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BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor CHAPTER 31 Plant Structure, Reproduction, and Development Modules 31.1 – 31.4 From PowerPoint® Lectures for Biology: Concepts & Connections Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A Gentle Giant • This giant sequoia, the General Sherman, is the largest plant on Earth – It is 84 m (275 ft) tall – Its trunk is 10m in diameter Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The General Sherman has been growing for about 2,500 years Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Growth rings mark each ______ in a tree's life – Rings vary in thickness depending on weather conditions during the growing season Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Humans depend on plant products – ______ – ______ – ______ – ______ – Industrial chemicals Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Plants are vital to Earth's well-being – They provide ______ for land animals – They offer ______ and breeding areas for animals, fungi, and microorganisms – Their roots ______ soil erosion – Photosynthesis in plant leaves helps ______ carbon dioxide and ______ oxygen to the air Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings PLANT STRUCTURE AND FUNCTION 31.2 The two main groups of angiosperms are the monocots and the dicots • ___________, or flowering plants, are the most familiar and diverse plants • There are two main types of angiosperms – ______ include orchids, bamboos, palms, lilies, grains, and other grasses – ______ include shrubs, ornamental plants, most trees, and many food crops Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Monocots and dicots differ in seed leaf number and in the structure of roots, stems, leaves, and flowers SEED LEAVES LEAF VEINS STEMS FLOWERS ROOTS MONOCOTS One cotyledon Main veins usually parallel Vascular bundles in complex arrangement Floral parts usually in multiples of three Fibrous root system DICOTS Two cotyledons Main veins usually branched Vascular bundles arranged in ring Floral parts usually in Taproot multiples of four or five usually present Figure 31.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 31.3 The plant body consists of roots and shoots • Root system – Provides ___________ – ______ and ______ minerals and water – Stores ______ • Root hairs ______ the surface area for absorption Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Shoot system – Consists of ______ , ______ , and ______ in angiosperms – Stems are located ______ the ground and support the leaves and flowers – ______ are the main sites of photosynthesis in most plants Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Terminal bud Blade Leaf Flower Petiole Axillary bud Stem SHOOT SYSTEM Node Internode Taproot ROOT SYSTEM Root hairs Figure 31.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The terminal bud is located at the tip of a ______ – It is the growth point of the stem • Axillary buds can give rise to ______ • In ______ dominance, the terminal bud produces hormones that inhibit the growth of axillary buds – This results in a taller plant that has greater exposure to light Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 31.4 Many plants have modified roots and shoots • Roots and stems are adapted for a variety of functions – Storing ______ – ______ reproduction – ______ • Plant breeders have improved the yields of root crops by selecting varieties, such as the sugar beet plant, with very large taproots Figure 31.4A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Modified stems include STRAWBERRY PLANT – ______, for asexual reproduction Runner POTATO PLANT – ______, for plant growth and food storage – ______, for food storage in the form of starch Rhizome IRIS PLANT Rhizome Tuber Taproot Root Figure 31.4B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Modified leaves include tendrils and spines – ______ help plants to climb – ______ may protect the plant from plant-eating animals Figure 31.4C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 31.5 Plant cells and tissues are diverse in structure and function Figure 31.5A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • There are five major types of plant cells – __________ – _________ – _________ – Water-conducting cells (______ ) – Food-conducting cells (______ ) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Parenchyma cells function in ______ storage, photosynthesis, and aerobic respiration. They have a primary cell wall that is thin and flexible and ______ a secondary cell wall. Primary wall (thin) Pit Figure 31.5B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Collenchyma cells provide ______ in parts of the plant that are still growing. They have an unevenly thick primary cell wall and ______ a secondary cell wall. The “strings” of celery are made of collenchyma cells. Primary wall (thick) Figure 31.5C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Sclerenchyma cells provide a rigid scaffold that supports the plant. They have very ______ primary and secondary cell walls that are fortified with ______ . Their function is purely for support. – Fiber cells Pits Secondary wall Fiber cells Primary wall FIBER Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 31.5D – Sclereids (stone cells) Secondary wall Primary wall