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Ch. 5 & 6- Flowers & Fruits. Angiosperms (flowering plants). Unique among plants because they have sexual reproductive structures contained in a flower derived from modified leaves seeds form inside fleshy fruit pollinated by insects or other animals.
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Angiosperms (flowering plants) • Unique among plants because they have sexual reproductive structures contained in a flower • derived from modified leaves • seeds form inside fleshy fruit • pollinated by insects or other animals Fruit as an adaptation for seed dispersal: Red berries and dandelion
Flower arrangements • Perfect: both stamens & carpels • Imperfect: missing either stamens or carpels • Monoecious: both male & female flowers on same plant • Dioecious: male & female flowers on separate plants female male Embryo sac fruit seed The structure of a flower
monoecious species, male (left) and female (right) begonia flowers
Pollination • place pollen onto stigma of a carpel • pollination agents • grasses, many trees: wind • many angiosperms: animals, including insects • self-pollination A relationship between an angiosperm and its pollinator: Hummingbird and flower (left); bee and Scotch broom (right)
How do flowers attract the pollinator of choice? • Insect: bright, showy petals with fragrant aromas, rich in nectar • E.g.: moths=white, night; flies=“smelly” • Hummingbird: bright, often red, no aroma • Wind: small and inconspicuous with copious production of dry, lightweight pollen
Fruits • What is a fruit? • What are the purpose of fruit? • How is a fruit formed?
Fruit = “mature ovary”purpose: protects seeds, dispersal aid Relationship between a pea flower and a fruit (pea pod)
Fruit or vegetable? • botanical: • Ripened ovary • Legal • Something that tastes sweet and is eaten as dessert
Types of Fruits • Dry fruits: Tough or papery pericarp • Fleshy fruits: Soft and juicy pericarp • Drupe • Berry • Aggregate • Multiple • Accessory
Development of fruit from flower • drupe • berry • simple = 1 ovary of 1 flower • e.g., cherry, soybean pod • compound = multiple ovaries • aggregate = of one flower • e.g., raspberry, blackberry • multiple = of many flowers (inflorescence) • e.g., pineapple • accessory = parts other than ovary • e.g., strawberry, apple, melon, tomato
Seeds • Contain embryonic plant plus nutritive tissue & tough outer coat • Starting point for next generation
Cotyledons (embryonic leaves) • Single cotyledon = monocot • Two large cotyledons = dicot • Cotyledons can be “fleshy” or “leafy” • Cotyledons can be kept belowground or elevated above ground
Seed Germination • imbibition: absorption of water • mobilization of food reserves • enzyme activity digests endosperm (converts starch to sugar)
Seed Germination • emergence of radicle • detects gravity & grows downward • epicotyl emerges through soil surface • light cues upward & straighter growth
Fig. 40.1 With light: Green Shorter Open cotyledons Straight stem Without light: Yellow Elongated Closed cotyledons Hooked stem