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Chapter 31 Plant Structure, Growth, and Reproduction PowerPoint Lectures Campbell Biology: Concepts & Connections, Eighth Edition REECE • TAYLOR • SIMON • DICKEY • HOGAN © 2015 Pearson Education, Inc. Lecture by Edward J. Zalisko PLANT STRUCTURE AND FUNCTION © 2015 Pearson Education, Inc. First, some basics about plants… • multicellular, photosynthetic autotrophs. • nonmotile—they cannot move from place to place. • cell walls that contain cellulose. • includes cone-bearing (gymnosperms) and flowering plants (angiosperms) as well as mosses and ferns. © 2015 Pearson Education, Inc. 31.2 The two major groups of angiosperms are the monocots and the eudicots © 2015 Pearson Education, Inc. 31.3 A typical plant body contains three basic organs: roots, stems, and leaves • Plant organs consist of several types of tissues that together carry out particular functions. • Plants use a root system to • anchor the plant in the soil, • absorb and transport water and minerals, and • store carbohydrates. • Root hairs are tiny finger-like projections off of roots that enormously increase the surface area for absorption. © 2015 Pearson Education, Inc. 31.3 A typical plant body contains three basic organs: roots, stems, and leaves • A shoot system consists of stems, leaves, and structures for reproduction. • A stem has • nodes, the points at which leaves are attached, and internodes, the portions of the stem between nodes. • The leaves are the main photosynthetic organs in most plants, although green stems also perform photosynthesis. © 2015 Pearson Education, Inc. 31.3 A typical plant body contains three basic organs: roots, stems, and leaves © 2015 Pearson Education, Inc. 31.4 Many plants have modified roots, stems, and leaves • Modifications of plant parts are adaptations for various functions, including • Roots - food or water storage - Unusually large taproots that store food in the form of carbohydrates such as starch are found in carrots, turnips, sugar beets, and sweet potatoes. • Stems - asexual reproduction and storage - stolons, tubers, rhizomes • Leaves - protection, climbing, and photosynthesis – tendrils, cactus spines © 2015 Pearson Education, Inc. 31.5 Three tissue systems make up the plant body • The organs of plants contain tissues, which are a group of cells that together perform a specialized function. • Xylem tissue contains water-conducting cells that convey water and dissolved minerals upward from roots • tracheids and vessel elements: xylem elongated cells dead at maturity • Phloem tissue contains cells that transport sugars and other organic nutrients from leaves or storage tissues to other parts of the plant • sieve-tube members: phloem tubes alive at maturity capped by sieve plates (porous end plates) • companion cells: (nonconducting) connected by to sieve tube by plasmodesmata . © 2015 Pearson Education, Inc. 31.5 Three tissue systems make up the plant body • Each plant organ (root, stem, or leaf) has three types of tissues. 1. Dermal tissue provides a protective outer covering (epidermis and cuticle). 2. Vascular tissue provides support and longdistance transport (xylem and phloem) 3. Ground tissue composes the bulk of the plant body and is involved in • Photosynthesis (mesophyll layer of leaves), • storage, and support (pith and cortex of roots). © 2015 Pearson Education, Inc. 31.5 Three tissue systems make up the plant body © 2015 Pearson Education, Inc. 31.5 Three tissue systems make up the plant body • In a leaf, the epidermis is interrupted by tiny pores called stomata, which allow exchange of CO2 and O2 between the surrounding air and the photosynthetic cells inside the leaf. • Each stoma is flanked by two guard cells that regulate the opening and closing of the stoma. © 2015 Pearson Education, Inc. 31.6 Plant cells are diverse in structure and function • Most plant cells have three structures that distinguish them from animal cells: 1. chloroplasts, the site of photosynthesis, 2. a central vacuole containing fluid that helps maintain cell turgor (firmness), and 3. a protective cell wall composed of cellulose. © 2015 Pearson Education, Inc. 31.6 Plant cells are diverse in structure and function • There are five major types of plant cells with different functions: 1. parenchyma cells: walls thin and flexible, no secondary walls, large central vacuole, main workhorse for photosynthesis 2. collenchyma cells: unevenly thick primary walls, used for plant support 3. sclerenchyma cells: support element strengthened by secondary cell walls with lignin (wood), dead at functional maturity, xylem cells are mostly sclerenchyma fibers (long, slender tapered - rope) and sclereids (shorter, irregular – nutshells, seed coats, pear grittiness) 4. 