Greener Journal of Agricultural Sciences

Vol. 10(2), pp. 57-62, 2020

ISSN: 2276-7770;

Copyright 2020, the copyright of this article is retained by the author(s)

http://gjournals.org/GJAS

 

 

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Effects of GA3, BAP and KNO3 on the Germination and DNA Content of Cucumber (Cucumis sativus L.)

 

 

Mensah, S.I.; Ejeagba, P.O.; Okonwu, K.

 

 

Department of Plant Science and Biotechnology, University of Port Harcourt,

P.M.B. 5323, Port Harcourt, Nigeria.

 

 

 

ARTICLE INFO

ABSTRACT

 

Article No.: 021720037

Type: Research

 

 

Effects of gibberellic acid (GA3), 6-benzylaminopurine (BAP) and potassium nitrate (KNO3) on the seed germination and DNA concentration of cucumber (Cucumis sativus) radicle were assessed. The concentrations of these growth stimulants were 0 mM, 1 mM, 5 mM and 10 mM. The cucumber seeds were surface sterilized in ethanol for 5 minutes and rinsed with distilled water before pretreatment with these growth stimulants. The germination study was allowed to stand for 14 days and DNA concentration of cucumber radicle with the highest germination count was determined for each growth stimulant. The study showed that cucumber seeds had higher germination count under the light condition than in the dark condition. However, it is not statistically different. The study also showed that percentage germination of cucumber seeds was enhanced by GA3 (57 72%) and BAP (62 70%) when compared to the Control (50%) except KNO3 (41 44%). Across the treatments, GA3 gave the highest germination percentage followed by BAP with 5 mM concentration producing the highest germination count while 10 mM recorded the highest in KNO3. The DNA concentration of the cucumber radicle that produced these highest germination percentage are: GA3 (47.40 ng/l), BAP (98.87 ng/l), KNO3 (103.23 ng/l) and Control (79.73 ng/l). The analysis of variance (ANOVA) showed that treatments are significant at p-value (0.0001) < 5% significant level for cucumber seed. The study recommends the use of 5 mM GA3 in germinating cucumber seeds.

 

Accepted: 19/02/2020

Published: 25/04/2020

 

*Corresponding Author

Okonwu, K.

E-mail: kalu.okonwu@ uniport.edu.ng

 

Keywords: growth stimulants; concentration; germination; cucumber seed

 

 

 

 

 

 

 


INTRODUCTION:

 

The germination of seed is said to follow a sequential manner starting with seed imbibition which triggers resumption of the metabolic activities therefore enforcing expression of the embryo and emergence of the radicle (Miransari and Smith, 2009; Nonogaki et al., 2010). Imbibition is a passive process and pressures caused by swelling are not sufficient to cause a rupture of the surrounding tissue. This is supported by the work of Mensah and Agbagwa (2004), who reported that embryo expansion is repressed by ABA in some physiologically dormant seeds, so that imbibition alone does not lead to complete seed germination. For complete germination, process of imbibition is followed by activation of hydrolytic enzymes, initiation of growth in the embryo, seed coat rupture and radicle emergence (Miransari and Smith, 2009). The different phases of germination are required for offshoot of seedlings and hence to achieve seedlings with quality yield and reduced disease attack; it is therefore necessary to hasten germination rate for early radicle emergence (Singh et al., 2001; Subedi and Ma, 2005).

Seeds have their different moisture requirements to achieve germination known as critical seed moisture content and once that critical level is achieved, the seed is then ready to initiate germination (Bewley et al., 2000). Finkelstein (2004) also added that this action will cause an increase in the volume of the seed, resulting to cracking of the testa which may differ from emergence of seedling as seen in Brassicaceae and Solanaceae. Major events after imbibition include DNA repair, initiation of respiration, mitochondrial repair, restoration of cellular integrity, synthesis of germination-related mRNAs and protein. (Nonogaki et al., 2010). The DNA content in the radicle tip cells of wild-type tomato seeds was reported to have increased prior to germination (Bino et al., 1992). Bewley et al. (2013) reported that initiation of DNA synthesis during germination is linked with DNA repair following imbibition of dry seeds and also comes before cell division that follows germination. Yanyan et al. (2018) further stated that the vigor of the seed can be marked by the time of initiation of DNA replication, moreover it takes a longer time for low quality seeds to achieve DNA repair prior to successful replication.

This research focuses on the germination and DNA studies of Cucumber (Cucumis sativus) seed treated with growth promoters.

