Non-primed Control Research Articles

Chemical Priming with Salt and Urea Improves Germination and Seedling Growth of Black Cumin (Nigella sativa L.) under Osmotic Stress

A common problem with vegetable production in saline areas is poor crop stand, but for black cumin (Nigella sativa L.) germination data are limited and inconsistent. The effects of chemical priming with Urmia lake salt and urea solutions for 16 h at 30 °C on seed germination and seedling growth of black cumin (Nigella sativa L.) were studied under various osmotic stress levels. For a more detailed assessment of chemical priming, the effects of hydropriming for 16 h at 30 °C were also studied. A seed lot that was not exposed to any treatment, except disinfection, was used as control. Osmotic stress levels were − 2, − 4, − 6, and − 8 bar, which were achieved with polyethylene glycol 6000 (PEG 6000). Seed germination of black cumin was reduced by 16.2%, 33.8%, 50.9%, and 74.9% under osmotic potential − 2, − 4, − 6, and − 8 bar, respectively, compared with non-stressed control. Improved germination index values, reduced mean germination time, and increased coefficients of velocity of germination were observed under osmotic stress in primed seeds compared with non-primed control. Averaged over priming treatments, priming improved the final germination percentage by 10.5%, 24.3%, 45.5%, and 74.6% under osmotic potential − 2, − 4, − 6, and − 8 bar, respectively. Post-germination growth was also inhibited under low osmotic potential compared with the non-stressed control. Nevertheless, priming improved length and weight of black cumin seedlings and enhanced peroxidase and catalase activity at all osmotic potential levels compared with non-primed seeds. Higher seedling vigor indices were recorded in seedlings from primed seeds with decreasing osmotic potential levels than non-primed seeds. Urmia lake salt priming had the greatest impact on improving seed germination and vigor indices, especially under osmotic stress conditions. Although seed priming did not completely eliminate the symptoms of osmotic stress in black cumin germination, it is an efficient method to mitigate the impact of osmotic stress on germination of this species.

Effects of seed priming with ABA and SA on seed germination and seedling growth of sesame (Sesamum indicum L.) under saline condition

In order to investigate the effect of seed priming with ABA and SA on germination indices of sesame in saline conditions, an experiment with three factors and four replicates arranged in completely randomized design. The first factor was type of growth regulator as ABA and SA, the second factor was concentration of growth regulator including 10, 50 and 500 ppm and the third factor was NaCl salinity (0, 2, 4, 6 and 8 dS/m). Seeds were soaked for 6 hours in distilled water, ABA or SA solutions, after which the solution was eliminated and the seeds were dried, deposited in separate Petri dishes between two filter papers and watered. During a 10-day period, germinated seeds number were counted daily and at the final day, randomly selected seedlings were weighed (fresh and dry) and their plumule and radicle lengths were recorded. The results showed that salinity decreased germination rate (GR) and uniformity (GU), but 10 and 50 ppm ABA or SA supply induced higher GP and GU at 4 dS/m and above, more pronounced at 8 dS/m. SA with 500 ppm concentration; however, impaired seed viability. On the contrary, plumule and radicle lengths of seeds primed by 10 and 50 ppm ABA and SA tended to be lower at 0, 2, 4 and 6 dS/m and higher at 8 dS/m than non-primed control. Almost similar results were obtained for seedling dry mass, although the effects of SA were more drastic. Overall, the results suggest a considerable ameliorative effect of ABA and/or SA seed pretreatment on germinability of sesame seeds under salinity but seedling growth may be retarded which is probably an acclimation and temporary response to salinity stress.

Aspirin priming circumvents the salinity-induced effects on wheat emergence and seedling growth by regulating starch metabolism and antioxidant enzyme activities

