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The effect of seed priming on germination and seedling growth of watermelon (Citrullus lanatus).

Introduction

Seed priming is nowadays being extensively used to improve seed germination and seedling emergence in a wide range of crop species[3] and is basically a physiological process in which the seeds are presoaked before planting which, by itself, allows partial imbibition though preventing the germination[7]. During the priming, several processes including storage, material handling, activation and synthesis of a number of enzymes and nucleic acids, repair and build up, ATP synthesis, and the cytoplasmic membrane repair in treated seeds will all start to develop[3].

Osmo-priming is a commonly used method for

priming the seeds. Priming generally induces faster and more uniform seed germination especially in adverse physical conditions of many crop species [6]. Sivritepe et al.[9] indicated that watermelon seeds priming with 1% NaCl for 3 day at 20 [degrees]C reduced salinity effects on germination of watermelon and increased watermelon tolerance to salinity in the early stages of growth. Jian Jun et al.[4] investigated effects of different osmotics which can be used in seed priming on watermelon germination and reported that priming with solutions of copper sulfate 1% for 4 h and zinc sulfate 0.2% for 24 h will enhance germination by respectively 17.1% and 73.3% compared with untreated seeds. Mavi (2004) evaluated the effects of osmo-priming (using solution of potassium nitrate for 6 days at 24[degrees]C) and hydropriming (using distilled water with temperature of 30[degrees]C for 18 days) on watermelon germination under 3 different temperatures of 15, 25, and 38[degrees]C, coming to conclusion that no significant impact of osmopriming and hydro-priming would be found between 25 and 38[degrees]C on seed germination. It was however, significantly increased in seed germination when using 15[degrees]C for both osmopriming and hydropriming. The beneficial effects of osmo- and hydro- primings are associated with increase in radicle and plumule lengths.

Priming also enhances the crop establishment in filed. Manigopa et al.[5] reported that priming in chickpea (Cicer arietinum L.) led to better crop establishment and growth and greater yield. Seed priming increased the number of plants at harvest, yield, germination, number of pods per plant, number of lateral branches per plant, and number of seeds per plant by respectively 12.8%, 9.6%, 9.4%, 6.4%, and 6.5%, over the non-priming treatment.

Hosseini and Koocheki[3] stated that in sugar-beet seed, different varieties can respond differently to priming. According to their data, the variety to be responded better over a wide range of varieties was K.V.S. The response of seeds to priming has been found to be dependent on the osmitica, duration of priming, seed maturity, cultivar, and environmental conditions[6].

Melon is an important horticultural crop cultivated mostly in arid and semi-arid region of the world where salinity, high temperature, rapid soil drying, and crust formation are barriers to good melon crop establishment. However, no study has been previously reported in the context of Iran on the effects of different osmotica on melon seed germination and early seedling growth. Consequently, the aim of this study was to elucidate the effects of osmo-priming on seed emergence and early seedling growth of watermelon under the same conditions on the farm.

Materials and Methods

The effects of osmo-priming on watermelon (Citrullus lanatus) seed germination and early seedling growth was investigated via a laboratory emergence test. The experiment was conducted with factorial arrangement of the treatment in a completely randomized design with 3 replicates. Experimental factors were 3 watermelon cultivars (Niagara, Charleston Gray, and Crimson Sweet) and 4 different osmotic solutions (0.1N Hydrochloric acid, 1.5N NaCl, 3% polyethylene glycol (PEG) 6000, 3% KN[O.sub.3]).

