현화식물의 생활 The Life of a Flowering Plant CHAPTER 28 현화식물의 생활 The Life of a Flowering Plant

California에 있는 giant sequoia tree는 지구상에서 가장 큰 식물이다. 일부 bristlecone pine trees는 이집트 피라미드 보다 오래 존재 했다.

한 개의 식물체는 수천 개의 복제물로 클론화 될 수 있다. 많은 현화식물들이 동물에 의존하여 번식한다.

BIOLOGY AND SOCIETY: PLANT CLONING — FEAST AND FAMINE 전 역사를 통하여 인류는 충분한 식량 공급을 위하여 식물을 재배하였다. 16세기에 유럽으로 도입된 감자가 좋은 예가 된다. 감자는 쉽게 클론 될 수 있어 널리 재배되었다. Cloned potatoes 1800년대에 많은 아일랜드 사람들의 식량이 되었다. 유전적 다양성의 부족으로 환경변화에 쉽게 영향을 받는다.

1840년대에 진균류 생물이 Irish potatoes 에 감염되어 기근의 주요한 원인이 되었다. Figure 28.1

식량 외에 식물은 인류의 삶에 중요한 매우 많은 재료가 된다.

THE STRUCTURE AND FUNCTION OF A FLOWERING PLANT 피자식물 (Angiosperms) 6천만 년 이상 육지의 우점 식물이 되고 있다. 식물계의 거의 90% 를 차지한다.

단자엽식물과 쌍자엽식물 Monocots and Dicots 식물학자들은 여러 구조적 특징에 근거하여 피자식물을 단자엽 식물과 쌍자엽 식물 2군으로 분류한다. Seed leaves Leaf veins Stems Flowers Roots Monocots Vascular bundles in scattered arrangement Floral parts usually in multiples of three Fibrous root system One cotyledon Veins usually parallel Dicots Floral parts usually in multiples of four or five Taproot usually present Two cotyledons Vascular bundles arranged in ring Veins usually branched Figure 28.2

The names monocot and dicot refer to cotyledons, or seed leaves found in the embryo Most angiosperms are dicots

Plant Organs: Roots, Stems, and Leaves 식물체는 a root system and a shoot system으로 구성되며, 각각은 서로 의존한다.

Flower Terminal bud Node Internode Axillary bud Shoot system Petiole Leaf Blade Stem Taproot Root hairs Root system Figure 28.3

Roots A plant’s root system Root hairs Anchors it in the soil Absorbs and transports minerals and water Stores food Root hairs Are tiny projections near the root tips Increase the surface area of the root

Stems 식물의 shoot system은 줄기 (stems), 잎(leave), 그리고 피자식물의 경우 꽃으로 (flowers) 되어있다. 식물의 줄기가 길이로 성장할 때 줄기 끝에 있는 정아에는 (terminal bud) 발달하는 잎이 있다. 많은 경우에, 정아는 호르몬을 생산하여 정단우세라는 (apical dominance) 현상이 나타나게 한다.

여러 종류의 식물에서 정아를 제거하면 액아의 (axillary buds) 성장이 촉진된다. Figure 28.4

Stems take many forms (a) Strawberry plant Runner (b) Potato plant Rhizome Tuber Taproot (c) Iris plant Root Rhizome Figure 28.5

Leaves 잎 (The leaves) 대부분의 식물에서 광합성 장소이다. 식물의 잎은 매우 다양하다.

Figure 28.6

Plant Cells 식물세포는 여러 가지 점에서 독특하다. 식물세포에는 엽록소가 (chlorophyll) 있는 엽록체 커다란 중앙 액포 (central vacuole) 세포벽 (Cell walls) 등이 있다.

Cell walls of adjoining cells Chloroplast Central vacuole Nucleus Endoplasmic reticulum Secondary cell wall Mitochondrion Primary cell wall Golgi apparatus Cell walls of adjoining cells Ribosomes Plasma membrane Microtubules Plasmodesmata Plasma membrane Figure 28.7

Cell walls of adjoining cells Chloroplas (21) (22) Nucleus (23) (28) (24) (29) (25) Cell walls of adjoining cells Ribosomes (30) (26) (27) Plasma membrane Figure 28.7

유조직 세포 (Parenchyma cells) 대부분의 식물에서 가장 흔한 종류의 세포 음식 저장, 광합성 등 다양한 기능을 수행한다. (food storage and photosynthesis) Primary wall (thin) (a) Parenchyma cell Figure 28.8a

