LABORATORY 13

ANGIOSPERMS: FLOWERS, FRUITS, and SEEDS

Including GERMINATION & TREE IDENTIFICATION

Angiosperms are the most complex and diverse of all higher plants. They exhibit amazing adaptation to various habitats having mastered the process of reproduction by cleverly attracting pollinators and insuring seed dispersal in a variety of ways. Though they may not always be conspicuous, angiosperms always produce 1) flowers, 2) fruits, and 3) seeds. They ovary of the flower matures into a fruit which contains seeds. Why is an early frost damaging to a fruit tree in flower? Review the life cycle of an angiosperm in your Photographic Atlas. Before coming to lab, locate and record the appropriate page and figure numbers requested from your textbook and photo atlas.

In this lab, we will examine these three important components of angiosperms: flowers, fruits, and seeds. A part of the lab will be spent outdoors using a simple dichotomous key to identify some trees on the campus. Let’s hope the weather is beautiful (but please dress accordingly)!

FLOWERS

1. Study the model of the flower. Refer to Figure ____ in Campbell and Atlas pp. _______. Concentrate on the following: petal, corolla, carpel: stigma, style, ovary, stamen: filament, anther, sepal, ovule, receptacle, and perianth. Also describe in your laboratory report the difference between a perfect and an imperfect flower; and the difference between a complete and an incomplete flower. What are the four basic floral organs? Which are reproductive? Which are non-reproductive? In your lab report, draw and label a complete flower. Define the term self-incompatible as it applies to flowers.

2. Study examples of monocots and dicots. In your lab report, construct a chart and list characteristics of each. Refer to your Atlas, p____.

FRUITS

1. Study the relationship between the flower and the fruit. Figure _____ may be helpful. In your lab report, describe the differences between the following

types of fruits and give an example of each: simple, aggregate, and multiple fruit. What are drupes, legumes, pomes, etc? Refer to p.___ in your Atlas.

2. What causes a fruit to become “sweeter” as it ripens?

3. Observe the different fresh fruits provided. How are the different fruits specialized for seed dispersal? Refer to p.____ in your Atlas.

SEEDS

1. Carefully dissect a bean seed so as to divide the two cotyledons. What reagent is used to test for starch? Apply a drop or two of this reagent and sketch the result in your lab notebook. Where is starch present in the bean? What is the function of this stored starch in the seed? Refer to pp. _____ in your Atlas.

2. Sketch a bean seed and label seed coat, cotyledons, epicotyl, hypocotyl,

plumule, and radicle. Describe the function of each of these components. Consult Figure __ in the Campbell text.

3. Dissect a corn seed. Identify endosperm, embryo; note the presence of only one cotyledon. Apply iodine to the endosperm to see if starch is present?

4. Sketch a corn seed and label the cotyledon, scutellum, coleoptile, plumule, coleorhiza, endosperm, and radicle. What is the function of each of these seed components? What difference exist between the corn and bean seeds? Why? Consult Figure ____ in Campbell.

5. Describe the process of germination. Consult Figure ___ in Campbell. Differentiate between epigean and hypogean germination and give an example of each.

6. Examine the Plastomounts of bean and corn germination. Explain the difference between epigean and hypogean germination. Are epigean and hypogean germination monocot and dicot characteristics? Explain.

TREE IDENTIFICATION

Trees have unique leaf structures, margins, venation patterns, arrangements, etc. that can be used to identify some common deciduous trees. The goal here is not to learn, necessarily, all of these trees by sight, but to gain experience in using a simple dichotomous key. Weather permitting, we will go outside and identify various trees on campus using the following key. Practice using the key so that each characteristic used is familiar to you. You will use a copy of this dichotomous key to identify a specimen on your lab exam next week.

Before coming to lab, review the common leaf arrangements of compound leaves (opposite or alternate; even pinnate or odd pinnate; palmate). Recall where to look for a lateral bud. Review some of the more common leaf margins (entire, serrate, doubly serrate, incised, etc.) Refer to p. ____ in your Atlas.