Three popular watermelon seeds (Niagara, Charleston Gray, and Crimson Sweet) were obtained locally. One hundred randomly selected seeds placed in a 10-cm diameter plastic Petri dish on a filter paper (Whatman filter paper No. 1). The Petri dishes were then covered by aluminum foil in order to prevent waste solution and were placed in a germinator (with a temperature of 20 [degrees]C and in constant darkness) and a period of 6 days was allocated to their growth. After the 6 days, seeds were rinsed in distilled deionized water for 2 minutes with an aim to wash off the solutions from the surface of the seeds, and were slowly dried at room temperature for 48 hours back to their original (nonprimed) moisture content as described in Demir and Mavi (2004). Unprimed seeds were used as control. Glasshouse experiments were carried out to compare the actual performance of the seed subjected to different priming treatments at Azad University of Sabzevar, Sabzevar, I. R. Iran. In each pot (sized 32 * 22* 6 cm, and filled with sand loamy soil), 25 seeds from each variety were sown at a depth of 3 cm. The pots were saturated in water by surfaceirrigation. During plant growth, pots were irrigated daily by spraying with water until water would drain from the bottom of the pot. Germination was measured daily for 18 days between 9 AM to 10 AM. Five seedlings were randomly harvested from each pot to determine plumule length, radicle length and plumule dry-weight of seedlings. The glasshouse temperature was maintained between 24 and 15 [degrees]C for days and nights, respectively.

Final germination-percent and mean germination-time were calculated according to the equation below [6]:

Final germination percent = T/S *100

Mean germination time = [SIGMA] ([N.sub.i]*100/[D.sub.i])

where T is the number of germinated seeds, [D.sub.i] is the number of days after starting the experiment, and S and [N.sub.i] represent the total number of planted seeds and of the germinated seeds on the ith day, respectively.

For the analysis of variance and to determine the significant differences between treatments, the SAS computer package (SAS Inc V 9.1) was used. Duncan's multiple-range test was applied for comparing the treatment means.

Results and Discussion

Final germination percentage:

No statistically significant differences (p<0.05) have been found to exist between the varieties on final germination percentage (Table 1). Charleston Gray had the greatest final germination percentage, while Niagara had the least final germination percentage (Table 2).

Different priming treatments significantly (p<0.05) influenced the final germination percentage (Table 1). Among the assessed osmotica, Potassium Nitrate had the most effective impact on the final germination-percent of sugar-beet seeds which increased the germination by 17.87% compared with that of the control (Table 3).

Positive effects of different solutions on final germination-percentage can be due to overcoming the seed dormancy or to improving the embryonic activity during germination. Observed decrease in the seeds treated with sodium chloride and PEG ,too, can be due to osmotic and ionic effects of ions of these two materials, which led to less water uptake and lower germination percentage by seeds.

These results are in line with Demir and Mavi (2004), who found increased germination and mean germination time of watermelon seeds treated with potassium nitrate.

Mean germination time:

Mean germination-time significantly changed between different varieties (Table 1). Charleston Gray exhibited the greatest mean germination-time, while Niagara had the least one (Table 2). It seems that higher storage materials in seeds may lead to greater mean germination-time in Charleston Gray.

There was a significant difference between different priming treatments in mean germination-time (Table 3). As it can be seen, mean germination-time followed a trend similar to final germination-percent. Seeds primed in Potassium Nitrate solution had the highest mean germination-time, followed by Hydrochloric acid, while priming with solutions of Sodium Chloride and PEG significantly declined this parameter over the control (Table 3). The results of this study are consistent with those of Hosseini and Koocheki[3], who reported that priming with solutions of Sodium Chloride and PEG significantly decreases mean germination-time in different varieties of sugar-beet.

Postponement in germination can be a result of the osmotic pressure and reduced water absorption by seeds. In the present study, negative effects of polyethylene glycol were greater than those of sodium chloride. In melon, it has also been reported that primed seed in salt solutions germinated faster compared with in PEG or in mannitol. The increased MET in primed seeds in the PEG than in sodium chloride could possibly be due to the fact that the melon seeds released some ions like K+ from seed embryos by Prisprm, and this, by itself, resulted in being less affected in saline solutions than in PEG (Nascimento and West, 1999).