5. water-conducting cells: xylem food-conducting cells: phloem © 2015 Pearson Education, Inc. PLANT GROWTH © 2015 Pearson Education, Inc. 31.7 Primary growth lengthens roots and shoots • Most animals are characterized by determinate growth, stopping growth after a certain size. • Most plants have indeterminate growth, continuing to grow throughout a plant’s life. • Plants are categorized based on the length of their life cycle. • Annuals complete their life cycle in one year. • Biennials complete their life cycle in two years. • Perennials live for many years. © 2015 Pearson Education, Inc. 31.7 Primary growth lengthens roots and shoots • Plant growth occurs in specialized tissues called meristems, consisting of undifferentiated cells that divide when conditions permit. • Apical meristems are found at the tips of roots and in the buds of shoots. • Primary growth • occurs at apical meristems, • allows roots to push downward through the soil, and • allows shoots to grow upward, increasing exposure to light and CO2. © 2015 Pearson Education, Inc. 31.7 Primary growth lengthens roots and shoots • The apical meristems of root tips are covered by a root cap. • Root growth occurs behind the root cap in three zones. 1. 2. 3. Zone of cell division: primary (apical) meristem Zone of elongation: cells elongate; pushes root tip Zone of differentiation: where cells differentiate into dermal, vascular, and ground tissues © 2015 Pearson Education, Inc. 31.8 Secondary growth increases the diameter of woody plants • Secondary growth • is an increase in thickness of stems and roots and • occurs at lateral meristems. • Lateral meristems are areas of active cell division that exist in two cylinders that extend along the length of roots and shoots. 1. Vascular cambium is a lateral meristem that lies between primary xylem and primary phloem. • Gives rise to secondary xylem (wood) and secondary phloem (inner bark - diameter increase, annual growth rings) 2. Cork cambium is a lateral meristem that lies at the outer edge of the stem cortex. • Produces cells in one direction – the outer bark (made of cork cells) © 2015 Pearson Education, Inc. 31.8 Secondary growth increases the diameter of woody plants © 2015 Pearson Education, Inc. 31.8 Secondary growth increases the diameter of woody plants • Wood annual rings = layers of secondary xylem. • The bark is sloughed off over time. • Wood rays transport water and nutrients, store organic nutrients, and aid in wound repair. • Sapwood: conducts xylem fluid (sap). • Heartwood: stores resins and wastes. • Secondary phloem near the vascular cambium transports sugars. © 2015 Pearson Education, Inc. REPRODUCTION OF FLOWERING PLANTS © 2015 Pearson Education, Inc. 31.9 The flower is the organ of sexual reproduction in angiosperms Flowers typically contain four types of floral organs. 1. Sepals protect a flower bud. 2. Petals are often colorful and fragrant, attract pollinators. 3. Stamens consist of the filament tipped by an anther, which contains pollen. 4. Carpels have a style with a sticky stigma at its tip. • The base of the carpel is the ovary, which contains one or more ovules, each containing a developing egg and supporting cells. © 2015 Pearson Education, Inc. 31.9 The flower is the organ of sexual reproduction in angiosperms • In the life cycle of a generalized angiosperm, 1. Fertilization occurs in an ovule. 2. The ovary develops into a fruit. 3. The ovule develops into the seed containing the embryo. The fruit protects the seed and aids in dispersing it. 4. Completing the life cycle, the seed then germinates (begins to grow) in a suitable habitat. 5. The embryo develops into a seedling, and the seedling grows into a mature plant. © 2015 Pearson Education, Inc. First some weird words for you… • Plant life cycles involve alternating diploid (2n) and haploid (n) generations. • The diploid plant is called the sporophyte. • Specialized diploid cells in anthers and ovules undergo meiosis to produce haploid spores. • The haploid spores undergo mitosis and produce the haploid generation. • The haploid generation is called the gametophyte, which produces gametes via mitosis. • At fertilization, gametes from male and female gametophytes unite to produce a diploid zygote. © 2015 Pearson Education, Inc. 31.10 The development of pollen and ovules culminates in fertilization • Pollen grains are the male gametophytes. • The cells that develop into pollen grains are found within a flower’s anthers. 1.Each cell first undergoes meiosis, forming four haploid spores. 