Seed Germination, Dormancy, and Storage

Seed Germination, Dormancy, and Storage 1

_________________

I. INTRODUCTION Seeds role in the germination process is a critical part in the plant 's survival. This is practically true in almost all of the plants species (Copeland & McDonald, 1995). As germination is defined as "the emergence and development from the seed embryo of those essential structure", which, for the kind of seed in question indicates "its ability to produce a normal plant under favorable conditions"(Seed Germination, n.d.), this varies on different crops. The University of California Reagents (2005) said that the presence of warmth, moisture and air will allow the normal growth of the plant from seeds. However, through time and the frequent evolution of plants species, seeds develop diffirent defense machanisms for the protection of the seed. One of which is dormancy. Dormancy as normally defined is the ability of the seeds to delay germination even in the present of favorable conditions. This natural phenomenon on plants, are the ones used by seed scientists in the preservation of seeds to be use in the future. Seed storage allows the availability of seeds for future uses. Clawford stated that in the absence of mechanical scarification, seeds that are dormant remains "impermeable" yet still viable, this characteristics is an ideal in the seed atorage processes. Dessicants, like silica gel, sawdust, ash, and lime also helps in the maintenance of moisture that is critical in seed storage. This exercise is done in the need of determining the relationship between seed germination, seed dormancy and storage. It is also aimed in determining the effects of several factors in the normal growth of the plant starting from the seed up to its maturity.

II. OBJECTIVES After obtaining and finishing all of the activities on Exercise 8, the student should be able to:
1. Discuss some basic seed quality attributes including seed viability, dormancy, and moisture content.
2. Demonstrate some tests for seed viability.
3. Conduct some special treatments to break dormancy.
4. Explain the basic principles of seed storage.
III. MATERIALS AND METHODS
A. Demonstrations
Different demonstration set-ups are prepared subsequently for the exercise. Each student was required to observe the set-ups before proceeding to the activities.
Demo 1. Different test for seed viability
a. Use of different media in seed germination test
b. Tetrazolium test of a dicot and monocot seed
c. Floatation method
Demo 2. Storage of small quantities of seeds.
Use of desiccants: silica gel, sawdust, ash, lime and charcoal.
Demo 3. Seed moisture content demonstration

B. Activities
Activity 1. Germination pattern of a dicot and monocot seed Materials: 50 seeds of corn 50 seeds of soybean Two moistened filter paper Two polyethylene bags

The students were assigned to germinate 50 seeds for each of the chosen monocot (Zea mays) and dicot seeds (Glycine max). The students are then asked to observe and illustrate the germination pattern for each seeds everyday for 6 days.

Activity 2. Breaking dormancy of Leucaena leucocephala (Ipil - ipil) seeds
Materials:
200 seeds of ipil-ipil
Sand paper
Nail cutter
50 ° hot water
Container
Polyethylene bags The given seed lots of ipil-ipil was divided into four equal portions. Using 50 seeds per treatment, the following are done: a) rubbing on sandpaper, b) clipping, c) soaking in hot water, (50 degrees Celcius) for 10 minutes, d) untreated or control. For each treatment, a germination test called the rolled filter paper technique was conducted. Samples that were able to germinate are placed in polyethylene bags to conserve water.

The number of normal seedlings that sprouted on the week that follows is counted and the percentage (%) germination was computed using the formula,

Activity 3. Storage of orthodox and recalcitrant seeds
Materials:
Part A
50 seeds of 11% moisture content rice seeds
50 seeds of 20% moisture content rice seeds
Two moistened filter paper
Two polyethylene bags

Part B
24 seeds of freshly extracted cacao seeds
24 seeds of cacao seeds stored for one week
Sand
Two containers

a. Effect of initial moisture content on the storability of rice seeds 50 seeds that is dried up to 20% moisture content and another 50 seeds up to 11% moisture content are tested for germination using the rolled filter paper technique. These seeds are kept in polyethylene bags and allowed to germinate, replicated twice. Observations are then recorded on Worksheet 3.

b. Storability of recalcitrant seeds
Seeds are extracted from a cacao fruit. The freshly extracted seeds are consisted on the first treatment. The second treatment consists the seeds stored for one week. It was germinated using the sand as medium, replicated twice. Observations are recorded on Worksheet 3.

C. Visit to a Seed Storage Facility
V. RESULTS AND DISCUSSION

Table 1. Rapid viability test in corn and beans

TETRAZOLIUM TEST
Corn
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

7
1
1
1
0
1
1
1
0
0
1
2
1
1
0
1
0
0
Bean
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

15
0
0
0
0
0
6
0
2
1
0
0
1
0
0
0
0
0

Table 1 shows the result of TTZ in corn seed and beans. For corn, 7 seeds (most) are in No.1, wherein 15 of the bean sample were placed.