Sclereid cells Pits SCLEREID Figure 31.5D continued Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Water-conducting cells, generally known as ______ , convey water from the roots to the stems and leaves Pits – Chains of ______ or ______ ______ form a system of tubes for water transport Tracheids Vessel element Pits Openings in end wall Figure 31.5E Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Food-conducting cells, generally known as ______ , function in the transport of sugars, other compounds, and some mineral ions – _________ members are arranged end-to-end, forming tubes – Their end walls are perforated with plasmodesmata, forming ______ plates – At least one companion cell flanks each sievetube member Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Sieve plate Companion cell Cytoplasm Primary wall Figure 31.5F Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Complex ______ are composed of more than one type of plant cell • Vascular tissues are complex tissues that conduct ______ and ______ – ______ contains water-conducting cells that convey water and dissolved minerals – ______ contains sieve-tube members that transport sugars Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 31.6 Three tissue systems make up the plant body • Roots, stems, and leaves are made of three tissue systems Leaf Stem – The ______ – The ______ tissue system – The ______ tissue system Root Epidermis Ground tissue system Vascular tissue system Figure 31.6A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The epidermis covers and protects the plant – The ______ is a waxy coating secreted by epidermal cells that helps the plant retain water • The vascular tissue contains xylem and phloem – It provides support and transports water and nutrients Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The ground tissue system functions mainly in ______ and _____________ – It consists of parenchyma cells and supportive collenchyma and sclerenchyma cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The ground tissue system of the root forms the ______ – The cortex consists mostly of parenchyma tissue • The selective barrier forming the innermost layer of the cortex is the ___________ Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings VASCULAR TISSUE SYSTEM Xylem Phloem Epidermis GROUND TISSUE SYSTEM Cortex Endodermis Figure 31.6B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • These microscopic cross sections of a dicot and a monocot indicate several differences in their tissue systems Figure 31.6C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The three tissue systems in dicot leaves – The epidermis consist of pores called ______ (singular, stoma) flanked by regulatory ______ ______ Figure 31.6D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings – The ground tissue system of a leaf is called ______ and is the site of photosynthesis Figure 31.6D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings – The vascular tissue consists of a network of veins composed of xylem and phloem Figure 31.6D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings PLANT GROWTH 31.7 Primary growth lengthens roots and shoots • Most plants exhibit indeterminate growth – They continue to grow as long as they live • In contrast, animals are characterized by determinate growth – They cease growing after reaching a certain size Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Terminal bud Axillary buds Arrows = direction of growth Root tips Figure 31.7A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • ______ complete their life cycle in a single year or growing season – Examples: wheat, corn, rice, and most wildflowers • ______ complete their life cycle in two years, with flowering occurring in the second year – Examples: beets and carrots • ______ live and reproduce for many years – Examples: trees, shrubs, and some grasses Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Growth in all plants originates in tissues called ______ – Meristems are areas of unspecialized, dividing cells • ______ meristems are located at the tips of roots and in the terminal buds and axillary buds of shoots – They initiate ______ growth, lengthwise growth by the production of new cells – Roots and stems lengthen further as cells elongate and differentiate Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cortex Epidermis DIFFERENTIATION Vascular cylinder CELL DIVISION ELONGATION Root hair Cellulose fibers Apical meristem region Root cap Figure 31.7B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 31.8 Secondary growth increases the girth of woody plants • An increase in a plant's ______ results from secondary growth • ___________ growth involves cell division in two cylindrical meristems – ______ cambium – ______ cambium Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 31.8A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Vascular cambium thickens a stem by adding ______ of secondary xylem, or wood, next to its inner surface – It also produces the secondary phloem, which is a tissue of the bark • Cork cambium produces protective ______ cells located in the bark Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Everything external to the vascular cambium is considered bark – Secondary phloem – Cork cambium – Protective cork cells • Heartwood in the center of the trunk