SEEDS and GERMINATION POLLINATION and FERTILIZATION Review Pollen

SEEDS and GERMINATION

POLLINATION and FERTILIZATION Review Pollen

POLLINATION Review Self pollination and Cross pollination

FERTILIZATION Review Fertilization Basics

FERTILIZATION Review Pollen grain with nuclei Pollen grain with pollen tube nucleus (1) and sperm nuclei (2)

FERTILIZATION Review

FERTILIZATION Review

ZYGOTE to EMBRYO

SEEDS MORPHOLOGY SEED COAT (testa) HILUM MICROPILE ANATOMY EPICOTYL HYPOCOTYL RADICLE FOOD SOURCE COTYLEDONS – dicots ENDOSPERM – monocots

SEED GERMINATION STEPS to GROWTH SEED imbibes WATER SEED COAT BURSTS (more O 2 + H 2 O) 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 SEED Favorable ENVIRONMENTAL conditions Favorable INTERNAL conditions The seed is said to be DORMANT, if seed is VIABLE and one or more conditions is not met.

CONDITIONS for GERMINATION VIABLE SEED Dependent on SPECIES VIABILITY prolonged by: COOL temperatures Low HUMIDITY (low H 2 O) Low O 2

CONDITIONS for GERMINATION Favorable ENVIRONMENTAL conditions H 2 O Saturated vs. not saturated O 2 Dry, sandy vs. clay soils TEMPERATURE Cool vs. warm season crops LIGHT Light – celery, lettuce, weeds No light - peas

CONDITIONS for GERMINATION LIGHT 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 GERMINATION Favorable INTERNAL conditions PHYSICAL barriers Seed coat IMPERMEABLE to H 2 O Seed coat RESISTS EXPANSION Remedy SCARIFICATION: MECHANICAL CHEMICAL TEMPERATURE

CONDITIONS for GERMINATION Favorable INTERNAL conditions PHYSIOLOGICAL barriers IMMATURE EMBRYO Remedy – TIME AFTER RIPENING Remedy – STRATIFICATION: Application of MOISTURE and LOW TEMPS or alternation Usually due to Abscissic Acid and low temperatures

CONDITIONS for GERMINATION Favorable 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 DORMANCY Insures GERMINATION during times that maximize SURVIVAL of SEEDLINGS