photosynthetic pigments and proline content were studied. The results indicated that fresh weight was increased in response to application of 0.29, 0.43 and 0.57 g/pot ammonium nitrate and 0.22 urea as compared to the control. Chlorophyll a content was increased at rate of 0.29 g ammonium nitrate/pot. Chlorophyll b and carotenoid contents were increased at rate of 0.15, 0.29, 0.43 and 0.57 g ammonium nitrate/pot. Chlorophyll a and b contents did not show any differences in response to application of urea, but carotenoid content increased at rate of 0.53 g urea/pot as compared to the control and 0.11 g urea/pot. Proline content was same as control under ammonium nitrate, but increased with urea, significantly. It was calculated that 300 kg/ha ammonium nitrate and 200 kg/ha urea were sufficient for optimum growth and leaf production of A. vera seedlings. These amounts with respect to nitrogen percentages of ammonium nitrate (35%) and urea (46%) are approximately equal to 100 kg/ha nitrogen.