Though seed priming has been emerged as an effective and pragmatic approach, efforts are being made to discover and optimize the new priming agents which are cheaper and easily accessible to the farmers. Here, we established two independent experiments, to ascertain the role of aspirin priming in salinity tolerance of wheat. In the first experiment, various concentrations of aspirin (125, 250, 375, and 500 ppm) were examined for emergence and seedling growth of wheat. A non-primed control, hydropriming, and hydrogen peroxide priming treatments were also maintained for comparison. Among the different treatments, seeds primed with 125 and 250 ppm aspirin depicted better emergence, vigorous seedling growth, and higher starch metabolism. Therefore, these treatments were further used in the second experiment under salinity stress (10 dS m−1). Salinity stress caused delayed and erratic emergence hampered the shoot and root growth, chlorophyll contents, and enhanced the lipid peroxidation and phenolics content in wheat seedlings. However, wheat seed priming particularly with aspirin effectively alleviated the negative effects of salinity on most of the observed parameters. Aspirin priming also significantly enhanced the activities of antioxidant enzymes (catalase, peroxidase, and superoxide dismutase), and reduced oxidative stress in wheat seedlings. Vigorous growth and greater salinity tolerance of wheat seedlings derived from aspirin primed seeds were related with better starch metabolism, strong antioxidative defense system, and lower lipid peroxidation.

The Effect of Storage Condition and Duration on the Deterioration of Primed Rice Seeds.

Seed priming is a successful practice to improve crop establishment under adverse environment. However, reduced longevity of primed rice (Oryza sativa L.) seeds during storage limited the adoption of this technique. Present study investigated the effect of temperature, relative air humidity (RH) and oxygen on the longevity of primed rice seeds in a range of 60 days storage. In addition, the biochemical and morphological mechanisms associated with deterioration of primed seeds during storage were explored. Three types of priming treated rice seeds and one non-primed control were stored under (1) low temperature-vacuum (LT-V), (2) room temperature-vacuum (RT-V), (3) room temperature-aerobic-low RH (RT-A-LH) and (4) room temperature-aerobic- high RH (RT-A-HH) for 0, 15, 30, 45, and 60 days. The results showed that storage of seeds under different conditions for 15–60 days did not influence the longevity of non-primed rice seeds. Meanwhile, the viability of primed rice seeds did not reduce when stored under LT-V, RT-V, and RT-A-LH, but was significantly reduced under RT-A-HH. Under vacuum condition, the increases of storage temperature (30°C) did not reduce the longevity of primed seeds. Likewise, the oxygen did not influence the longevity of primed rice seeds stored under low RH. Nevertheless, increase of RH significantly reduced the viability of primed seeds stored for 15–60 days. Reduced starch metabolism, the consumption of starch reserves in rice endosperms, the accumulation of malondialdehyde and the decreases of antioxidant enzyme activities might be associated with the deterioration of primed rice seeds during storage. In conclusion, storage of primed seeds under high RH condition beyond 15 days is deteriorative for germination and growth of rice. The primed rice seeds are recommended to store at vacuum or low RH or low temperature condition to ensure good crop establishment.

Seed priming with sorghum extracts and benzyl aminopurine improves the tolerance against salt stress in wheat (Triticum aestivum L.).

Salt stress impedes the productivity of wheat (Triticum aestivum L.) in many parts of the world. This study evaluated the potential role of benzyl aminopurine (BAP) and sorghum water extract (SWE) in improving the wheat performance under saline conditions. Seeds were primed with BAP (5mgL-1), SWE (5% v/v), BAP+SWE, and distilled water (hydropriming). Soil filled pots maintained at the soil salinity levels of 4 and 10dSm-1 were used for the sowing of primed and non-primed seeds. Salt stress suppressed the wheat growth; seed priming treatments significantly improved the wheat growth under optimal and suboptimal conditions. Total phenolics, total soluble sugars and proteins, α-amylase activity, chlorophyll contents, and tissue potassium ion (K+) contents were increased by seed priming under salt stress; while, tissue sodium ion (Na+) contents were decreased. Seed priming with SWE+BAP was the most effective in this regard. Under salt stress, the tissue Na+ contents were reduced by 5.78, 28.3, 32.2, 36.7% by hydropriming, seed priming with SWE, seed priming with BAP, and seed priming with SWE+BAP, respectively over the non-primed control. Effectiveness of seed priming techniques followed the order SWE+BAP>BAP>SWE>Hydropriming. In conclusion, seed priming with SWE+BAP may be opted to improve the tolerance against salt stress in wheat.

