Germination and Seedling Growth of Wheat as Affected by Seed Priming and its Duration

Insufficient seedling emergence and inappropriate stand establishment are the main restraints in areas receiving less rainfall [1]. One of the important aspects of quality grain production is a speedy emergence and beneficial seedlings establishment in the field. Thus, quick and uniform field emergence is the necessity to attain high yield in annual crops [2]. One of the most important strategies to accelerate germination, to produce high-quality seedling and plant optimal establishment seed priming is used. The beneficial effect of priming has been demonstrated for many crops such as wheat, soybean, maize, and sunflower [3]. Seed priming has been mostly used to reduce the time between seed sowing and seedling emergence and to synchronize emergence [4]. It is reported that seed priming is one of the most important developments to help rapid and uniform germination and the emergence of seeds and to increase tolerance to adverse and environmental conditions [5,6]. The mean time for 50% germination at 20 °C of 12 Indian wheat cultivars was nearly halved, from 51h to 27h, by soaking seed in water for 8h prior to sowing. A delay of 24h without further soaking, intended to simulate postponement of sowing, reduced the time saved by priming to 16%. Priming had no effect on the final germination percentage [7]. Moringa leaf extracts improve seedling vigor, growth, and productivity of wheat crop [8]. Polyethylene glycol and KNO3 solutions increased the fresh and dry weight of roots in maize at 2% and 5% concentration primed for 12h and 18h and it also increased the vigor index [9]. Therefore, the aim of this trial was to find out the effect of seed different priming techniques with 6 and 12hrs priming duration on emergence, vigor, and growth of wheat. It has also been reported that seed priming improves emergence, stand establishment, Germination index, Shoot length, Root length, Shoot fresh and dry weight, and Root fresh and dry weight. Keeping in view the desirable effect of seed priming on seed germination and further establishment, the experiment was planned to evaluate the effect of different seed priming with different time duration.

with a completely randomized design. Wheat OPV Pirsabak-2013 were used in the experiment. The experiment comprised of two factors, the 1 st factor was priming techniques (Dry seed, Halo, Osmo, Solid matrix priming). 2 nd factor was priming durations (6 and 12 Hours), with three replications. Parameters that were studied in the experiment were "Mean emergence time, Time taken 50% germination, Final emergence %, Germination index, Shoot length(cm), Root length (cm), Shoot fresh weight (g), Shoot dry weight (g), Root fresh weight (g), Root dry weight (g)".

Mean germination time
Mean emergence time (MET) was calculated according to the equation of Ellis and Roberts 1981 [10].
Where n is the number of seedlings emerged on day D, and D is the number of days counted from the beginning of emergence.

Time taken 50% germination
Time to get 50% emergence (E 50 ) was calculated [11] and [12]. Where N is the final number of seedling emerged, and ni and nj the cumulative number of seedling emerged by adjacent counts at times ti and tj when ni< N/2<nj.

Germination index (GI)
Germination index was calculated according to ISTA

Mean emergence time (days)
Analyses of the data revealed that mean emergence time was significantly affected by priming media and priming duration ( Table 1). The interaction between priming techniques and its duration was found non-significant. Among different priming techniques halo priming with CaCl 2 resulted in the minimum value of mean emergence time (2 days) which was statistically similar to Osmo priming with PEG-6000 (2 days). Solid matrix priming with press mud took (3 days) to mean emergence time. Control (dry seeds) took more days to mean emergence time (4). Among different priming durations, 12 hours priming took fewer days to mean emergence time (2) while 6 hours priming took more days to mean emergence time (3). [14] confirm our result he stated that hormonal priming with GA3 and osmopriming with PEG-6000 for 24 hours gave faster and earlier germination followed by hydro priming. [15] also indicated that seed priming for 24 hours caused a significant reduction in the time to 50% emergence which took mean minimum germination time compared to untreated seeds.

