فصلنامه فرآیند و کارکرد گیاهی
سال هشتم شماره 6 (پیاپی 34، Feb and Mar 2019)

Lack of chickpea cultivars tolerant to extreme freezing is a limiting factor for autumn planting of this crop in cold areas. In this study, 58 Kabuli-type chickpea genotypes and a control (an international sensitive genotype) were planted in pots and first exposed to -10°C and then to -15°C after being acclimated in natural conditions. No destructive effect of -10°C was observed in plants. So, acclimation was repeated and plants were transferred to -15°C. Survival percentage was measured after three-weeks recovery period. In continue, 19 genotypes with higher survival percentage along with the control were exposed to temperatures of -16, -18 and -20°C after they were acclimated in controlled conditions. Experiments were arranged as Completely Randomized Design with three replications. Results indicated that seven genotypes had survival percentage more than 80%, 24 genotypes more than 25% and 25 genotypes could not survive in -15°C. MCC803 had the highest and MCC808 and MCC510 the lowest survival percentage. All the genotypes were killed in -18 and -20°C. Among 19 studied genotypes, eight were able to tolerate -16°C. Among factors affecting cold tolerance such as soluble carbohydrates, proline, total phenol, photosynthetic pigments, DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity and malondialdehyde, soluble carbohydrates showed significant positive correlation with chickpea survival percentage. Generally, among the studied genotypes four genotypes (MCC53, MCC770, MCC776, MCC809 and MCC815) are recommended as promising genotypes for freezing tolerance.

In this study, rapeseed Okapi cultivar was treated under three NaCl levels (0, 50 and 100 mM) and four Zinc oxide nanoparticles (ZnO NPs) concentrations (0, 20, 40 and 80 mgL-1) at flowering stage. The experiment was performed in a completely randomized design (CRD) in the greenhouse of Biology Department of Urmia University, in 2015. Results showed that NaCl (100 mM) significantly enhanced total phenolic, flavonoids, anthocyanin and phosphorus contents and increased ability to scavenge the DPPH radical scavenging activity. Treatment with ZnO NPs (80 mgL-1) significantly elevated total phenolic and decreased anthocyanin, phosphorus and zinc contents and seed weight. Foliar application of ZnO NPs ameliorated the negative impacts of NaCl by reduction in phenolic, anthocyanin and phosphorus contents and elevation in seed oil content (20.82%) and seed weight (79.28%) at 50 mM salinity and 20 mgL-1 of ZnO NPs compared to NaCl (50 mM) alone. In conclusion, foliar application of ZnO NPs at 20 mgL-1 is recommended to farmers as replacement for fertilizers to alleviate the adverse effects of salinity stress.

This study was conducted to assess the induced-changes in the content of total phenolics and individual phenolic acids, total and individual polyamines and some organic acids in the leaves of two important Iranian grapevine cultivars under different durations of drought stress, and to determine their involvement in grapevine drought tolerance. For this purpose, ‘Yaghuti’ as a drought-tolerant and ‘Bidanesefid’ as a drought-sensitive vine were subjected to 6, 12 and 18 days of drought stress. Our results showed that as compared to respective control vines, 18 days drought stressed plants of ‘Yaghuti’ and ‘Bidanesefid’ had the highest concentration of total phenolics (31.55 vs. 27.40 mg.g-1Fw), total polyamines (98.40 vs. 70.11 ng.g-1Fw) and total organic acids (3.30 vs. 3.08 mg.100g-1Fw). Based on comparative analyses of individual phenolic acids, it seems that in drought stress condition and especially in ‘Yaghuti’, Caffeic acid and Gallic acid can be used as biochemical markers of stress responses. In our study, only 18 days of drought stress resulted in a significant increase in spermidine concentration in ‘Yaghuti’ cultivar while putrescine and spermine concentration of this cultivar increased at the onset of stress, so it seems that these two polyamines have a more important role in drought tolerance of ‘Yaghuti’. In the current study, different duration of drought stress remarkably increased the amounts of individual organic acids (tartaric, malic, oxalic and ascorbic acid) in both cultivars. The contents of quantified organic acids were not often significantly different between the two cultivars in the same durations of drought stress. Totally it seems phenolic acids and polyamines are more effective markers for drought resistance investigation of vines.

Carbon nanotubes (CNTs) are known to have many unique physical and chemical properties. Because of these features, they accelerate the germination process, root growth, and photosynthesis rate that can result in increased crop productivity. In the present study, the effects of 4 multi-walled carbon nanotubes (MWCNTs) levels including 0 (control), 50 (low concentration), 100 (moderate concentration), and 200 (high concentration) mg/l were evaluated on morphological and anatomical characteristics of stem, root and leaf in two Okra cultivars namely Bamia and Emerald. In both cultivars, the value of height and biomass of shoot and root increased after addition of 50 and 100 mg/l MWCNTs. Based on microscopic results, the root and shoot diameters in both cultivars more affected by increased cortex thickness and central cylinder in 50 and 100 mg/l of MWCNTs treatments whereas these parameters were more affected by increased cortex thickness in the high concentration of MWCNTs. Our study indicated that the thickness of mesophylls and spongy layers increased in low level of MWCNT, whereas these parameters were decreased in moderate and high levels of MWCNT in both cultivars. The statistical analysis showed that Stomata size increased value in low and moderate levels of MWCNT in Bamia cultivar. In this study Stomata index measurement showed that this parameter was increased in moderate and high levels of MWCNT only in Emerald cultivar. We observed that diameter of xylem and phloem in the shoot were increased in low (50 mg/l) and moderate (100 mg/lit) levels of MWCNTs whereas these parameters were decreased in high MWCNT level. Although this study revealed that low treatments of MWCNTs caused an increase of root xylem diameter in both cultivars.

