Expert Opinion on Environmental BiologyISSN: 2325-9655

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Research Article, Expert Opin Environ Biol Vol: 5 Issue: 1

Standardizing the Methods for Breaking Seed Dormancy to Enhance Germination of Gloriosa superba Seeds

Singh D1*, Mishra M2 and Yadav AS1
1Department of Botany, Govt. MVM, Bhopal, Madhya Pradesh, India
2Ecosystem Management & Tech Forestry, IIFM, Madhya Pradesh, India
Corresponding author : Dharmendra Singh
Department of Botany, Govt. MVM, Bhopal, Madhya Pradesh, India
Tel: 919098793083
E-mail: [email protected]
Received: August 19, 2015 Accepted: September 25, 2015 Published: September 30, 2015
Citation: Singh D, Mishra M, Yadav AS (2015) Standardizing the Methods for Breaking Seed Dormancy to Enhance Germination of Gloriosa superba Seeds. Expert Opin Environ Biol 5:1 doi:10.4172/2325-9655.1000123

Abstract

Standardizing the Methods for Breaking Seed Dormancy to Enhance Germination of Gloriosa superba Seeds

Studies on imposing seed germination in glory lily revealed that the seeds scarifies by GA3 treatment method was recorded to be the best treatment with maximum germination of 17.6 ± 1.2 seeds within a minimum time interval. Treatments of GA3 not only break the seed dormancy, but also promote the growth of plant. So, the seed treatment can be recommended as a nursery practice. The aim of this study was to enhance the germination rate of G. superba seeds which have a very low germination rate under normal conditions. Chemical scarification was very efficient in breaking dormancy and promoting germination.

