The Effect of Seed Sources Variation and Presowing Treatments on the Seed Germination of Acacia catechu and Elaeocarpus floribundus Species in Bangladesh
The seed germination of seed sources and presowing treatments of Acacia catechu and Elaeocarpus floribundus seeds were conducted in the nursery of Bangladesh Agricultural University. The seeds were collected from matured and healthy trees from four different locations in Bangladesh and treated with six presowing methods. The germination test was conducted in polybags with a mixture of topsoil and cow dung in a ratio of 3 : 1. The results of ANOVA showed no significant differences among seed sources but statistically significant differences among the presowing treatments for both species. Thus the presowing methods affected the germination process of seeds, and then the highest germination success was found to be 91.26% in hot water (80°C for 10 min), treatment in Acacia catechu and the highest germination success (89.81%) of Elaeocarpus floribundus was found in H2SO4 treatment followed by 86.35% and 78.42% in treatments with hot water (100°C for 12 min) and scarification. The study also revealed that the interactions between seed source variation and presowing methods effect significantly differed in seed germination percentages. Therefore, it is concluded that hot water treatment can be suggested on seed germination of both species for developing nurseries and rural Bangladesh.
Seeds provide the most natural resources of plant reproduction, preservation of genetic variability, transportation, and propagation of flora. Though, viable seeds do not germinate even under favorable environmental conditions for many cases; this phenomenon is termed seed dormancy . Several internal factors cause dormancy which includes seed coat, embryo, or inhibitors, which influence the seed germination rate . To overcome these factors, different pretreatment methods have to be adjusted to individual species and seed lots depending on the type of plant species and dormancy. Physical dormancy is caused due to water-resistant seed coat or fruit enclosure which stops imbibition and sometimes also gaseous exchange. It may be overcome either by pretreatment methods of scarification of the seed coat by piercing, nicking, clipping, filing, or burning with the aid of knife, needle, hot wire burner, or abrasion paper ; by hot water treatment [4, 5]; or by acid treatment .
Acacia catechu Willd. (locally known as Khair), a member of the family Mimosaceae, is a medium sized deciduous tree which grows up to 15 m in height. The brown, beaked seed pods of A. catechu are 50–125 mm long on a short stalk and contain between four and seven seeds, which are dark brown, flat, and 5–8 mm in diameter . A. catechu is the principal source of tannin, one of the most highly valuable forest products presently traded internationally . It is found growing in both natural and plantation forms in Bangladesh and it is also found throughout India, Sri Lanka, Pakistan, Southeast Asia, and South China . It is found in tropical savannah, dry deciduous forests, and arid steppe climates. It is a valuable bioresources and multipurpose tree species. The heartwood of the tree is mainly used for extracting Katha and Cutch (decoction obtained after filtration); Cutch is used for tanning leather and as dye to a great extent. After that, Cutch is used as adhesive in plywood industry and it is also used in preparing polishes and paints . The wood is durable and widely used by the inhabitants for house building material as poles and to prepare furniture. A. catechu has a great socioeconomic importance and it has tremendous ecological significance. Because of its leguminous nature and soil binding abilities, it could be a suitable species for wasteland development . However, poor seed germination, due to seed dormancy of this species, restricts plantation programs. Other tree species of Elaeocarpus floribundus Blume belong to the family Elaeocarpaceae, which is an evergreen moderate sized tree with spreading crown and clean bole of 12 to 16 m length. The seed of E. floribundus is a stone-3 celled, each having a spindle shaped seed, and despite hard seed coat (stone), the seeds are recalcitrant . E. floribundus usually grows on hill slopes and ridges with sandy to clay soils and occurs in the forests of Chittagong, Chittagong Hill Tracts, Cox’s Bazar, Sylhet, and Mymensingh districts in Bangladesh, but it can also be seen in India, Indo-China, Thailand, Malaysia, Philippines, and Indonesia. Its fruits are edible, which are used for pickle and also have medicinal value for treating several diseases . The wood of E. floribundus is used for light interior construction and plywood. It is suitable for the manufacture of particle board, fiberboard, and paper pulp . But seed germination rates of this species are usually very low due to seed dormancy (personal contract with the nursery owners).
