نشریه پژوهش های بذر ایران
پیاپی 2 (پاییز و زمستان 1393)

The effect of seed rate of alfalfa (Medicago sativa L.) and efficiency of plant growth promoting bacteria (PGPR) that facilitates phosphorus uptake with different doses of phosphate fertilizer were evaluated on seed quality. For this purpose، the germination and seed vigor tests before and after accelerated aging were performed in a split split plot experiment based on randomized complete block design with three replications in 2010 in the field of education and research in the College of Agriculture and Natural Resources، Tehran University، Karaj. Phosphorus factor at 4 levels (0، 30، 60 and 90 kg Phosphorus. ha-1) in main plots، PGPR (Pseudomonas) in three levels (no bacteria، bacterial strains، No. 9 and bacterial strains No. 41) in sub plots and rate of seed factors on three levels (2، 6، and 10 kg of seed per hectare) were the sub-subplots. The results showed the highest rate of germination and seed vigor obtained by use of 6 kg seeds per hectare، PGPR No. 41 strains with 30 kg Phosphorus per hectare and after accelerated aging. The highest rate of germination and seed vigor at 10 kg of seed per hectare were found for PGPR No. 41 strains، with 60 kg Phosphorus ha-1 treatments. After accelerated aging practices to achieve maximum germination index and vigor، seed rates and phosphorus requirement were more than standard conditions. Based on obtained results for the storage conditions، bacterial strains No. 41 had better effect on increasing seed vigor than bacterial strains No. 9. To produce alfalfa seed with high vigor and obtain better results، use of optimum seed rates and phosphorus (6 and 30 kg. ha-1، respectively) along with PGPR (strain No. 41) could be considered in crop plants.

Seed priming is one of the most important techniques used to improve seed germination under biotic and abiotic stresses. For this purpose, germination and seedling growth characteristics of primed seeds of Tall wheat grass (Agropyron elongatum (Host.) P. Beauv) were evaluated under drought and low temperature condition. A factorial experiment was conducted on the basis of randomized completely block design with three factors with four replications. The experimental factors were priming with two levels including urea primed (using urea -4 bar at 10 °C for 36 h) and non-primed seeds; germination temperatures, including 3, 6, 9, 12, 15, 20 and 25 °C; and osmotic potential including zero (distilled water), -3, -6, -9, and -12 bars (applied by polyethylene glycol 6000). Increasing trend have been observed for all germination indices, except mean germination time, with increasing temperature from 3 to 25 °C and seeds revealed the greatest sensitivity to temperatures below 9 °C. However, this trend was reversed with increasing drought stress, the seeds sensitivity to drought stress started from the potential of -6 bar and reached to maximum in -12 bar. However, primed seeds compared to non-primed seeds have demonstrated better germination under both drought and low temperature stresses. The results of this study showed that the highest seedling vigor index and germination rates achieved in the temperature range of 20-25 °C and water potential of zero to -3 bar.

Osmotic stress is the most important of the abiotic stresses that leads to limitation of growth and yield in rapeseed. This study was conducted to examine the effect of cycocel seed priming on osmotic stress tolerance in germination and early growth stages of rapeseed, as a factorial experiment based on completely randomized design at Agriculture College of Shiraz University in 2012. The treatments included seed priming in three cycocel concentrations: 0 (without priming as control), 2.5 and 3.5 g L-1 and osmotic stress in five levels: 0 (as control), -0.3, -0.6, -0.9 and -1.2 MPa using polyethylene glycol. The results showed that osmotic stress was significantly reduced germination percentage (15.1%), germination rate (15.3%), radicle length (29.5%), plumule length (31.6%), radicle fresh weight (22.4%), plumule fresh weight (37.6%) and vigor index (39.9%). Furthermore, osmotic stress leads to increase radicle to plumule fresh weight and radicle to plumule length ratio as 6.8 and 24.3 percent, respectively. Seed priming with cycocel reduced the adverse effects of osmotic stress on measured parameters. Although, there was no positive effect on germination percentage and rate under osmotic and non osmotic conditions for cycocel in both concentrations but cycocel at 3.5 g L-1 appeared to have a greater positive effect than 2.5 g L-1. Considering positive impact of cycocel seed priming on the reduction adverse effects of osmotic stress; further research on cycocel seed priming and osmotic stress tolerance is recommended under field conditions.

