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FLOWERING PLANT REPRODUCTION
Introduce the topic: The floral industry attracts both the artist and the scientist. The floral industry involves flower production, distribution, design, retailing, operations, marketing, publishing, importing, research, teaching, greenhouse design and engineering, climate control systems engineering, soil analysis, sales and pest management. Field-work with a theme of ”wildflower hunting” is a wonderful way to get students to understand how a tiny flower can be such an important part of an entire ecosystem, thus promoting sensitivity to sustainability as well as teaching students about wild flower ethics. Students need to understand that wildflowers are fragile and many wilt and perish soon after being picked. Yet, the loss of an unknown to be endangered flower is not the only reason why wildflowers should not be picked. Students need to realize that wildflowers support entire ecosystems for pollinators, birds, and small animals on a micro scale. Insects, small birds, and animals depend on seeds, nectar, and pollen for their food supply and life support system. It may be a new idea to introduce students to some pollinators which are not very mobile, have very small home ranges, or depend on just one species of plant and die once their habitat has been destroyed. Basic biology of flower reproduction Sexual reproduction in plants occurs when the pollen (male sex cell/ gamete) from an anther is transferred to the stigma in a process called pollination. Self-fertilization occurs when pollen fertilizes the egg (female sex cell/ gamete) found inside the ovule of the same flower. The transfer of pollen to the stigma of an entirely different plant, a process called cross-pollination, may lead to cross-fertilization when the pollen fertilizes the egg inside the ovule. When the egg inside an ovule is fertilized, the ovules will develop into seeds. The petals of the flower fall off leaving only the ovary behind, which will develop into a fruit. There are many different kinds of fruits, including apples and oranges and peaches. A fruit is any structure that encloses and protects a seed, so fruits are also "helicopters" and acorns, and bean pods. When you eat a fruit, you are actually eating the ovary of the flower.
Exercise 1 To learn how to draw a biological diagram using a flower from their local ecosystem To understand the significance of biological magnification To relate the structure of a flower to seed production, whilst learning relevant terminology, such as, pollination, fertilization. The students can be asked to draw on the blank (next page) a selected flower (magnified approximately 5X) found in their local ecosystem (link with learning aims of activity 3: inquiring for the name of an unknown plant) indicating clearly the reproductive organs. Instructions for a biological drawing
Read more: How to Draw a Biological Diagram | eHow.com http://www.ehow.com/how_5695958_draw-biological-diagram.html Drawing Magnification (D.M.)
Further information is given to the students in order to obtain uniform drawings and labeling of the reproductive organs of the flower The female reproductive structures are called carpels. In most flowers, the carpels are fused together to form a pistil. The stigma at the top is often sticky and is where the pollen attaches. Draw the stigma (J). The style is the long tube that attaches the stigma to the ovary. Each pollen, found on the stigma, will grow a tube, down the style, towards the ovule (s). Each ovule, contains an egg, is stored in the ovary. Draw the style (K), and the ovary (L). Draw the ovules (O). Be sure to draw only what you see (refer to biological drawing instructions above).
Plants can only fertilize eggs of the same species. Special chemicals prevent sperm from fertilizing the eggs of flowers that are not of the same kind.
The male reproductive structures are called the stamens. Draw and label the stamens (H). Each stamen consists of an anther (A), which produces pollen, and a filament (F), which supports the anther. Pollen produced by the anther is carried by insects, or other animals, to the pistil of another flower where it may fertilize an egg.