consists of older, clogged layers of secondary xylem • Sapwood consists of younger, secondary xylem that still conducts water Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • A woody log is the result of several ______ of secondary growth Sapwood Rings Wood rays Heartwood Sapwood Vascular cambium Bark Secondary phloem Cork cambium Cork Heartwood Figure 31.8B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings PLANT REPRODUCTION 31.9 Overview: The sexual life cycle of a flowering plant • The angiosperm flower is a reproductive shoot consisting of Anther Carpel Stigma Ovary – ______ – ______ Stamen – ______ Ovule – ______ Sepal Petal Figure 31.9A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Sepals are usually ______ and resemble leaves in appearance – Sepals enclose and ______ the flower bud before the flower opens • Petals are often ______ and ______ – They attract insects (___________ ) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • ______ are the male reproductive organs of plants – Pollen grains develop in anthers, at the tips of stamens – Each pollen grain contains ______ haploid cells (a ______ cell and two ______ cells) • ______ are the female reproductive organs of plants – The ovary at the base of the carpel houses the ovule Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 31.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The life cycle of an angiosperm involves several stages Ovary, containing ovule Embryo Fruit, containing seed Seed Mature plant with flowers, where fertilization occurs Seedling Germinating seed Figure 31.9B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 31.11 The ovule develops into a seed • After fertilization, the ovule becomes a seed – The fertilized egg (first sperm cell) within the seed divides to become an ______ – The other fertilized cell (second sperm cell) develops into the endosperm, which stores food for the ______ • A resistant seed coat ______ the embryo and endosperm Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Triploid cell OVULE Zygote Two cells Cotyledons Endosperm Seed coat Shoot Embryo Root SEED Figure 31.11A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Seed ___________ is an important evolutionary adaptation in which growth and development are suspended temporarily – It allows time for a plant to disperse its seeds – It increases the chance that a new generation of plants will begin growing only when environmental conditions favor survival Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Comparison between dicot and monocot seeds Seed coat Embryonic shoot Embryonic leaves Embryonic root Cotyledons COMMON BEAN (DICOT) Fruit tissue Cotyledon Seed coat Endosperm Embryonic leaf Sheath CORN (MONOCOT) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Embryonic shoot Embryonic root Figure 31.11B 31.12 The ovary develops into a fruit • The ovary develops into a ______ which helps protect and ______ the seeds Figure 31.12A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • There is a correspondence between flower and fruit in a pea plant – The wall of the ovary becomes the ______ – The ovules develop into the ______ Upper part of carpel Ovule Seed Ovary wall Sepal Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Pod (opened) Figure 31.12B – The small, threadlike structure at the end of the pod is what remains of the upper part of the flower's carpel – The sepals of the flower stay attached to the base of the green pod Upper part of carpel Ovule Seed Ovary wall Sepal Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Pod (opened) Figure 31.12B • ______ fruits develop from a flower with a single carpel and ovary – Apples, pea pods, cherries • ______ fruits develop from a flower with many carpels – Raspberries • ______ fruits develop from a group of flowers clustered tightly together – Pineapples Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 31.12C 31.13 Seed germination continues the life cycle • A seed starts to ______ when it takes up water, expands, and bursts its seed coat • Metabolic changes cause the embryo to resume growth and absorb nutrients from the endosperm • An embryonic root emerges, and a shoot pushes upward and expands its leaves Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Pea germination (a dicot) Foliage leaves Embryonic shoot Cotyledons Embryonic root • Corn germination (a monocot) Foliage leaves Protective sheath enclosing shoot Embryonic root Cotyledon Figure 31.13A, B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 31.14 Asexual reproduction produces plant clones • Many plants can reproduce asexually via ______ , ______ , or ______ • Asexual reproduction often involves _____________ – Fragmentation is the separation of parts from the parent plant and regeneration of those parts into whole plants Figure 31.14A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Sprouts from the roots of a coast redwood tree may eventually take the place of its parent in the forest Figure 31.14B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • These creosote bushes came from generations of vegetative reproduction by roots Figure 31.14C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Most grasses can propagate asexually by sprouting shoots and roots from runners Figure 31.14D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 31.15 