후각조직 세포 (Collenchyma cells) 아직 성장하는 식물체 부위를 지지 Primary wall (thick) (b) Collenchyma cell Figure 28.8b

후벽조직 세포 (Sclerenchyma cells) 두꺼운 2차 세포벽을 가지고 있어 식물체를 지탱하는 기능 Secondary wall Primary wall (c) Sclerenchyma cell Figure 28.8c

물 통도 세포 (Water-conducting cells) 뿌리에서 줄기와 잎으로 물을 운반 Vessel element Tracheids Secondary wall Openings in end wall (d) Water-conducting cell Figure 28.8d

음식 통도 세포 (Food-conducting cells) 식물체 여러 곳에 음식을 운반 Plasmodesmata Primary wall (e) Food-conducting cell Figure 28.8e

Plant Tissues and Tissue Systems The cells of plants Are grouped into tissues with characteristic functions Plant tissues Are organized into tissue systems

Vascular tissue called xylem Contains water-conducting cells Vascular tissue called phloem Contains food-conducting cells

Roots, stems, and leaves are made up of three tissue systems Leaf Stem The dermal tissue system, the vascular tissue system, and the ground tissue system Root Dermal tissue system (epidermis) Vascular tissue system Ground tissue system Figure 28.9

The vascular tissue system The ground tissue system The epidermis Covers and protects the leaves, young stems, and roots The vascular tissue system Is made up of xylem and phloem The ground tissue system Makes up the bulk of a young plant

A cross section of a root shows what the three tissue systems look like under a microscope Figure 28.10

The three tissue systems in leaves Upper epidermis Mesophyll (ground tissue system) Lower epidermis Guard cells Xylem Cuticle Lower surface of leaf Vein Phloem Vein Stoma Guard cells Stoma Figure 28.11

Stomata, tiny pores that allow gas exchange Occur in the epidermis of leaves The mesophyll Is the ground tissue system in a leaf

THE LIFE CYCLE OF A FLOWERING PLANT Many plants can reproduce both sexually and asexually

Through asexual reproduction, a plant can produce many identical plants quickly and efficiently Figure 28.12

The Flower Sexual reproduction in plants produces genetically distinct offspring

In angiosperms The structure specific to sexual reproduction is the flower Petal Stamen Carpel Anther Stigma Filament Style Ovary Ovule Sepal Figure 28.13

The flower’s reproductive organs are the stamen and the carpel

The stamen, the male organ of a flower Consists of the filament and the anther In the anther Meiosis occurs, producing pollen grains that house the cells that develop into sperm

The carpel, the female organ of a flower Consists of the stigma, style, and ovary The stigma receives pollen grains The style leads to the ovary, which houses ovules that contain developing eggs, at the base of the stigma

The sexual life cycle of an angiosperm Is defined as the time from when the plant begins to grow from a seed through flowering and seed production to death Embryo Seed Ovary, containing ovule Fruit, containing seed Germinating seed Mature plant with flowers, where fertilization occurs Seeding Figure 28.14

Pollination and Fertilization The plant life cycle Alternates between haploid and diploid generations

The diploid plant body The haploid plant body Is called the sporophyte Is called the gametophyte

The life cycle is completed Fertilization Occurs when the female and male gametes unite, producing a diploid zygote The life cycle is completed When the zygote divides by mitosis and develops into a new sporophyte

The formation of the male and female gametophytes Development of male gametophyte (pollen grain) Haploid nuclei of two cells Anther Meiosis Mitosis Cell within anther 1 2 Four haploid spores 3 Pollen grain released from anther Two haploid nuclei of large, central cell Ovary Ovule Meiosis Mitosis Embryo sac Development of female gametophyte (embryo sac) 1 2 3 Surviving cell (haploid spore) Egg cell (with haploid nucleus) Figure 28.15

The first step leading to fertilization is pollination, the delivery of pollen to the stigma of a carpel

Pollen grain germinates Stigma 1 Pollination 2 Pollen grain germinates Stigma Pollen tube 3 Two sperm Ovule Triploid (3n) nucleus Embryo sac 4 Double fertilization Diploid (2n) zygote Egg cell Two sperm about to be discharged into ovule Figure 28.16