Sung and Chiu[10] found that in primed watermelon seeds, faster germination depends on the weight and thickness of seeds. Seed priming by softening the seed coat reduces the restrictions to radicle protrusion through the seed coat. One of the reasons for low germination in watermelon seeds is stiffness of its seed coat.

Plumule length:

Analysis of variance revealed that plumule length was affected by different priming treatments, whereas plumule length was not significantly different across varieties (Table 1). Trend of observed changes in plumule length across priming solution were similar in plumule length and MET.

Priming with solutions of potassium nitrate and acid hydrochloric exhibited the greatest plumule length, while priming with PEG had the least plumule length (Table 3). Faster seed-germination can cause greater plumule length in seeds treated with potassium nitrate and acid hydrochloric. Nascimento [6], too, has reported that the pre-treatment of melon seeds with different solutions increased plumule length resulted from the longer period of time for seedling growth as a result of a faster germination.

Plumule dry weight:

Plumule dry-weight was affected by varieties and different osmotica (Table 1). The greatest plumule dry-weight was observed in Charleston Gray (Table 2). The Charleston Gray was also superior in other characteristics compared to other varieties. Faster germination provided more time for seedling growth in this variety, which leads to a higher dry-weight of Charleston Gray plumule. The effect of different Priming treatments on the dry-weight of plumule is given in Table 3. As it was expected, primed seed in Potassium Nitrate and PEG exhibited the greatest and the least plumule dry-weights, respectively.

Radicle length:

No statistically significant differences were found to exist between the varieties and the different priming treatments on radicle lengths, whereas the interaction of cultivar * priming treatment on radicle length was significant (Table 1). Trend of radicle length in different cultivars revealed that the greatest radicle length in Charleston Gray occurred when seeds primed with Potassium Nitrate solution, while in Niagara seed priming with hydrochloric acid caused the highest radicle length. Primed seed in all three studied varieties had the least radicle lengths when primed with Sodium Chloride and PEG. Studies on the sugar-beet showed that seed pretreatment with Sodium Chloride and PEG, compared with distilled water, decreased the radicle length[3].

[FIGURE 1 OMITTED]

Conclusion:

Results of the present investigation with osmopriming of three popular watermelon varieties using four different osmotic solutions showed that the priming solutions regarded as advisable are: potassium nitrate and hydrochloride acid. Similar responses in germination among different varieties may be due to genetically similar varieties investigated in this experiment.

References

[1.] Demir, H. and K. Mavi, 2004. Seed priming of male sterile muskmelon (cucumis melo L.) for low temperature germination. Seed Science and Technology, 23(4): 881-884.

[2.] Demir, I., H.A. van de Venter, 1999. The effect of priming treatments on the performance of watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) seeds under temperature and osmotic stress. Seed Science and Technology, 27(3): 871875.

[3.] Hosseini, A. and A. Koocheki, 2007. The effect of different priming treatments on germination percent and mean germination time of four varieties of sugar beet. Journal of Agronomic Research, 5(1): 69-76.

[4.] Jian, J.F., C.K. Jie, K.J. Yoen, X. Yong, Z.X. Yang, L.J. Qiang, 2007. Effect of seed priming on seedling growth and disinfection to Acidovorax avenae Subsp. Citrulli in triploid watermelon seeds. Acta Phytopathologica Sinica., 37(5): 528-534.

[5.] Manigopa, C., J. Ghosh, D.S. Virk, S.C. Prasad, 2007. Effect of seed priming on germination, growth and yield of horsegram cultivars. Journal of Arid Legumes, 4(1): 56-58.

[6.] Nascimento, W.M., 2003. Muskmelon seed germination and seedling development in response to seed priming. Scientia Agricola, 60(1): 71-75.

[7.] Nascimento, W.M. and F.A.S. Aragao, 2004. Muskmelon seed priming in relation to seed vigor. Scientia Agricola, 61(1): 114-117.