2.Each spore then divides by mitosis, forming two haploid cells, called the tube cell and the generative cell. 3.The resulting pollen grain is ready for release from the anther. © 2015 Pearson Education, Inc. 31.10 The development of pollen and ovules culminates in fertilization • The female gametophyte is an embryo sac. • A cell in the ovule undergoes meiosis to produce four haploid spores. • Three of the spores degenerate. • The surviving spore undergoes a series of mitotic divisions to produce the embryo sac, the female gametophyte. • The sac contains a large central cell with two haploid nuclei. • One of its other cells is the haploid egg, ready to be fertilized. © 2015 Pearson Education, Inc. 31.10 The development of pollen and ovules culminates in fertilization • Pollination: pollen goes from anther to stigma (wind, water, animals). • The pollen grain germinates on the stigma. • The pollen tube grows toward ovule and mitosis forms two sperm. • Pollen tube enters ovary and discharges its two sperm. • One sperm fertilizes the egg to form the 2n zygote. • Other sperm combines with two haploid nuclei to form 3n endosperm (foodstoring tissue which nourishes the developing seed) • This formation of a diploid zygote and a triploid endosperm is called double fertilization. © 2015 Pearson Education, Inc. 31.11 The ovule develops into a seed • After fertilization, the ovule begins developing into a seed. • Near the end of its maturation, the seed loses most of its water and forms a hard, resistant seed coat. • Seed dormancy allows time for a plant to disperse its seeds and increases the chance that plants will begin growing only when environmental conditions, such as temperature and moisture, favor survival. © 2015 Pearson Education, Inc. 31.11 The ovule develops into a seed • In eudicots, most endosperm is converted into cotyledons; stays mostly endosperm in monocots. © 2015 Pearson Education, Inc. 31.12 The ovary develops into a fruit • While the seeds are developing from ovules, hormonal changes triggered by fertilization cause the flower’s ovary to grow, thicken, and mature into a fruit. • A fruit is a mature ovary that protects seeds and helps disperse them. © 2015 Pearson Education, Inc. 31.12 The ovary develops into a fruit • Various adaptations of fruits help disperse seeds. • Seeds of some flowering plants, such as dandelions and maples, are contained within fruits that function like kites or propellers. • Coconuts are adapted to dispersal by water. • Many angiosperms rely on animals to carry seeds clinging to fur or ingested with fruits. Fleshy Fruits Dry Fruits © 2015 Pearson Education, Inc. 31.13 Seed germination continues the life cycle • At germination, a seed takes up water and restarts the growth that was suspended during seed dormancy. • In eudicots, the embryonic root emerges first and grows downward and shoots emerge from the soil with the apical meristem “hooked” downward to protect it. • In monocots, • A protective sheath pushes upward and breaks through the soil and the shoot tip then grows up through the tunnel provided by the sheath. • The cotyledon remains in the soil and decomposes. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. You should now be able to 1. Explain how the cultivation of wheat has changed over the past 10,000 years. 2. Compare the structure of monocots and eudicots. 3. Compare the structures and functions of roots, stems, and leaves. 4. Distinguish between a taproot, stolon, rhizome, tuber, bulb, petiole, and tendril, and indicate common examples of each from a vegetable garden. © 2015 Pearson Education, Inc. You should now be able to 5. Define a tissue system. Describe the three main types of tissue systems found in young eudicot roots, stems, and leaves. 6. Describe the three unique structures found in most plant cells. 7. Describe the structures and functions of the five major types of plant cells. 8. Distinguish between (a) indeterminate and determinate growth and (b) annuals, biennials, and perennials. © 2015 Pearson Education, Inc. You should now be able to 9. Describe and compare primary and secondary growth. 10. Describe the parts of a flower and their functions. 11. Describe the processes and events that lead to double fertilization. 12. Explain how a seed forms. Compare the structures of eudicot and monocot seeds and explain the significance of seed dormancy. © 2015 Pearson Education, Inc. You should now be able to 13. Describe the structure and functions of fruit. 14. Describe and compare germination in bean and corn plants. 15. Describe examples of cloning in plants. 16. Compare the advantages and disadvantages of asexual versus sexual reproduction. 17. Describe plant adaptations that permit very long lives. © 2015 Pearson Education, Inc. Figure 31.UN01 Terminal bud (grows stem) Flower (reproductive organ) Shoot system (site of photosynthesis) Stem (supports leaves and flowers) Axillary bud (produces a branch) Node Internode Blade Petiole Root system (anchors, absorbs nutrients, and stores food) © 2015 Pearson Education, Inc. Leaf (main organ of photosynthesis) Root hairs (microscopic; increase surface area for absorption) Figure 31.UN02 Shoot tip (shoot apical meristem and young leaves) Vascular cambium Axillary bud meristem Cork cambium Lateral meristems Root apical meristems © 2015 Pearson Education, Inc. Figure 31.UN03 Pollen (n) Ovary Embryo sac (n) Fertilization within ovule Ovule Mature plant (2n) Fruit (from ovary) Seed (from ovule) Embryo (2n) Germinating seed (2n) © 2015 Pearson Education, Inc. Figure 31.UN04 Endosperm nucleus (3n) (2n central cell plus sperm) Zygote (2n) (egg plus sperm nucleus) © 2015 Pearson Education, Inc.