In order to evaluate the electrical conductivity and seedling growth characteristics of red bean seed grown under drought stress and foliar application of zinc and manganese, a split factorial experiment was conducted in a Randomized Complete Block Design in field and also laboratory experiment at Shahrekord University in 2011. Factors inclouded three levels of drought stress (irrigation after 50, 70 and 90 mm evaporation from class A pan) as the main plot and three levels of zinc foliar application (with water, 100 and 200 grams per hectare zinc), and three levels of manganese foliar application (with water, 150 and 300 grams per hectare manganese) in a factorial combination as sub plot. The results showed that severe drought stress led to decrease of electrical conductivity while the seedling and root length of red bean seed were increased. In the measured characteristics, Mn foliar application had significant effect on electrical conductivity and root dry weight. In different Mn foliar application treatments, the lowest electrical conductivity was related to control while the maximum seedling dry weight was observed at 150 g Mn foliar application per hectare. Zn foliar application had significant effect on all the traits measured during this experiment. Based on means comparison, the highest seedling dry weight, shoot, seedling and root length as well as the lowest electrical conductivity was belong to the 100 g Zn foliar application per hectare. The highest root dry weight was obtained for 200 g Zn per hectare which no significant difference was observed with 100 g Zn per hectare. According to the results of this experiment, mild stress and foliar application of zinc and manganese led to increase the quality of the produced seeds. In total, foliar application of zinc and manganese (at the amount of 100 and 300 g ha-1 respectively) with mild stress (irrigation after 70 mm evaporation from class A pan) are recommended for production of seeds with high vigor under this region conditions.

Trittipyrum is an important annual grass plant for forage production in arid and semiarid regions. The effects of drought stress on Trittipyrum lines were evaluated in the field experiment in a randomized complete block design with factorial experiment involving three replications in 2012. Treatments were water stress (field capacity (FC), 75% of FC, 50% of FC and 25% of FC throughout the experimental period and 13 primary Trittipyrum lines ((St/b)(Cr/b)F4, (Ma/b)(Cr/b)F4, (Ma/b)(Cr/b)F3, (Ka/b)(Cr/b)F2, (Ka/b)(Cr/b)F3, (Ka/b)(Cr/b)F5, (Ka/b)(Cr/b)F6, La(4b,4d)/b, St/b, Cr/b, La/b, Ka/b, Az/b). The results showed that drought stress had significant effects on seedling traits. Drought stress significantly decreased shoot length, root length, shoot dry weight, root dry weight, seedling dry weight, seedling length vigor index and seedling weight vigor index. The results of mean comparison revealed that (az/b)(cr/b)F5 and Kz/b lines were the most sensitive and the most tolerant lines to drought stress in early vigor stage, respectively. Although the response of Trittipyrum lines were different to drought stress, but the result indicated that Trittipyrum lines are sensitive to drought at emergence stage.

In addition to common vegetative multiplication, potato crop can be reproduced by true potato seed (TPS). Only the limited number of pests and diseases, which are the most important causes of decrease in potato production, can be transmitted by true potato seed. Hence, to evaluate the potential of true potato seed in comparison to potato seed tuber and mini tuber, an experiment was conducted in Marvdasht at Fars Province during summer of 2012. Treatments were arranged in a split plot experiment using a randomized complete blocks design with three replications. The main factor consisted of three planting date including 10 July, 20 July, 30 July and sub-factor was allocated to different multiplication methods in 7 levels composed of 3 seed tuber cultivar (Agria, Marfona, Santé), 3 mini tuber varieties, the same as seed tuber varieties, and BSS296 hybrid of true potato seed. The results showed that the effect of main factor (planting date) on yield of tuber, weight of marketable tuber, number of marketable tuber, and biomass was significant. The interaction effect between main and sub-factors on all characteristics were significant except for yield of tuber, number of marketable tuber and dry matter traits. The highest yield of plant was achieved in Santé seed tuber (36.5 t/ha) in the first planting date (10 July) and the lowest one was observed in Marfona mini tuber (19.07 t/ha). The maximum biomass was measured in the first planting date of TPS (338.1 g/plant). The marketable tubers yield in second planting date of TPS was in lower level than Marfona seed tuber; however, it was placed at the same statistical level with other seed tubers but it was better than all mini tubers. The results of this study suggested that TPS was better than mini tubers in mostly measured characteristics, but TPS in comparison to different seed tubers at three mentioned planting date indicated variable situations.

