Chapter 22: The Plant Kingdom Lecture Outline Enger, E. D., Ross, F. C., & Bailey, D. B. (2012). Concepts in biology (14th ed.). New York: McGraw- Hill. 22-1
What is a plant? 22-2 Eukaryotic Heterotrophic Multicellular Contains chlorophyll a and b Has cellulose cell walls Lives in a variety of terrestrial habitats And a few shallow aquatic habits Exhibits alternation of generations
Plant Diversity 22-3
Alternation of Generations 22-4 A life cycle that involves two generations Sporophyte generation Diploid Undergoes meiosis to generate haploid spores Spores germinate and divide by mitosis to give rise to the gametophyte generation. Gametophyte generation Multicellular haploid generation Undergoes mitosis to produce haploid gametes Gametes unite to form a zygote Zygote divides by mitosis to form the sporophyte generation.
Alternation of Generations 22-5
The Evolution of Plants Photosynthetic algae are thought to be the ancestors of plants. Green algae have the same types of chlorophyll. There is extensive DNA homology between plants and green algae. The evolution of plants shows two trends. Toward greater specialization for living in a dry environment Toward a more prominent sporophyte generation 22-6
The Evolution of Plants Primitive plants Lack vascular tissue to carry water Have flagellated sperm; no seeds Have to live in moist habitats Have dominant gametophyte generation More advanced plants Have specialized cells that transport water Have seeds that do not require water for distribution Have dominant sporophyte generation 22-7
The Taxonomy of Plants 22-8
Nonvascular Plants 22-9 Include Mosses, hornworts, liverworts Known as the bryophytes Common features Lack vascular tissue Use diffusion and osmosis to obtain water and nutrients Do not have true roots or leaves Gametophyte is dominant Sperm swim to egg Must have water to reproduce sexually Are small and confined to moist habitats
Moss Life Cycle 22-10
Kinds of Nonvascular Plants Mosses Grow as a carpet of many individual gametophyte plants Each individual is less than 5 cm tall. Liverworts and hornworts Form flat sheets only a few cells thick Each cell contains one large chloroplast. 22-11
The Significance of Vascular Tissue Vascular tissue is an adaptation to living in dry environments. Allows plants to transport water and nutrients throughout the plant Associated with the development of Leaves for photosynthesis Roots for absorbing water and minerals Vascular tissue allowed for an increase in plant size Accompanied by the appearance of a waterproof coating on the plant surfaces Two types of vascular tissue Xylem Phloem 22-12
Xylem 22-13 A series of dead, hollow cells that form tubes Vessel elements Form long tubes with cells end-to-end Tracheids Tapered cells with holes Overlap to form a sieve-like tube The walls of these cells are strengthened by cellulose and lignin. Transports water and minerals from the soil to the leaves
Xylem 22-14
Phloem Carries organic molecules produced in the leaves to the rest of the plant Sugar Amino acids Consists of two types of cells Sieve-tube elements Lack a nucleus and organelles, but have cytoplasm Have holes in the end walls for the transport of material Companion cells Actively transport sugars and amino acids out of the leaf cells and into the sieve-tube elements 22-15
Phloem 22-16
The Development of Roots, Stems, and Leaves 22-17 The appearance of vascular tissue allowed for the development of specialized plant parts. Roots are specialized for absorption. Stems are specialized for transport. Leaves are specialized for photosynthesis.