[8.] Sivritepe, H.O., N. Sivritepe, A. Eris and E. Turhan, 2005. The effects of NaCl pre-treatments on salt tolerance of melons grown under longterm salinity. Scientia Horticulturae, 106: 568581.

[9.] Sivritepe, N., H.O. Sivritepe, A. Eris, 2003. The effects of NaCl priming on salt tolerance in melon seedlings grown under saline conditions. Scientia Horticulturae, 97: 229-237.

[10.] Sung, J.M., K.Y. Chiu, 1995. Hydration effects on seedling emergence strength of watermelon seed differing in ploidy. Plant Science, 110: 2126.

(1) Mohammad Armin, (2) Mohammad Asgharipour and (3) Mohammad Razavi-Omrani

(1) Islamic Azad University, Sabzevar Branch, Sabzevar, Iran

(2) University of Zabol, Zabol, Iran

(3) Islamic Azad University, Quchan Branch, Quchan, Iran

Mohammad Armin, Mohammad Asgharipour and Mohammad Razavi-Omrani: The Effect of Seed Priming on Germination and Seedling Growth of Watermelon (Citrullus Lanatus)

Corresponding Author

Mohammad Armin, Islamic Azad University, Sabzevar Branch, Sabzevar, Iran Email: m_asgharipour@yahoo.com
Table 1: Analysis of variance table for the final germination
percentage, mean germination time, plumule length, radicle length
and plumule dry weight of watermelon seedlings.

                      Studied traits

SOV                   Final          Mean           Plumule
                      Germination    germination    length (mm)
                      percentage     time (day-1)
Cultivar              ns             0              ns
Priming               0              **             0
Cultivar * Priming    ns             ns             ns

SOV                   Plumule dry    Radicle
                      weight (mg)    length (mm)

Cultivar              ns             ns
Priming               ns             ns
Cultivar * Priming    ns             0

ns: not significant; (*) and (**) represent significant difference
over control at P < 0.05 and P < 0.01, respectively.

Table 2: Effect of verities on final germination percentage, mean
germination time, plumule length, radicle length and plumule dry weight
of watermelon seedlings.

                   Studied traits

Cultivar           Final          Mean           Plumule
                   Germination    germination    length (mm)
                   percentage     time (day-1)

Niagara            92.14a         4.89b          148.1a
Crimson Sweet      94.9a          5.02ab         149.04a
Charleston Gray    96.39a         5.32a          154.7a

Cultivar           Plumule dry    Radicle
                   weight         length (mm)
                   (mg)

Niagara            0.131a         21.9a
Crimson Sweet      0.154a         24.1a
Charleston Gray    0.153a         24.3a

* Values followed by the same letter within the same columns do not
differ significantly at P = 5% according to DMRT.

Table 3:  Effect of priming treatments on final germination percentage,
mean germination time, plumule length, radicle length and plumule dry
weight of watermelon seedlings.

priming media        Final          Mean           Plumule
                     Germination    germination    length (mm)
                     percentage     time (day-1)

Hydrochloric acid    94.35a         5.24a          155.56ab
PEG                  55.25c         3.21c          140.95b
Sodium chloride      64.73bc        3.42c          141.62b
Potassium nitrate    96.74a         5.47a          161.26a
Control              79.45b         4.45b          153.71ab

priming media        Plumule dry    Radicle
                     weight of      length (mm)
                     (mg)

Hydrochloric acid    0.145a         24.37a
PEG                  0.141a         21.26a
Sodium chloride      0.137a         22.70a
Potassium nitrate    0.156a         25.44a
Control              0.141a         23.53a

* Values followed by the same letter within the same columns do not
differ significantly at P = 5% according to DMRT.
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Title Annotation:Original Article
Author:Armin, Mohammad; Asgharipour, Mohammad; Razavi-Omrani, Mohammad
Publication:Advances in Environmental Biology
Article Type:Report
Geographic Code:7IRAN
Date:Sep 1, 2010
Words:2536
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