Plant Structure, Reproduction, and Development Chapter 31 Plant Structure, Reproduction, and Development

A Gentle Giant Gymnosperms Are one of two groups of seed plants A Gentle Giant Gymnosperms Are one of two groups of seed plants Bear seeds in cones

Angiosperms, or flowering plants Are the most familiar and diverse group of plants

TALKING ABOUT SCIENCE 31.1 Plant scientist Natasha Raikhel studies the Arabidopsis plant as a model biological system Natasha Raikhel Is one of America’s most prominent plant biologists Figure 31.1A

Dr. Raikhel works with Arabidopsis A popular model organism for studying biological systems Figure 31.1B

PLANT STRUCTURE AND FUNCTION 31.2 The two main groups of angiosperms are the monocots and the dicots Monocots and dicots differ in The number of seed leaves and in the structure of roots, stems, leaves, and flowers Fibrous root system MONOCOTS Seed leaves Leaf veins Stems Flowers Roots One cotyledon Main veins usually parallel Vascular bundles in complex arrangement Floral parts usually in multiples of three Two cotyledons Main veins usually branched Vascular bundles arranged in ring Floral parts usually in multiples of four or five Taproot usually present DICOTS Figure 31.2

31.3 A typical plant body consists of roots and shoots A plant’s root system Anchors it in the soil Absorbs and transports minerals and water and stores food

The shoot system of a plant Is made up of stems, leaves, and adaptations for reproduction, flowers

The body of a dicot Figure 31.3 Terminal bud Blade Leaf Flower Petiole Axillary bud Stem Taproot Root hairs Epidermal cell Root hair Internode Node Flower Shoot system Leaf Figure 31.3

31.4 Many plants have modified roots, stems, and leaves Some plants have unusually large taproots That store food in the form of carbohydrates Figure 31.4A

Many plants have modified stems That store food or function in asexual reproduction Strawberry plant Potato plant Stolon (runner) Taproot Rhizome Tuber Ginger plant Root Figure 31.4B

Other types of plants have modified leaves That function in protection or climbing Figure 31.4C

31.5 Plant cells and tissues are diverse in structure and function Most plant cells have three unique structures Chloroplasts, the sites of photosynthesis A central vacuole containing fluid A cell wall that surrounds the plasma membrane Chloroplast Central vacuole Cell walls Primary cell wall Middle lamella Secondary cell wall Plasma membrane Cell walls of adjoining cells Plasmodesmata Pit Plasma membrane Microtubules Ribosomes Golgi apparatus Mitochondrion Endoplasmic reticulum Nucleus Figure 31.5A

Plants have five major types of cells Parenchyma, which perform most of the metabolic functions Collenchyma, which provide support Primary cell wall (thin) Pit Starch-storing vesicles LM 270 Figure 31.5B Primary cell wall (thick) LM 270 Figure 31.5C

Sclerenchyma, the main component of wood Secondary cell wall Pits Fiber cells Primary cell wall Sclereid cells Fiber Sclereid LM 266 LM 200 Figure 31.5D

Angiosperms have water-conducting cells Tracheids and vessel elements Pits Openings in end wall Vessel element Tracheids Colorized SEM 150 Figure 31.5E

Are food-conducting cells Sieve-tube members Are food-conducting cells Sieve plate Companion cell Primary cell wall Cytoplasm Figure 31.5F

Two kinds of vascular tissue are Xylem, which conveys water and minerals Phloem, which transports sugars

31.6 Three tissue systems make up the plant body Each plant organ is made up of three tissue systems The dermal, vascular, and ground tissue systems Vein Guard cells Cuticle Upper epidermis Mesophyll Lower epidermis Stoma Xylem Phloem Dicot leaf Dicot stem Sheath Vascular bundle Cortex Pith Epidermis Monocot stem Vascular cylinder Endodermis Dicot root Key Dermal tissue system Ground tissue system Vascular tissue system Figure 31.6

The dermal tissue system Covers and protects the plant The vascular tissue system Contains xylem and phloem and provides long-distance transport and support The ground tissue system Consists of parenchyma cells and supportive collenchyma and sclerenchyma cells

31.7 Primary growth lengthens roots and shoots PLANT GROWTH 31.7 Primary growth lengthens roots and shoots Meristems, areas of unspecialized, dividing cells Are where plant growth originates

Initiate primary (lengthwise) growth by producing new cells Apical meristems Are located in the tips of roots and in the terminal and axillary buds of shoots Initiate primary (lengthwise) growth by producing new cells Figure 31.7A Terminal bud Axillary buds Root tips Arrows = direction of growth

Roots are covered with a root cap That protects the cells of the apical meristem Vascular cylinder Root hair Cortex Epidermis Zone of maturation Zone of elongation Zone of cell division Root cap Apical meristem region Cellulose fibers Key Dermal tissue system Ground tissue system Vascular tissue system Figure 31.7B