Seed Priming with Salts of Nitrate Enhances Nitrogen use Efficiency in Rice

An experiment was conducted to investigate the absorption and utilization of nitrogen by rice seed treatment with Nitrate salts (halo priming) and distilled water (hydro-priming) in two successive years. Results revealed that seed priming with Mg (NO3)2, KNO3 and Distilled water always perform better than non-primed control sets in enhancing seed germination and nitrate reductase enzyme activity in leaves that promote to nitrogen accumulation in different plant parts. This seed priming technique further enhanced soluble and insoluble nitrogen content in seed, and also the nitrogen gathering capacity in seed and straw (Kg h-1). Seed priming was also found beneficial in encouraging grain yield after applying Kg-1 nitrogen in the soil. This technique proved promising in more nitrogen accumulation and less nitrogen loss. Among seed priming treatment Mg (NO3)2 performed the best in respect to all measured parameters followed by KNO3 and hydro-primed one in comparison to control sets. These results clearly indicated that higher yield in rice can be achieved via improving the nitrogen absorption and utilization by growing crop, raised with seed priming treatment especially using Mg (NO3)2 salts.

Seed priming improves chilling tolerance in chickpea by modulating germination metabolism, trehalose accumulation and carbon assimilation

Chilling stress is one of the major abiotic stresses affecting chickpea productivity worldwide. This study evaluated the potential role of seed priming in improving resistance to chilling stress in chickpea (cv. Punjab, 2008). The priming treatments involved soaking seeds of chickpea cultivar Punjab 2008 in either water for 8 h (on-farm priming), aerated water (hydropriming) for 18 h, or CaCl2 solution (ψs −1.25 MPa; osmopriming) for 18 h. Primed and untreated seeds were grown either at 18/15 °C (control) or 13/10 °C (chilling stress). Chilling stress suppressed the growth of chickpea while seed priming mitigated the adverse effects of chilling stress by improving stand establishment, growth, water relations, photosynthesis, α-amylase activity, sugar metabolism, antioxidant enzyme activity, membrane stability, and leaf accumulation of proline, nitrogen, potassium and soluble phenolics. Seed priming also improved the performance of chickpea under optimal (control) conditions. The overall order of improvement in resistance to chilling by using seed priming was osmopriming > hydropriming > on-farm priming. Osmopriming improved seedling dry weight, specific leaf area, leaf CO2 net assimilation rate, maximal photochemical efficiency of PSII, α-amylase activity, trehalose content and leaf relative water content by 10, 22, 17, 20, 73, 48 and 7%, respectively, relative to the non-primed control under chilling stress. Under optimal temperature conditions, the corresponding values were 30, 32, 16, 10, 83, 75 and 5%, respectively. Sugar metabolism, especially trehalose content, was strongly linked with stand establishment, photosynthesis, antioxidant potential (under chilling stress) and plant biomass. Overall, seed priming improved chickpea performance under both optimal temperature conditions and chilling stress through better germination metabolism and the accumulation of trehalose, which protected from oxidative damage and helped to maintain carbon assimilation and seedling growth.

Adaptation of Reactive Saccades is Influenced by Unconscious Priming of the Attention Focus

ABSTRACTThe authors investigated whether the size of the attention focus can influence saccadic adaptation, and whether this influence changes in older age. Using the scrambled sentence task, young and older participants were either primed for a wide attention focus, or primed of a narrow attention focus, or were not primed for any specific attention focus. Subsequently, all participants underwent a double-step saccadic adaptation paradigm aimed at changing the direction of reflexive saccades. The authors found that compared to the nonprimed control group, priming for a wide attention focus enhanced saccadic adaptation in both age groups by a similar amount; the benefit persisted throughout the adaptation phase, but was absent during the deadaptation phase. In contrast, the authors found no effects of priming with a narrow attention focus on saccadic adaptation. From this the authors conclude that a wide attention focus is beneficial for workaround strategies but not for adaptive recalibration, and that those benefits are similar in young and older persons.

Hydro and halo priming: influenced germination responses in wheat Var-HUW-468 under heavy metal stress

The beneficial effect of seed priming in improving critical growth stages like seed germination and early growth phases has been accepted by Plant Physiologists for many important field crops. In the present investigation, studies were made to see the effect of heavy metal stress imposed during germination using solution of HgCl2 in four different concentrations (0.0, 0.50, 0.75 and 1.00 mM) in Petri dishes on primed and non-primed seeds of wheat. Priming has been done with distilled water (hydro), Mg(NO3)2 and Ca(NO3)2 (halo) salts. Different germination parameters, such as germination percentage, radicle and plumule lengths, seedling emergence, soluble and insoluble sugar contents and activity of α-amylase in endosperm were studied at different study periods. Primed seeds increased all the germination parameters except insoluble sugar content in respect to non-primed control in the absence of HgCl2. However, the use of primed seeds has shown to overcome the inhibitory effects of heavy metal stress imposed in the form of HgCl2 solution during the period of germination. Hence, the work concludes the mitigating effects of priming under heavy metal stress.

