Biology Lab

—————–QUESTIONS——————

1.

Plant NamealstroemeriairisTulip or lily
Sepal #
Petal #
Stamen #
Symmetry
Monocot or dicot?

2. Which structure, the endosperm or embryo, contains starch?

3. What resemblance do you see between the ovary cross section of the lily flower and the cross section of the tomato?

4. Obtain a pea pod, which is also a fruit. If the pod is a fruit, is it simple, aggregate, multiple, or accessory?

5. What floral structures were the “peas” inside the pea pod?

6.

Plant NameFruit TypeDispersal Method
Cherry tomato
Apple
Peach
Acorn
Strawberry
Pea Pod

7. Distinguish between pollination and fertilization in a flowering plant.

8. Does pollination take place before or after fertilization?.

9. Cross-pollination is more favorable than self-pollination for most plants. Why is this so?

10. What are the advantages of seeds being in a dried-out state while they are lying in the soil?

11. Define imbition.

12. Why is it necessary for a seed to absorb water before it can germinate?

=====================================Resorces==========================

Flowers, Fruits, Seeds, and Growth Lab

You will need to purchase fruits, flowers, and seeds from the local grocery store or Wal-Mart for this lab. Depending on the time of the year, you may be able to find some of the fruits and flowers outside. Luckily you can eat the fruits afterwards and keep the flowers for a display! Please be sure to soak the bean seed overnight (at least 24 hours) before completing that portion of the lab. Answer the questions in Moodle as you go along, and the remaining questions in Moodle using information from this lab and your textbook.

Materials Needed:

· Razor, sharp knife, or scalpel

· Iodine or food coloring

· 2 lily or tulip flowers

· 1 Alstroemeria flower

· 1 iris flower (NOTE: these are common bouquet flowers and you should be able to find them, but if you absolutely cannot, consult with your instructor first about other options).

· Cherry tomato

· Pea pod

· Apple

· Peach (or plum, cherry, mango – if peaches cannot be found)

· Strawberry

· Acorn (or an almond from the store if an acorn cannot be found outside)

· The common Bean (Phaseolus vulgaris)

· A Corn grain (Zea mays)

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Pea Pod Corn grains Common beans

Flowers

Flowers consist of a series of modified leaves that collectively produce, protect, and ensure the union of, the gametes. In a typical flower there are four sets of floral parts, the female gynoecium of carpels, the maleandroecium of stamens, thecorolla of petals, and the calyx of sepals. All of these parts are arranged in whorls (circles). The whorls are attached to a receptacle, the expanded end of the flower stalk. Flowers may be solitary, or occur in groups known asinflorescences.

Flowers are usually hermaphrodite (contain both male and female parts), but sometimes they are unisexual. This comparatively unusual situation is found mainly among wind-pollinated plants and the flowers lack either the stamens or carpels. Unisexual flowering plants are divided into two groups:

a) Monoecious plants: these have the male and female flowers on same plant, e.g. hazel, beech, oak, and sycamore.

b) Dioecious plants: these have the male and female flowers on separate plants, e.g. holly, willow, poplar.

As well as varying in their sexual makeup the flowers of different species may also vary in the numbers, arrangement, and degree of fusion of their component parts. Here are some of the main variations seen between flowers:

Sepals: their number is variable as is their degrees of fusion; they may be green and leaf-like, or colored and petal-like (petaloid).

Petals: their number varies considerably; they show varying degrees of fusion and in some cases join to form a tube (corolla tube); their color and scent varies widely and they may or may not hold nectaries; sepals and petals may be fused or indistinguishable from one another, in which case they form, together, the perianth.

Stamens: the number of stamens may be large and variable or smaller and fixed; the anthers vary in size while the filaments may vary in length and in the mode of attachment to the anther; The base of the filaments may be attached to the petals or perianth rather than the receptacle; the stamens may also show fusion, and in extreme cases form a tube round the carpels.

Carpels: their number may be large and variable or smaller and fixed; styles vary in length and may be separate or joined; if joined there is much variation in the method of fusion; the ovary may stand proud upon the receptacle (superior ovary) or be sunk down into the receptacle (inferior ovary).

Flowers also vary in their symmetry. The flower may be radially symmetrical (actinomorphic) or bilaterally symmetrical (zygomorphic) (diagram 1). Examples of actinomorphic flowers include buttercup, lily, tulip and bindweed. Zygomorphic flowers include sweet pea, deadnettle, snapdragon and orchids.

Diagram 1

A. Zygomorphic flower B. Actinomorphic flowerA zygomorphic flower can be cut in only one plane to give two equal and opposite halves; an actinomorphic flower, however, may be cut in more than one plane to give two equal and opposite halves.In order for a flower to complete its reproductive purpose pollen grains must pass from the anther to a stigma. This transfer of pollen is called pollination. Much of the variation in flower parts can be attributed to their modes of pollination. Insect-pollinated flowers such as the buttercup tend to have showy petals, with lines (honey-guides) pointing towards a source of nectar, nectaries, scent and large sticky spiny pollen grains. Wind-pollinated flowers such as grasses tend to lack showy petals, nectar-guides, nectar, nectaries and scent. They usually have stamens which hang outside the flower and which produce large quantities of small, smooth, dry, light pollen grains. The stigmas are exposed to the wind and have a large surface area.

