growth is the initial growth of plant organs. It also provides growth in length. Lateral meristem is responsible for sec

Transcription

1 Ill Lab 11 Flowering Plants: Structure, Function and Reproduction Flowering plants or anpiosperms begin to appear during the Cretaceous period. They are the most diverse plant groups. All angiosperms belong to division Anthophyta. There are two classes: monocotyledon (monocot) and dicotyledon _ (dicot). They are named after the number of seed leaf produced in their development processes. Figure 1 illustrates the anatomical and morphological differences between these two groups. The body of flowering plant is divided into the shoot system and the root system (Figure 2). The shoot system includes stems and leaves. It is usually aerial. The root system is underground. During the reproductive period, a shoot produces flowers. There are four types of plant tissues (Figure 3) throughout the whole plant body. Dermal tissue or epidermis cov ers the plant body. It is made of a single layer of tightly compact cell. In woody plants, dermal cells arc replaced by cork cells. Vascular tissue consists of xylem and phloem. It transports water, mineral and organic products. Ground tissue is the most abundant plant tissue type. It carries photosynthesis, stores food and secretes hormone. Meristematic tissue is the embryonic tissue. It provides growth. There are two types of meristem cells, apical meristem and lateral meristem. Apical meristem, located at tip of shoots and roots, provides primary growth. In plants, primary growth is the initial growth of plant organs. It also provides growth in length. Lateral meristem is responsible for sec ondary growth which provides growth in width. Activity A. Root Anatomy and Function Roots anchor the plants, absorb water and minerals from soil, and store food molecules such as starch. Most of roots are subterranean. However, there are adventitious roots. Prop roots from corn arise aboveground. 1. Obtain a prepared slide of a cross section of Ranunculus (buttercup) root from the slide box at your station. 2. Observe the slide under the microscope. 3. Use Figure 4 to identify the root structure. 4. Make a sketch on your answer sheet.

2 112 Activity B. Herbaceous Stem Anatomy and Function Stems support, transports nutrients, and displays leaves and flowers. Modified stems such as stolons, rhizomes, and tubers arc frequently mistaken for roots. Dicot and monocot plants differ in the arrangements of their vascular bundles as shown in Figure Place a prepared cross section of Helianthux (sunflower) under the microscope. Terminal bud 2. Use Figure 5 to identify the stem structure. 3. Make sketches on the answer sheet. 4. Observe the displayed modified stems. M0N0COTS DICOTS One cotyledon Two cotyledons Embryonic leaves -Shoot Branching veins Mature leaves Narrow leaves ' Parallel veins Broad leaves Root Roots Fibrous root system Taproot system Root hairs Figure 2 Anatomy of a Flowering Plant Reproduced from A Laboratory Guide to the Natural World. (2003) by permission of Prentice-Hall. Inc. Meristematic tissue Vascular bundles Scattered throughout stem Arranged in ring in stem Type of growth Only primary growth May have secondary woody growth Dermal tissue Vascular tissue round tissue Flower parts Multiples of three Multiples of four or five Examples Orchids, wheat, rice, bananas Oak and maple trees, cacti, sunflowers Meristematic tissue Figure I Characteristics of Monocots and Dicois Reproduced from A laboratory Guide to the Natural World, I2003) by permission of Prcnticc-Hall". Inc. Figure 3 Four Types of Plant Tissues Reproduced from /\ Uiboratory Guide to the Salurul World. (2003) by permission of Prenticc-Hali. Inc.

3 113 Epidermis - WTH - Stele PARENCHYMA CCUENCHYMA 1" CCRIEX CORK EPIDERMIS WOOOY DICOT STEM. X S. OF TILIA Figure 4 Herbaceous (Rammulus) Root Cross Section Reproduced from A Laboratory Guide to the Natural World. (2003) by permission of Prentice-Hall, Inc. Figure 6 Wood Stem Cross Section Vascular bundle -STNIA Figure 5 Herbaceous Stem Cross Section Reproduced from A Laboratory Guide to the Natural World. (2003) by permission of Prentice-Hali, Inc. Figure 7 Leaf Cross Section Labeled

4 114 Activity C. Wood Stem Anatomy Many plants have secondary growth. Secondary growth is the growth in diameter in stem and roots. During secondary growth, epidermal cells are replaced by cork cells. Tree rings are formed through the activity of vascular cambium from seasonal changes. The age of a tree can be determined by counting the number of annual tree rings. 1. Go to the demo desk. 2. Use Figure 6 to determine the age of this mature tree under the microscope, at the demo desk. 3. Record your answer on the answer sheet. 4. Observe the modified stems provide by the instructor. Activity D. Leaf Anatomy and Function The primary function of the leaf is to conduct photosynthesis. Modified leaves may store food, catch insects and defend plants against herbivores. Leaves also transpire through stomata. 1. Place a prepared cross section of Lif-usiriun leaf under the microscope. 2. Use Figure 7 to learn the structure of the leaf. 3. Finish the labeis on your answer sheet. 4. Observe the modified leaves provide by instructor at the demo desk. Activity E. Flowering Anatomy and Function The flower of angiosperms is composed of four whorls (Figure 8a). Sepal is the outmost whorl of flowers. Sepals may be green, brown, or colored like the petals. Sometimes they may appear smaller than petals, or appear as small scales or even look like petals. Calyx is the name for the whole collection of sepals. Petal is located inside of the sepals. The petals are collectively called Corolla. If each petal looks the same as the rest of the petals, it is called regular flower. If at least one petal looks different than the rest of petals, the flower is called corolla irregular. Both calyx and corolla provide the pro tection to the flowers. They also make the flower appear attractive to pollinators. Figure 8 Flower Structures ANTHER > STAMEN FILAMENT' t STIGMA LODICULE LEMMA RACHILLA FLORET a. A typical dicot flower b. A typical grass flower Floret