Standardization of Azospirillum concentration and duration of biopriming for rice seed vigour improvement

Azospirillum lipoferum is nitrogen fixing biofertilizer which can be used in seed treatment for improving seedling vigour. In order to standardize the optimum concentration of liquid Azospirillum for rice biopriming seed treatment and duration of biopriming, a laboratory experiment was conducted in Department of Seed Science and Technology, Tamil Nadu Agricultural University, Coimbatore in CompletelyRandomizedDesign with four replicates. Rice hybrid CORH 4 and its parental lines COMS 23A and CB 174R seeds were bioprimed separately with 10, 15 and 20 per cent of Azospirillum for 6, 12, 18 and 24h of durations. Unprimed and hydroprimed seeds were used as control. The result revealed that rice seeds bioprimed with 20 per cent Azospirillum for 12 h was found to be the best seed biopriming treatment for both CORH 4 rice hybrid and its parental lines to enhance the germination rate, total germination percentage, seedling growth and vigour. In rice hybrid CORH 4, biopriming with 20 per cent liquid Azospirillum for 12h expressed an increase of 14 per cent of vigour index over the non-primed control seeds.

Physiological and Biochemical Mechanisms of Seed Priming-Induced Chilling Tolerance in Rice Cultivars.

Rice belongs to tropical and subtropical environments and is extremely sensitive to chilling stress particularly during emergence and early stages of seedling development. Seed priming can be a good approach to enhance rice germination and stand establishment under chilling stress. The present study examined the role of different seed priming techniques viz., hydropriming, osmopriming, redox priming, chemical priming, and hormonal priming, in enhancing the chilling tolerance in rice. The most effective reagents and their pre-optimized concentrations based on preliminary experiments were used in this study. Two different rice cultivars were sown under chilling stress (18°C) and normal temperatures (28°C) in separate growth chambers. A non-primed control treatment was also maintained for comparison. Chilling stress caused erratic and delayed germination, poor seedling growth, reduced starch metabolism, and lower respiration rate, while higher lipid peroxidation and hydrogen peroxide accumulation in rice seedlings of both cultivars. Nevertheless, all the seed priming treatments effectively alleviated the negative effects of chilling stress. In addition, seed priming treatments triggered the activities of superoxide dismutase, peroxidase, and catalase, and enhanced the accumulations of glutathione and free proline in rice seedlings, which suggests that these measures help prevent the rice seedlings from chilling induced oxidative stress. Chemical priming with selenium and hormonal priming with salicylic acid remained more effective treatments for both rice cultivars under chilling stress than all other priming treatments. The better performance and greater tolerance of primed rice seedlings was associated with enhanced starch metabolism, high respiration rate, lower lipid peroxidation, and strong antioxidative defense system under chilling stress.

Effect of seed bio-priming on seed quality parameters of lentil under mid Himalayas

To formulate proper seed priming strategy, the response of four lentil varieties to seed bio-priming with Pant Bioagent-3 (Pseudomonas fluorescens + Trichoderma harzianum), Azotobacter sp. and Bavistin, in terms of field performance and seed quality was assessed. Seed bio-priming with Azotobacter formulation and Pant bioagent-3 significantly increased the field emergence (77.66% and 71.66% respectively), seed yield per plot. Germination and viability were improved through seed priming to 80% and 88.66% in DPL-62 with Azotobacter bio-priming. Vigour index improved to 18.8, 17.0 and 14.9 with bio-priming as compared to 10.13 in non-primed control in variety DPL-62. Significant improvement in the seed health was also observed in case of bio-primed seed. Seed discolouration reduced to the level of 12.33%, in Kali Masoor with Pant Bioagent-3 bio-priming, while least seed infection (11.66%) was in fungicide (Bavistin) seed treatment for DPL-62. Seed bio-priming improved seed health, in addition to enhancing the seed quality..

