The success of any tree planting activity will depend mainly on the knowledge,   availability of seeds and other planting materials needed. When, where, and how many seeds should be collected are the primary factors to be considered in the preparation and establishment of a nursery and in the production of planting stocks for plantation establishment. However, availability of seeds would be useless if dormancy and viability would be taken for granted.

Seed dormancy of different forest tree species seems to be an environmental adaptation to uncomplimentary conditions. In order for seeds to survive and sustain viability, dormancy would be primarily needed until conditions become favorable.Large number of seeds is often available in forest nurseries. However, dormancy of the seeds usually becomes a hindrance in forest nursery activities. Dormant seeds sometimes do not germinate when needed thus offsetting nursery schedules. 

METHODOLOGY

Description of seeds

1.      Samanea saman seed – oblong, laterally compressed, 1 cm long, 0.7 cm wide, and 0.5 cm thick.

2.      Parkia timoriana seed – black, oblong, 15-20 mm long and 8-10 mm wide.

3.      Acacia mangium seed – small, 2.5 mm long and 4 mm wide, hang by orange, fleshy funicules.

Breaking seed dormancy

1.      Scarification or cutting the seed coat

Ten (10) seeds of each specieswere scarified using a scalpel or blade. Scarification was done by cutting through a portion of the outer seed coat until inner tissues were exposed. The scarified seeds were placed on petri dishes with one (1) layer of filter paper moistened enough with 15ml of distilled water and then placed in the laboratory locker. The seeds were germinated at room temperature and germination percentage was recorded daily.

2.      Water Flotation + Blotter Test

In order for the resources to be maximized, twenty (20) seeds of each species were soaked in water for 1 minute before placing on petri dishes filled with 3 layers of filter paper, then subjected to blotter test in order to test seed health. Germination was carried out at room temperature.

3.      Hot water treatment

Twenty (20) seeds of A. mangium and P. timoriana were used. One set of ten seeds were soaked in boiling water for 1 minute before placing on petri dishes. There were two (2) replicates per treatment. Germination was carried out at room temperature and germination was recorded as percentage of the total number of disseminated seeds.

4.      Light quality treatment

Forty (40) seeds of Mangium were sown equally on 4 petri dishes lined with filter papers. 15 ml of distilled placed in each petri dish. There were two (2) replicates per treatment. The petri dishes were treated as follows:

a.       Dark – one set of Mangium was immediately placed in a dark cabinet.

b.      Blue – another set was wrapped with blue cellophane and placed under incandescent lamp.

c.       Red – third set was wrapped with red cellophane and placed under incandescent lamp.

d.      Far-red light – a fourth set was wrapped with red and blue cellophane and placed under incandescent lamp.

Testing for seed viability

            Ten (10) seeds of Acacia mangium were subjected to water – flotation test. The seeds were placed in cup of water for 1 minute. The seeds that descended are considered viable.

            For the biochemical methods, ten (10) Zea mays seeds were soaked in tap water for 1 hour then dissected into half longitudinally through the center of the embryo. The dissected seeds were completely immersed in 1% aqueous solution of 2, 3, 5 triphenyl tetrazolium chloride for another 1 hour. After the prescribed soaking hours, viable seeds were determined based on the presence of red to normal pink coloration in the embryos.

 Results and Discussion

The ability of the seeds to delay germination until favorable conditions are given is an important mechanism in order for the seeds to survive. Dormancy is due to physical and physiological mechanisms of the seed. It is maybe due to impermeability of oxygen and water or maybe due to immaturity of the embryo.

The methods of breaking seed dormancy are also the methods for accelerating seed germination. Different methods on breaking seed dormancy or accelerating the germination of the seeds were used. Results are summarized in Table 1.

Table 1.Summary of the effect of different methods of breaking seed dormancy and hastening the germination of seeds.

 Legend:

D = Dark

B = Blue

R = Red

FR = Far-Red

Physical scarification was discovered to be the one of the effective methods of breaking the dormancy of the seed as well as accelerating the germination for the majority of tree species used. Scarification was done to facilitate the entry of water and oxygen as well as to lessen the resistance of the seed coat to the developing embryo. For the seeds ofSamanea saman (Rain tree), percent germination was 35%while in Parkia timoriana(Kupang), germination percentage was 20% as compared to the 0% and 5% which was the recorded under water flotation method in combination with blotter test using the same species. Furthermore, about 60% contamination of S. saman was recorded underwater flotation and blotter test method.

Hot water treatment was found to be the most effective method of breaking the dormancy and accelerate the germination of Acacia.mangiumresulting to 85% seed germination in 14 days which is significantly higher compared to the seeds subjected to light treatment where no seed germinated. On the other side, percent germination of P. timorianasignificantly decreased to 15% as compared to scarification method. Also, 10% contamination was recorded only on one P. timoriana replicate.

Different light quality treatments namely red, blue, far-red, and dark (control) failed to hasten or at least break the dormancy of A. mangiumhaving 0% seed germination within the span of 14 days of observation which implies that the used method is not effective for the species tested.

Water-flotation of A. mangium seeds was observed after one (1) minute of dispersing seeds in a cup of water and seen that no seed floated which implies that all seeds subjected to the treatment are viable.

Ten (10) Zea mays seeds that were cut into half were subjected to 1% aqueous solution of 2, 3, 5 triphenyl tetrazolium chloride and presence of black coloration was observed on a half (1/2) seed, fading pink coloration was seen on one and a half (1 ?, and red to normal pink coloration appeared on 16 seeds implying that eight (8) out of ten (10) seeds can still be considered viable.

CONCLUSION

The methods that will be used on breaking seed dormancy will also be the methods for hastening seed germination. Different methods will yield different or maybe almost the same results depending on the set up and species used. Hence, selection of species will be primarily vital in conducting the said experiment.

Contamination was also recorded in two (2) treatments namely water flotation in combination with blotter test method, and only in one replicate of hot water treatment. Same species were used on the other methods but only these two (2) had shown contamination which indicates that the seeds used were not the onlysource of contamination. Aside from that, only one replicate of P. timoriana was contaminated which indicates that the way that the experiment was conducted was one of the primary sources of contamination. Therefore, subjecting seeds to water had increased the contamination rate as moisture increases.

Sources of photos:

www.shutterstock.com for the Parkia timoriana seeds

www.brazilplantseeds.com for the Acacia mangium seeds 

 ctahr.hawaii.edu for the Samanea saman seeds