Large scale plantations in agroforestry, social forestry, and home gardens are limited due to poor seed germination and deferred nursery establishment [12–14]. Seed treatment can ensure success in both seed germination and germination speed and guarantee that germination procedures are quick and homogeneous [15, 16]. The effects of pretreatments on seed germination of some tropical forest tree species have been reported by Ahamed et al. , Matin and Rashid , Ali et al. , Koirala et al. , Khan et al. , Alamgir and Hossain [22, 23], Azad et al. [24, 25], and Matin et al. . A good planning and profitability of forest nurseries depend on the proper techniques that gear up the germination process and attain a more dependable germination seed sown [20, 22]. Suitable presowing techniques of seed germination can enhance the germination rate and overall process [24, 25]. After that, tree species of A. catechu and E. floribundus are distributed throughout the country. Thus, variation in seed sources is very important for seed germination and seedling growth when seeds are selected for further use in afforestation, reforestation, and breeding programs in the country. Seed collection from suitable locations can enhance the germination procedure and thereby speed up plantation programs. Similar studies have been reported by Sneizko and Stewart  in Acacia albida, Vakshasya et al.  in Dalbergia sissoo, Nautiyal et al.  in Quercus leucotrichophora, Bhat and Chauhan  in Albizia lebbeck, Close and Wilson  in Eucalyptus regnans, Esen et al.  in Prunus serotina, and Shivanna et al.  in Pongamia pinnata. Therefore, the objective of the study was to recognize the effects of seed source dissimilarity on different aspects of seed germination and to determine the best presowing seed treatment that will ensure their main germination process within the shortest period of time at the nursery stage.
2. Materials and Methods
2.1. Study Area
The experiment was conducted in the nursery of Bangladesh Agricultural University, Bangladesh. The geographic position of the study area is situated between 24°44′N and 90°24′E. The climate of the study area is known as subtropical in nature, like the other part of the country. The experiment was done in January–July 2013. The air temperature ranged between 26° and 32°C and the relative humidity was 65%–80% during the experiment.
2.2. Seed Collection and Growing Media in the Experiment
The seeds were collected from 15- to 25-year-old matured and healthy trees from four different locations in Bangladesh (Table 1). All seeds were dried in the sunlight and then stored in airtight polybags till the treatments were applied. The collected seeds were checked to remove the discolored, damaged seeds. Healthy dried seeds were used for the experiment. The germination trial was carried out by sowing the seeds in 4 cm × 6 cm polybags, in a medium of topsoil and cow dung in the ratio of 3 : 1. Then the beds were laid in a systematic order and it was made with a slightly above from the ground surrounding areas so that water could not remain for a long time. Polybags were filled with soils and composts. Then the good and healthy seed was sown in each polybag after applying presowing treatment. One seed was sown in each polybag at a depth of 0.5–1.5 cm. Polybags were kept in the shade throughout the experiment and watering was carried out manually once a day.
2.3. Experimental Design and Treatments
Randomized Block Design (RBD) with four replications was used for the experiment. The treatment combination consisted of two factors, namely, seed source/location and presowing methods. In support of each presowing method 384 polybags (for A. catechu) and 320 polybags (for E. floribundus) were used for four different seed sources designated as L1, L2, L3, and L4. Thus, the total number of polybags used for seed germination was 2304 for A. catechu and 1920 for E. floribundus. There were six presowing methods in the experiment as follows:(S1)control (seeds provided no treatment);(S2)seeds immersed in hot water (80°C) for 10 min, followed in cold water soaking for 24 h;(S3)seeds immersed in cold water (4°C) for 24 h;(S4)seeds immersed in hot water (100°C) for 12 min, followed by cold water soaking for 24 h;(S5)seeds immersed in concentrated H2SO4 (80%) for 20 min;(S6)scarification with sand paper.In total, there were twenty-four treatment combinations and were denoted as follows: T1: S1L1; T2: S1L2; T3: S1L3; T4: S1L4; T24: S6L4.
2.4. Determination of Seed Germination
The number of seeds germinated in each treatment was recorded regularly. The starting and closing dates of seed germination were also recorded. At the end of the germination period, the germination percentage and rate of germination  were calculated using the following equations: that is, where is the germination percentage, the number of germinated seeds, the total number of seeds planted, and the rate of germination.