The embryo sac starts by having a single haploid nucleus which is formed by meiosis from an embryo sac mother cell. The haploid nucleus of the embryo sac then undergoes successive mitotic divisions to give a total of eight nuclei, two of which will fuse to form a central endosperm mother cell. Each of the seven resulting nuclei becomes surrounded by membranes to give the cells shown in Diagram 2E. The antipodal cells at the chalazal (upper) end of the embryo sac are thought to provide nourishment for the embryosac, the synergids at the micropyle end are nonfunctional eggs and degenerate. In the act of fertilization the egg cell (ovum) fuses with one male nucleus from the pollen while the second pollen nucleus fuses with the nuclei in the endosperm mother cell. Hence this process is called double fertilization.A. Obtain a lily or tulip flower, and identify the four different rings, or whorls, of partsSterile PartsThe non-reproductive structures of a flower are sepals and petals. The outermost ring of parts is formed of sepals; all the sepals together are called the calyx. In lilies and tulips there are three sepals. The sepals are often green and protect the flower in bud, and the petals are usually brightly colored and serve to attract pollinators, however they can also be indistinguishable in some plants (including tulips and lilies). The next inner ring of parts is comprised of petals. There are three petals in lilies and tulips. All the petals together are called the corolla.Fertile partsThe reproductive structures include the stamen and the carpel. Next inwardly are the stamens. Each stamen consists of an anther, made up of four pollen sacs located at the tip, and a narrow stalk-like filament. Because the pollen grains ultimately produce sperm, stamens are associated with male reproductive function. Remove a stamen from the flower. Cut open the anther with a razor or scalpel. When pollen (the male gametophyte) is shed, it usually has two cells, one that divides to produce two sperm, and one which directs the growth of the pollen tube.At the center of the flower is the carpel. Normally, the carpel has three regions: 1) the ovary, the ovule-bearing basal section, 2) the style, the narrow midsection, and 3) the stigma, the sticky pollen-collecting tip. The ovary contains one or more ovules that following pollination and fertilization will form the seeds. Use your razor to make a cross section through the ovary. How many separate chambers do you see? Often several carpals fuse together, each one represented by a separate chamber. Keep this ovary section to look at later.Look at the image below showing a germinated pollen tube. Fertilization takes place after a pollen grain germinates on the stigma. It produces a pollen tube that grows through the style into the ovary, into the embryo sac. By the time the seed is mature, much of its food will have been transported to a part of the embryo called the cotyledon.Floral variationThe flowering plants show great variation in floral structure. In particular there is variation in the number of sepals, petals, stamens, and carpels. Their shape and color vary; sometimes one of the floral parts is lacking; often floral parts are fused. Flowers also differ in their symmetry (discussed above) and in production of nectar and scent.Lay out the 3 flowers that you bought, (alstroemeria, carnation, and chrysanthemum) and fill in the chart in question 1 in Moodle LAB REPORT . Use your floral vocabulary to complete the chart. If a particular part is missing from the flower mark the box as “not applicable” or “NA.”SEEDS

