Seeds – variation in form, development and sprouting. Lesson plan

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Seeds – variation in form,

development and sprouting

Lesson plan

Ilona Żeber-Dzikowska, Urszula Poziomek

dr hab. Ilona Żeber-Dzikowska: Department of Zoology

and Biology, Institute of Biology, Jan Kazimierz University of Kielce

Subject: Seeds – variation in form, development and sprouting.

This lesson is intended for post lower secondary school pupils pursuing an extended biology pro-gramme.

Teaching resources:

• pupil’s worksheet,

• seeds of various types of beans (broad bean, string bean) and grains, such as oats or wheat, poppy seeds, sunflower or pumpkin seeds.

• tweezers/group or pair,

• razor blade or scalpel/group or pair,

• Lugol’s iodine – one bottle for several groups,

• observation of secondary source materials – pipet-te/group or pair.

Reference:

• Manual,

• J. Kopcewicz, St. Lewak, ed., Fizjologia roślin, Wydawnictwo Naukowe PWN, 2005;

• T. Kopczewski, Allelopatia – czy rośliny potrafią się komunikować?, Edukacja Biologiczna i Środowiskowa, no. 3/2014, pp. 3-8;

• O. Andrzejczak, A. Gniazdowska, Tlenek azotu – podstawowe pytania i odpowiedzi dotyczące roli tej cząsteczki w regulacji wzrostu i rozwoju roślin, Edukacja Biologiczna i Środowiskowa, no. 4/2014. Duration of course: 2 teaching hours

Reference to the core curriculum

Educational aims:

I. Learning about the world of organisms at various levels of life.

III. Developing further knowledge in the area of rese-arch methods in biology.

IV. Searching for, using and creating information. V. Reasoning and arguing.

Teaching content:

8. Plants – reproduction. The pupil will:

3) (…) present the development and sprouting of seeds from angiospermous plants;

4) describe the main methods of seed dispersal (by air, water and animals) and indicate the relevant adaptations in the structure of the seed.

Form of teaching: learning activities in the classroom. Type of lesson: introduction of new material.

Classroom organization: work in pairs/groups Strategy: operational

Teaching methods: Observation:

• observation of secondary source materials,

• observation of primary source materials. Verbal:

• analysis of source materials,

• presentation of group work results.

Translation into English: Barbara Przybylska

mgr Urszula Poziomek: Science Section of Educational

Research Institute (IBE), biology teacher in LXXV Secondary School (Jan III Sobieski) in Warsaw

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Lesson plan:

2. Reference to the subject – pupils repeat informa-tion on the development of male and female game-tophytes, the structure of the ovule and embryo sac and the process of double fertilization (textbook, digital illustrations or posters).

II. Implementation:

I. Analysis of the morphology of the seeds of select-ed species of angiospermous plants. Using their worksheets, pupils will:

a) observe the structural elements of various types of seeds using primary source material (natural ob-jects).

b) compare the elements of the external structure of seeds and present this information in a compara-tive table.

c) draw conclusions about the similarities and differ-ences of the observed features.

II. Analysis of the anatomy of a bean seed in relation-ship to the structure of the ovule after fertilization. Using their worksheets, the pupils will:

• remove the seed coat and observe the internal stru-cture of the broad bean seed, which was previously soaked in water,

• compare the anatomy of the seed with the illustra-tion of an ovule before and after fertilizaillustra-tion, as well as after double fertilization.

• draw conclusions about the link between the spe-cific anatomical elements of both structures and complete the table describing the parts of the seed that develop due to the transformation of the ovule after fertilization.

• use a pipette to place a drop of Lugol’s iodine on the slightly scored (using a scalpel or tweezers) sur-face of one cotyledon of the bean seed and draw conclusions about the type of material stored in the cotyledons.

III. Analysis of the environmental conditions and the metabolic processes occurring when a seed sprouts.

Pupils analyze the source material provided in the worksheet.

III. Summary:

Summary of the work – presentation of results by a selected pair, the remaining pupils supplement this with additional information and, if necessary, correct any mistakes made by the presenters.

The teacher collects the completed worksheets and assesses the pupils’ work.

Homework

Mini-project carried out individually – multimedia presentation on the ways seeds disperse and the struc-tural adaptations of fruit which enable such dispersal (for example, dandelion, palm coconut, burdock, etc.). Pupils send their presentations to the teacher electroni-cally.

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Pupil’s worksheet

First and last name: ... class ...

1. Take note of the common and distinct features of the morphology selected plant species’ seeds (broad bean, string bean, grain, such as oats or wheat, poppy seed, sunflower or pumpkin seed). Use Figure 1 in your analysis.