Time taken to 50% emergence
Analysis of data revealed that the time taken to 50% emergence was significantly affected by priming techniques and duration ( Table 1). The interaction between priming techniques and durations was found non-significant. Among different priming techniques halo priming (CaCl 2 ) reduced time to 50% emergence (1 day) which was statistically similar with Osmo priming with PEG-6000 (1 day). Solid matrix priming with press mud took (1 day) to 50% emergence. Control took more days to 50% emergence (2 days). Among different priming duration, 12 hours priming took fewer days to the time taken 50% emergence (1 day) while 6 hours priming took more days to the time taken 50% emergence (2 days). A significant reduction in emergence time and enhancement in final germination may be due to fact that seed priming activate biochemical changes such as hydrolysis, activation of enzymes and breaking of dormancy in the seed [16,17] and [15] also indicated that seed priming for 24 hours caused significant reduction in the time 50% emergence which took mean minimum germination time compared to untreated seeds.

Germination %
Analysis of data revealed that final germination was significantly affected by priming techniques and durations ( Table   1). The interaction between priming techniques and durations was found non-significant. Among different priming techniques, Osmo priming with PEG-6000 resulted in high final germination Agricultural Research & Technology: Open Access Journal (85.8%) whereas halo priming with CaCl2 resulted in (81.6%) to final germination while solid matrix priming with press mud resulted in (78.3%) final emergence. Control (dry seeds) resulted in less final germination (61.6%). Among different priming durations, 12 hours priming resulted in more final germination (80.0%) while 6 hours priming resulted in less value to final germination (74.0%). A significant reduction in emergence time and enhancement in final emergence may be due to the fact that seed priming stimulates an array of biochemical changes such as hydrolysis, activation of enzymes and dormancy breaking in the seed [16,17], which are required to initiate the germination process.

Germination index
Analysis of data showed that germination index was significantly affected by priming techniques and duration ( Table  2). The interaction between priming techniques and durations was found non-significant. Among different priming techniques, Osmo priming with PEG-6000 resulted in higher germination index (39.2). Halo priming with CaCl 2 resulted in (33.6 germination index. Solid matrix with press mud priming resulted in (30.1) value of germination index. Control (dry seeds) resulted in (18.0) less value of germination index. Among different priming durations, 12 hours priming resulted in (31.4) higher value of germination index while 6 hours priming resulted in (29.1) less value of germination index. The possible reason for improvement in germination % and germination index by hormonal priming and osmopriming for 24 hours may be due to greater hydration of colloids higher viscosity and elasticity of protoplasm, offer an increased inbound water content, lower water deficit and increased metabolic activity [18,19], also stated that different seed enhancement techniques positively affected the germination index, vigor index and final emergence of maize hybrid in a laboratory-based experiment.

Root length
Analysis of data revealed that root length was significantly affected by priming techniques and durations ( Table 2). The interaction between priming techniques and durations was found non-significant. Among different priming techniques, solid matrix priming with press, mud resulted in a higher value of root length (15.3cm) which was statistically similar to Osmo priming with PEG-6000 (14.1cm). Halo priming with CaCl2 resulted in (13.8cm) root length. Control (dry seeds) resulted in less root length (9.9cm). Among different priming durations 12 hours seeds priming resulted in (13.7cm) higher value of root length while 6 hours priming resulted (10.1cm) less value of root length. Karmore et al. [15] stated that root and shoot length were positively affected by seed priming techniques compared to untreated seed [12], also supported the present like-wise, improved performance by osmopriming with CaCl 2 to expedite germination, vigor index and seedling vigor in spring maize.

Shoot length
Analysis of data revealed that shoot length was significantly affected by priming techniques and durations ( Table 2). The interaction between priming techniques and durations was found non-significant. Among different priming techniques solid matrix priming with the pressmud resulted in large shoot length (14.6cm) which was statistically similar to halo priming with CaCl 2 (14.3cm). While Osmo priming with PEG-6000 resulted in (14.3cm) shoot length. Control (dry seeds) resulted in less shoot length (6.5cm). Among different priming durations 12 hours seeds priming resulted in higher (15.0cm) shoot length while less value of shoot length was produced by 6 hours priming (13.7cm). Karmore et al. [15] stated that root and shoot length were positively affected by seed priming techniques compared to untreated seed. Improved seedling growth by hormonal priming with SA may be attributed to increase cell division within the apical meristem and regulate plant growth through enhanced cell enlargement and cell division within the growing seedlings [20,21].

