Plants!

STS Biology

Unit 6

Mrs. Stein

Plant Kingdom Characteristics

– Eukaryotic– Autotrophic (photosynthetic)– Multicellular

Many aquatic “plants” are algae – No seeds or true roots

Life on land required many adaptations

Evolution of Plants

Land Plants Need to be protected from drying out and

methods to transport materials Early land plants were non-vascular and

live in very moist environments– Mosses and liverworts

Vascular plants have transport tissue– Xylem – thick, dead tissue which moves water

UP from roots to leaves

– Phloem – living tissue, transports FOOD (sugar) in both directions

Ferns were the first vascular plants

Seed Plants

Cycads, ginkos, pines, spruce

Seed Ferns

Extinct

1st seed plants

Gymnosperms

“naked” seed

Conifer: gametes in cones, not

fruits

Monocot

Angiosperms

Flowering plants

Oaks, corn, tulips

Seed(s) contained in fruits

Dicot

Male cone

Female cone

Advantages of Seed Plants Can live on land Seed coat provides protection and

prevents drying out - the seed can survive longer in harsh conditions

Contains food supply for embryo Water is not needed for

reproduction – pollinators and seed dispersal

Roots, stems, and vascular tissue moves materials greater distances

Seed Structures A cotyledon is a food storage organ which

functions as the first seed leaf Monocots – one cotyledon Dicots – two cotyledons Endosperm is also food storage Embryo will grow into the new plant Hypocotyl is below the cotyledon and

becomes the lower stem Epicotyl is above the cotyledon and

becomes the upper stem and leaves Radicle becomes the roots

Corn and Bean

Seed Germination

Monocots & Dicots

Vascular bundles scattered

Vascular bundles in a ring

Stem

Arranged in 3’sArranged in 4’s or 5’s

Petals

ParallelBranchedLeaves

FibrousTaprootRoots

1 cotyledon2 cotyledonsSeeds

MonocotDicotPlant Part

Monocots & Dicots

Leaves Function in food production (photosynthesis) Epidermal cells – outer layer of cells, covered

with a waxy cuticle– Stomata surrounded by guard cells

Mesophyll – cell layers containing chloroplasts– Palisade Layer – tall, closely packed, sit of most

photosynthesis– Spongy Layer – loosely packed, air spaces allow

gases to enter and exit the leaf

Leaf Cross Section

UpperEpidermis

Cuticle

Vein (vascular tissue)

LowerEpidermis

Spongy Mesophyll

Palisade Mesophyll

Stoma

Guard Cells

Stomata Greek for “mouth” Opening of stomata are regulated by guard

cells Water exits through stomata (transpiration) Site of gas exchange – CO2 in, O2 out

Roots Functions

– Absorb water and nutrients from soil

– Food storage (ie: carrots)– Anchoring the plant

Structure– Xylem and phloem– Epidermis – thin layer that

absorbs water and nutrients– Cortex – food storage– Meristematic Tissue – only site

of mitosis, found at tips of roots and shoots

Vascular Bundles in Roots Dicot roots have xylem in an “X” in the

center of the root Monocot roots have vascular bundles in

a circular pattern

Dicot Root Monocot Root

XYLEM

PHLOEMDicot RootVascular Cylinder

Stems Function

– Support plant, hold leaves up to the sun– Transport foot and water

Arrangement of vascular bundles– Dicots – arranged in a ring– Monocots – scattered throughout

Stems

Dicot Stem Monocot Stem

Flowers Reproductive structures of angiosperms Sepals are the outermost layer which

encloses a bud and protects the developing flower

Petals are just inside sepals, fragrance and color attracts pollinators

The receptacle is where sepals, petals, and sex organs attach

Flowers (cont.) Stamen - male sex organ

– Anthers produce pollen– Filaments hold the anther up for

pollinators or wind Pistil (aka carpel) – female sex organ

– The stigma is the sticky end where pollen lands

– The style is the “neck” which connects the stigma to the ovary

– The ovary contains ovules, when mature the ovary becomes a fruit

Flower Anatomy

FilamentSta

men

Anther

PistilStyle

Stigma

Petal

Ovary

Ovule

Receptacle

Sepal

Pollination Pollen transfers from anther to stigma

– Self-pollination – pollen fertilizes the ovule of the same plant

– Cross-pollination – pollen fertilizes ovules of another plant, thus increasing genetic variation

Cross Pollination Methods Wind Pollination

– Inefficient, high pollen production – Flowers (if present) are small and not

colorful

Cross Pollination Methods

Vector pollination uses animals to carry pollen between plants

More efficient, less pollen produced Plants attract pollinators by:

– Colorful petals– Fragrance– Nectar production

Coevolution Two species evolve in response to

changes in one another

Bee Pollination

Butterfly Pollination

Bat Pollination

Moth Pollination

Seed Dispersal Wind scatters seeds

– Maple trees, dandelions

Animal dispersal occurs when barbs stick to animal fur– Burdock plant

Animals eat and digest fruits, seeds are excreted

Fertilization

1. Pollen lands on stigma

2. Pollen tube grows into the style

3. Sperm and egg unite forming and zygote

Double Fertilization Two sperm enter the ovary The 1st sperm fertilizes the

egg resulting in a zygote (2N) The 2nd sperm fertilizes the

polar nuclei forming the endosperm (3N)

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