2. Draw a table to record the information from your observations. Table 1.

3. Formulate two conclusions based on your analysis of the morphology.

1) ……… ……… 2) ……… ……… seed coat small opening (remainder of the micropyle)

scar from the funicle (hilum)

Fig. 1. External structure of a broad bean seed.

Source: „Biologia cz.2”, Roberts M, Wydawnictwo Szkolne PWN, Warszawa 2000, p. 140.

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4. Remove the seed coat from a previously soaked broad bean seed. Using Figure 2, analyze its anato-my.

5. Analyze the anatomy of the grain of wheat illustrated in Figure 3.

6. Do this exercise: lightly score the surface of the cotyledon of a broad bean (pea) seed with tweezers or a dissecting needle and place a drop of Lugol’s iodine on it. Write down the result of your observation, drawing a conclusion about the type of material stored in the cotyledons.

Result of the observation:

……… ………

Conclusion:

……… ………..

Fig. 2. The anatomy of a broad bean seed.

Source: „Biologia cz.2”, Roberts M, Wydawnictwo Szkolne PWN, Warszawa 2000, p. 140.

Fig. 3. Anatomy of a wheat grain.

Source: „Biologia cz.2”, Roberts M, Wydawnictwo Szkolne PWN, Warszawa 2000, p. 142. plumule radicle cotyledons plumule cotyledon radicle endosperm (contains starch) seed coat embryo

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7. Complete Table 2 using Figure 4 (structure of the ovule after fertilization) and Text 1.

Fig. 4. Double fertilization and the development of a seed.

Source: http://education-portal.com/academy/lesson/ovary-of-a-flower-function-definition-quiz.html, adapted.

Text 1

The seeds of angiosperm plants develop in the ovary as the result of the development of the ovules, which normally occurs after pollination and double fertiliza-tion. A typical seed consists of an embryo, endosperm, and seed coat. (...) The endosperm is a nutritive tissue for the developing embryo. The triploid (typically) nu-cleus of the endosperm stem cell usually divides before the first division of the zygote, so that the development of the endosperm somewhat precedes embryonic devel-opment. (...) The seed coat is an encasement, which de-velops from the integuments and protects the seed from excessive drying and damage. The walls of its cells are usually strong and cork-like, with a cuticle developing on the surface.

Source: A.Szweykowska, J.Szweykowski, Botanika. Morfologia, Wydawnictwo Naukowe PWN, 1996, Warszawa.

polar nuclei integuments

egg mature ovule sperm cells double fertilization zygote endosperm

ovule after fertilization

fruit / pericarp

embryo

endosperm 3n

seed coat fruit with seed

Complete Table 2:

Element of the seed

develops as the result of transformation

Element of the ovule

Seed coat

……… Plumule and radicle

………. Endosperm

……….

8. Answer, how do the broad bean seed and grain seed differ in terms of the storage of nutrient reserves required for the development of the embryo? ………

……… ……… ……… ……….

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9. Based on Figure 5 and 6, and your own knowledge, complete Table 3, describing the environmental conditions required for the seed to begin sprouting and the processes trig-gered by these conditions.

Table 3.

Environmental factor Process triggered

1. Aleurone starch is accumulated in the cotyledons or endosperm, water is imbibed by the embryo, the seed swells, the embryo receives water

2. The watered embryo releases gibberellins into the seed (GA – gibberellins)

3. The gibberellins cause the aleurone layer to release enzymes, such as amylase, which breaks down the starch

4. Glucose and other organic substances move to the embryo, enabling it to grow and develop during sprouting

Fig. 5 Phases of seed sprouting.

Source: N. Campbell, J. Reece, Biology, Pearson, 2005, p. 798.

phase I phase II phase III

sprouting time (hours) H₂O (mg . g-1 _{of seeds}

O₂ (nmol . min-1₎

sprouting (%)

Fig. 6. Relationship of seed sprouting to the absorption of water and oxygen from the surrounding environment.

Source: J. Kopcewicz, St. Lewak, ed., Fizjologia roślin, Wydawnictwo Nau-kowe PWN, Warszawa, 2005, p. 489.

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10. Analyze the description and illustrations of the experiment and do sections a) and b).

Fig. 7. Illustration

Source: N. Campbell, J. Reece, Biology, Pearson, 2005, p. 803.

Description

Sunflower seeds were placed in the proper condi-tions of moisture and temperature for sprouting. They were exposed to the effect of darkness, red light, and far-red light in various configurations. The results are presented in the photographs.

Source: N. Campbell, J. Reece, Biology, Pearson, 2005, p. 803

a) Formulate the research problem, which could be answered by this experiment.

……… ………

b) Plan an experiment to determine whether the sprouting of other plant species’ seeds depends on the presence and type of light. Present the research problem, hypothesis, control sample, research sample, repeat tests, and data col-lection methods.