Comparative proteomic analysis of β-aminobutyric acid-mediated alleviation of salt stress in barley

The non-protein amino acid β-aminobutyric acid (BABA) is known to induce plant resistance to a broad spectrum of biotic and abiotic stresses. This is the first study describing the effect of BABA seed priming on physiological and proteomic changes under salt stress conditions in barley (Hordeum vulgare). The aim of our study was to investigate the changes of fresh weight, dry weight and relative water content (RWC) as well as root proteome changes of two barley lines contrasting in salt tolerance (DH14, DH 187) in response to salt stress after seed priming in water or in 800 μM BABA.Seed priming with BABA significantly increased (p ≤ 0.05) RWC in both barley lines, which indicates considerably lower water loss in BABA-primed plants than in the non-primed control plants. Dry and fresh matter increased significantly in line DH 187, whereas no changes were detected in line DH14.BABA-primed plants of both lines showed different proteomic patterns than the non-primed control plants. The root proteins exhibiting significant abundance changes (1.75-fold change, p ≤ 0.05) were separated by two-dimensional polyacrylamide gel electrophoresis (2D- PAGE). Thirty-one spots, representing 24 proteins, were successfully identified by MALDI TOF/TOF mass spectrometry.The most prominent differences include the up-regulation of antioxidant enzymes (catalase, peroxidase and superoxide dismutase), PR proteins (chitinase, endo-1,3-β-glucosidase), and chaperones (cyclophilin, HSC 70). Our results indicate that BABA induces defence and detoxification processes which may enable faster and more effective responses to salt stress, increasing the chances of survival under adverse environmental conditions.

In vitroImprovement in Regeneration Potentiality by Using Kinetin Primed Seeds of Rice (var. MTU-7029)

The present study deals with the somatic embryogenesis of rice (var. Swarna/MTU-7029), where a comparative characterization of the calli were made, using dehusked, sterilized whole seeds, obtained from kinetin primed and nonprimed one. For callus induction 30gL−1 sucrose + 1gL−1 casein hydrolysate and 30gL−1 maltose + 1gL−1 casein hydrolysate were added in MS medium separately which was supplemented with 2 mgL−1 2,4-D. In the regeneration medium (MSR1 to 6) different concentration of BAP, kinetin and NAA (2:0:1, 3:0:1, 4:0:1, 2:3:1, 3:2:1 and 4:1:1 mgL1) were used respectively. For regeneration of roots half strength MS basal medium was used supplemented with IBA 1mgL−1, sucrose 2% (w/v) and 0.8% (w/v) agar. Different concentrations (2.5 and 5 ppm) of the kinetin used for priming before using the seeds for inoculation in the culture medium, showed promising results regarding the total callus induction percentage, total embryogenic calli percentage, fresh and dry weights, proline content, nitrate reductase and superoxide dismutase activities in respect to non primed one. 2.5ppm (T2) kinetin primed seeds showed best result than 5ppm(T3) kinetin primed seeds. Among the entire regenerated medium, MSR6 showed highest regeneration (%), number of shoots regenerated per calli and recovery of plantlets from 50 tubes in all the treatments. The plantlets recovered from inoculated primed seeds calli have more number of roots in respect to non-primed one. Plantlets obtained from primed and non-primed control seeds were hardened in polyhouse and studied in detail upto the formation of panicle. On the basis of the above data T2 was found better than control.

Effect of osmotic potential of activator solution and temperature on viability and vigour of wheat seed

Experiment was conducted to investigate if seed priming with polyethylene glycol (PEG) activator solutions affects the viability and vigour of deteriorating wheat (Triticum aestivum L. cv. Caxton) seed lot. Seeds were subjected to PEG priming solutions with varying osmotic potentials (-1, -2, -3 MPa) at temperatures of 15 or 20°C for 6, 12, 18 or 24 h and compared to the non-primed control. Highest germination percentage at first and final count, length of plumule and dry weight of seedling were all associated with Treatment -1 MPa/20°C/6 h (92%, 94%, 9.2 cm, 0.0133 mg, respectively) compared to the control (82.5%, 86%, 7.8 cm, 0.0112 mg, respectively). The best values of coefficient of velocity of germination (CVG), mean germination time (MGT) and germination rate index (GRI) were associated with Treatment -2 MPa/15°C/24 h. There were significant interactions between the factors under study and whilst most positive effects decreased with incubation time the opposite was true at 15°C Treatment -2 MPa where an initial decrease in germination after 6 h was restored with longer incubation times. Significant correlations were found between most of the characteristics under study although these did not always account for a high percentage of variation but CVG and MGT were very highly correlated. It was concluded that, 6 h in Treatment -1 MPa PEG at a temperature of 20°C resulted in significantly improved germination percentage whilst 24 h Treatment -2 MPa at 15°C was optimal for the highest CVG and MGT. The highest speed of germination was not associated with the highest germination percentage. Key words: Osmotic potential, priming, soaking, temperature, Triticum aestivum L., wheat.