Keywords: G. superba; Seed dormancy; Germination

Keywords
G. superba; Seed dormancy; Germination
Introduction
The seed has a pivotal role in human and animal nutrition and life. Many of the seeds, after distribution of mother plants or harvest do not germinate in optimal conditions due to a period of Dormancy. Seed dormancy is a physiological phenomenon in wild and crop plants, and is more common in wild plants than the crop plants [1]. There are two types of seed dormancy: Exogenous (seed coat dormancy) and Endogenous (embryo dormancy). Some seeds have hard seed coats preventing water absorption and the exchanges of gases. Without water absorption and gas exchange, germination would be impossible. There are several treatments to break dormancy for inducing germination. Scarification and Soaking are two pretreatment techniques that we have chosen to highlight. They are simple and effective and we use them for overcoming physical seed coat dormancy. The objective of a pretreatment is to open the seed coat in order to make the seed permeable to water and gases, without damaging the embryo and endosperm within the seed. Dormancy can be causing keep some plant species in particular environmental conditions, and one of the most important survival mechanisms in plants, is their ability to delay seed germination until conditions of the location and time be suitable for germination [2]. Thus the delay in seed germination is not a random and in many seeds in dormancy some morphological and physiological changes should be occur for germination [3,4]. These Seed dormancy is an innate seed property that defines the environmental conditions in which the seed is able to germinate [5]. An understanding of dormancy mechanisms is of ecological and economic importance. Seed dormancy and germination are regulated by a complex interaction of environmental, edaphic, physiological, and genetic factors [6]. The relationship between seed dormancy and the success of a plant as an agricultural weed is significant. Seeds vary extensively with respect to a degree, duration, and dormancy source. The existence of large seed populations with varying degrees and states of dormancy is the basis for the annual weed problem [7]. Seed germination studies are key tools in conservation programs because they can be used for management programs and species reintroduction [8]. Over the past 30 years, dormancy has been widely studied, but the regulatory principles behind changes in several types of dormancies remain unclear. To accelerate breaking seed dormancy, many methods have been applied in several studies [9]. Hormone supply method one of them. Gibberellic acid (GA3) is one of the hormones proposed to control primary dormancy by inducing germination [10]. Plant growth regulators such as GA3, chemicals, Such as sulfuric acid [11] and mechanical scarification such as hot water [12] have been recommended to break dormancy and enhance germination. An acid treatment method comes from natural method. In nature, Scarification occurs naturally when a bird swallows a seed that then passes through the digestive system. Acids eat through the tough seed coat. When the bird eliminates the seed it’s ready to germinate.
The seeds of G. superba are very hard, covered with a layer of dark red colored pulp. This protects the seed and prevents the loss of viability during storage [13]. Due to poor germination, plants propagated from seeds take 3–4 years to bloom.
Hence, the present investigation was contemplated with the objective of standardizing seed dormancy breaking methods to induce better germination of G. superba seeds.
Materials and Methods
Seed collection and processing
The seeds of G. Superba were collected using random sampling techniques from the forest area of Betul district of Madhya Pradesh in India. Seeds were separated from the undesired materials, on arrival at the laboratory and dry stored in a sealed plastic box at 5ºC with 10% seed moisture content.
Seed viability test
Viability of 3 replicates of 30 seeds/species was assessed using the tetrazolium chloride (TZ) staining technique [14]. Seeds were initially hydrated on plain agar for 24 h at room temperature before being scarified (away from the embryo axis) and placed in TZ solution at 30ºC and darkness for 24 h. Seeds were then cut in half and examined. Only uniformly stained red/dark pink embryos were considered ‘viable’.
Treatments to break seed dormancy
The seeds were surface sterilized by soaking in 5% sodium hypochlorite (NaOCl), solution for 5 min and subsequently rinsed thoroughly with sterilized water prior to applying any treatment.
Chemical stratification
In the chemical stratification treatment, a set of seeds was immersed in different concentration of sulfuric acid (H2SO4) for 30 min treatment time. Thereafter, the seeds were rinsed several times in clean distilled water and tested for germination.
Hot water treatment
The seeds treated were soaked in hot water at 100°C for about 15 minutes and air-dried before sowing according to Aleiro 2004 [15].
Mechanical scarification
In the mechanical method, the seeds were scarified by mechanical force. The selected seeds were rubbed against the rough surface of the sand paper until the slight exposure of the cotyledon of the seed and then seeds were tested for germination.
Treatment of growth regulators
The growth regulators that have proven very helpful in breaking certain types of dormancy are gibberellic acid (GA3). The aqueous solutions of this chemical should be used at room temperature. The concentration and length of treatment depends on the species to be treated. Seeds soaked in GA3 should be stirred occasionally and not rinsed afterwards, unless specified, but sown immediately. After this soaking, they can also be air-dried and stored for short periods and then sown or given a subsequent treatment.
Germination