 

 

MATERIALS AND METHODS:

 

The matured cucumber (Cucucmis sativus L.) seeds (Plate 1) were obtained from fruit garden Port Harcourt, Nigeria. The seeds were properly identified by the Curator at the Herbarium Unit of Department of Plant Science and Biotechnology, University of Port Harcourt. Viability test was carried out on the seeds to ascertain its viability; hence, non-viable seeds were discarded. The viable seeds were surface-sterilized with ethanol for five (5) minutes and rinse with distilled water. Germination studies of cucumber seeds were first carried out both under light and dark conditions.

The growth stimulants used in the study were gibberellic acid (GA3 350 g/mol), BAP (6-benzylaminopurine 225.3 g/mol) and potassium nitrate (KNO3 101.1 g/mol). The concentrations (1 mM, 5 mM and 10 mM) of these growth promoters were prepared, respectively. Water was used as the Control treatment. These concentrations were used to pretreat cucumber seeds with 20-seeds per batch. Each treatment was replicated five times. The seeds were germinated under room temperature of 25oC, monitored daily and the process lasted for 14 days. Germination percentage of seeds taken for each treatment. Also, the DNA concentration of the radicle with the highest germination count across treatments were assessed using a Quick DNA miniprep kit for isolation of the total DNA from the radicle sample of cucumber ensuring that there was no contamination with RNA.

The data obtained from the study were subjected to statistical analysis using SAS 9.1.3 version.


 

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Plate 1: Cucumber seeds

 

 


RESULTS:

 

The percentage germination of cucumber seeds germinated under light and dark conditions are presented in Figure 1. The light condition promotes the germination of cucumber seed than under dark condition. However, this is not statistically different at p-value (0.0001) > 5% significant level.

The percentage germination of cucumber seeds treated with different concentrations of GA3, BAP and KNO3 are presented in Figure 2. The study showed that percentage germination of cucumber was enhanced by GA3 and BAP concentrations when compared to the Control except KNO3 concentrations. Across the treatments, GA3 gave the highest germination percentage followed by BAP with 5 mM concentration producing the highest germination count followed by 10 mM for GA3 and BAP treatments.

The cucumber radicles of Treatments with the highest percentage germination were analyzed for DNA contents as shown in Figure 3. There is no positive trend between highest percentage germination and DNA contents in cucumber radicles. Seeds treated with 5 mM GA3 gave 72% germination and DNA content of 47.40 ng/l; 5 mM BAP gave 70% germination with DNA content of 98.87 ng/l; 10 mM KNO3 gave 44% germination with DNA content of 103.20 ng/l while Control gave 50% germination with 79.73 ng/l DNA content. The results indicated generally that treatments with low percentage germinations (KNO3 and Control) have higher DNA contents while treatments (GA3 and BAP) with high percentage germinations gave lower germinations. The analysis of variance (ANOVA) showed that treatments are significant at p-value (0.0001) < 5% significant level for cucumber seed. Also, the multiple comparisons using least significant difference (LSD) showed that the Control is significantly different at 5% significant level from GA3.


 

 

 

 

 

 

 

 


DISCUSSION:

 

The findings (Figure 2) indicated that GA3 and BAP enhanced percentage germination compared to the Control. KNO3 treatments did not enhance germination, as the germinations are comparable to Control treatment. The effects of GA3 and kinetin in enhancing germination of dormant and non-dormant seeds are well documented (Miyoshi and Sato, 1997; Mensah and Agbagwa, 2001; Zeb et al., 2018) and supported the findings noted in this study.

This study did not observe positive trend or relationship between highest percentage germinations and DNA contents, indeed the reverse appeared to be the case, that is, treatments with low germination gave high DNA contents and those with high germinations, except 5 mM BAP that gave 70% germination and recorded DNA content of 98.87 ng/l. Gibberellin and kinetin have been extensively reported to play a role in RNA and protein synthesis, hydrolytic enzymes, substrate mobilization and elongation of embryo axis in dormant and non-dormant seeds (Chrispeels and Varner, 1967; Pinfield and Stobart, 1969; Jones and Armstrong, 1971; Varner and Ho, 1976; Jones and Jacobsen, 1982; Vishal and Kumar, 2018). The study of the action of GA and kinetin has focused on those molecular events that lead to de novo protein synthesis (Jones, 1973; Jacobsen et al., 1979; Jones and Jacobsen, 1982). The same suggestions or arguments cannot be inferred in this study because treatments (Control and KNO3) gave high DNA contents. However, it could be suggested that GA and kinetin rather than act on the molecular level through de novo synthesis, may act through the release of pre-formed enzymes (hydrolases) in enhancing germination. It is suggested that further work need to be undertaken to clearly establish the relationship between the hormone enhancement of germinations and its molecular action.