Connection: Vegetative reproduction is a mainstay of modern agriculture • Propagating plants from cuttings or bits of tissue can increase agricultural productivity – But it can also reduce genetic diversity Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Test-tube cloning is the growth of a plantlet from a few meristem cells cultured on a chemical medium – A single plant can be cloned into thousands of copies that will continue to grow when planted in soil – Orchids and certain pine trees used in mass plantings are propagated this way Figure 31.15A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • "GM" (genetically modified) plants are created when foreign genes are incorporated into a single parenchyma cell – The cell is then cultured until it develops into a new plantlet • The commercial adoption of GM crops has been rapid – However, many people are concerned about the potential environmental risks associated with their use Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Monocultures are large areas of land planted with a single crop • Gene-cloning techniques and monocultures have led to crop plants with little genetic diversity – This increases the likelihood that a small number of diseases could devastate large crop areas Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings THE UPTAKE AND TRANSPORT OF PLANT NUTRIENTS 32.1 Plants acquire their nutrients from soil and air • As a plant grows, its roots absorb water, minerals (inorganic ions), and some oxygen from the soil – Its leaves take carbon dioxide from the air Figure 32.1A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Photosynthesis makes use of the uptake of water, carbon dioxide, and minerals to produce ______ – These sugars are composed of carbon, oxygen, and hydrogen • The nitrogen and magnesium absorbed from the soil are components of __________ • _________, also absorbed from the soil, is a major component of nucleic acids, phospholipids, and ATP Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings – The ability to move water from roots to leaves and to deliver sugars to specific areas of the body are remarkable feats of evolutionary engineering Figure 32.1B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 32.2 The plasma membranes of root cells control solute uptake • Root hairs greatly ___________ a root's absorptive surface Figure 32.2A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • In order for upward transport, water and solutes must enter the ______ by passing through the Casparian Strip. • Water and solutes move through the root's epidermis and cortex by two main routes – Through cells (intracellular route) – Between cells (extracellular route) • Water and solutes typically follow a combination of routes and passages through numerous plasma membranes and cell walls en route to the xylem Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Epidermis Root hair Cortex Phloem Xylem Casparian strip Endodermis EXTRACELLULAR ROUTE, via cell walls; stopped by Casparian strip Casparian strip Xylem Root hair INTRACELLULAR ROUTE, via cell interiors; through plasmodesmata Epidermis Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cortex Endodermis Figure 32.2B • The Casparian strip stops ______ and ______ from entering the xylem via cell walls – Thus water and ions that travel the extracellular route can enter the xylem only by crossing a plasma membrane into an endodermal cell Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 32.3 Transpiration pulls water up xylem vessels • Xylem ______ is the solution of inorganic nutrients conveyed in xylem tissue from a plant's roots to its shoots • Root ______ can push xylem sap up only a few meters – Solute transport raises water pressure in the xylem • Plants ______ xylem sap upward from the soil through the transpiration-cohesion-tension mechanism Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Transpiration is the loss of ______ from the leaves – It exerts a ______ on the xylem sap • Cohesion causes water molecules to ______ together – It relays the ______ of transpiration along a string of water molecules all the way to the roots • The adhesion of water molecules to xylem cell walls helps counter the effect of gravity Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 32.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 32.4 Guard cells control transpiration • Guard cells surrounding stomata in the leaves control transpiration – The opening and closing of stomata is an adaptation to help plants regulate their water content and adjust to changing environmental conditions H2O Guard cells H2O H2O H2O H2O H2O K+ Vacuole H2O H2O H2O H2O Stoma opening Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Stoma closing Figure 32.4 32.5 Phloem transports sugars • While xylem sap flows ______ from the roots, phloem sap moves throughout the plant in ______ directions • The main function of phloem is to transport the ______ made by photosynthesis Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Phloem contains food-conducting cells arranged end-to-end as tubes Sievetube member Sieve plate Figure 32.5A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Phloem transports food molecules made by photosynthesis by a pressure-flow mechanism – Sugar is ______ into a phloem tube at the sugar source, raising the solute concentration