Plant Reproduction & Response to the Environment

Plant Reproduction & Response to the Environment

Seeds

A plant structure that contains an embryo, contains nutrients for the embryo, and is covered with a protective coat

These features enableseeds to survive harsh environmental

conditions and then sprout when favorable conditions exist.

• Seeds have one or more cotyledons that store or help absorb food for the sporophyte.

Seeds

• Plants whose seeds are part of fruits are called angiosperms (flowing plants)

• Plants whose seeds are not part of fruits are called gymnosperms (non-flowering plants)

Alternation of Generations Gametophyte (haploid)generation produces gametes.

Sporophyte (diploid)generation produces spores that can grow to form the next gametophyte generation.

Sporophyte generation—maple tree

Gametophyte generation—maple pollen

Alternation of Generations

• Diploid sporophyte generation alternates with a haploid gametophyte generation

• Gametophyte of gymnosperms are in the cones, and in angiosperms they are in the flowers

• Two types of cones: – Pollen cone (male cone) – produce pollen– Seed cone (female cone) – contains the ovules,

where the eggs are held

• Pollination – transfer of pollen from the male structure to the female structure

• Fertilization and development then occur

Reproduction in Gymnosperms

Reproduction in Gymnosperms

• Occurs in the flower • Most angiosperms are pollinated by animals

(insects, birds) • Double fertilization – One sperm fertilizes the egg and becomes the zygote – A second sperm fertilizes the embryo sac and

becomes the food supply

Reproduction in Angiosperms

Reproduction in Angiosperms

Reproduction in Angiosperms

• The ovary becomes the fruit

• Seeds are dispersed by animals, wind, and water

• Germination – early growth of the plant

Germination

• Sepals – enclose the bud • Petals – attract pollinators • Stamen – male structure – Filament – long, thin stalk that supports the anther – Anther – produces pollen

• Carpels (or pistils) – female structure – Ovary – contains the ovules – Style – stalk of the carpel – Stigma – sticky surface where pollen lands

Structure of a Flower

Structure of a Flower

Asexual Reproduction• Vegetative reproduction

– production of new plants from stems, leafs, and roots

• Cutting – pieces of plant cut off and planted

• Grafting & budding – a stem or bud is cut from one plant & attached to another

Plant Hormones

• Auxins – stimulate cell elongation

• Cytokinins – stimulate cell division

• Gibberellins – produce increases in size

• Ethylene – stimulates fruit to ripen

• Tropisms – responses of plants to environmental stimuli– Gravitropism – response to gravity– Phototropism – response to light – Thigmotropism – response to touch

• Positive – in the direction of the stimulus • Negative – away from the stimulus

Plant Responses

Plant Responses