Study on Characters of Hard Seeds of Amphicarpaea edgeworthii Benth. (Leguminosae) and Methods for Breaking Dormancy

[Objective] This study aimed to understand the characters of hard seeds of Amphicarpaea edgeworthii Benth. （Leguminosae） and explore the methods for break- ing dormancy. [Method] For both aerial and subterranean seeds of A. edgeworthii, the morphological characteristics were observed and the appropriate temperature for germination was explored. For aerial seeds of A. edgeworthii, the characters of hard seeds were studied, and concentrated sulfuric acid treatment, hot water soak treat- ment and mechanical damage treatment were compared to explore the methods for breaking seed dormancy. [Result] The aerial seeds were oblate and averaged 3.38 mm in length, 3.02 mm in width, 1.88 mm in thickness, 15.32 g in thousand grain weight, with a hard seed rate after of up to 98% natural maturation. The subter- ranean seeds were approximately oblate with a maximum diameter of 15 mm and a hundred grain weight of （50.08-58.26 g）; among all the treatments for breaking hardseededness, cutting seed coat treatment and concentrated sulfuric acid treatment for 20 minutes were the most effective methods, whereas hot water soak treatment was the least effective method; constant temperature between 20 and 30 ℃ was optimum for the germination of aerial seeds, and alternative temperature of 30/20 ℃ was most appropriate for the germination of subterranean seeds. [Conclusion] Cutting seed coat treatment and concentrated sulfuric acid treatment for 20 minutes were the most effective methods to break the hardseededness of A. edgeworthii.

Breaking seed dormancy in Cupressus atlantica Gaussen,an endemicand threatened coniferous tree in Morocco

Cupressus atlantica Gaussen （Cupressaceae） is an endemic and endangered coniferous tree geographically restricted to the N＇Fis valley in South-Western Morocco. Like many forest species, C. atlantica exhibits dormancy which delays and reduces germination. To improve seed germination, different pre-treatments were conducted on C. atlantica seeds after storage for different periods （one, two and five years） including： scarification with sandy paper; soaking seeds in hot distilled water at 60℃ and 80℃ for 15 min and soaking seeds for 48 h in a gibberellic acid （GA3） at 1,000 and 2,000 mg·L-1. Results showed that scarification with sandy paper increased the germination rate of Atlas cypress by up to 67%, indicating that the species possess essentially an exogenous dormancy （physical dormancy） due to the hard seed coat （hardseededness）. Exogenous application of gibberellic acid （GA3） at 1,000 mg.L-1 was also effective in breaking seed dormancy and germination induction. These two treatments induced faster speed germination expressed by low number of days to first germination （8-10 days） and low values of mean germination times （MGT）. However, germination rate, under any treatment, is greatly dependent on the year of seed collection. Seeds collected in year 2004 gave the highest value, suggesting that even after five years of storage, the germination capacity of C. atlantica seeds could remain high. This observation is very interesting in the ex-situ conservation of such endemic and endangered species where the production of seeds is irregular over the years.

Effects of different treatments on seed germination and breaking seed dormancy of Prosopis koelziana and Prosopis Juliflora

For improving seed germination of Prosopis koelziana and Prosopis juliflora, different treatments of seeds were conducted, including scarification with sulfuric acid 98% for 10 and 15 min, sandy paper, hot water for 5 and 10 min, potasium nitrate 0.1%, gibberellic acid at 250 mg·L^-1 and 500 mg·L^-1 and combinational treatment of scarification with gibberellic acid of 250 mg·L^-1 and 500 mg·L^-1. The results show that scarifications with sandy paper and sulfuric acids 98% were the most effective treatments on breaking seed dormancy and seed germination induction. Scarification with sulfuric acid 98% for 15 min was the best treatment. According to the positive effect of scarification and lack of reaction of seeds against KNO3 and gibberellic acid, the kind of seed dormancy was determined as exogenous.

Study on Dormancy Mechanism and Dormancy-breaking Method of Velvetleaf(Abutilon theophrasti)Seeds

[Objectives]This study was conducted to explore how can we better break the dormancy of velvetleaf seeds and the best method to promote seed germination.[Methods]With the seeds of velvetleaf(Abutilon theophrasti)as experimental materials,the dormancy of velvetleaf seeds was revealed through seed vigor determination,water absorption rate determination and germination tests,and the seeds of velvetleaf were treated by physical and chemical methods to explore the best method for breaking dormancy of velvetleaf seeds.[Results]Poor water permeability of seed coat and endogenous inhibitory substances present in the seeds were the main reasons leading to the dormancy of velvetleaf seeds.The shell-breaking treatment,98%concentrated sulfuric acid treatment and 40%NaOH strong alkali treatment all could break the dormancy obstacle of velvetleaf seed coat.Compositing the above measures with 200 mg/ml gibberellin solution could further improve the germination ability of seeds.Among them,compositing the mechanical shell-breaking treatment with gibberellin had the best effect,followed by the composite of 10 and 15 min of 98%concentrated sulfuric acid treatment with gibberellin.[Conclusions]This study lays a foundation for the utilization and development and the comprehensive prevention and control research of velvetleaf seeds.

Gibberellin A_(3) Treatment Breaks Hypocotyl Dormancy of Paeonia anomala subsp.veitchii Seeds

We studied the roles of different concentrations of gibberellin A_(3)(GA_(3))in breaking hypocotyl dormancy of Paeonia anomala subsp.veitchii,aiming to provide a theoretical basis for the efficient elimination of seed dormancy.The seeds of P.anomala subsp.veitchii were treated with different concentrations of GA_(3)(0,100,200,300,and 400 mg/L)under dark conditions at 16℃,and then the rooting indicators including rooting rate,rooting vigor,rooting index and mold rot rate were determined.The treatment with 400 mg/L GA_(3) for 4 h showed the best performance in breaking the hypocotyl dormancy.Specifically,the treatment shortened the rooting time to 12 d,increased the rooting rate,rooting vigor,and rooting index to 84.00%±5.29%,80.67%±5.03%,and 2.25±0.16 respectively,and decreased the mold rot rate to 0.67%±1.16%.To sum up,there were germination inhibitors in the seeds of P.anomala subsp.veitchii,while the addition of exogenous hormone GA_(3) can release the inhibitory effect on the hypocotyl,which indicated that GA_(3) can promote the breaking of hypocotyl dormancy.

The MKK3–MPK7 cascade phosphorylates ERF4 and promotes its rapid degradation to release seed dormancy in Arabidopsis

Seeds establish dormancy to delay germination until the arrival of a favorable growing season.In this study,we identify a fate switch comprised of the MKK3–MPK7 kinase cascade and the ethylene response factor ERF4 that is responsible for the seed state transition from dormancy to germination.We show that dormancy-breaking factors activate the MKK3–MPK7 module,which affects the expression of some a-EXPANSIN(EXPA)genes to control seed dormancy.Furthermore,we identify a direct downstream substrate of this module,ERF4,which suppresses the expression of these EXPAs by directly binding to the GCC boxes in their exon regions.The activated MKK3–MPK7 module phosphorylates ERF4,leading to its rapid degradation and thereby releasing its inhibitory effect on the expression of these EXPAs.Collectively,our work identifies a signaling chain consisting of protein phosphorylation,degradation,and gene transcription,by which the germination promoters within the embryo sense and are activated by germination signals from ambient conditions.