Deficiency of nitrogen may lead to decrease in yield and yield potential of crop plants. An experiment was done under glasshouse conditions in order to investigate nitrogen levels and salicylic acid interaction on some physiologic traits of borage (Borago officinials L.). In this experiment various levels of nitrogen (including; 27.5, 55, 110, 220 and 330 mg/L from ammonium nitrate) and salicylic acid (including; zero, 400, 800 and 1200 µM) was used. The results indicated that stomatal conductance, photosynthesis rate, respiration rate, chlorophyll a, chlorophyll b, carotenoids, proline, and ascorbate peroxidase, were increased by increasing of nitrogen level. However, intercellular CO2 concentration, anthocyanin, flavonoids, soluble carbohydrates, catalase, and peroxidase were decreased. Among nitrogen levels, the maximum effect was obtained by 220 and 330 ppm treatments. Furthermore, salicylic acid spraying led to promote stomatal conductance, photosynthesis rate, transpiration rate, photosynthetic pigment content, proline, anthocyanin, flavonoids, soluble carbohydrates, and catalase, peroxidase and ascorbate peroxidase enzyme, but not intercellular CO2 concentration. The highest values of stomatal conductance, photosynthesis rate, transpiration rate, photosynthetic pigment content, proline, anthocyanin, flavonoids, soluble carbohydrates, and activities of catalase, peroxidase, and ascorbate peroxidase enzymes were achieved by 800 and 1200 µM concentrations of salicylic acid and 330 ppm of nitrogen. The results showed that appropriate concentrations of salicylic acid can recover nitrogen shortage and improve the measured traits.

Increasing nitrogen absorption efficiency reduces use of excessive application of N. The effect of rootzone temperature on nitrogen absorption needs clarification. The experiment was conducted to investigate low (15°C, RTZ1), high (35°C, RTZ2) and optimum (25°C, RTZ3) root zone temperatures and nitrogen 52.5 (ND1), 78.75 (ND2) and 105 (ND0) mg∙L-1 levels on cucumber (Cucumis sativus L.), cv. Super N3, cultured in Johnson nutrient solution. Shoot and root fresh and dry weights, chlorophyll content, maximum photochemical quenching )Fv/Fm(, antioxidant activity, total phenol and nitrate reductase (NR) activity increased with N. Shoot fresh and dry weights, chlorophyll content, total phenol, antioxidant and NR activity was reduced at high and low root zone temperature compared to the optimum temperature. Shoot fresh and dry weights increased in RTZ1 and RTZ2 for the ND2 and ND0 treatments. The SPAD value increased in RZT2 at all nitrogen levels. The highest Fv/Fm occurred at ND0 at all temperature levels. Antioxidant activity increased for the ND0 and ND2 treatments with increasing root zone temperature. Total phenol content increased in ND1 and ND2 at low and high temperatures compared to the optimum temperature, and increased with increasing temperature level in ND0 treatment. The NR activity increased at the high root zone temperature in ND2 and ND0 treatments. The ND0 and ND2 treatments alleviated the root zone temperature effect on cucumber grown in hydroponic culture.

Lack of available water in arid and semi-arid regions has a negative effect on the production of soybean (Glycine max L.). Nano zinc chelate (ZnO) has the potential to alleviate this issue through overcoming zinc deficiency and thereby improve plant function. Therefore, to evaluate the effectiveness of ZnO application on soybean in drought stress conditions, a split-plot experiment based on randomized complete block design was conducted. Irrigation treatments (100%, 80%, 60% and 40% water requirement) was the main plot and foliar application of nano-zinc (2ml.L-1 foliar treatment vs. no-application control) was the subplot. The results showed that drought stress had negative effects on plant yield and productivity. Under drought, grain yield, seed oil percentage, oil yield, palmitic acid, stearic acid, cis-oleic acid and linoleic acid were decreased. ZnO application significantly increased proline content, catalase and peroxidase activities. However, the percentage of palmitic acid, stearic acid, linoleic acid and α-linoleic acid decreased with the ZnO foliar spray. In general, results showed that, ZnO treatment, with enhancing antioxidant enzymes activity and changing physiological parameters decreased adverse effects of drought stress on soybean plants.

The effects of salt stress on growth and some physiological parameters of halophytic plant, Leptochloa fusca L. Kunth, were investigated. The seedlings were irrigated with half-strength Hoagland solution and then treated with different concentrations of NaCl (0, 100, 300, 500 and 700 mM) for 15 days. The fresh and dry weights of both root and shoot were unchanged at 100 mM NaCl and decreased at higher concentrations. Relative water content significantly decreased at high NaCl treatments. The significant increase in the contents of chlorophylls and carotenoids due to NaCl stress was observed in all salinity treatment except for100 mM NaCl. Leaf Na+/ K+ ratio increased with increase in medium salinity. Moderate (300 mM) and high (700 mM) salinities dramatically increased proline content as compared to that of control group. With a progressive increase in salinity, catalase, ascorbat peroxidase and guaiacol peroxidase activities also increased gradually in this species. It seems that antioxidant enzyme activity for scavenging reactive oxygen species and proline accumulation for osmotic adjustment play an essential protective role in L. fusca under salinity stress. In summary, these data indicate that salinity tolerance is well programmed in L. fusca allowing adaptation to harsh environmental conditions in the natural habitat.