نشریه تحقیقات بذر
پیاپی 28 (پاییز 1397)

In order to identify the eco-physiological factors affecting on dormancy break and create optimal conditions germination of prosopis species seeds, an experiment was conducted in a completely randomized design with three replications. Treatments included: control (distilled water), WS 80 (warm stratification (Bain marie) at 80 ºC temperature for three days), WS 65 (warm stratification (Bain marie) at 65ºC temperature for three days), W65 (warm stratification (oven) at 65 ºC temperature for three days), W80 (warm stratification (Oven) at 80 ºC temperature for three days), (CS5)+ (WS65) (cold stratification at 5 ºC temperature for three days then warm stratification (Bain marie) at 65 ºC temperature for three days), (CS5)+ (WS80) (cold stratification at 5 ºC temperature for three days then warm stratification (Bain marie) at 80 ºC temperature for three days), (CS5)+ (W65) (cold stratification at 5 ºC temperature for three days then warm stratification (Oven) at 65 ºC temperature for three days), (CS5)+ (W80) (cold stratification at 5 ºC temperature for three days than warm stratification (oven) at 80 ºC temperature for three days). The results showed that the highest seed germination percentage (40.45) was observed in (CS5)+(WS65) for three days, and the lowest one in control (zero). The highest SV II index seed related to (CS5)+ (WS65), for three days (245.26). Also, (CS5)+ (WS65) treatment for three days increased break of seed dormancy and germination rate. In general, effective treatment for dormancy break of prosopis species, is recommended (WS65) treatment for three days.

This experiment was conducted in a completely randomized design with three replications in 2016 in Laboratory of Agricultural College, Mohaghegh Ardebili University. Medicinal plants included Artemisia sieberi L., Achillea millefolium L., Salvia officinalis L., Matricaria chamomilla and control (distilled water). The results showed that the medicinal plants extract significantly reduced germination percentage, length and dry weight of Datura stramonium L. seedling compared to the control. Among the medicinal plants, extract of Artemisia sieberi L., and Salvia officinalis L, compared with other extracts, reduced germination percentage by 32% and 24%, respectively, compared to the control. In the extracts of Artemisia sieberi L., and Salvia officinalis L, dry weight of Datura stramonium L seedlings decreased compared to other plants extracts. In general, these herbs, especially Artemisia sieberi L. and Salvia officinalis, can be used in rotational programs to reduce the presence of weeds.

Soil salinity is one of the most important problems in crop production. Improvement in salt tolerance in major food crops is an important way for the economic utilization of saline area.The effects of pretreatment of salicylic acid on phoenix canariensis seed germination, lipids peroxidation, superoxide dismutase (SOD), catalase (CAT), polyphenol oxidase (PPO) peroxidase (POX) activity in salt stress condition were investigated. Treatments of Phoenix canariensis seedlings with different concentrations of salicylic acid (SA) for seedling growth were: (0, 0.5, 1 and 2 mM). Salt stress was inducted by NaCl solution (0, 100, 200 and 200 mM). After three mounths, number of germinated seed, radical length, seedling length and dry weight were recorded. Antioxidant enzymes activity and lipid peroxidation were analysed too. The results showed that high concentration of NaCl (400mM) decreased germination to 8.57 % than control. Influence of SA was significant and increased percent of germination in stressed and control treatments. Enzymes assay showed enzyme activity increased in salt stress conditions and SA reduced activity of antioxidant enzyme. In general, SA treatment reduced damage of salinity on seedling growth and accelerated the restoration of growth processes.

In order to investigate the effect of humic acid and folic acid on seed germination of Echinacea purpurea under natural salinity stress, a factorial experiment based on completely randomized design was conducted in three replications at Seed Technology Lab of Shahed University in 2017. The experiment factors consisted of humic acid at three levels (0, 200 and 400 mg/lit), folic acid at three levels (0, 200 and 400 mg/lit) and salinity stress at four levels (0, 4, 8 and 12 ds/m). The results showed that there were significant differences in humic acid, folic acid and salinity stress interaction on germination percentage, germination average, stem length, seedling fresh weight and seedling index. The highest germination percentage (100%) was observed in the combination of humic acid and folic acid at 200 mg.lit-1 and no salinity stress. Under stress conditions of 12 dS.m-1 , the amount of humic acid 200 mg.lit-1 and folic acid 400 mg.lit-1 improved germination to 75.55%. Maximum length and weight index of seedling straw was related to non-use of organic acids and lack of salt stress with a mean of 58.63 and the application of humic acid at 200 mg.lit-1 and folic acid at concentration of 400 mg.lit-1 in 12 ds.m-1 stress with an average of 0.68. Application of organic acids improved seed germination characteristics and growth indices of coneflower plant in salt stress conditions.