Worksheet 1.1 Germination pattern of a dicot and monocot seed.

A. Germination of a dicot seed
Scientific name: Glycine max
Type of germination: Epigeal germination

Figure 1. Germination pattern of soybean

In Figure 1, we can readily determine soybean 's germination type: epigeal. The radicle of the seed emerges during the second day and showed signs of leaf emergence only during the fourth day when the roots also starts to develop. During the fifth day up until the sixth, the seeds endosperm was already visible.

B. Germination pattern of a monocot seed.
Scientific name :Zea mays
Type of germination: Hypogeal germination

Figure 2. Germination pattern of corn

In corn, roots emerges on the second day until tge fourth day. It is only in the fifth day when the radicle emerged and grows until the last day. Because corn is known to be hypogeal, it can be observed that the seeds remain underground.

Worksheet 2. Breaking dormancy of Leucaena leucocephala seeds.

Table 2. Percent germination of Ipil-ipil seeds in different treatments
% GERMINATION
REPLICATION
Treatment
1
2
Average
Rubbing on sand paper
92
0
46
Clipping
38
10
24
Soaking in hot water (50°)
0
5
2.5
Control
34
0
17

In Table 2, different procedures on breaking down seed dormancy have been applied to practice.Without undergoing any treatment, ipil-ipil seeds carry out a 34% and 0% result with am average of 17%.Upon rubbing on sand paper, 92% and 0% of the seeds germinated respectively with an average of 46%. In clipping, an average of 24% from 38% and 10% germination rate. However, when the seeds are soaked in hot water, the least rate takes place, an average of 2.5% from 0% and 5%. This shows that the partial removal of seed coat, technically termed as scarification, seeds have a higher tendency to germinate.

Worksheet 3. Storage of orthodox and recalcitrant seeds.

I. Effect of initial moisture content on the storability of rice seeds.

Table 3. Percent germination of rice in 11% and 20% moisture content

% GERMINATION
REPLICATION
Treatment
1
2
Average
11% Moisture Content
82
96
89
20% Moisture Content
24
2
13

The initial amount of moisture in seeds also affects its ability to germinate. Table 3 shows that 11% moisture content rice seeds have an avarage of 89% germination from 82% and 92%. This average is higher than the results obtained in 20% moisture content rice seeds which only have 13% germination rate from 24% and 2%. Thus, rice tends to grow best when it has lower moisture content. It is an orthodox seed.

II. Storability of recalcitrant seeds.

Table 4. Percent germination of cacao seeds in two treatments

% GERMINATION
REPLICATION
Treatment
1
2
Average
Freshly Extracted Seeds
75
100
87.5
Stored for one week
0
0
0

Table 4 shows that cacao seeds are recalcitrant - seeds that need higher moisture content to germinate. Freshly extracted seeds when sowed have high germination percentage of 75% and 100% - an average of 87.5 % all in all. Those seeds sowed after being stored for a week, did not germinate any, 0% germination rate.
VI. REFERENCES
Copeland, L. & McDonald M. (1995). Fundamentals of seed science. (3rd ed.). Massachusetts: Chapman & Hall.
Dennis, F. (2002). Dormancy: Manifestation and causes. In Pessarakli, M. (Ed.) Handbook of plant and crop physiology. USA: Marcel Dekker

Garcia, J., Barker, D.& Etienne-Pascal J. (2006 November). Seed storage and germination. Retrieved March 9, 2014 from http://www.noble.org/Global/medicagohandbook/pdf/SeedStorage_Germination.pdf
The University of California Reagents. (2005 January). Germinating seeds. Series. Retrieved March 9, 2014 from http://intl.plantcell.org/content/9/7/1055.full.pdf

References: Copeland, L. & McDonald M. (1995). Fundamentals of seed science. (3rd ed.). Massachusetts: Chapman & Hall. Dennis, F. (2002). Dormancy: Manifestation and causes. In Pessarakli, M. (Ed.) Handbook of plant and crop physiology. USA: Marcel Dekker Garcia, J., Barker, D.& Etienne-Pascal J. (2006 November). Seed storage and germination. Retrieved March 9, 2014 from http://www.noble.org/Global/medicagohandbook/pdf/SeedStorage_Germination.pdf The University of California Reagents. (2005 January). Germinating seeds. Series. Retrieved March 9, 2014 from http://intl.plantcell.org/content/9/7/1055.full.pdf