Roots 22-18 Underground parts of a plant that Anchor in the soil Absorb water and nutrients Move the nutrients into the vascular system Grow from the tips Explore new areas of soil for water and nutrients Root tips have root hairs that increase their absorptive surface. Can be important storage sites Many plants store carbohydrates in their roots during growing season to be used during the winter. Carrots, turnips, radishes, maple trees, rhubarb, grasses
Kinds of Roots 22-19
Stems Above-ground structures that Support the leaves Transport raw material from the roots to the leaves Transport manufactured material from the leaves to other parts of the plant Vary greatly in diameter and length Tree trunks are large and support branches. Dandelion stems are short. Some stems are underground. 22-20
Stems The structure of cell walls allows the stem to support the leaves. Cell walls are made of cellulose interwoven into a box. When cells are full of water, the cell walls will not stretch. This makes the cells turgid, stiff, and able to support weight. Woody plants have especially thick cell walls. These have lignin in them Allows woody plants to grow tall and withstand wind 22-21
Stems Stems contain a lot of vascular tissue. Stems also Store food Sugar cane Yams Potatoes Photosynthesize Have waterproof layers Can be waxy or woody 22-22
Leaves Specialized for photosynthesis Have large surface area to collect sunlight Relatively thin to allow light penetration Have bundles of vascular tissue to transport Water and minerals needed for photosynthesis into the leaf The sugar that is made out of the leaf Thick cell walls for support Are arranged to minimize shading of lower leaves 22-23
The Structure of a Leaf 22-24
Leaves Specialized for photosynthesis Covered by a waxy coating to minimize water loss Water evaporates from leaves through transpiration. Pulls water and nutrients up from the roots Transpiration must be regulated so plant doesn t lose too much water. Water and oxygen exit, and carbon dioxide enters, through stomata. 22-25
Stomates 22-26
Seedless Vascular Plants Include Whisk ferns Horsetails Club mosses Ferns Have vascular tissue Are not limited to aquatic environments Do not have seeds Have flagellated sperm Must have moist conditions to reproduce 22-27
Fern Life Cycle 22-28
Kinds of Seedless Vascular Plants Ferns Most common seedless vascular plant Whisk ferns Lack roots and leaves Anchored by an underground stem Modifications of the stem serve the functions of roots and leaves. 22-29
Kinds of Vascular Seedless Plants 22-30 Horsetails Low-growing plants with jointed stems Most photosynthesis occurs in the stems. Have silicon dioxide in their cell walls Called (and used as) scouring brushes by pioneers Club mosses Usually evergreen Low-growing, branching plants Some are called ground pines.
Seed-producing Vascular Plants A seed is a specialized structure that contains An embryo Stored food A protective outer coating (seed coat) that prevents drying Seeds allow plants to live in dry habitats. Aid in dispersal Gymnosperms and angiosperms produce seeds. Accompanied by the development of pollen Encased sperm (male gametophyte generation) Allows plants to reproduce without water 22-31
Gymnosperms Means naked seed Woody, perennial plants Produce seeds that are not enclosed (naked) Produce seeds in cones 22-32
The Pine Life Cycle 22-33
Kinds of Gymnosperms Cycads Wood plants with a ring of fern-like leaves at the top Live in tropical regions Ginkgo Ginkgo biloba is the only living species A tree with fan-shaped leaves Used in many herbal medicines 22-34
Kinds of Gymnosperms Conifers Trees and shrubs that bear cones Have needle-shaped leaves Called evergreens because they do not lose their leaves Do shed needles throughout the year Used in the production of lumber 22-35
Several Gymnosperms 22-36
Angiosperms Produce flowers Have vascular tissue, seeds, and pollen Have seeds enclosed in a fruit A modification of the ovary wall 22-37
Flower Structure Composed of highly modified leaves Petals are usually colorful. Sepals surround petals Petals and sepals are arranged in whorls. Specialized for sexual reproduction Female parts in the center Pistil (stigma, style, and ovary) Ovary produces eggs 22-38
Flower Structure Male parts surround the pistil. Stamens (filament and anther) Anther produces sperm. Perfect flowers have both pistils and stamens. Imperfect flowers have either pistils or stamens. 22-39
Flower Structure 22-40
The Life Cycle of a Flowering Plant 22-41
Pollination Strategies Wind Plants with inconspicuous flowers are usually wind-pollinated. Produce large numbers of flowers and pollen Many species are wind-pollinated. Grasses and sedges Aspens, birches, and oaks Responsible for hay fever Some people have allergic reactions to pollen. 22-42
Strategies for Pollination 22-43 Animals Plants with showy flowers are usually animalpollinated. These flowers usually produce nectar. Also smell good to attract animals Flowers attract insects, birds, and small mammals. The animals feed on the nectar and pick up the pollen. Then move to another plant for more nectar, transferring the pollen
Wind- and Insect-pollinated Flowers 22-44
Fruit 22-45 A modification of the ovary that contains seeds Involved in dispersal of seeds Many fruits are nutritive to animals. The animals eat the fruit and ingest the seeds. The seeds pass through the digestive tract unharmed and get planted in the animals feces. Other fruits burst open and release light seeds that are dispersed by wind. Other fruits have sticky surfaces that cling to animals that pass by.