Axillary bud meristems Are found near the apical meristems Leaves Axillary bud meristems 1 2 LM 103 Figure 31.7C

31.8 Secondary growth increases the girth of woody plants Secondary growth arises from cell division In a cylindrical meristem called the vascular cambium

The vascular cambium thickens a stem By adding layers of secondary xylem, or wood, next to its inner surface Year 1 Early Spring Late Summer Year 2 Growth Primary xylem Vascular cambium Primary phloem Cor tex Epidermis Secondary xylem (wood) Cork cambium Secondary phloem Bark Shed epidermis Secondary xylem (2 years’ growth) Key Dermal tissue system Ground tissue system Vascular tissue system Figure 31.8A

The heartwood and sapwood Consist of different layers of xylem Outside the vascular cambium, the bark consists mainly of Secondary phloem, cork cambium, and protective cork cells Heartwood Sapwood Rings Wood rays Vascular cambium Secondary phloem Cork cambium Cork Bark Figure 31.8B

REPRODUCTION OF FLOWERING PLANTS 31.9 Overview: The sexual life cycle of a flowering plant The angiosperm flower consists of Sepals, petals, stamens, and carpals Stigma Style Ovary Anther Filament Stamen Petal Ovule Sepal Carpel Figure 31.9A

Pollen grains develop in anthers At the tip of stamens

The tip of the carpel, the stigma Receives pollen grains The ovary, at the base of the carpel Houses the egg-producing structure, the ovule Ovary, containing ovule Fruit, (mature ovary), containing seed Mature plant with flowers, where fertilization occurs Seedling Germinating seed Seed Embryo Figure 31.9B

31.10 The development of pollen and ovules culminates in fer tilization In the diploid sporophyte of an angiosperm Haploid spores are formed within ovules and anthers

The spores in the anthers Give rise to male gametophytes, pollen grains, which produce sperm A spore in an ovule Produces the embryo sac, the female gametophyte, which contains an egg cell

Pollination Is the arrival of pollen grains onto a stigma A pollen tube grows into the ovule And sperm pass through it and fer tilize both the egg and a second cell in a process called double fer tilization

Gametophyte development and fertilization in an angiosperm Development of male gametophyte (pollen grain) Development of female gametophyte (embryo sac) Anther Cell within anther Meiosis Four haploid spores Single spore Wall forms Mitosis (of each spore) Two cells Pollen grain released from anther Ovary Ovule Surviving cell (haploid spore) Pollen germinates Embryo sac Egg cell Two sperm in pollen tube Pollen tube enters embryo sac Two sperm discharged Triploid (3n) endosperm nucleus Double fer tilization occurs Diploid (2n) zygote (egg plus sperm) Pollination Figure 31.10

Secondary xylem (wood) 31.11 The ovule develops into a seed After fertilization, the ovule becomes a seed And the fertilized egg within it divides and becomes an embryo Growth Secondary xylem (wood) Cork cambium Secondary phloem Shed epidermis Triploid cell Ovule Zygote Embryo Endosperm Shoot Cotyledons Seed coat Seed Root Two cells Figure 31. 11A

The other fertilized cell Develops into the endosperm, which stores food for the embryo

The internal structures of dicot and monocot seeds Differ in a variety of ways Figure 31.11B Embryonic leaves root Seed coat Cotyledons shoot Common bean (dicot) Cotyledon leaf Sheath Fruit tissue Endosperm Shoot Corn (monocot)

31.12 The ovary develops into a fruit Angiosperms form fruits Which help protect and disperse the seeds 1 2 3 Figure 31.12A Upper part of carpel Ovule Sepal Ovar y wall Seed Pod (opened) Figure 31.12B

May differ in size and development Angiosperm fruits May differ in size and development Figure 31.12C

31.13 Seed germination continues the life cycle A seed starts to germinate When it takes up water and star ts to expand The embryo resumes growth And absorbs nutrients from the endosperm An embryonic root emerges And a shoot pushes upward and expands its leaves

In dicot germination, the root emerges first Followed by the shoot, which is covered by a protective hook Foliage leaves Embryonic shoot root Cotyledons Figure 31.13A

In monocot germination A protective sheath surrounding the shoot breaks the soil Foliage leaves Protective sheath enclosing shoot Embryonic root Cotyledon Figure 31.13B

31.14 Asexual reproduction produces plant clones Asexual reproduction can be achieved via Bulbs, sprouts, or runners Figure 31.14A Figure 31.14B Figure 31.14D Figure 31.14C

1.15 Asexual reproduction is a mainstay of modern agriculture CONNECTION 1.15 Asexual reproduction is a mainstay of modern agriculture Propagating plants asexually from cuttings or bits of tissue Can increase productivity but can also reduce genetic diversity Figure 31.15