In order to evaluate the different methods of tomato seed preparation, an experiment was conducted in a completely randomized design with four replications in Laboratory of Seed Science and Technology of Mohaghegh Ardabili University, Ardabil, Iran. Factors included: washing with tap water, fermentation (temperatures: 25, 30, 35 and 40˚C; times: 24, 36, 48 and 60 hour), washing with acid (HCl: 5, 10, 15 and 20 ml.kg-1 fruit; times: 10, 20, 30 and 40 min). To determine the quality of processed seed, the standard seed germination test was implemented. Results showed that seeds processed by fermentation at 25° C for 24 hours had the highest percentage and germination speed, seedling length, dry weight and vigor index. Between different levels of acid washing, 10 ml hydrochloric acid and 20 minutes duration showed higher seed germination and seedling growth indices.

Seed priming is a technique in which seeds are physiologically and biochemically prepared to germinate prior to planting and facing with environmental conditions. In this way, two separate experiments were carried out to evaluate the effect of priming of clary sage seeds with plant growth promoting bacteria and plant growth regulators as a completely randomized design with three replications in the Horticultural Sciences Laboratory at Islamic Azad University, Miyaneh Branch, Miyaneh, Iran in 2015. Biopriming treatments including 15 types of PGPRs belonged to Herbaspirillum, Azotobacter-12, Azospirillum, Flavobacterium and Pseudomonas genera and hormonal priming including gibberellic acid and kintin at concentrations of 50 and 100 ppm along with hydroperiming and control (no priming) tratments. Twenty five primed seeds were placed in each petri dishes containing filter paper and seed germination numbers were recorded every other day. Results showed that biopriming affected on all traits exept mean germination time (MGT) and coefficient of velocity of germination (CVG). Biopriming with Azotobacter-12 reduced germination percentage (GP), germination speed (GS) and mean daily germination (MDG) and only increased daily germination speed (DGS). In hormonal priming, all germination indices were affected by treatments and application of growth regulators reduced CVG and increased MGT. Also, kinetin at 100 ppm concentration reduced GP, GS and MDG and only increased DGS.

Drought stress and seed pre-treatment has a major influence on germination characteristics of plants. In order to investigate the effects of pre-treatment of seed on germination and growth characteristics of wheat seedling (Triticum aestivum L.; cv. Alvand) under drought stress, an experiment was conducted based on completely randomized design with three replications in Research Laboratory of University of Maragheh, Iran in 2015. Treatments included two levels of drought stress induced by polyethylene glycol (0 and -12 bar, PEG-6000) and two levels of pre-treatment of seed (control or non-priming and hydro-priming). The results showed that the effect of hydro-priming treatment was significant on seedling length, seedling dry weight, mean germination time and seed vigor index of wheat (p < 0.05). The highest and the lowest values of the traits, except for the mean germination time, were obtained in hydro-priming and control (non-priming) treatments, respectively. The effect of drought stress on all studied traits was significant. Increase of drought stress significantly decreased the measured characteristics. So that, seedling length, seedling dry weight, allometry index, germination percentage and seed vigor index of wheat in -12 bar water potentials decreased to 38.3, 45.1, 54.1, 2.0 and 39.5 percent, respectively. But, increased mean germination time by 47.9 percent. In general, hydropriming improved germination and growth characteristics of wheat seedling under drought stress conditions and increased the resistance of wheat to drought stress in germination phase.

In order to study the effect of priming on germination and seedling growth of sesame under salinity stress, a factorial experiment was conducted in a completely randomized design in Seed Technology Laboratory of Shahed University in 2016. Factors included priming in three levels (GA3 250 ppm, GA3 500 ppm and potassium nitrate 0.4%) and five levels of salinity (0, 3, 6, 9 and 12 dS/m) in three replicates. Measurement traits included percentage and germination rate, mean germination time, root and shoot length, seedling fresh and dry weight and relative water content. The results showed that priming treatments, salinity stress and their interaction effect on the studied traits had a significant effect. The results of mean interactions showed that the highest percentage and rate of germination were observed in 500 ppm gibberellic acid pretreatment with no salt stress. Salinity stress reduced seed germination traits, growth parameters and relative water content of sesame seed. Application of gibberellic acid and potassium nitrate pre-treatments improved germination and seedling growth of sesame seeds exposure to salinity stress.