inside the tube Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 32.5B – Water is drawn into the tube by ______ , raising the pressure in the tube – Sugar and water leave the tube at the sugar sink Figure 32.5B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings – The increase in ______ at the sugar source and decrease at the sugar sink causes phloem sap to flow from source to sink Figure 32.5B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Plant biologists have used aphids to study phloem sap – These studies have supported the pressureflow model Honeydew droplet Stylet of aphid Figure 32.5C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings PLANT NUTRIENTS AND THE SOIL 32.6 Plant health depends on a complete diet of essential inorganic nutrients • A plant must obtain ______ from its surroundings • ______________, such as carbon, oxygen, nitrogen, and phosphorus, are needed in large amounts – They are used to build organic molecules Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 32.6B • ______________, including iron, copper, and zinc, act mainly as cofactors or enzymes • Growing plants in solutions of known composition enables researchers to determine nutrient requirements – Hydroponic culture Complete solution containing all minerals (control) Solution lacking potassium (experimental) Figure 32.6A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 32.7 Connection: You can diagnose some nutrient deficiencies in your own plants • Stunting, wilting, and color changes indicate nutrient deficiencies – Compared to the healthy tomato plant on the left, the plant on the right is not getting enough nitrogen Figure 32.7A, B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings – Phosphorus deficiency is sometimes indicated by a purplish leaf color – Yellow leaves can result from potassium deficiency Figure 32.7C, D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 32.8 Soil contains rock particles, humus, organisms, water, and crucial solutes • Soil characteristics determine whether a plant will be able to obtain the nutrients it needs to grow • ______ soil contains a mixture of small rock and clay particles – They hold water and ions and allow oxygen to diffuse into plant roots Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • ______ is decaying organic material – It provides nutrients, holds water and air, and supports the growth of organisms that enhance soil fertility Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Soil horizons are distinct ______ of soil • Horizon A, or ______ , contains rock particles (sand and clay), humus, and living organisms • Horizon B contains fine clay particles and nutrients that have drained down from Horizon A • Horizon C is composed mainly of partially broken-down rock Figure 32.8A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • A plant's root hairs are in direct contact with the water that surrounds the tiny particles of topsoil • The root hairs take up dissolved oxygen, ions, and water from the film of soil water that surrounds them Soil particle surrounded by film of water Root hair Water Air space Figure 32.8B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Anions, such as nitrate (NO3-), are readily available to plants because they are not bound to soil particles – But they tend to drain out of the soil quickly – This reduces soil fertility Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 32.9 Connection: Soil conservation is essential to human life • Good soil management includes – water-conserving ______ – ______ control – the ______ use of herbicides and fertilizers Figure 32.9A, B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 32.10 Connection: Organic farmers avoid the use of commercial chemicals • ______ farmers rely on the principles of ecology rather than the use of synthetic chemicals or pesticides that can damage the environment – Organic farmers try to restore as much to the soil as is drawn from it Figure 32.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 32.11 Fungi help most plants absorb nutrients from the soil • Relationships with other organisms help plants obtain nutrients • Many plants form mycorrhizae – A network of fungal threads increases a plant's absorption of nutrients and water – The fungus receives some nutrients from the plant Figure 32.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 32.12 The plant kingdom includes parasites and carnivores • Some plants have evolved ______ ways of obtaining food from other plants – Dodder obtains organic molecules from other plant species using specialized roots that tap into the host’s vascular tissue Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 32.12A – Mistletoe supplements its diet by siphoning ______ from the vascular tissue of its host plants Figure 32.12B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Carnivorous plants obtain some of their nutrients from ______ tissues – The sundew and Venus flytrap use insects as a source of ______ – This nutritional adaptation enables them to thrive in highly acidic soil Figure 32.12C, D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 32.13 Most plants depend on bacteria to supply nitrogen • Plants cannot use atmospheric nitrogen, gaseous N2, although it is very plentiful – Instead, nearly all plants depend to some extent on nitrogen supplies in the ______ Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Bacteria in the soil convert N2 from the air and nitrogen compounds from decomposing organic matter into forms that plants can take up and use – Nitrate ions (N03-) and ammonium ions (NH4+) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • This process of converting atmospheric nitrogen to ammonium is called nitrogen ______ ATMOSPHERE N2 Amino acids Nitrogen-fixing bacteria N2 NH4+ NH4+ (ammonium) Soil Ammonifying bacteria Organic material Nitrifying bacteria NO3– (nitrate) Root Figure 32.