the germination of seeds of the native plant acacia

The Germination of Seeds of the Native Plant Acacia decurrens Practical Report Biology 1 Introduction: In a botanical sense, “germination is the process of emergence of growth from a resting stage. ” (http://encyclopedia. laborlawtalk. com/germination). Under favourable conditions, the seed begins to germinate, and the embryonic tissues resume growth, developing towards a seedling. Soils from a Cumberland Plain Woodland community were investigated to determine the presence of a soil seed-bank; and whether species richness and abundance of plants germinating from it were affected by heating such as that experienced in a fire.

It was found that certain seeds reacted differently, and he the phsyical action of heating, whether at low or high temperatures affected the rate at which the seeds germinated. (Hill & French 2003). Acacia seeds will not usually germinate without the use of a pre-treatment. As they have a hard outside coating which is generally impermeable to water. For Many Acacia seeds the breaking of the dormancy occurs with heat and although smoke and ash stimulate seed germination for many species with hard coats, heat is the main factor influencing the germination of Acacia decurrens.

In the natural environment, the hard coating of the Acacia seeds may be broken down due to a bush fire allowing the plant to begin rejuvenation (Hill & French 2003). The intention for this experiment was to determine whether the effects of heat increased or decreased the rate at which Acacia decurrens germinated. The hypothesis to be tested is; “If the Acacia decurren seeds are exposed to heat, then the rate at which they germinate will be increased. ” Hypothesis: If the Acacia decurren seeds are exposed to heat, then the rate at which they germinate will be increased.

Experimental Design and Method: The main utensils used in this experiment were the assortment of 60 Acacia decurrens seeds, cotton wool and 2 petri dishes, which were all supplied by the university. The seeds appeared to be a random sample, differing in shape, size and form. The decision to randomly select and divide the seeds into four groups of 15 was made. These 4 seed groups were placed into the four separate petri dishes and were titled Heated 1 & 2, and Control 1& 2.

In order to determine the effects of heat, the experiment needed a control group of non heat treated seeds, and also for the experiment to be duplicated to observe whether it was through the purposeful actions which the seeds were subjected to that may cause germination or whether external or uncontrollable factors also caused the seeds to germinated. Therefore of the four seed groups, both Heated 1 & 2 would be subjected to heat treatment process and the Control groups would be used as a standard by which to compare experimental observations.

The Heated 1 & 2 groups of seeds were placed into beakers, and had potable boiling water poured over them. They were then left submersed in this water [which eventually cooled to room temperature] for a period of 24hrs. The remaining 2 Control groups of seeds, were soaked the in same way but soaked in cold water and again left for 24hrs. All four beakers were filled so that the seeds were fully immersed and covered over by the water.

After 24 hours, each group of seeds were placed into 4 separate Petri dishes. Each Petri dish was covered in a layer of cotton wool, which was moistened with potable water. This moistening of the cotton wool pieces was repeated numerous times daily or whenever wool piece was seen to become dry. The Petri dishes were labelled: Heated 1, Heated 2, Control 1 and Control 2. The seeds were checked once daily for 10 days to take specific note of germination progress, or of any change in physical appearance.

Daily observations were recorded in a diary and then placed into a table of results featured below. Results: Effects of heat on Acacia Decurrens | No. Germinated| No. did notGerminate| First sign ofGermination| % seeds thatGerminated | Heated 1| 9| 6| Approx. 96hrs| 60%| Heated 2| 11| 4| Approx. 72hrs| 73%| Control 1| 0| 15| 0| 0| Control 2| 0| 15| 0| 0| Both Heat treated groups 1 & 2 had seeds that germinated within 3-4 days of receiving this heat treatment. This averaged the amount of 66. % of the total seeds germinated. In contrast both Control groups that were not subjected to any form of heat treatment but were still soaked in cold water did not show signs of germination at all within the 10 days time limit. Discussion: The results of the experiment demonstrate that if Acacia decurrens seeds are subjected to the heat treatment by placing the seeds in boiling water and leaving them in that same water for a period of 24 hours, then the rate at which the seeds germinate will be affected.

It can be suggested that this increased germination rate occurs because the boiling water, by which the seeds were soaked in, breaks down the hard coating on the outside layer of the seed, thus allowing the seedling to penetrate through the coating and begin the germination process. This controlled experiment is a simulated example of what might happen during a bushfire, when after the fire is put out most of the vegetation begins to rejuvenate due to the fact that the heat from the fire it self, has increased the rate at which certain seeds including the Acacia Decurrens germinate.

Furthermore, for a more scrupulous analysis of this subject, the experiment performed ideally should be repeated a number of times which include a higher variety of climatic conditions. This would allow for further investigation into the exacting factors and specific limits which affect the seed germination process. Moreover, the time span in which the seeds are observed should also be increased. These differing aspects would allow for a more accurate report and examination on the effects of heat treatment on the Acacia decurrens seeds.

Conclusion: Through the results collated it is evident that the hypothesis of; If the Acacia decurrens seeds are exposed to heat, then the rate at which they germinate will be increased, is in fact true. As mentioned above, the hard outer layer of the Acacia decurrens seed means that germination of this seed is difficult without the subjection to some form of heat. In this instance the heat source was from boiling water, but other heat treatments may also increase this germination rate. References: * Auld, T.

D. , O’Connell, M. A. (1991) Predicting patterns of post-fire germination in 35 eastern Australian Fabacaeae, Australian Journal of Ecology 16, 53-70 * Hill SJ ; French K (2003) Response of the soil seed-bank of Cumberland Plain Woodland to heating, Austral Ecology 28, 14-22(9) * Dictionary. Oxford Dictionary of Science Fourth ed (2003) Oxford University Press Inc. New York * Dictionary. Labour Law Talk (2005) Available at http://encyclopedia. laborlawtalk. com/germination (accessed 01/04/2008)

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