Radical radicles: Flowers, fruits, & seeds

Flower development Plant must be mature Environmental triggers activate floral genes Growth bud becomes flower bud Flower buds don’t elongate Tissues differentiate

Flower structure Most flowers are “Perfect” Have male & female parts (pistil = stigma + ovary) Male parts (stamen = anthers + filaments) Male Female Most flowers are “Perfect” Have male & female parts Always monoecious Some are “Imperfect” Not always dioecious Squash, corn, begonia

Flower structure: Composites Sunflower – many small perfect flowers Skunk cabbage & Anthurium – many small perfect flowers Calla lily – females below, males above (imperfect flowers) Asters – “Florets” Arums – “Spadices”

Pollination Required for seed development Pollen germinates, Pollen tubes Required for seed development Pollen germinates, fertilizes ovule(s) Ovule(s) becomes seed(s) Preventing self-pollination Location, timing, sexual incompatibility… Some do self-pollinate

Pollination Strategies Wind, insect, animal Nectar as an attractant Flowers look different in UV Some pollen glows!

Pollination Strategies Sphinx moths Star orchid Darwin predicted this moth’s existence 40 years before it was discovered in Madagascar! Oregon wild ginger

Pollenation Strategies Sphinx moths Star orchid Darwin predicted this moth’s existence 40 years before it was discovered in Madagascar! Oregon wild ginger

Seed Development After pollination, petals drop Ovule matures to final form (fruit, pod, capsule, etc.) Cell division Cell expansion Starch accumulation Ripening or hardening

Seed Dispersal Strategies “Samara” Seeds Always come from flowers No pollination, no seeds! Many dispersal strategies Fruits Designed to be eaten Sweeten when seeds mature Seeds dispersed by animals

Kinds of Fruits (botanically) Berries: multiple seeds from a single ovary in a single flower. Grape, tomato, squash, papaya, cucumber, eggplant, banana, peppers, citrus, blueberry Aggregates: multiple seeds from multiple ovaries in a single flower. Blackberry, raspberry, strawberry Drupes: single seed from a single ovary in a single flower. Plum, cherry, peach, olive, apricot, mango, coffee, almond, pistachio, walnut, pecan Pomes: from the Malinae subgroup of the Rose family. Apple, pear, quince, loquat Multiples: from several flowers that fuse into one fruit. Pineapple, fig, mulberry, breadfruit, jackfruit Nuts: from hardened ovary wall, seed within usually unattached. Filbert, acorn, chestnut, beechnut Legumes: from a single ovary in a single flower, forming a pod. Beans, peas, lentils, carob, peanut, tamarind, alfalfa

Conifers & Cones Cones develop from female flower Forgotten seed cache Cones develop from female flower Seeds borne under bracts Have single wing Some cones are “serotinous” and open only after fire

Seed Germination Environmental triggers Epigeal germination Hypogeal germination Environmental triggers Temperature, moisture, sunlight Scarification: physical or chemical Stratification: temperature Radicle is first root Cotyledons are first leaves Endosperm is energy reserve until leaves developed

Questions?