Shoot fresh weight
Analysis of data revealed that shoot fresh weight was significantly affected by priming techniques and duration ( Table  3). The interaction between priming techniques and durations was found significant. Among different priming techniques solid matrix priming with press mud resulted (0.95g) higher shoot fresh weight followed by Osmo priming with PEG-6000 (0.14g). Halo priming resulted with CaCl2 (0.13g) shoot fresh weight. Control (Dry seeds) resulted in (0.07g) less shoot fresh weight. Among different priming durations 12 hours seeds priming resulted in more shoot fresh weight (0.32g) which statistically similar with 6 hours (0.32g). These results are supported by [22], who found that seed priming treatments considerably enhanced fresh seedling weight.

Shoot dry weight
Analysis of the data revealed that shoot dry weight was significantly affected by priming techniques and durations ( Table  3). The interaction between priming techniques and durations was found also significant. Among different priming techniques solid matrix priming with pressmud resulted in (0.03g) higher shoot dry weight followed by halo priming with CaCl 2 (0.02g) which was statistically similar to Osmo priming with PEG-6000 (0.02g). Control (dry seeds) recorded in less shoot dry weight (0.01g). Among priming durations, 12 hours priming resulted (0.03g) higher shoot dry weight while 6 hours priming resulted in (0.02g) less shoot dry weight. The higher dry weight of seedlings and more shoot length was earlier reported by priming with CaCl 2 [23], which might be due to the emergence of seedlings. Improved seedling FW might be due to increased cell division within the apical meristem of seedling roots, which cause an increase in plant growth, which resulted in early stand establishment [24].

Root fresh weight
Analysis of data revealed that root fresh weight was greatly affected by priming techniques and durations ( Table 3). The interaction between priming techniques and durations was found non-significant. Among the priming techniques, solid matrix priming with press mud was resulted in (0.40g) higher root fresh weight followed by Osmo priming with PEG-6000 (0.22g). Halo priming with CaCl2 resulted in (0.07g) value for root fresh weight. Control (dry seeds) resulted in (0.05) less value for root fresh weight. Among priming different durations 12 hours seeds priming resulted in (0.30g) higher value of root fresh weight while 6 hours seeds priming resulted in (0.06g) less value of root fresh weight. Thangarasu et al. [25], reported that the combination of plant growth promoting rhizobacteria enhanced the root weight. Jha Y & Subramanian RB [26], also reported that the plants inoculated with PGPR showed higher dry weight.

Root dry weight
Analysis of data revealed that root dry weight was significantly affected by priming techniques and durations ( Table 3). The interaction between priming techniques and durations was also found significant. Among different priming techniques solid matrix priming with press mud was resulted in (0.12g) higher root dry weight followed by Osmo priming with PEG-6000 (0.03g) which was statistically similar with halo priming with CaCl 2 (0.03g). Control (dry seeds) recorded in less root dry weight (0.02g). Among the priming durations 12 hours seeds priming resulted in (0.08g) higher value of root dry weight while 6 hours seeds priming resulted in (0.02g) less value of root dry weight. The higher dry weight of seedlings and more shoot length was earlier reported by priming with CaCl 2 [22], which might be due to the early emergence of seedlings. Jha et al. [26], also reported that the plants inoculated with PGPR showed higher dry weight.

Conclusion and Recommendation
Osmopriming with PEG-6000 and solid matrix priming with press mud improved germination and seedling growth of wheat compared to other priming techniques. Among seed priming duration's seed primed for 12 hours speed up the germination and enhanced crop growth. On the basis of the above conclusion, it is recommended that Osmo priming with PEG-6000 and solid matrix priming with press mud for 12 hours is recommended for obtaining higher germination and crop growth.

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