2.5. Data Analysis
Seed germination data were statistically analyzed by using computer software SPSS version 20 to explore potential treatment variations. Analysis of variance (ANOVA) and Duncan Multiple Range Test (DMRT)  were carried out to analyze the data. The ANOVA was carried out to determine the effect of variation in seed source (L), presowing method effect (S), and interaction (S × L) on starting and closing dates of germination, germination periods, germination percentages, and rates of germination. DMRT was conducted to compare mean germination closing dates, germination periods, and germination percentages of the effect of different presowing methods.
3. Results and Discussion
3.1. Effects of Variation of Seed Sources on Seed Germination
Germination started somewhat earlier from the seeds originating in L2 for Acacia catechu and Elaeocarpus floribundus than from other sources (Table 2). Germination closed later in L4 for Acacia catechu and L3 for Elaeocarpus floribundus than in the others. In the case of Acacia catechu, the highest germination success was found at 56.15% in L1 () and the lowest was 49.05% in L4. In another case, Elaeocarpus floribundus, the highest germination percentage was shown at 47.43% in L1 () and the lowest was 40.44% in L2 (Table 2). The results of ANOVA showed no significant differences () in starting dates and closing dates in germination, germination periods, germination percentages, and rates of germination among seed sources.
3.2. Effect of Presowing Treatments on Seed Germination of Acacia catechu
Seed germination started in advance for the seeds immersed in hot water (80°C) for 10 min (S2) than other treatments, followed by cold water soaking for 24 h (S2) than other treatments. Germination closed later in the control (S1) and cold water treatment (S3) () than in hot water (80°C) for 10 min (S2) and immersion in concentrated H2SO4 (80%) for 20 min (S5) treatments (Table 3). It took an average of 8 days to complete seed germination in the hot water (80°C) and germination was completed within 5–16 days after sowing the seeds collected from all sources (Table 3). The highest germination success (91.26%) in hot water (80°C) for 10 min, followed in cold water soaking for 24 h treatment (S2), differed significantly () with the lowest germination success (69.58%) in the control treatment (S1). DMRT showed no significant difference () of seed germination among the treatments of S1 (69.58%), S3 (74.22%), S4 (80.67%), and S5 (73.15%), but these differed significantly () from S2 (91.26%) and S6 (85.94%) (Table 3). There was no significant difference () between the treatments of S2 and S6 (Table 3). The cumulative germination success (%) of A. catechu under control (S1) and the highest germination of hot water (80°C for 10 min) treatment (S2) was shown in Figure 1. After that, ANOVAs showed no significant difference () in germination starting dates and rates of germination among the treatments but there were significant differences () in germination closing dates, the germination periods, and germination percentages for presowing methods effects (Table 4). The interactions between seed source variation and presowing methods showed no significant differences () among starting dates, periods, and rates of germination, but it did show significant differences () among germination closing dates and germination percentages (Table 4). The germination percentage of these interactions for A. catechu was also shown in Table 5.
That means from the consideration of germination period, germination percentage, and rate of germination the best treatment for A. catechu is S2 treatment. The main reason behind the successful germination of S2 is that seed of A. catechu might require hot water in the first time to break the dormancy and after that soaking in cold water for 24 h in second time makes the seed coat softer, which ensures the maximum successful germination of seed. Azad et al.  reported highest germination (52%) in hot water treatment in A. lebbeck may be due to the variation of seed coat thickness. The difference of seed germination success may be due to the variation of boiling time and temperature applied. Sajeevukumar et al.  carried out an experiment on seed dormancy and germination on Albizia falcataria and A. procera and found that hot water treatments by 40, 60, 70, and 80°C significantly increased germination in these two Albizia species. Bowen and Eusebio , Koffa , and Diangana  conducted experiments on A. falcataria and obtained similar results. It may be due to the fact that imbibition can be almost completed at higher temperatures, although sometimes poor germination responses occurred in a hot water treatment which was sensitive to the embryo . The present study clearly shows that the seed coat of A. catechu softens when immersed in hot water (80°C for 10 min), followed in cold water soaking for 24 h. Azad et al.  found 69% germination success in hot water (80°C for 10 min) treatment on Melia azedarach. It may be due to the difference of seed coat thickness. Ali et al.  carried out an experiment on hot water treatment (50°C and boiling for 3 min) on A. procera and found 43% seed germination.
