Plant nt Reprodu oduction ction 2. Fruits 3. Double - - PDF document

3/19/2017 1

Plant nt Reprodu

• duction

ction

Angios

• spe

perm rms

Angio iosp sperm rms: flowering plants Uniqu ique e Featu tures res

• 1. Flowers
• 2. Fruits
• 3. Double fertilization

(by 2 sperm)

Angiospe sperm rm Life Cycle

Altern rnat ation

• n of generat

ration

• ns:

s: life cycle regularly alternates between a haploid phase and diploid phase

• Sporoph
• phytes: (2n)

produces haploid spores by meiosis

• Spore: haploid reproductive

cell (gametophyte)

• Gametop
• phyte: haploid phase

gametes give rise to diploid phase by mitosis

Cycles

s differ r only in which phase ses s become diploi

• id.

Parts s of the Flowe wer

Male

• Stamens- male reproductive organs
• stamens have stalks (filament) & terminal

anthers which carry pollen sacs

• pollen sacs produce pollen
• pollen grain- gametophyte
• sperm-producing structure

Femal ale

• Carpels- female reproductive organs
• ovary at the base
• slender neck - style
• within the ovary are 1 or more ovules
• within ovules are embryo sacs
• female gametophyte - embryo sac
• egg-producing structure

Plant t Reproducti ction

• n Types

Asexu exual (vegetative reproduction)

• runners, bulbs, grafts, cuttings, vegetative (grass), fragmentation,

test-tube cloning

• clones
• simpler (no pollinator needed)
• suited for stable environments

tubers bulbs runners grafting

Plant t Reproducti ction

• n Types

Sexu xual

• flower  seeds
• genetic diversity
• more complex and hazardous for seedlings
• advantage in unstable environments

3/19/2017 2

Pollinatio ation

Transfer of pollen from anther to stigma

• Self

lf pollin inatio tion

• Cross

ss Pollin inatio tion

• Maximizes genetic variation

Mechanism sms Prevent Self Pollinati tion

• n
• Stamen

mens s & carpels pels may mature re at differen erent t times s

• Arranged so that animal pollinator won’t transfer pollen

from m anth thers ers to stigma ma of same e flower er

• Self

lf-in incompa patib tibilit ility: plant rejects own pollen or closely related plant

Fertilizatio ation

Double e fertilization

2 sperm from pollen 1 sperm fertilize zes egg - diploi

• id zygot
• te

1 sperm fuses with 2 polar r nuclei to form 3n endosp sperm rm endospe

• sperm

rm - food tissue in seed

• coconut milk
• grains

Developm

• pment

t of the Sporoph

• phyte

te

(plant embryo)

Seeds and Plant Embryo

Seed offers:

• protection for embryo
• stored nutrients for growth
• f embryo

coytle tledo dons- “seed leaves”

• first leaves of new

plant

Seeds

Matu ture re seed (dorma mant) t)

• Low metabolic rate
• Growth & development

suspended

• Resumes growth when

environmental conditions suitable for germination

3/19/2017 3

Seed Dispers rsal al

• Plants produce enormous numbers of seeds to

compensate for low survival rate

• Vast amount of genetic variation for natural selection

to screen

• Co- evolution: flowers and pollinators

r-strategy K-strategy

Seed Germinatio ation

• Seeds take up water (imbibit

bitio ion)

• triggers metabolic changes to begin growth
• root develops  shoot emerges  leaves

expand & turn green (photosynthesis)

• Very hazardous time for plants
• vulnerability to predators, parasites, wind

Seed Developme pment into a Plant Fruit

Fruit it is a mature re ovary ry seeds develop from ovules wall of ovary thickens to form fruit fruits protect dormant seeds & aid in their dispersal