TERMINOLOGY

complete flower	sepals	pollination	epicotyl	simple fruit	homosporous
incomplete flower	petals	self-incompatibility	scutellum	aggregate fruit	heterosporus
perfect flower	carpels	endosperm	coleorhiza	fragmentation	Anther-filament
imperfect flower	stamens	seed coat	coleoptile	corolla	epigen germination
monoecious	microspores	hypocotyl	pericarp	perianth	hypogean germination
dioecious	megaspores	radicle	colyledon	calyx	stigma-style-ovary

Dichotomous Key: Selected Trees on VSCC Campus
1A	Trees with needle‑like leaves	2
1B	Trees without needle‑like leaves	6
2A	Leaves in bundles of two or more	3
2B	Leaves occurring individually	4
3A	Leaves in bundles of 5; main branches whorled  Pinus strobus (white pine)
3B	Leaves in bundles of 3 . . Pinus taeda (loblolly pine)
4A	Leaves yellow‑green and soft Taxodium distichum (bald cypress)
4B	Leaves not yellow‑green nor soft	5
5A	Leaves blue‑green   Picea pungens (blue spruce)*
5B	Leaves green Picea abies (Norway spruce)**
6A	Leaves fan‑shaped with two lobes; veins roughly parallel Ginkgo biloba (ginkgo)**
6B	Leaves not as above	7
7A	Leaves compound	8
7B	Leaves simple	13
8A	Whole leaves opposite on the twig Fraxinus americana (white ash)
8B	Whole leaves alternate on the twig	9
9A	Leaves once pinnately compound	10
9B	Leaves twice pinnately compound	12
10A	Base of leaf stalk conceals a lateral bud (remove leaf from  twig to check for hidden bud) Cladrastis lutea (yellowood)
10B	Lateral bud not concealed by petiole	11
11A	Twigs have chambered pith (cut twig longitudinally through the pith); crushed leaves smell like green walnuts Juglans nigra (black walnut)
11B	Pith not chambered; leaves don't smell like green walnuts Robinia pseudoacacia (black locust)
12A	Leaf subdivided into more than 300 leaflets Albizia julibrissin (mimosa)**
12B	The compound leaf is subdivided into less than 300 leaflets Gleditsia triacanthos (honeylocust)
13A	Leaves in a whorled arrangement (3 per node)Catalpa bignonioides (southern catalpa)
13B	Less than 3 leaves per node	14
14A	Leaves opposite on the twig	15
14B	Leaves alternate on the twig	19
15A	Leaves toothed and palmately veined	16
15B	Leaves entire and pinnately veined	18
16A	Leaves deeply 5‑lobed; white to silvery beneath; flaky bark Acer saccharinum (silver maple)
16B	Characteristics not as above . . . . . . . . . . .  17	17
17A	Flowers appear before leaves; young fruits are red; leaves usually 3‑lobed; teeth small Acer rubrum  (red maple)	17A
17B	Flowers appear as the leaves expand or after; leaves 5‑lobed and have large teeth Acer saccharum (sugar maple)	17B
18A	Leaf veins curve inward strongly close to the margin; leaves rarely more than 3.5 inches long at maturity; leaf base rounded  Cornus florida (flowering dogwood)
18B	Leaf veins don't curve inward strongly; leaves more than 3.5 inches long at maturity; leaf base      tapered Chionanthus virginicus (fringe tree)
19A	Leaves entire	20
19B	Leaves toothed and/or lobed	24
20A	Leaves heart‑shaped Cercis canadensis (redbud)
20B	Leaves not heart‑shaped	21
21A	Leaves large, thick and evergreen; a stipular scar encircles the twig at each node  Magnolia grandiflora (southern magnolia)
21B	Leaves deciduous; stipular scars absent	22
22A	Leaves not clustered at tips of twigs; main limbs at right angles to the trunk Nyssa sylvatica (blackgum)
22B