Flowers & Flowering

Why flowers? location for sexual reproduction in Angiosperms co-evolved with the pollinators symbiotic relationship – all species involved benefit!

Flower Anatomy Many sizes, shapes and colors Most contain the following organs in some shape or form Petals Sepals Stamens Pistols

Petals Usually brightly colored Often have perfume or nectar at the base Provide surface for pollinators to rest on as they feed All of the petals together are called the corolla

Sepals Usually found in a ring at the base or outermost portion of the flower Serve as protective covering for the flower bud All of the sepals together are called the calyx

Stamen – male reproductive structure Made up of the anther and filament The anther is found at the tip of the filament – this is where pollen is produced The number of stamens varies from flower to flower

Pistil/Carpel – female reproductive structure Made up of the Stigma, Style and Ovary The stigma is at the top of the pistil. It’s role is to receive the pollen The style connects the stigma to the ovary The ovary is at the base. It contains ovules that produce eggs The number of ovaries varies in flowers

Complete vs Incomplete Flowers Perfect vs Imperfect Flower Complete flowers: pistils, stamens, sepals and petals Incomplete flower: lacking any of the parts Perfect flower: has both pistils and stamens Imperfect flower: lacks either pistils or stamens

Monoecious vs Dioecious Monoecious –separate male and female flowers on the same plant Ex. Corn, pecans, walnuts, cucumbers, and squash Dioecious – separate male and female plants Ex. Holly, ginkgo, pistachio, and marijuana

Photoperiodism Photoperiodism: response of flowering plants to daily daylight-darkness conditions Ensures all plants of the same species bloom at the same time

Critical Period The specific daylight-darkness conditions that will make flowering begin Day length is not what matters – amount of darkness is what matters The names are misleading – the categories were named before scientists realized it was darkness, not light, that prompted flowering

4 Categories Short-day: daylight is shorter than critical period – asters, poinsettias, strawberries Long-day: daylight is longer than critical period – carnations, petunias, potatoes Day neutral – flowers over a range of daylight hours, day length is not what induces flowering Intermediate day – will not flower if days are longer or shorter than critical period – sugarcane and grass