Germination Rate Of Different Seed Species Biology Essay

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Germination is the resumption of growth activity for plants from a resting mode commonly known as dormancy. Germination takes place when seeds are exposed to a germinating medium or warm, moist soil. It starts with the swelling of the seed after taking up moisture. The seed coat softens and ruptures to expose plumule and radicle. The latter grows downwards and forms the root system. Plumule grows upward in respect to gravity to form the stem part of a plant. In the early stages of plant, growth from seedling gets it nourishment from endosperm or cotyledons. Cytokinins enzymes promote cell division by mobilizing food reserves in the seed to develop the shoot and the root. The root starts absorbing nutrients from the substrate or germinating medium. The shoot starts to manufacture nutrients using light in photosynthesis together with water and carbon dioxide.

There are two instances of germination where cotyledons remains underneath the soil surface, hypogeous germination and others push above the soil surface, epigeous germination. In epigeous germination, cotyledons transform to green and act as the first leaves of the plant. They however, are not real leaves but act as food reserve for young plant. They support the seedling up to a point where new leaves are fully developed for proper photosynthesis to take place. Germination is considered complete after the plant has started to manufacture its own food and shed the cotyledons. The seedlings are capable of existing independently after germination is successful.

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In my germination experiment, I studied five seed species. I wanted to find out the percentage germination of different seeds species in ten days. The seeds were place in similar conditions that are optimum for germination. These seeds are then counted as they germinate. The number of germinated seeds is used to calculate the percentage rate.

Problem statement

Which plant seed has greatest germination percentage?

Do different species take different time to germinate under similar conditions?

Does size of the seed species affect the depth at which it should be planted?

In the germination rate experiment, I studied five seed namely: wheat, barley, corn, cabbage and carrot.

Hypothesis

The average sprouting time for different seeds is almost similar but differs according to their size and that carrot will germinate faster with highest percentage.

The goal of the experiment was to find germination percentage and average germination time of each seeds species.

Literature review

Several tests are done on seeds before they are sowed either on nurseries or directly on field. Seed tests are important in establishing the plant density. These tests include germination rate, germination percentage, viability, vigor test, seed health and seed purity (Bationo, Waswa, Okeyo, Maina, Kihara, 2012). Optimum conditions are required for seeds to germinate which include moisture, optimum temperature, oxygen and substrate (Schmidt, 2000). Accurate germination tests are very hard to conduct due to the expensive facilities required for controlled optimum conditions. Schmidt, noted that seed testing requires advanced seed laboratory, which are capable of performing major routine test using standards stipulated by international rules (2000). However, quick quality tests are done on simple practical conditions to act as guidelines for daily handling of seedlings.

The seed have embryo, which require optimum conditions to germinate. The embryo in seeds requires some nutrients stored in the seed to sustain germination for some time before it sprouts. Small seeds should be planted near the surface so that they may be able to sprout fast to the surface and get light (pessarakli 2001). Each plant species has unique requirements for light, temperature, moisture, oxygen and soil depth. The main factors can be generally achieved when seed germinate (Alexander, Knutson, Harrington and Bottomley, 2000). The depth becomes a challenge for smaller seeds due to little space by which they store nutrients in the endosperm for use by the embryo (pessarakli 2001). Smaller seed species can be placed shallowly to get optimum depth for them to sprout.

Experiment setup

I had following constants for my germination experiment: constant lighting conditions, constant moisture, constant temperature, same substrate for each kind of seeds, same number of seeds for testing same depth for holes.

My variable was seed species.

Materials in experiment:

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Twenty corn seeds

Twenty wheat seeds

Twenty barley seeds

Twenty carrot seeds

Twenty cabbage seeds

Five plastic transparent containers with lids

Approximately five hundred milliliters of distilled water in each plastic container

Substrate (potting soil)

Masking tape for labeling

Chart for recording my results

Procedure

All the seeds are soaked in water overnight first to break the seed dormancy in preparation for germination test. Labeling the five containers according to the seed species was important for better result collection. I labeled both the plastic containers and the lids. The containers and lids had some hole pricked to allow oxygen to enter into potting soil. I did place potting soil half way in all plastic containers. Twenty seeds of each species were put in the plastic containers that correspond with the labels. Poke twenty shallow holes in the soil while ensuring that they are of equal depth and evenly spaced in a grid-like format. Place a seed in each hole in four rows of by five. Remember to put twenty seeds of each species in correct plastic containers. Cover the seeds with soil by leveling the surface of the soil with hand. Water the soil in each plastic container with fifty milliliters of water.

Water was to be added again in twenty milliliters in each of the five plastic containers. All the containers were covered with transparent lid to conserve moisture for the firs two days. Observe the plastic containers every twenty-four hours for ten days and count the number of seeds that have sprouted in each plastic container. The shoot has to be visible to counted. Record the results on the chart in corresponding seed species. It should be noted all the plastic containers must be placed in similar environmental conditions indicated above as constants.

Results

I checked each of the five containers on periodical of 24 hours, count germinated seeds and recorded results on a chart. Seed counted as germinated if the shoot was visible. No germinated seeds were detected in the first four days. On the eighth day and ninth day of my experiment, no germinated seed was found.

Table 1: result of germination of seeds according to species

Number of Seeds Germinated

Day

Corn Seeds

Wheat

Seeds

barley Seeds

Cabbage

seeds

Carrot

seeds

2

 0

 0

 0

0

0

3

0

 0

 0

0

0

4

0

0

0

0

0

5

1

 0

 0

0

0

6

 2

 0

 0

0

0

7

 16

 14

 13

3

0

8

0

0

0

0

0

9

0

0

0

0

0

10

0

0

0

0

0

Percentage= (no. germinated seeds /20)*100

Most of the corn seeds germinated by day seven

Most of the wheat seeds germinated by day seven

Most of the barley seeds germinated by day seven

Few of the cabbage seeds germinated by day ten

None of the carrot seeds germinated by day ten

Corn germination percentage (19/20*20) 95%

Wheat germination percentage (14/20*20) 70%

Barley germination percentage (13/20*20) 65%

Cabbage germination percentage (3/20*20) 15%

Carrot had zero percentage.

Discussion

Corn seeds germinated first on fifth day while wheat, barley and cabbage seeds germinated on day seven. Corn had the highest percentage germination rate. Carrot did not germinate at all this was may be because I placed the seeds ant the same depth without regard to their sizes. Cabbage managed to have three seeds germinate which was a merely 15%. The optimum number of days for the seeds in my experiment was seven. However, corn seeds had some early germination perhaps because they had enough storage of nutrients for germination purposes. The soaking of seeds for a night may have caused the carrot and cabbage seeds to rot since most did not germinate. The reason for soaking the seeds was to remove seed dormancy and to activate the enzyme, which in turn increases respiration. Respiration is responsible for plant cells duplication. The tip of the root emerges first to enable plant to absorb the water. Shoot of a plant follows afterwards to enable photosynthesis to take place. The spouting of the shoot was my interest in this experiment.

Conclusion

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During the experiment, I leaned that seed size is very important factor in relation to depth at which seed should be buried in soil. Seeds germinated at the different percentages with regard to their sizes. Carrot did not germinate with the highest percentage rate as I had thought. The hypothesis was incorrect since some of the species did not even have a single germination. Bigger seeds can be buried deeper in the soil. With the same optimum germination conditions, size of the seeds is another factor of importance. The amount of nutrients in seeds should be able to last the seedling before it starts to manufacture its own food. The size corresponds with the amount of stored nutrients foe the embryo to use in the initial stages of germination.