In order to investigate the effect of priming techniques on germination parameters of ajowan (Carum copticum L.) seed, an experiment was conducted in completely randomized design with four replications. The experiment treatments included a control (no priming), three hydropriming levels with distilled water (24, 36, and 48 h), three osmopriming levels with PEG (solutions with osmotic potential of -4, -8 and -12 bar), three hormone priming levels with GA3 (50, 100 and 150 ppm), three halopriming levels with KNO3 solution (2, 3, and 4%) and three zinc sulfate levels (0.1, 0.2 and 0.3 %). The results showed that priming treatments had a significant effect on all traits. The rate and percentage of germination were declined in some priming treatments compared to control. Radicle length and root dry weight were decreased in polyethylene glycol -8 bar. Polyethylene glycol -4 bar and 24h hydropriming treatments significantly decreased shoot length and allometry coefficient. However, the treatment of 100 ppm hormone priming significantly increased these traits. Hydropriming 24 h treatment significantly increased germination rate, percentage and seed vigor, but hydropriming 48 h significantly increased radicle and shoot length in compared to control. In conclusion, according to priority of germination or radicle, shoot growth and seed priming cost as well, the hydropriming 24 or 48 h can be recommended as most appropriate priming type for ajowan seeds.

Application of zinc can improve the tolerance and resistance of plants especially sunflower to environmental stresses and be effective on kernel set and yield. To investigate the effects of zinc oxide nano particles on the length, effective period, rate of kernel filling and kernel weight in sunflower cultivars, a factorial experiment based on randomized complete block design with three replications was conducted at the University of Mohaghegh Ardabili, Ardabil, Iran. Treatments were three sunflower cultivars as Aline 191, Aline 122 and Farrokh and three concentrations of nano zinc oxide including 0, 0.5 and 1 g lit-1 which sprayed at three stages. Results showed that interaction of cultivar and nano zinc oxide was significant on kernel filling rate, effective period of kernel filling, maximum kernel weight and duration of kernel filling. Rate of filling and maximum kernel weight increased with 0.5 g lit-1 spraying of Nano zinc oxide in Aline 191 and 122, but in Farrokh cultivar was significantly reduced in comparison to the control. Also, no significant difference was found between 0, 0.5 and 1 g lit-1 of nano zinc oxide on kernel filling rate, effective kernel filling period and duration in Farrokh cultivar. In conclusion, foliar application of zinc oxide nano particles led to improvement of kernel weight and their filling parameters and more appropriate response was observed in foreign cultivars for this treatment, while final kernel weight decreased in Farrokh cultivar. Therefore, it can be used 0.5 g lit-1 of nano zinc oxide for increasing grain yield in foreign cultivars of Aline.

Seed quality is one of the most important factors affecting seed germination and seedling growth. In order to investigate the effects of seed aging on germination and seedling growth of sunflower cultivars, a factorial experiment was conducted based on completely randomized design with three replications in seed research laboratory of Shirvan Higher Education Complex. To create 7 different treatments of seed aging, seeds of three cultivars Ghasem, Farrokh and Barzgar (as the first factor) were kept at a high temperature (43◦ C) and high relative humidity (100%) for 0 (control), 24, 48, 72, 96, 120 and 144 hours (as a second factor). The results of mean comparison showed that germination percentage, rate and seedling growth of Farrokh cultivar was more than other cultivars in each aging level. Germination percentage, rate and uniformity, seedling dry weight, radicle and stem length reduced linearly with increase in the duration aging in the all cultivars. Under the aging conditions the time to beginning and ending of germination was significantly increased. Overall, it was concluded that seed quality of sunflower cultivars was seriously decreased under the aging conditions.

To evaluate the effect of priming on seed germination of Cucurbita pepo in drought stress conditions, a factorial experiment was conducted as completely randomized design with three replications. Treatments included drought stress at five levels of osmotic potential (zero, 0.3, 0.6, 0.9 and 1.2 MP), priming at levels of GA3 (250 ppm to 24 hours), KNO3 (0.2% for 24 hours) Hydro prime (H2O) (to 24 hours) and control. The results showed that priming effect was significant on germination percentage, germination rate, mean daily germination, average time required for germination and germination rate index. Significant difference was found between drought stress on seed germination rate. In addition, the interaction of seed priming and drought stress was significant on all traits (germination percentage, germination rate, average daily germination, average time required for germination, germination rate daily, coefficient of germination rate and the seed vigor). Seed priming, particularly in severe drought stress levels, led to increase significantly in mean germination percentage, germination rate and seed vigor. Furthermore, the results of our study indicated that Cucurbita pepo seed priming had partial resistance against drought. Gibberellin acid in the first grade and the hydro priming in second grade can improve the germination and growth of the seedlings under drought stress.