3.3. Effect of Presowing Treatments on Seed Germination of Elaeocarpus Floribundus
Seed germination started earlier for the seeds immersed in concentrated H2SO4 (80%) for 20 min (S5) than other treatments. Germination closed later in hot water treatment (80°C) for 10 min (S2) and scarification with sand paper treatment (S6) () than other treatments of immersed in hot water (100°C) for 12 min (S4) and immersed in concentrated H2SO4 (80%) for 20 min (S5) (Table 3). The shortest period required for germination was observed in S4 (10–31 days) and S5 (9–30 days), and the longest period of germination was observed in S2 (11–33 days). The highest germination percentage was found in S5 (89.81%) followed by S4 (86.35%) and S6 (78.42%) and the shortest germination percentage was found in S2 (68.19%). From DMRT, it was also found that seed germination percentages were significant differences () of H2SO4 treatment with other treatments (S1 (72.16%), S2 (68.19%), S3 (74.42%), and S6 (78.42%)), but no significant difference () was found between hot water (100°C) for 12 min (S4) and concentrated H2SO4 (80%) for 20 min (S5) treatment (Table 3). The cumulative germination success (%) of E. floribundus under control (S1) and the highest germination of H2SO4 treatment (S5) and hot water (100°C for 12 min) treatment (S4) were shown in Figure 2. After that, ANOVAs showed no significant difference () in germination starting dates and periods among the treatments but there were significant differences () in germination closing dates, percentages, and rates of germination for presowing methods effects (Table 4). The interactions between seed source variation and presowing methods showed no significant differences () among germination closing dates and periods, but it did show significant differences () among germination starting dates, percentages, and rates of germination (Table 4). The germination percentage of these interactions for E. floribundus was also shown in Table 5. Azad et al.  found a similar result in 80% concentrated H2SO4 treatment for 20 minutes (84%) on presowing treatment effect on the seed germination of Xylia kerrii in Bangladesh. Pipinis et al.  noted that concentrated sulphuric acid treatment proved more effective in breaking dormancy. Consequently, Ren and Tao  reported that concentrated sulphuric acid treatment recorded superior germination rate in Calligonum species compared to scarification treatment. We also showed that several authors have argued that different methods of presowing treatments to break the seed dormancy increase the germination rate and speed up the germination process [22–25, 40, 41, 44].
The present study revealed that there were differences in seed germination starting dates, closing dates, germination period, germination percentages, and rates of germination among the different seed sources, but variation in seed sources did not affect significantly () different aspects in the seed germination of A. catechu and E. floribundus. This may be due to variation in the microclimate among the seed sources which was very similar. Besides these factors, the subtropical climate conditions throughout the country help to adopt this species in Bangladesh. Azad et al.  carried out a similar study on seed germination of Albizia procera in Bangladesh and found no significant difference of seed germination among the seed sources. For establishing a nursery of particular species for predicting the maximum number of quality seedling with minimum cost, time, and labor, presowing treatments of seeds are essential. As a result, the forest department, nursery owners, farmers, NGOs, and researchers to know the effect of presowing treatments on germination and thereby they can apply these treatments to get best quality seedlings within the shortest period of time for large scale production of seedling.
Presowing seed treatments play a key role to enhance the seed germination under nursery condition. Among the presowing treatments, hot water immersion (80°C for 10 min and 100°C for 12 min) and acid treatment performed very well for both species. The best treatment of A. catechu was found by seeds immersed in hot water (80°C) for 10 min, followed in cold water soaking for 24 h. Effective presowing treatments of E. floribundus were shown by soaking in concentrated H2SO4 (80%) for 20 min and hot water (100°C) for 12 min that has no significant difference appeared. Though, the use of sulfuric acid techniques is somewhat risky and troublesome. Therefore, it is suggested to apply hot water treatment at 80°C for a period of 10 min for A. catechu and 100°C for a period of 12 min for E. floribundus in Bangladesh to get high seed germination success rates.
Conflict of Interests
The author declares that there is no conflict of interests regarding the publication of this paper.
I would like to thank Bangladesh Agricultural University for their permission of field works. I also thank the support staff of the forest nursery of Mymensingh, Bangladesh for providing help and cooperation during the experiment.
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