Effects of CaCl2 pretreatment on antioxidant enzyme and leaf lipid content of faba bean (Vicia faba L.) seedlings under cadmium stress

In the present investigation we studied the role of CaCl2 pretreatment on physiological and biochemical characteristics in faba bean (Vicia faba L.) seedlings subjected to cadmium (Cd) stress. The seeds of faba bean were treated with H2O and 2 % CaCl2 before germination for 6 h. Primed or nonprimed (control) seeds were then germinated under increasing concentrations of Cd (0, 10, 50 and 100 μM) for 21 days. The contents of Cd, soluble protein (SP), malondialdehyde (MDA), total membrane lipid contents, fatty acid composition and the activities of superoxide dismutase (SOD EC 1.15.1.1), catalase (CAT EC 1.11.1.6), guaiacol peroxidase (GPX EC 1.11.1.7), lipoxygenase (LOX) in the seedlings leaves were tested. Exposure of the plants to Cd caused a gradual decrease in the shoot and root dry weight. Seed pretreatment with CaCl2 alleviated the negative effect of Cd on plant growth parameters. The same tendency was observed for the chlorophyll content. The level of lipid peroxidation (as indicated by MDA content) was higher in Cd-treated plants, and remained unchanged in CaCl2-pretreated plants. The same results for the total lipid content, fatty acids composition and SP level were observed. Treatment of plants with Cd drastically decreased CAT activity and caused an increase in both SOD and GPX activity. However, in CaCl2-pretreated plants, CAT activity exhibited a slight decrease under Cd treatment. An increased of SOD and GPX activity in leaves of pretreated plants was also demonstrated. The data suggest that CaCl2 pretreatment may protect faba bean seedlings against Cd toxicity.

Alterations in seed vigor and antioxidant enzymes activities in Silybum marianum under seed priming with KNO3

This study evaluated the effects of the best priming treatment on germination responses of milkthistle (Silybum marianum) seeds. Seeds of S. marianum are two ecotypes namely (Amol and Majar) primed with KNO3 in -2, -4, -6, -8 and -10 bar for 6, 12 and 18 h at 25°C, followed by air-drying to their initial moisture level. Then, based on germination percentage, germination rate, mean germination time (MGT) and seed vigor, the best priming treatment was selected. Antioxidant enzymes activity of S. marianum were determined in primed (-2 bar 6 and 18 h in Amol and Majar, respectively) and non-primed seeds in 24 and 96 h after sowing during germination. Results indicated that osmo-priming increased germination percentage, germination rate and seed vigor and shortened MGT than non-primed. The best priming treatment in Amol and Majar was -2 bar 6 and 18 h, respectively. Moreover, priming also enhanced the anti-oxidative enzymes of peroxidase (POX) and ascorbate POX (APX) and soluble proteins level of treated seeds but catalase (CAT) activity decreased in primed seeds than non-primed control. Majar had greater activity of APX enzyme and soluble proteins level than Amol. As a result, Majar had higher germination percentage and seed vigor and faster germination rate as compared to that of Amol. Activity of POX was higher in Amol than Majar. The soluble proteins levels in 24 h after sowing was greater than 96 h after sowing and in 96 h after sowing decreased but activities of APX and POX were greater in 96 h after sowing than 24 h after sowing. The enhanced anti-oxidative enzyme activities of APX and POX and soluble proteins levels might explain in part why primed milk thistle seeds germinated better than non-primed seeds. Key words: Seed priming, antioxidative enzymes, germination, Silybum marianum.

