Chapter 20

Life of a Flowering Plant

20.1 Reproductive Adaptations

Flower is a specialized shoot with modified leaves

sepals: outermost ring; covers flower bud

petals: second ring; colorful to attract pollinators

stamens and carpels: center ring; reproductive structures

Reproductive Structures

Male Gametophytes

produced in stamens

anther: sac on top of stalk of stamen

Spores develop into pollen grains

Pollen = 2 cells with protective wall

Female Gametophytes

produced in carpels Ovary at base Ovules produce 4 cells

each; 3 die Each undergo 3

cycles of mitosis embryo sac: resulting

gametophyte style: leads to ovary stigma: sticky tip

Pollination pollination: pollen grains released from

anthers land on stigma Pollen grain absorbs water and extends a

pollen tube which grows toward ovary Pollen cell divides forming 2 sperm (n)

One fertilizes egg = zygote (2n) = embryo The other fertilizes the central cell = (3n)

endosperm

Seed Dispersal

Fruits protect seeds and help disperse Travel by sticking to animal’s fur (burr) Fleshy fruit that attracts animals; seeds

are passed through digestive system Water; coconuts Wind; puffy dandelion

Seed Development Seed coat: outer layer around seed that protects

embryo and endosperm Miniature root and shoot cotyledon: storage and

transfer of nutrients to embryo Dicots = dicotyledon = 2 Monocots=

(mono)cotyledon

Embryo grows through a few

stages of mitosis and stops to be

dispersed (stage that you see in

fruit)

Seed Germination germination: embryo grows when

conditions are favorable Soak up water

split seed

coat trigger

metabolic

changes

Adaptations and Conditions Protections for developing

shoots Hooked tip Sheath covering

Seedling: young plant that has just emerged from the soil

Vary among species Desert plants: after heavy rainfall Harsh winters: only after long period of cold Fire: clears other growth

Asexual Reproduction

vegetative reproduction: asexual reproduction Cacti; dropped shoots become new plant Strawberries and grasses send out runners Some trees send out shoots from underground stems

Different Life Cycles

Annuals: complete life cycle in one year Biennials: 2 years, flower in second Perennials: multiple times per year

20.2 Plant Structure Roots fibrous root: mat of

thin roots spread out below the soil surface Increased surface area grasses

taproot: one large vertical root with smaller branches Starch-storing Carrots

Stems, leaves, and flowers stems: support leaves and flowers nodes: point where leaves and stems attach internodes: portions of stem between nodes Transport water and nutrients

Shoots

buds: undeveloped shoots Terminal bud: tip of stem Axillary: in the angles of a leaf - branches

blade: main part of the leaf Primary photosynthesis site

petiole: stalk that connects leaf to stem veins: throughout leaves to carry water and

nutrients Some plants have modified leaves

Celery stalks are leaves; onion is underground shoot

Plant Tissues

Dermal Vascular Ground

Meristematic: differentiates into the others

Dermal Tissue

Outer covering or “skin”

Epidermis: tissue of nonwoody organs One or more layers of

cells Covers and protects

young parts Secretes waxy cuticle

Periderm: older tissue

Vascular Tissue

Transports water, mineral nutrients, and organic molecules; structure

xylem: water and dissolved minerals

phloem: food; made in leaves and transported to parts that don’t photosynthesize

Ground Tissue

Fills the spaces between dermal and vascular

Most of young nonwoody plant

Photosynthesis, stoage and support

cortex: ground tissue in a root

Leaf Structure

Types of Plant Cells parenchyma: thin cell walls and large

central vacuoles Food storage Photosynthesis and cellular respiration Fruits Phloem

collenchyma: unevenly thick cell walls Grouped in strands or cylinders Support to young parts Young stems and petioles

sclerenchyma: specialized for support Die and leave behind a “skeleton” xylem

20.3 Primary Growth

Plants continue to grow their entire lives meristems: tissues that differentiate into

new dermal, vascular, and ground tissue apical meristems: tips of roots and buds of

shoots Grow in length and branches primary growth: growth in length

Primary Growth of Roots root cap: tip of the root

Protects dividing cells of apical meristem

Apical meristem Replaces cells of root cap Produces cells for primary

growth Forms 3 cylinders of

cells; dermal, ground, vascular

Cells elongate by taking up water

Primary Growth of Shoots

Apical meristem: tip of terminal bud Elongation just

below

Auxillary buds Formed as

elongating cells push upward

Cylinders of cells

20.4 Secondary Growth

Growth in plant width Woody plants; vines,

shrubs, trees Vascular cambium and

cork cambium vascular cambium:

cylinder of actively diving cells between xylem and phloem Adds secondary

vascular tissue to primary

Accumulates as wood

Cork cambium

cork cambium: meristem that develops from parenchyma cells Produces tough outer

layer of cork Dead cork cells leave

thick, waxy walls; protects and prevents water loss

bark: everything outside vascular cambium Phloem, cork, cork

cambium

Tree Rings

Rings = yearly activity of vascular cambium

Spring; cells are larger and thinner Cool and wet

Summer: cells are smaller and thicker Hot and dry

Heartwood - dead xylem

Sapwood - xylem transports water