Types of Fruits 22-46
Angiosperm Diversity Classified as either monocots or dicots Refers to the number of cotyledons found in the seeds of the species Monocots have one cotyledon (peanut). Dicots have two cotyledons (lima bean). Cotyledons (seed leaves) store food for the growing embryo. They emerge as the first leaves. 22-47
Embryos in Dicots and Monocots 22-48
Monocots vs. Dicots 22-49
Angiosperm Diversity Monocots Yuccas and palms are woody. The rest are herbaceous. Dicots Wheat, rice, corn, sweet potatoes, onions, bananas Mints, carrots, cabbages, mustards, tomatoes, and potatoes are herbaceous dicots. Aspen and sagebrush are woody dicots. These are deciduous. 22-50
Deciduous Trees 22-51 Lose their leaves once a year Occurs in the fall before they go dormant The bark of the tree is the phloem. Produce a new layer of xylem and phloem each year Therefore, the trunk increases in diameter each year.
Growth of Woody Plants Woody plants have the ability to grow continuously for many years. They get taller and grow in diameter each year. Growth occurs at the tips of the roots and stems. 22-52
Growth of Woody Plants Grow in diameter by adding new xylem and phloem to the outside of the stem Vascular cambium is made of xylem in the middle and phloem around the perimeter (bark) Between the xylem and phloem is the cambium. The cambium is responsible for lateral growth. Cambium cells go thought mitosis, making two cells. One cell remains cambium; the other cell forms vascular tissue. As the xylem accumulates, it becomes wood. 22-53
A Cross Section of Woody Stem 22-54
Plant Responses to their Environment Plants are constantly changing in response to changes in their environment. They produce flowers at certain times of year. Grow toward the light Can mount an attack against a competitor 22-55
Tropisms Growth toward or away from a stimulus Phototropism Growing toward light Involves a hormone called auxin The tip of the stem produces auxin Transported into the stem on the shaded side Stimulates cells on that side to divide and elongate Causes the stem to bend toward the light 22-56
Phototropism 22-57
Tropisms Thigmotropism Climbing vines can wrap around an object using tendrils. Tendrils wave about and when they touch an object, they wrap around it. Once attached, the tendrils harden. Sweet peas, grape vines, and ivy exhibit thigmotropism. 22-58
Thigmotropism 22-59
Seasonal Responses Plants can measure the length of the day. In response to day length, plants make hormones that trigger development of fruit or flowers. In deciduous trees, shortening days triggers leaves to fall off. Plants can sense changes in temperature. In dormant plants, warming of the soil triggers above ground growth. Plants can sense the amount of water. During dry seasons, certain plants will lose their leaves and go dormant. When it begins to rain, these plants begin to grow and flower. 22-60
Response to Injury Plants are attacked by pathogens and herbivores. Plants can fight infection and repair damage by forming scar tissue. Plants defend themselves against predation. By producing toxins that interfere with herbivores metabolism Once leaves are eaten, the new leaves produce even more toxin. 22-61
Coevolution of Plants and Animals 22-62 Plants evolved before animals. Insects and amphibians followed terrestrial plants. Symbiotic relationships evolved between plants and animals. Many flowering plants are pollinated by insects and birds. These flowers are brightly colored, have nectar and have odor. Grasses and grazers have coevolved. Grass has silicon that wears down grazers teeth. Grazers have very long teeth that take a long time to wear down. Many angiosperms produce nutritive fruit. Animals eat the fruit and distribute the seeds.