Iranian Journal of Seed Research

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 nanoparticles on the length, effective period, the 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, the effective period of kernel filling, maximum kernel weight and duration of kernel filling. The 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 nanoparticles led to the improvement of kernel weight and their filling parameters and the 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.

Extended abstract
Introduction: Stevia (Stevia rebaudiana Bert.) is a herbaceous perennial plant that belongs to the family of Asteraceae. Stevia is a self-incompatible herb and the seeds resulting from this plant have low germination ability. Steviol glycosides found in this plant are 250-300 times sweeter than sucrose and despite their sweet flavor; they are not absorbed by the body. In general, the poor germination capacity of Stevia seeds is a major impediment for its large-scale cultivation. Priming is one of the seed enhancement techniques that could lead to an increase of germination percentage and germination rate under stress conditions. Therefore, the present study was conducted to evaluate the impact of priming with salicylic acid (SA), iron (Fe) and zinc (Zn) on some germination indices, seedling growth as well as the content of photosynthetic pigments in Stevia under normal and drought stress conditions.
Materials and methods: A factorial experiment using a completely randomized design was carried out in the Seed Science and Technology Laboratory of Agricultural College, Shahed University, in 2017. The factors studied comprised four levels of drought stress (0, –0.3, –0.6 and –0.9 MPa) and seven priming combinations with SA, Fe and Zn. Non-primed seeds (dry seeds) were also considered as control. In this experiment, Fe and Zn were supplied by sources of iron (II) sulfate heptahydrate (FeSO₄.7H₂O, 0.5%) and Zinc sulfate heptahydrate (ZnSO₄.7H₂O, 0.5%), respectively. The traits examined in this study included germination percentage, radicle length, plumule length, seedling weight vigor index and the content of photosynthetic pigments and carotenoid.
Results: The results of this experiment indicated that the plumule length was more sensitive to drought stress, as compared with the root length. With increased intensity of drought stress from 0 to – 0.9 MPa, the content of photosynthetic pigments in Stevia significantly decreased in all the priming treatments, so that the lowest amounts of chlorophyll a, b and carotenoid were observed at the potential of – 0.9 MPa. Priming with SA + Fe + Zn was found to be more effective than other treatments in improving the germination characteristics and the chlorophyll content of Stevia under normal and drought stress conditions. At the highest level of drought stress, germination percentage, radicle length, plumule length, seedling vigor index and total chlorophyll content increased by 55.7, 50.5, 74.3, 90.3 and 85.5%, compared with the control in the concurrent application of Fe, Zn, and SA.
Conclusion: In general, seed priming by micronutrient elements (Fe and Zn) and salicylic acid, and particularly their integrated application, could be recommended to increase the resistance of Stevia to drought stress in the germination phase.
 
 
Highlights:

1. Drought stress at the germination stage has a significant effect on the seedling growth and the content of photosynthetic pigments in Stevia.
2. Seed priming increases drought tolerance of Stevia at the germination stage.
3. The integrated application of SA, Fe, and Zn is more effective than their separate application to alleviate the drought-induced damaging effects.

Extended abstract
Introduction: Seed deterioration is a physiological phenomenon that affects all germination, biochemical, cytological, and growth characteristics of plants. So it is necessary to use seed vigor enhancement methods to resolve these problems. One of these methods is the application of seed priming techniques to reduce deterioration effects. Therefore, the present study aimed to investigate the effect of different pre-treatments by using Nano-zinc, ascorbic acid, humic acid, gibberellin and KNO₃ on germination indices and chromosomal aberration of aged onion seeds.
Material and Methods: This experiment was performed as factorial based on a completely randomized design with 3 replications (100 seeds per replicate) in the faculty of agriculture at Urmia University. The first factor was the level of aging at 4 levels (control, 12h, 24h, and 48h) and the second factor was seed pre-treatments at 6 levels (control, Nano-zinc (30 mg), ascorbic acid (100 mg), humic acid (150 mg), gibberellin (200 mg/l) and KNO₃ (0.1%). Given that the germination was not similar at different levels of aging, the seeds were germinated at control and 12h of aging after 6 days, at 24 and 48h of aging after 8 and 9 days, respectively. Hence, germination percentage, germination rate, normal seedling, mean germination time, and seed vigor were evaluated after the mentioned times. Chromosomal aberrations were also examined.
Results and Discussion: The results showed that the interaction effect of aging and seed pre-treatments on germination indices were significant at %1 probability level. By increasing the period of aging, all germination characters decreased significantly. The highest germination percentage (80%, 70%, 50%) and germination rate (5.350, 3. 316, 1.525 seed/day) were obtained by using Nano-zinc At 12h, 24h and 48h ageing levels. Nano-zinc and gibberellin had the highest effect on seedling vigor and normal seedlings. Seedling vigor increased significantly by using Nano-zinc and gibberellin at 12h (1133, 933.9), 24h (742.9, 692), and 48h (369.9, 323.3). The chromosomal aberration was reduced by using pre-treatment.
Conclusion: In this study, the most effective pre-treatments to improve germination characteristics and reduce chromosomal aberrations were gibberellin (200 mg/l) and Nano-zinc (30 mg). Therefore, it can be stated that the use of Nano-zinc and gibberellin as seed pre-treatments can significantly reduce the effects of deterioration on onion seeds.

Highlights:
1- Nano-Zinc and gibberellin were the most effective priming treatments on seed germination and growth characteristics of the aged onion seeds.
2- Priming treatment reduced the percentage of chromosomal aberration in the onion and the highest effect was obtained using Nano-zinc and gibberellin.

Highlights:

1. Goharan barley cultivar responds more positively to foliar application under late season drought stress conditions.
2. Foliar application of potassium sulfate, zinc sulfate and super oxidase superoxide on Goharan cultivar maternal plant under late season drought stress condition led to the highest seedling root length, root dry weight and shoot dry weight.