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 32.14 Legumes and certain other plants house nitrogen-fixing bacteria • ______ and certain other plants have nodules in their roots that contain nitrogen-fixing bacteria Shoot Nodules Roots Figure 32.14A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Most of the nitrogen-fixing bacteria in legume nodules belong to the genus ______ • The relationship between the plant and the nitrogen-fixing bacteria is ______ beneficial Bacteria within vesicle Figure 32.14B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings PLANT NUTRIENTS AND AGRICULTURE 32.15 Connection: A major goal of agricultural research is to improve the protein content of crops • Plants are the main nutritional source for most people in the world – Therefore, improving the protein content of crops is an important research goal Figure 32.15A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • One of the most promising lines of agricultural research is directed toward improving the output of the Rhizobium bacteria that inhabit the root nodules of legumes Rhizobium DNA Genes for nitrogen fixation TURN OFF GENES Nitrogen compounds in root nodules Nitrogen-fixing enzymes N2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 32.15B PLANT HORMONES 33.1 Experiments on how plants turn toward light led to the discovery of a plant hormone • Hormones coordinate the activities of plant cells and tissues • The study of plant hormones began with observations of plants bending toward light – This phenomenon is called phototropism Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 33.1A • Experiments carried out by Darwin and others showed that the tip of a grass seedling detects light and transmits a signal down to the growing region of the shoot Light Control Figure 33.1C Tip removed Tip covered by opaque cap Tip covered by transparent cap DARWIN AND DARWIN (1880) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Base covered by opaque shield Tip separated by gelatin block Tip separated by mica BOYSEN-JENSEN (1913) • It was discovered in the 1920s that a hormone was responsible for the signaling Darwin observed – This hormone was dubbed ______ – Auxin plays an important role in phototropism Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 33.2 Five major types of hormones regulate plant growth and development • Hormones regulate plant growth and development by affecting – cell ______ – cell ______ – cell ______ • Only small amounts of hormones are necessary to trigger the signal-transduction pathways that regulate plant growth and development Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 33.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Plants produce ______ (IAA) in the apical meristems at the tips of shoots – At different concentrations, auxin stimulates or inhibits the elongation of ______ and ______ STEMS ROOTS 0.9 g/L Figure 33.3B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Phototropism results from faster cell growth on the ______ side of the shoot than on the illuminated side Shaded side of shoot Light Illuminated side of shoot Figure 33.1B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The effect of auxin on pea plants Figure 33.3A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Auxin stimulates cell division and the development of vascular tissues in vascular cambium – This promotes growth in stem diameter • Auxins are also used as a rooting powder to develop roots quickly in plant cuttings. • Synthetic auxins can be sprayed on tomato plants to induce fruit production without pollination producing seedless tomatoes Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 33.4 Cytokinins stimulate cell division • ___________ are hormones that promote cell division and delay senescence (aging) by inhibiting protein breakdown. – They are produced in actively growing roots, embryos, and fruits • The antagonistic interaction of auxin and cytokinin may be one way a plant coordinates the growth of its root and shoot systems Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Cytokinins from roots may balance the effects of auxin from apical meristems, causing lower buds to develop into branches – The basil plant on the right has had its terminal bud removed – The inhibitory effect of auxin on axillary buds was thus eliminated Terminal bud No terminal bud – Cytokinins from the roots activated the axillary buds, making the plant grow more branches Figure 33.