Effect of seed priming with different concentrations of potassium nitrate on the pattern of seed imbibition and germination of rice(Oryza sativa L.)

Low germination and vigor of rice seed associated with dry-seed broadcasting are common problems encountered by rice growers.The objectives of this study were to evaluate the role of potassium nitrate（KNO3）on the pattern of seed imbibition and to determine the effect of seed priming with KNO3 on the germination percentage,speed and uniformity of germination in rice seed.Experiment 1 compared the patterns of seed imbibition of six concentrations of KNO3（0,0.25,0.50,1.00,1.50,and 2.00%）in two rice cultivars-KDML105 and RD15.The results showed that soaking rice seed in KNO3 at higher concentrations could delay the imbibition time.The higher concentrations of KNO3 delayed the imbibition time of rice seed and took a longer time to reach the end of phases 1 and 2 compared to the lower concentrations.The patterns of seed imbibition using distilled water of both rice cultivars（KDML105 and RD15）were quite similar,but with different concentrations of KNO3,the imbibition time taken to reach the end of phases 1 and 2 was slightly postponed in KDML105 suggesting that different rice cultivars may need different imbibition times for soaking seed in the priming process.Experiment 2 evaluated the effects of seed priming with 1.0 and 2.0%KNO3 at different imbibition times.It was found that priming with 1.0%KNO3 showed better seed germination than priming with 2.0%KNO3 and seed priming with 1.0%KNO3 at the imbibition time of early phase 2（or 28 h for KDML105）improved seed germination and increased both the speed and uniformity of seed germination.The results of this study show promise for the use of priming with 1.0%KNO3 soaked until early phase 2 of seed imbibition for improving the seed germination and vigor of rice in dry seed broadcasting.

Ethanol production and mitochondrial-related gene expression of maize(Zea mays) seed during storage

Mitochondrial degradation plays a vital role in seed deterioration.Novel markers were investigated based on a new method for quantifying maize seed deterioration during 12 months’storage under ambient(lab bench,~27℃ and 50-80%relative humidity(RH))or controlled((15±1)℃ and(50±5)%RH in bags with low oxygen permeability)conditions involving two techniques:1)fast ethanol assay and 2)quantitative RT-PCR(qPCR)with four mitochondrial-related genes in maize seed:alcohol dehydrogenase(ADH1),alternative oxidase(AOX1),cytochrome c oxidase(COXc),and ATPase.Ethanol production during imbibition and the expression of genes using the new method were compared to the results of two conventional methods:a germination test and an accelerated ageing test.The results showed that germination following ambient seed storage reduced significantly compared to the controlled conditions,especially at 9 months of storage.Ethanol production of maize seed measured by fast ethanol assay increased during storage.After 6 months,the mean(n=4)ethanol production from seed under ambient conditions was 400μg L^-1 which was higher than under the controlled conditions(240μg L^-1).Stored mRNA level of COXc and ATPase significantly decreased over time in ambient storage but were quite stable under the controlled conditions.Maize seed was also treated for artificial ageing at 42℃ in 100%RH for 12,24,and 48 h.At 24 h after treatment(HAT),maize seed produced significantly more headspace ethanol than at 12 HAT and more than the control(non-treated seed).The transcription level of ADH1 and ethanol production increased.The transcription level of COXc was directly related to the severity of the ageing treatment.In conclusion,a combination of fast ethanol assay and qPCR enhanced understanding of maize seed deterioration and provided new possibilities for the evaluation of seed storability based on transcriptional levels.

The Seed Water Sorption Isotherm and Antioxidant-Defensive Mechanisms of <i>Hordeum vulgare</i>L. Primed Seeds

The key successful for seed priming technique was the management of seed imbibition process. This study was aimed to indicate the seed moisture sorption characteristics of Hordeum vulgare L. cv. Samerng 2 in relation to the seed priming technique and its effect on the seed qualities. The experiment was designed by Completely Randomized Design (CRD) with four replications. Seed hydro-priming technique was done under 25 degree Celsius, and 40% - 60% RH. Barley seed moisture content was determined every hour after imbibition for 24 hours. Then, primed barley seed qualities were evaluated at 6, 8, 10, 12, 14, and 16 hours of hydrotime. The results revealed that barley seeds were imbibed rapidly from 10.55% to 37.69% seed moisture content during 0 - 9 hours of imbibition. The constantly seed moisture content was continued until 17 hours of imbibition. Radicle was protruded with 42.74% seed moisture content. Seed moisture sorption characteristic equation was Y = 0.0055x3- 0.267x2 + 4.5931x + 13.348. Coefficient of determination (R2) was 0.916. Primed seed germination was not affected by hydrotime. Primed seeds were improved in speed of germination and seedling growth rate. The best primed barley seed vigorous was noted at 14 - 16 hours of hydrotime. In addition, catalase activity (CAT) and superoxide dismutase activity (SOD) were not significantly different for non-primed and 14 - 16 hours primed seeds. However, lipoxygenase activity (LOX) was increased and malondialdehyde (MDA) content was decreased for 14 - 16 hours primed seeds. Subsequently, 14 - 16 hours primed barley seeds can maintain high seed germination and vigor for 8 - 12 months under 5 degree Celsius. Thus, it could be concluded that hydro-priming for 14 - 16 hours enhances barley seed quality by reducing germination time, induced defenses mechanism, and could be stored for 8 - 12 months.