5 115 The reproductive components of a flower consist of the stamen and pistil. Stamen is the male reproductive part of a llower, which produces pollen grain. Pistil is the female reproductive structure. A Perfect (bisexual) flower contains both stamen and pistil. Otherwise the flower is called imperfect (unisexual). If a flower has all four whorls (sepal, petal, stamen and pistil), it is referred to as a complete flower. Otherwise it is called an incomplete flower. The incomplete flower lacks at least one whorl. Grass has small flowers called florets (Figure 8b). The florret lacks a calyx and corolla. The male and female parts are enclosed by modified leaf bracts lemma and palea. A. Flower Anatomy 1. Obtain a flower. 2. Identify the flower structures according to the above figures. 3. Dissect three flowers and tape their floral parts individually in Table 2. B. Flower and Pollinator During the process of reproduction, pollen is transferred to stigma of a flower, pollination occurs. Flowers have distinct shape, color, and fragrance to attract the animals. Some pollinators tend to be attracted to cer tain types of flowers. As a matter of fact, plants coevolved with the pollinators. Table 1 summarizes these cues from human perspectives. Of course, animals are opportunists. They may go for the non typical flowers as well. 1. Observe the displayed flowers, charts, or diagrams of pollinators. 2. Record examples in provided answer sheet.

6 116 TABLE 1 POLLINATION AND FLORAL ADAPTATION Pollination Method Visual Characteristics Chemical Characteristics Wind Dull colored, small, flowers often group in a cluster, stigma none feathery Bat (night) Large dull or white flowers Odors: fruity, fermenting Bee Bright colors such as yellow, pink, orange and blue, flowers with ultraviolet marking, Sweet irregular flowers with "landing" platform Beetles Dull or white colored Strong odors: ranging from fruity, spicy to foul Butterflies Bright colors such as red, pink, orange, yellow, blue; flowers Strong odor: sweat often long tubular; sometime forms a cluster for landing Flics Large flowers, dull or reddish color Rotten meat or foul odor Hummingbirds Red, yellow tubular flowers Sugary nectar, odor or odorless

7 117 C. Fruit After fertilization of sperm and egg in a flowering plant, the fertilized egg develops into an embryo inside of the ovule. The ovule develops into a seed. The rest of the flower develops into a fruit (Figure 9). The fruit protects the seeds. If a fruit is developed from one single ovary in one flower, it is called a simple fruit. Aggregated fruits such as strawberries are formed from many ovaries in one flower. Multiple fruits are formed from the ovaries of many flowers, for example, pineapple. CALYX EPIDERMIS SEED SEPAL OVULE OVARY OVARY WALL RECEPTACLE -PEDICLE EXOCARP MESOCARP I- PERICARP ENDOCARP. HYPANTHIUM Pearson Custom Publishing APPLE-POME Figure 9 Rower structure and fruit relationship apple Procedures 1. Use the provided key below identify the type of fruits, or use fruit charts to give examples of fruits. 2. Record your results in Table 2. Key to Fruits I. Fruits dry. do not contain moisture at maturity A. Fruit with one seed 1. Ovary wall and seed coat are fused achene 1' Ovary wall hard or woody but not fused with seed coa nuts A' Fruit with two to many seeds I. Ovary with several cavities and contains several to many seeds capsule 1' Ovary with one cavity a. Mature ovary open along both sides legume a' Mature ovary opens along one side follicle I". Fruits wel. contain moisture at maturity A. Ovary with one seed, which is surrounded by a very hard stone drupe A". Ovary with many seeds: internal tissues do not contain a "stone" 1. All of the mature ovary tissue is soft and fleshy berry I'. Ovary tissue is woody and forms a "core" around seeds pome

8 119 Answer Sheet Flowering Plants: Structure, Function and Flower Name Section Number Activity A. Root Anatomy and Function 1. Sketch the section of root and label vascular tissue, ground tissue, epidermis, and starch granules. 2. List three functions of the roots. a. b. c.

9 120 Activity B. Herbaceous Stems Anatomy and Structure 1. Sketch and label the epidermis, vascular bundles including xylem and phloem, and ground tissues of the sunflower stem. Is the sunflower a monocot or dicot? 2. Describe the functions of stems. 3. Your favorite modified stem is Activity C. Woody Stem Anatomy I. How old is your basswood specimen? 2. What part of stem do you observe to find out?_

10 121 Activity D. Leaf Anatomy and Function I. Label the cuticle, upper and lower epidermis, mesophyll, vascular bundles, and stomata. 2. A typical dicot leaf has a distinct mesophyll. The palisade cells on top of leaf contain a lot of chloroplasts. Explain the advantage of the palisade mesophyll cells being closed packed together. 3. Plants lose about 80-90% of water through stomata. Does upper epidermis or the lower epidermis seem to have more stomata? And why might this be an advantage for the plants? 4. Your favorite modified leaf is

11 Activity E: Flower Structure A. FLOWER ANATOMY TABLE 2 FLOWER DISSECTION Features Plant Name Petal Sepal Stamen Pistil Perfect or Imperfect flower Complete or incomplete flower

12 123 B. POLLINATORS Plant Name Observed Pollinator C. FRUITS Fruit Name Key Steps Fruit Type Apple (example) FAT Pome