A seed is a mature ovule. After fertilization of the egg within the embryo sac of the ovule, a number of development events occur. The nutritive endosperm develops. The zygote divides mitotically to form the embryo. The seed coat of the ovule hardens. The seeds of some angiosperms thus consist of the embryo, a protective seed coat surrounding the embryo, and the endosperm, which serves as a food supply for the embryo. In other angiosperms the nutrients of the endosperm are completely absorbed by the developing embryo and stored in the cotyledons of the embryo. These seeds lack true endosperm when mature. When conditions are right, the seed imbibes water and germinates. The young root, called a radicle, is the first organ to emerge through the seed coat. This is followed by the plumule, or young shoot. A seedling is a young, immature plant recently germinated from a seed. During germination the embryo resumes active growth and emerges from the seed coat to become the seedling. The seedling will continue to rely on the food stored in the endosperm or cotyledons for energy and raw materials for growth until it becomes photosynthetic. The embryonic plant and its store of food inside are covered and protected by a tough seedcoat called the testa. When the embryo is almost fully developed the tissues round it lose water, leaving the seed hard and dry. The seed can stay like this for a long time until conditions are right for it to grow.A. Bean (Phaseolus vulgaris)Obtain a bean that has been soaked overnight. This is an individual seed (a mature ovule) that was taken out of a bean fruit. Notice the seed coat on the outside. Everything inside the seed coat is embryo. The most obvious features of the bean embryo are its two large fleshy cotyledons (seed leaves). The endosperm has been digested and their nutrients transferred to cotyledons, which are large structures that make up the bulk of the bean seed. Between the two cotyledons is the rest of the plant body. Identify the embryonic root and the feather-like embryonic shoot.B. Corn (Zea mays)Examine a corn grain. The corn grain is actually a fruit containing one seed. The seed coat of corn, like that of other grasses, is fused with the fruit wall. For this reason the outer covering of the corn grain is actually the fruit wall rather than the seed coat. At one end of the grain you may see a scar left by the style (silk) of the corn carpel, at the other end a scar where the grain was attached to the cob.Cut the corn grain exactly in half lengthwise with a razor blade to reveal the endosperm and the embryo. Put a drop of iodine or food coloring onto the cut surface to detect the starch. Which structure, the endosperm or embryo, contains starch? Question 2 in Moodle.The part of the embryo closest to the endosperm is the single cotyledon. The root end of the embryo is toward the base of the grain, the shoot end toward the apex.FruitsThe ovary becomes a container for the angiosperm seeds, called the fruit. Fruits not only protect seeds, but also provide a variety of mechanisms for their dispersal. A fruit is a mature ovary. Most fruits are simple fruits that develop from a single ovary. Aggregate and multiple fruits are compound fruits consisting of several to many units of one of the simple fruit types (for example, a blackberry fruit is an aggregate of small drupes). In addition to the ovary wall and its enclosed seeds, a fruit may include a variety of accessory structures such as outer flower parts or receptacle tissue. Some botanists lump all fruits with non- ovarian tissue into a fruit type called accessory fruits.Obtain a cherry tomato (Lycopersicon). The tomato is a fruit, even though it is called a vegetable at the grocery store; there is no botanical definition for the word vegetable. The tomato is a type of fruit called a berry because of its fleshy wall. Cut the tomato in cross section and compare it with the cross section you made earlier of the lily.What resemblance do you see between the ovary cross section of the lily flower and the cross section of the tomato? Question 3 in Moodle LAB REPORT.Obtain a pea pod, which is also a fruit. If the pod is a fruit, is it simple, aggregate, multiple, or accessory? Question 4 in Moodle LAB REPORT.What floral structures were the “peas” inside the pea pod? Question 5 in Moodle LAB REPORT.Types of Fruit and Seed DispersalSeeds and fruits may be dispersed by wind, water, or animals. Dispersal is made possible by modifications of the seed coat, the ovary wall, other flower parts, or even parts of the plant outside the flower (like the stem in pineapples which becomes soft and juicy).For each of the fruits that you bought (cherry tomato, apple, strawberry, pea pod, acorn, peach), fill in the table in question 6 in Moodle :1) Determine how it developed from the flower. Did the fruit develop from a single ovary or more than one? Look for remnants of other floral parts (sepals, petal, etc.) to provide hints.2) Examine the fruit wall. Is it fleshy or dry at maturity? If fleshy, is there a hard pit or core protecting the seeds? If dry, does the fruit wall open to release the seeds?3) Use the figure below and the following key for various fruit types. Speculate as to how the fruit is dispersed.Key to Various Fruit Types1. Simple fruits – derived from a single ovary of a single flower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . …21. Compound fruits – derived from either the ovaries of several flowers orfrom several ovaries of a single flower . . . . . . . . . . . . ….. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . … . 112. Fruits obviously fleshy at maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32. Fruit dry at maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . 53. Inner layer of fruit wall is entirely fleshy, usually more than one seed . . . . . . . . . . . . . . . . . . . Berry3. Inner layer of fruit wall not entirely fleshy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44. Fleshy outer region surrounds a leathery, cartilaginous, or bony coreenclosing several seeds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . Pome4. Inner layer of fruit is hard and stony making up a “pit”, usually only one seed. . . . . . . . . . . . . Drupe5. Indehiscent fruits (not opening at maturity) . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 65. Dehiscent fruits (splitting open at maturity) . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 96. Seed with fruit forming winglike extension(s) for dispersal . . . . . . . . . . . . . . . . . . . . . . . . . . Samara6. Lacking wings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 77. Fruit wall very hard and stony enclosing a relatively large seed not fused to the wall . . . . . . . . . . . Nut7. Fruit wall never stony (may be hard or papery). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88. Seed entirely fused to the fruit wall, so inseparable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Grain8. Small seed not entirely fused to relatively soft or thin fruit wall(may be attached at one point) . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Achene9. Composed of one compartment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109. Composed of more than one compartment fused together, opens by various slits or pores . . . Capsule10. Opening along one suture (i.e. longitudinal slit). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Follicle10. Opening along two sutures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . Legume11. Fruit derived from several ovaries of several flowers, fused together . . . . . . . . . . . . . . . Multiple fruit11. Fruit derived from several ovaries of a single flower . . . . . . . . . . . . . . . . . . . . . . . Aggregate fruit

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