POLLINATION and FERTILIZATION Review

Pollen

POLLINATION ReviewSelf pollination and Cross pollination

FERTILIZATION ReviewFertilization Basics

FERTILIZATION ReviewPollen grain with

nucleiPollen grain with

pollen tube nucleus (1) and sperm nuclei (2)

FERTILIZATION Review

FERTILIZATION Review

ZYGOTE to EMBRYO

SEEDSMORPHOLOGY

SEED COAT (testa) HILUM MICROPILE

ANATOMY EPICOTYL HYPOCOTYL RADICLE

FOOD SOURCE COTYLEDONS – dicots ENDOSPERM – monocots

SEED GERMINATIONSTEPS to GROWTH

SEED imbibes WATERSEED COAT BURSTS (more O2 + H2O)EMBRYO produces HORMONES (Gibberellic Acid)

which activate ENZYMES (alpha-amylase) converting STARCHES to SUGARS and transported to the EMBRYO

RESPIRATION STARTS > ENERGY > produces new CELLS, TISSUES and GROWTH

RADICLE emerges (germination)HYPOCOTYL and EPICOTYL emerge

SEED GERMINATION

CONDITIONS for GERMINATION

VIABLE SEEDFavorable ENVIRONMENTAL conditionsFavorable INTERNAL conditions

The seed is said to be DORMANT, if seed is VIABLE and one or more conditions is not met.

CONDITIONS for GERMINATIONVIABLE SEED

Dependent on SPECIES

VIABILITY prolonged by: COOL temperatures Low HUMIDITY (low H2O)

Low O2

CONDITIONS for GERMINATIONFavorable ENVIRONMENTAL conditions

H2O Saturated vs. not saturated

O2 Dry, sandy vs. clay soils

TEMPERATURE Cool vs. warm season crops

LIGHT Light – celery, lettuce, weeds No light - peas

CONDITIONS for GERMINATIONLIGHT

Pigment PHYTOCHROME Blue-green pigment Exists in two forms Pr (660 nm) Pfr (730 nm)

Amount of Pr or Pfr in tissues is determined with the type of light present

CONDITIONS for GERMINATIONFavorable INTERNAL conditions

PHYSICAL barriers Seed coat IMPERMEABLE to H2O Seed coat RESISTS EXPANSION

Remedy SCARIFICATION: MECHANICAL CHEMICAL TEMPERATURE

CONDITIONS for GERMINATIONFavorable INTERNAL conditions

PHYSIOLOGICAL barriers IMMATURE EMBRYO

Remedy – TIME

AFTER RIPENINGRemedy – STRATIFICATION:

Application of MOISTURE and LOW TEMPS or alternation

Usually due to Abscissic Acid and low temperatures

CONDITIONS for GERMINATIONFavorable INTERNAL conditions

CHEMICAL barriers

INHIBITORS in SEED COAT Remedy – LEACH with WATER

Desert seeds - Phenolic acid

INHIBITORS in FRUIT Remedy – SOAK and REMOVE PULP

Tomatoes, Arisaema triphyllum

SEED DORMANCYInsures GERMINATION during times that

maximize SURVIVAL of SEEDLINGS