Field appraisal of seed priming to improve the growth, yield, and quality of direct seeded rice

Poor crop stand and high weed infestation are the major constraints of direct seeded rice. Seed priming has the potential to improve the seedling emergence and crop stand. This study was conducted to evaluate the on-farm assessment of direct seeded rice by employing different priming techniques such as on-farm priming, hydropriming, hardening, and osmohardening with CaCl_2 and KCl. Untreated seeds were taken as control. Among all the seed priming techniques, osmohardening with CaCl_2 improved the stand establishment, allometric response, agronomic traits, yield, and quality of harvested paddy compared with other priming techniques, and non-primed control in direct seeded culture. Improved crop stand as indicated by lower values of time to emergence and higher values for emergence index and final emergence, higher crop growth rate, and improved plant height, tiller numbers, and straw and kernel yield with high harvest index were recorded from osmohardening with CaCl_2. In addition, seed priming treatments also improved the kernel quality. Osmohardening with CaCl_2 was the best way to reduce sterile spikelets, abortive and chalky kernels, and improve kernel length. However, none of the seed priming techniques could improve the number of kernels per branch, 1000-kernel weight, kernel width, and kernel water absorption ratio. Moreover, improved phosphorus, calcium, and potassium contents were also observed from osmohardening with CaCl_2 followed by KCl. Osmohardening with CaCl_2 can therefore be employed for better crop stand, growth, yield, and quality in direct seeded rice.

Effects of Seed Priming on Germination and Seedling Growth Under Water Stress in Rice

For disclosing the effects of seed priming with water and polyethylene glycol (PEG) on physiological characteristics in rice ( Oryza sativa L.), the seeds of 4 rice cultivars were treated with H 2O and different concentrations of PEG before germination. Primed or nonprimed (control) seeds were then germinated under drought stress conditions simulated with PEG in a serious of concentrations. The contents of proline, soluble protein (SP), total soluble sugar (SS), malonicdialdehyde (MDA), and the activities of phenylalanine ammonia lyase (PAL), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in the seeds or seedlings after 10-day stress were tested, and the indices for seed germination and seedling characteristics were determined. In seeds with priming treatments, the contents of proline and SP were significantly higher than those in the corresponding controls, and the contents of SS and MDA were significantly lower than those in the controls. Seed priming accelerated the process of glucose metabolism, enhanced the activities of PAL, SOD, CAT, and POD in the stressed seeds of all cultivars. Compared to hydro-priming, priming with PEG in a proper concentration had a better effect on seed germination and seedling growth under drought stress, and the optimal priming concentrations of PEG were 20% for Gangyou 527 ( indica hybrid rice) and 10%–15% for Nongken 57 (conventional japonica rice). Even higher concentrations of PEG had negative effects on seed germination. Moderate priming intensity improved metabolism of rice seed, germination indices, seedling quality, and drought tolerance of seedlings under drought stress for all cultivars. However, such effects had limited capability, and severe drought stress inhibited germination and caused damages of rice seedlings. Rice cultivars had significant impact on priming effect, and indica rice showed better performance than japonica rice.

Improving emergence and early seedling growth of two cool season grasses affected by seed priming under saline conditions

Soil salinity threatens initial stages of emergence and early seedling growth in cool season grasses, although it may be tolerant in its adult stages. Today, seed priming has been known as an effective technique for improving seed germination, seedling vigor, and emergence rate and seedling establishment under different environmental stresses. A pot experiment was conducted to evaluate osmopriming effects in ameliorating emergence rate (ER) and final emergence percentage (FEP), seedling growth, Na+ and K+ accumulated in shoot at early growth stages of two cool season grasses including tall wheat grass (Agropyron elongatum Host.) and bulbous barley (Hordeum bulbosum L.) when seeds were imbibed with CaCl2, -1.5 MPa, and NaCl, -1 MPa for a duration of 2 and 5 days respectively, in response to seven salinity concentrations of NaCl (0, 50, 100, 150, 200, 250 and 300 mM) under greenhouse conditions. With increasing salinity levels, ER and FEP and seedling growth were significantly decreased in both grasses for primed and non-primed (control) seeds (p 0.05) but for non-primed seeds increasing the accumulation of Na+ in shoot, led to significant decline (r= -0.62, P< 0.01) of shoot dry weight. The results suggest that seed priming could significantly improve the threshold value especially for FEPin both grasses under different levels of salinity. Also, it seems that seed priming could better improve root and shoot growth at early seedling growth stage perhaps by decreasing toxicity of Na+ concentration and adjusting Na+ and K+ ratio under saline conditions. Key words: Early seedling growth, emergence rate, seed priming, salinity stress, cool-season grasses.