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 33.5 Gibberellins affect stem elongation and have numerous other effects • ____________ stimulate cell elongation and cell division in stems and leaves. This causes rapid growth in some stems known as bolting. Figure 33.5A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Gibberellins, in combination with auxin, can influence fruit development – Gibberellins can make grapes grow ______ and farther apart in a cluster – The grapes at right were treated with gibberellin, while those at left were not Figure 33.5B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Fig. 40.23 • Gibberellin-auxin sprays can make apples, currants, and eggplants develop without fertilization • Gibberellins released from embryos function in some of the early events of seed germination Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 33.6 Abscisic acid inhibits many plant processes • Abscisic acid (ABA) ______ the germination of seeds • The ratio of ABA to gibberellins often determines whether a seed will remain dormant or will germinate Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Seeds of many plants remain dormant until their ABA is inactivated or washed away – These flowers grew from seeds that germinated after a rainstorm in the Mojave Desert Figure 33.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • ABA also acts as a “stress hormone” – It causes stomata to close when a plant is dehydrated – Thus the rate of transpiration is decreased and further water loss prevented Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 33.7 Ethylene triggers fruit ripening and other aging processes • Ethylene is a gaseous hormone that triggers fruit ______ • Ethylene is given off as cells age • These bananas were exposed to different amounts of ethylene over the same time period Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 33.7A • Fruit growers use ethylene to control ripening – Apple farmers take measures to retard the ripening action of natural ethylene – Tomato farmers pick unripe fruit and then pipe ethylene into storage bins to promote ripening Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The shorter days of autumn trigger a changing ratio of auxin to ethylene Leaf stalk Stem (twig) – This is the likely cause of the changes seen in deciduous trees — color changes, drying, and the loss of leaves Protective layer Figure 33.7B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Stem Abscission layer Leaf stalk 33.8 Connection: Plant hormones have many agricultural uses • Plant hormones have a variety of agricultural uses – Farmers use auxin to delay or promote fruit drop – Auxin and gibberellins are used to produce seedless fruits – A synthetic auxin (2,4-D) is used to kill weeds Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • There are many questions and concerns about the safety of using such chemicals in food production Figure 33.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings GROWTH RESPONSES AND BIOLOGICAL RHYTHMS IN PLANTS 33.9 Tropisms orient plant growth toward or away from environmental stimuli • Plants sense and respond to environmental changes in a variety of ways • Tropisms are growth responses that change the shape of a plant or make it grow toward or away from a stimulus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Phototropism is the bending ______ light – It may result from auxin moving from the illuminated side to the shaded side of a stem Figure 33.1A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Gravitropism is a response to ______ – It may be caused by the settling of special organelles on the low sides of shoots and roots – This may trigger a change in the distribution of hormones Figure 33.9A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Gravitropism is an important adaptation – It ensures that the shoot will grow upward toward light and the roots will grow down into the soil, no matter how the seed lands in the soil Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Thigmotropism is a response to ______ – It is responsible for the coiling of tendrils and vines around objects – It enables plants to use other objects for support while growing toward sunlight Figure 33.9B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Haploid Art) Fig. 29.03(TE Gametophyte (n) Mitosis Spore Sperm Egg n n n n Spores Meiosis Gamete fusion Spore mother 2n cell 2n Zygote 2n Embryo Sporangia Sporophyte (2n) Diploid Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 29.05(TE Art)Sperm Antheridium FERTILIZATION Zygote Egg Archegonium Developing sporophyte in archegonium Mature sporophyte n 2n Male Female Gametophytes Sporangium MEIOSIS Bud Mitosis Rhizoid Germinating Spores Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings spores Parent gametophyte Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 29.13(TE Art) Mitosis Archegonium Antheridium Rhizoids Spore Gametophyte n Sperm MEIOSIS FERTILIZATION 2n Mature sporangium Mature frond Egg Embryo Sorus (cluster of sporangia) Leaf of young sporophyte Adult sporophyte Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Rhizome Gametophyte Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 29.15(TE Art) Megaspore Pollen tube Mature seed cone (2nd year) Mitosis Pollination Pollen FERTILIZATION (15 months after n pollination) Mitosis Mitosis Embryo Microspores Longisection of seed, showing Microspore mother cell 2n embryo Pine seed Pollen-bearing Scale Mitosis cone Megaspore mother cell Seedling Scale Ovulate (seed-bearing) cone Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Sporophyte Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings