فصلنامه گیاه و زیست بوم
پیاپی 34 (بهار 1392)

Drought stress is one of the significant, limiting, environmental factors in the crop production. Previous research indicated that the salicylic acid plays an important role in the germination and the regulation of the physiological processes in plants. The present study was carried out in an attempt to investigate the effects of drought stress and the salicylic acid on the germination of two maize cultivars and to compare their drought tolerance. The experiment followed a factorial, completely randomized, research design and was carried out in three replications. The factors included: the drought stress (i.e. water potential at six levels: 0, -2, -4, -8 and -10 Mpa) and the salicylic acid (0 and 0.2 mM). The results indicated that the drought stress and the salicylic acid had significant effects on all of the traits under study, i.e. germination percentage, germination speed, mean time germination, germination rate, radicle and shoot lengths, fresh and dry radicle weight, fresh and dry shoot weight, and dry seedling weight. With an increase in the drought stress, all of the aforementioned straits significantly decreased except for the mean time germination which demonstrated an increase. Similarly, the salicylic acid had a significant effect on all of the traits under analysis. Comparing the two cultivars, it was found that the 647 cultivar demonstrated more tolerance against the drought stress at germination level in comparison to the 704 one. In addition, the salicylic acid increased drought tolerance at germination level in both of the cultivars.

Anise hyssop (Agastache foeniculum [Pursh] Kuntze) is a herbaceous, perennial, and aromatic plant which belongs to the Lamiaceae family and originated from the North America. It has various medicinal qualities and is used for curing stomach and liver inflammations as well as prostate problems. This plant is also applied in food and beverage industries. Given that dryness is one of the prominent features of Iran’s geography, the effect of drought stresses on agricultural products has been widely investigated. However, there appears to be a dearth of research on the enzyme-changes of the medicinal plants. The present experiment was carried out in a randomized complete block design with three replications. The changes in the activity of the anti-oxidative enzymes (i.e. catalase, glutathione peroxides, superoxide dismutase) in Anise hyssop (Agastache foeniculum [Pursh] Kuntze) in response to drought stress were analyzed using 7 irrigation treatments which included: 100%, 85%, 70% and 55% field capacity, 100% field capacity (vegetative stage), -85% field capacity (reproductive stage), 100% field capacity (vegetative stage), -70% field capacity (reproductive stage), 85% field capacity (vegetative stage), and -100% field capacity (reproductive stage). On the basis of the results, the highest portion of the anti-oxidative enzymes was found in the 55% field capacity. It indicated that the plant applies enzymes in response to the drought conditions. Considering the high adaptability of this plant to drought stress conditions, its cultivation in dry areas is suggested.

Rice (Oryza sativa L.) is one of the most significant crops in the world, which is an important food crop for more that 50% of the people in the world. Abiotic stresses such as salinity are important barriers against crop production in different parts of the world specially the arid and semiarid regions. In an attempt to investigate the effects of salinity stress in different sodium chloride (NaCl) concentrations on the germination and the primary growth of the plantlets, a factorial experiment was carried out on the seeds of six different types of rice, following a completely randomized design with three replications. Different traits including: the percentage and speed of germination, radicle and plumule lengths, and the reduction percentage of each of the traits in the comparison between the salinity (11.2dSm-1) and control treatments, were measured 7 days after the beginning of the experiment. The results of the analysis of the variance indicated that there was a significant difference, at P<0.01, between cultivars, salinity treatments, and their interaction effects for all of the four traits. With an increase in the amount of salinity, the percentage and speed of germination and the radicle and plumule lengths demonstrated a significant decrease. The results also indicated that the reduction percentage of the traits was significant. In other words, the aforementioned traits significantly decreased under the salinity treatments. The results of the present study indicated different degrees of salinity tolerance in the germination traits. Comparing the cultivars in different salinity treatments, it was found that the improved cultivar under study was more tolerant in germination stage in comparison to the landrace ones.

Dittrichia graveolens (L.) Greuter is indigenous of the Mediterranean region and belongs to the Asteraceae family. It is effective in treatment of the chronic diseases such as cough, cold, cynosite inflammation, and bronchitis. It also protects lymphatic system and decreases acne infection of the skin. The essence of this plant decreases the mucus content and contains bornyl acetate, borneol, and T-cadinol. Germination is a fundamental part in the life of the plants and the establishment of the seedling is the first stage in plant growth which has a high significance in enhancing plant yield and performance in the soils which are under salinity stress. Salinity might significantly decrease the speed and percentage of germination and in effect prohibit the expansion of plant’s vegetation and the crop yield. The present study investigated the optimum temperature and the effect of different salinity concentrations on the germination of this plant. For determining the optimum temperature, various temperatures including: 0, 5, 10, 15, 20, 25, 30, 35⁰C were examined. In addition, the analysis of the effect of the salinity stress on plant germination was carried out at different concentrations including: 0, 25, 50, and 75 mM NaCl. The results indicated that the optimum temperature for the seed germination of this plant was 20⁰C and the highest percentage of germination and root and shoot lengths were observed in the control treatment.

One of the most significant objectives of plant breeding experts is enhancing the salinity tolerance of crops and screening the tolerant ones. The present study was carried out in an attempt to evaluate and screen the salinity tolerance of the wheat cultivars at germination and seedling stages. The experiment followed a split plot, randomized complete block design and was conducted in three replications. The main and sub plots respectively included: the wheat cultivars and the salinity levels (i.e. 0, 50, 100, and 150 mM NaCl). The traits under analysis at germination stage included: germination percentage, radicle length, hypocotile length, coleoptile length, radicle fresh and dry weight, and hypocotile fresh and dry weight. In addition, shoot fresh and dry weight, relative water content (RWC), sodium and potassium contents, potassium to sodium ratio, chlorophyll content, prolin, and the total leaf area were investigated at the seedling stage. The results indicated that there was significant difference at P<0.01 among the wheat cultivars, considering all of the traits and salinity levels. Salinity significantly increased sodium and prolin, while it significantly decreased all of the other traits. The regression analysis revealed that there was a linear relation between all of the traits except for the coleoptile length, potassium content, potassium to sodium ratio, prolin, and the total leaf area. Finally, on the basis of the most significant salinity tolerance indices, i.e. dry weight, sodium content, potassium to sodium ratio, RWC, prolin, and the total leaf area, Hamoon and Hirmand cultivars might be introduced as tolerant cultivars. Alvand cultivar demonstrated moderate tolerance. The cluster analysis also placed Hamoon and Hirmand cultivars in one group, which confirms the aforementioned results.

Soil salinity is one of the major abiotic stresses that adversely decreases the crop yield and quality. In an attempt to study the effects of salinity on crop yield and quality, a factorial experiment was conducted including two factors, i.e. salinity at four levels (0, 33, 66, and 99 mM sodium chloride) and the zinc fertilizer at two levels (0 and 10 mg kg-1 soil). The study followed a randomized, complete block design and was carried out with three replications in the greenhouse of the faculty of Agriculture in Kurdistan University. The results indicated that the treatments had significant effects on shoot dry and fresh weight, chlorophyll content, the soluble proteins of the leaves and the root, and potassium (K), sodium (Na), and phosphor (P) concentrations of the leaves. The application of zinc did not have any significant effect on phosphor (P) and sodium (Na) concentrations of soybean leaves. Salinity decreased shoot dry and fresh weight, yield, the soluble proteins of the leaves and the root, and chlorophyll content at three growth stages (before flowering, after flowering, and seed filling). Nonetheless, the application of zinc significantly increased these parameters. Potassium (K) and phosphor (P) concentrations of leaves significantly decreased under salinity stress, whereas sodium (Na) concentration of the leaves increased in NaCl-treated plants.

In an attempt to identify drought tolerance lines and screen the quantitative parameters of drought tolerance, seventeen lines of bread wheat genotypes in addition to Koohdasht wheat were analyzed under two drought conditions, i.e. mild and severe stress, in a randomized complete block design with four replications in Gachsaran Dryland Agricultural Research Station. On the basis of the mild (Yp) and severe (Ys) stress yields, the quantitative parameters of drought tolerance including: mean productivity (MP), tolerance index (TOL), geometric mean productivity (GMP), harmonic mean (HM), stress susceptibility index (SSI), and stress tolerance index (STI) were measured. The results of the mean comparison indicated that there was a significant difference among all of the genotypes with respect to all of the indices and the yields in both environments. This demonstrated the existence of genetic diversity and the possibility of selecting the tolerant genotypes against drought and applying the superior ones in breeding programs. The results of the correlation analysis between the two conditions and drought tolerance indices indicated that the MP, GMP, STI, and HM indices were the best parameters for screening bread wheat genotypes. Considering these four indices and the high yield in the two conditions, the genotypes number 1 and 4 were selected as the most tolerant genotypes against drought. The biplot multivariate technique revealed that the genotypes number 1 and 4 were located along the vectors of drought tolerance indices. In addition, the spread of the genotypes in the biplot demonstrated the existence of genetic diversity among the genotypes regarding drought tolerance.

The present study investigated the effects of different concentrations of salicylic acid (0, 0.5 and 1 mM) and cadmium chloride (0, 50, 100 and 150 µM), together and separately, on certain physiological parameters of Cicer arientinum L. The activity of peroxides and catalase, proteins, and anthocyanin contents increased with an increase in cadmium chloride. By increasing the salicylic acid, the activity of peroxides and catalase decreased, while the total amount of protein and the anthocyanin contents increased. The interaction of salicylic acid and cadmium chloride decreased the catalase activity in the lower concentrations but the total amount of protein increased. In addition, the activity of peroxides and the anthocyanin content increased in most of the interaction treatments. The results indicated that chickpea is not a tolerant plant against the cadmium stress.

Drought stress is the most significant factor that confines the growth of crops such as safflower (Carthamus tinctorius L) in the arid and semiarid regions of the world. In an attempt to investigate the effect of drought stress on some of the features of the autumn safflower cultivars, a field experiment was conducted, during 2009, in the research farm of the Islamic Azad University, Shahr-e Rey branch. The research followed a split plot, randomized, complete block design and was carried out with four replications. The main plots included: two irrigation levels (irrigation throughout the growing period and the withholding of irrigation at the heading stage) and the sub plots consisted three genotypes (i.e. Goldasht, Padideh, and KW). The results indicated that the drought stress significantly reduced the grain yield and yield components. Generally speaking, it decreased the number of plant heads (11.46%), seed pods (27.65%), 1000-seed weight (14.31%), and the grain yield (45.75%). Under the control conditions, Goldasht cultivar had the highest grain yield in comparison to the other ones, but under the drought stress conditions, the difference between the cultivars was not significant.