Many angiosperms are dependent on animals to transfer their pollen

After pollination The pollen grain germinates on the stigma forming two sperm Each sperm fertilizes a cell in the ovule in a process called double fertilization One fertilizes the egg, and the other fertilizes a second cell in the ovule

Seed Formation After fertilization The ovule begins developing into a seed

The zygote Divides via mitosis into a ball of cells that becomes the embryo The endosperm also forms from the other fertilized cell and provides nourishment for the embryo

The result of embryonic development is a mature seed with a tough protective seed coat Triploid nucleus of large, central cell Ovule Zygote Two cells Cotyledons Embryo Shoot Seed coat Root Endosperm Seed Figure 28.17

Fruit Formation A fruit Is a matured ovary that houses and protects seeds and aids in their dispersal

Pea pods Are a type of fruit Figure 28.18

Fruits are highly varied Figure 28.19

Seed Germination Germination Usually begins when the seed takes up water The hydrated seed expands and bursts its seed coat

Germination in a garden pea Involves the formation of the root and then the shoot Foliage leaves Embryonic shoot Cotyledons Embryonic root Figure 28.20

PLANT GROWTH Most plants display indeterminate growth, continuing to grow as long as they live

Species called annuals Complete their life cycle in a single year or growing season Species called biennials Complete their life cycle in two years

Plants known as perennials Live and reproduce for many years Figure 28.21

Primary Growth: Lengthening Growth in all plants Is made possible by tissues called meristems A meristem Consists of unspecialized cells that divide and generate new cells and tissues

Apical meristems Terminal bud Are found at the tips of roots and in the terminal and axillary buds of shoots Axillary buds Root tips Figure 28.22

Primary growth Consists of cell division in the apical meristems of roots and shoots Produces the new cells that enable a plant to grow in length

A growing root Is pushed through the soil by primary growth Cortex A growing root Vascular system Epidermis Is pushed through the soil by primary growth Contains a root cap that protects the actively dividing cells Differentiation Root hair Elongation Cell division Apical meristem region Root cap Figure 28.23

Secondary Growth: Thickening Results in the thickening of stems and roots Involves division in two meristems, the vascular cambium and the cork cambium

The vascular cambium Gives rise to wood near its inner surface Growth Pith Primary xylem Epidermis Vascular cambium Gives rise to wood near its inner surface Primary phloem Cortex Sloughed off cells Growth Primary xylem Secondary xylem Vascular cambium Secondary phloem Cork Cork cambium Primary phloem Growth Second year First year Secondary xylem (2 years’ growth) Vascular cambium Secondary phloem Bark Cork cambium Figure 28.24 Cork

Figure 28.24 (8) (9) (13) (10) (11) (12) Sloughed off cells Growth (8) (9) (13) (10) (11) (12) Sloughed off cells Growth Primary xylem Secondary xylem Vascular cambium Secondary phloem (14) (15) Primary phloem Growth (16)year (17)year (18)Xylem (19) Secondary phloem (20) Cork cambium Figure 28.24 Cork

The cork cambium Is outside the vascular cambium and produces cork, one component of bark

Over the years, a woody stem adds more layers, resulting in annual growth rings Wood rays Heartwood Sapwood Vascular cambium Secondary phloem Bark Cork cambium Cork Figure 28.25

EVOLUTION CONNECTION: THE INTERDEPENDENCE OF ANGIOSPERMS AND ANIMALS Most angiosperms Depend on various animals for pollination and seed dispersal

The flowers of many angiosperms Attract pollinators that rely entirely on the flowers’ nectar and pollen for food Figure 28.26

Many animals Have very defined relationships with various flower species

SUMMARY OF KEY CONCEPTS Monocots and Dicots Visual Summary 28.1

Plant Organs: Roots, Stems, and Leaves Flower (reproductive organ) Terminal bud Stem (supports leaves and flowers) Shoot system (photosynthetic center) Axillary bud Internode Node Leaf (main photosynthetic organ) Blade Petiole Root system (anchors, absorbs, nutrients, and stores food) Root hairs (microscopic; increase surface area for absorption) Visual Summary 28.2

Fertilization within ovule Pollination and Fertilization Pollen (n) Ovary Ovule Embryo sac (n) Fertilization within ovule Fruit (from ovary) Mature plant (2n) Seed (from ovule) Embryo (2n) Germinating seed (2n) Visual Summary 28.3