The receptacle is the part of the branch on which a flower forms. Draw the receptacle (B). Sepals are leaf like structures that surround and protect the flower before it blooms. Draw the sepals (C). Petals are the colorful part of the flower that attracts insects and even other small animals, such as mice, birds, and bats. Draw the petals (D). All flowering plants have flowers, but some are not brightly colored. The petals of these flowers are reduced or absent and the plant relies on the wind or water for pollination. Questions Identify a flower which has a visiting insect . Why do insects visit flowers? Draw a circle around the characteristic of the flower A. Large petals B. Small petals C. Hanging anthers D. Small anthers E. Presence of large numbers of pollen F. Presence of small numbers of pollen Additional information Identification of pollen can be used in criminology investigations-forensics- and also to study climate change. Pollen grains and spores form the basis of palaeoclimate reconstruction, generally referred to as pollen analysis, or palynology. Where pollen and spores have accumulated over time, a record of the past vegetation of an area may be preserved. Often, changes in the vegetation of an area may be due to changes of climate. Interpreting past vegetation through pollen analysis may therefore offer a form of palaeoclimatic reconstruction. Sediments containing fossil pollen have been taken from peat bogs, lake beds, alluvial deposits, ocean bottoms and ice cores. Unfortunately, the difficulties associated with pollen analysis have meant that most palaeoclimate reconstructions have proceeded in a qualitative way only - the climate was wetter/drier or warmer/colder. Exercise 2 Collect pollen from flowers and observe it under a microscope
Introduce the topic; Pollen grains produced by different species of plant have a distinctive appearance. This allows us to work out what type of plant they came from, which in turn tells us the plants that used to grow in the area. We can observe the distinctive features of different types of pollen using a microscope. This helps us to identify what they are. Two useful features for identifying pollen are pores and furrows. Pores are holes in the surface of a pollen grain. Furrows are slits in the surface of a pollen grain. Safety: Be considerate of sensitivity to pollen Follow the methodology below describing how to collect pollen from flowers and observe it under a microscope
Extended possibilities for higher classes
Exercise 3 To inquire about the life cycle of a named insect and its role in pollination To inquire about the effects of Global warming in seasonal flowering, pollination and seed biology Ask the students to read the passage below: Changes in habitat or habitat loss pose the greatest threat to migratory pollinators. A single change along a migratory route can have long lasting and rippling effects that spread beyond any one population of pollinators. “Bats, hummingbirds, moths and butterflies are among the pollinators that seasonally migrate long and short distances between mountain ranges, regions and countries. Their migratory routes are often well-defined "nectar corridors" where the sequence of flowering plants over a season offers pollinators sufficient energy to sustain their journey. Many of these nectar corridors are no longer fully intact. Land conversion has eliminated many floral resources over 20 to 60 mile segments, in some cases longer than the distance energy-depleted pollinators can fly in one day." (Our Forgotten Pollinators: Protecting the Birds and Bees. By Mrill Ingram, Gary Nabhan and Stephen Buchmann.) Questions 1. Investigate the life cycle of an insect or another organism that is involved in pollination or requires a specific plant to feed that you have identified in the field study. 2. Inquire about the possibility of new emerging trends in flowering, linking with Global Warming (Refer to the activity of taxonomy). 3. Inquire whether the pollinator that you have identified follows a migratory route of long and short distances between mountain ranges, regions and countries. Exercise 4 To understand the structure of seeds To evaluate the methods used by seed banks in the conservation of endangered plants Use the web link and the passage below to introduce research that takes place in the Royal Botanic Gardens( RBG) in Australia: http://www.rbgsyd.nsw.gov.au/science/ Horticultural_ Research/seed_biology The seed research program is integral to the Seed Quest project, and has provided strong collaborative links to other Millennium Seed Bank partners via projects, such as seed longevity testing. Seeds of many Australian species are expected to be long-lived in storage, with groups, such as, acacias, eucalypts, and casuarinas topping the list. However, the longevity of seeds of most species is unknown. In order to address this, the RBG are collaborating with Australian partners of the Millennium Seed Bank Project to rank a wide range of species according to the longevity of their seeds (Martyn, 2009). The ranking is useful for prioritizing, which species must be cleaned and stored first - a key task at the end of a busy collection season. The ranking will determine which species’ seeds are likely to survive for long periods in storage, help us set appropriate re-testing schedules for banked seeds, and work out which species will need to be regenerated or replenished regularly with fresh seed. Experimental work for this project has concluded in late 2009, with data analysis and a draft publication was produced . Question: Inquire in the network about the final status of the publication? Additional information Research also informs the germination testing program within the SeedQuest in New South Wales (NSW) Seedbank. More than 900 germination tests have been conducted during the SeedQuest NSW project, with more than 680 tests exceeding 75% germination. A review of seed quality, viability and germination has been conducted on NSW Seedbank collections in the family Rutaceae, confirming that these parameters are highly variable and reinforcing the need to take these issues into account for ensuring optimal regeneration of plants from conservation seed banks (Martyn, Seed, Ooi and Offord 2009). Threatened species in the family Rutaceae were more likely to have low seed fill than common species, while viability and germination were similar. This suggests that poor seed fill is a contributing factor to threat status and is an important parameter to measure. In addition, two short publications describing seed collection methods in Zieria arborescens (Frith et al, 2009). have been submitted to a restoration-focused journal. Question: Inquire in the network about the final status of the germination testing program. Additional information Significant efforts have been made to educate students and seed bank practitioners in best-practice techniques for seed handling, storage and germination. This extension was made through seminars, formal training, community talks and seedbank tours, and the drafting of updated guidelines for 'Plant Germplasm Conservation in Australia' (Offord and Meagher 2009). Exercise 5 Ask the students to design and perform an experiment to investigate the time that they can store selected seeds (e.g. from a tomato fruit) without loss in the germination rate. Further information Seeds are considered viable if they can germinate and produce a radicle (young root), which protrudes through the seed coat (testa). However with time, all seeds lose their ability to germinate. Scientists operating in a seed bank need their seeds to remain viable while in storage. Find the Seed Bank Projects in your country, which conduct research to determine the longevity of the seeds they store. Draw a flow chart to summarize the processes involved in the storage of seeds in a seed bank. Students should realize that seed banks storing seeds have a role in scientific research and in reintroducing species to the wild. Possible questions
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