Germination experiments were conducted using 3 replications of 30 seeds per treatment under in vivo condition. Seeds were placed on cotton bed moistened with 10 ml of distilled water in sterilized Petri dishes with 15 cm diameter. All dishes were sealed with a trip of parafilm to reduce water loss. Petri dishes were transferred to a germinator with alternate light/darkness (12h each) and temperatures of 20 and 8ºC respectively, and relative humidity of 70 to 75%. Germinated seeds were counted and removed every 24 h for 60 days. A seed was considered germinated when the tip of the radicles had grown free of the seed coat [16,17]. The % of germination was calculated as follows:
% Germination= {Germinated seeds/ Total no. of seeds} X 100
Statistical analysis
The results were subjected to analysis of mean, standard deviation and error as suggested by Panse et al. [18].
Results
Statistically significant differences were observed among the various dormancy breaking seed treatments for the characters observed (Table 1).
Table 1: Effect of different treatments on seed germination of G. superba.
Seed viability
Seed viability of G. superba was 57%, according to TZ staining. All treatments had a significant effect on the germination rate of the seeds.
Chemical stratification
Soaking seeds in different concentration of H2SO4 treatment did not show significant results on seed germination. However, no significant result in germination observed between seeds treated with H2SO4 concentration (30% and 98%) at time 30 min. Concentrate sulfuric acid reduced the germination due to charcoal preparation of hard seed coat and did not show healthy plant due high acid effect on the embryo.
Hot water treatment
Seed treated with hot water had 30% germination which higher than chemical treatment, but seed treated with hot water takes a long time for germination and provide unhealthy plant as compare others.
Mechanical scarification
Treatment with sandpaper was very effective in breaking seed dormancy (Table 1). Results indicated that the germination of seeds that were mechanically scratched with sandpaper significantly increased to 56.6% as compared to other treatments. In addition, seeds mechanically scarified with sandpaper had the minimum response time, but the method is time taking and required more hard work and labor.
Effect of growth regulators
The response of GA3 was depending on concentration of GA3 and a significant difference in germination was observed among seed treated with various concentrations (1, 2 and 5%) of GA3. As a whole different GA3 treatment conspicuously increases the germination rate and percentage. At higher concentration germination was increased at about 58.6 % plants at 5% of GA3 concentration within minimum germination time (Figure 1).
Figure 1: Growth of G. superba plant by seed after different treatment in different medium (A) Conc. Sulfuric acid (B) 30% sulfuric acid (C) Mechanical (D) Hot water and (E) GA3.
Discussion
The strong inhibitory effect of the seed coat on seed germination may be caused by several possible mechanisms, including mechanical constraint, prevention of water and oxygen uptake, and retention or production of chemical inhibitors [19]. The integument breaking or softening, for instance, is needed to remove dormancy imposed by seed coat hardness or impermeability. Dormancy is a condition where seeds will not germinate even when the environmental conditions (water, temperature and aeration) are favorable for germination. Poor and delayed seed germination in G. superba was reported and the germination was erratic, which took one month to three months. In the present study, various dormancy breaking treatments like soaking in hot and chemical and mechanical method was tried and the results revealed that the mechanical scarification by sandpaper had the highest speed of germination, which agrees with the report of [20] that seed dormancy resulting from an impermeable seed coat may be overcome by peeling off the coat. Germination must have occurred as a result of the partial exposure of the cotyledons of the seeds which permits the process of hydrolysis whereby hormones such as auxins and ethylene which could increase nucleic acid metabolism and protein synthesis are released [21]. In our current experiment, application of GA3 not only stimulated the germination of all seeds, but also reduced the germination time, when compared to the control treatment. This response was dependent on the concentration of applied GA3. GA3 is widely used to break dormancy of seeds of various plant species. It is reported that dormant seeds which require chilling, dry storage after ripening and light as a germination stimulator, are often treated with GA3 to overcome their dormancy [22]. Treatment with high concentrations of GA3 is effective in overcoming dormancy and causing rapid germination of seed. Patel and Mankad [23] also reported the effect of gibberellins on seed germination of Tithonia rotundifolia Blake. The maximum percentage of seed germination was at 500 ppm GA3. Venudevan et al. [24] optimized the dormancy breaking treatments for germination improvement of Gloriosa superba L. seeds.
Conclusion
In conclusion, it seems that the application of GA3 is more effective treatments than the any other ones. According to the obtained results from the present research, the higher concentration of GA3 could desirably promote seed germination rates as well as seedling growth of G. superba. Concentrated sulfuric acid or hot water can be used to pre-treat seeds in order to scarify or break the impermeable seed coat but this treatment destroy the embryo and reduce germination. Treatment with GA3 reliable and reproducible method to get high frequency seed germination. When compared to any other treatments, it is very simple and rapid one. Damaging and breaking possibilities of seeds are very low and percentage of seed germination was higher. Thus, this method can be adopted as a better alternative than the other treatments for a higher percentage of seed germination.
Acknowledgment
The authors are acknowledging to the principal of Govt. MVM, Bhopal and Director of CMBT for their encouragement and providing research facilities.
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