The fact that GA3 and BAP effectively enhanced germination is important for early emergence to avoid attack or damage the growing seeds may encounter during unfavourable conditions (Singh et al., 2001; Subedi and Ma, 2005). According to Bewley et al. (2013), treated seeds initiate imbibition rapidly and therefore hasten the phase II duration, making the interval between hydration and radicle emergence short. Yanyan et al. (2018) reported that the vigour of the seed can be marked by the time of initiation of DNA replication, moreover it takes a longer time for low quality seeds to achieve DNA repair prior to successful replication. Gibberellic acid regulates the production of numerous enzymes by activating the aleurone cells, notably alpha-amylase in growing cereals (Miransari and Smith, 2014).

 

 

CONCLUSION:

 

The study reveals that GA3, BAP and KNO3 enhanced germination of cucumber seeds with 5 mM concentration of GA3 and BAP been the concentration with highest germination percentage while 10 mM for KNO3 treatment. Control treatment had higher germination count than KNO3 treatment. The DNA concentration of the cucumber radicle depends on the chemical used in treating the seeds of cucumber and there is no clear relationship or trend between treatments and DNA contents.

 

 

REFERENCES:

 

Bewley JD, Hempel FD, McCormick S and Zambryski P (2000). In: Buchanan BB, Gruissem W, Jones RL, (eds). Biochemistry and Molecular Biology of Plants. American Society of Plant Physiologists, Rockville, MD; Pp. 9881403.

Bewley JD, Kent J, Bradford K, Hilhorst H and Nonogaki H (2013). Seeds: Physiology of Development, Germination and Dormancy, 3rd Edition. Springer New York; Pp. 1-399.

Bino RJ, De-Vries JN, Kraak HL and Van-Pijlen JG (1992). Flow cytometric determination of nuclear DNA replication stages in tomato seeds during priming and germination. Annals of Botany; 69: 231-236.

Chrispeels MJ and Varner JE (1967). Gibberellic acid-enhanced synthesis and release of α-amylase and ribonuclease by isolated barley aleurone layers. Plant Physiol., 42: 398-406.

Finkelstein RR (2004). The role of hormones during seed development and germination. In: Davies, P.J. (Ed.), Plant Hormones: Biosynthesis, Signal transduction, Action! The Netherlands, Kluwer Academic Publishers, Dordrecht. Pp. 513537.

Jacobsen JV, Higgins TJV and Zwar JA (1979). Hormonal control of endosperm function during germination. In The Plant Seed. eds. I. Rubenstein, B. G. Gegenbach, R. L. Phillips and C. E. Green. Academic Press, New York, pp. 241-262.

Jones RL (1973). Gibberellins: their physiological role. Ann. Rev. Plant Physiol. 24: 571-598.

Jones RL and Armstrong JE (1971). Evidence for osmotic regulation of hydrolytic enzyme production in germinating barley seeds. Plant Physiol., 48: 137-142.

Jones RL and Jacobsen JV (1982). The role of endoplasmic reticulum in the synthesis and transport of α-amylase in barley aleurone layers. Planta 156: 421-432.

Mensah SI and Agbagwa IO (2001). The responses of seeds of Capsicum frutescens L. to the exogenous application of some growth promoters. J. Agric. Biotechnol. Environ., 3: 37-47.

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Miyoshi K and Sato T (1997). The effects of kinetin and gibberellin on the germination of dehusked seeds of Indica and Japonica rice (Oryza sativa L.) under anaerobic and aerobic conditions. Annals of Botany, 80: 479-483.

Nonogaki H, Bassel G and Bewly J (2010). Germination still a mystery. Plant Science, 179: 574-581.

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Yanyan LV, Qing MO, Alison AP and Yanrong W (2018). DNA replication during seed germination, deterioration and its relation to vigor in alfalfa and white clover. Crop Science; 58(3): 1393-1401.

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Cite this Article: Mensah, SI; Ejeagba, PO; Okonwu, K (2020). Effects of GA3, BAP and KNO3 on the Germination and DNA Content of Cucumber (Cucumis sativus L.). Greener Journal of Agricultural Sciences 10(2): 57-62.

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