Flowers, Fruits, and Seeds

1. Flowers, Fruits, and Seeds Chapter 8

2. Outline • Introduction • Differences Between Dicots and Monocots • Structure of Flowers • Fruits • Fruit and Seed Dispersal • Seeds

3. Introduction • Annual Plants -cycle completed in single season • Cycle = from seed germination to mature plant producing seeds • Biennial Plants -cycle completed in 2 growing seasons • Perennial Plants -cycle takes several to many growing seasons or plant produces flowers on new growth, while other plant parts persist indefinitely

4. Differences Between Dicots and Monocots • 2 major classes of flowering plants: • Magnoliopsida (dicots) • Liliopsida(monocots)

6. Structure of Flowers • Flowers begin as embryonic primordiumthat develops into bud • Flowers occur as specialized branches at tips of peduncles • May have branchlets of pedicels • Receptacle -swollen end of peduncle or pedicel • Other parts of flower attached to receptacle in whorls: sepals, petals, stamens, and pistil

7. Structure of Flowers

8. Structure of Flowers • Ovaries evolved from carpels with margins rolled inward • Carpel -leaf with ovules on margins • Carpels may be fused together into compound ovary • Pistil can consist of 1 to several carpels

9. Structure of Flowers • Superior Ovary -calyx and corolla attached to receptacle at base of ovary • Inferior Ovary -receptacle grows up and around the ovary • Calyx and corolla appear attached at top of ovary • Ovary contains ovules • Ovules develop into seeds after fertilization

10. Structure of Flowers • Flowers can be produced singly or in inflorescences • Inflorescence -group of flowers

11. Fruits • Fruit -matured ovary and its accessory parts • Contains seeds • Develop from flower ovaries and found exclusively in flowering plants Tomato fruit

12. Fruits • Fruit Regions • Exocarp – skin • Endocarp -inner boundary around seed(s) • Mesocarp -tissue between exocarp and endocarp Peach fruit • 3 regions collectively called pericarp

13. Fruits • Variability of fruits • Can consist of only ovary and seeds • Can include adjacent flower parts • May be fleshy or dry at maturity • May split or not split • May be derived from 1 or more ovaries

14. Fruits • Fleshy Fruits -mesocarpat least partly fleshy at maturity. • Simple fleshy fruits develop from flower with single pistil • Drupe -simple fleshy fruit with single seed enclosed by hard, stony endocarp (pit) Drupes: peaches, almonds, olives

15. Fruits • Simple fleshy fruits • Berry • From compound ovary, with > 1 seed, and with fleshy pericarp • True Berry -with thin skin and relatively soft pericarp • Tomatoes, grapes, peppers, blueberries, bananas • Pepo -relatively thick rind • Pumpkins, cucumbers Grape berries

16. Fruits • Berry cont’d. • Hesperidium - leathery skin containing oils • Citrus • Pome – flesh from enlarged floral tube or receptacle that grows up around ovary • Endocarp papery or leathery Apple pomes • Apples, pears - core • and little of adjacent tissue from ovary; remainder from floral tube and receptacle

17. Fruits • Dry Fruits -mesocarpdry at maturity • Dehisicent or indehiscent • Dehiscent fruits -split at maturity • Follicle -splits along 1 side • Larkspur, milkweed, peony • Legume -splits along 2 sides • Legume family: peas, beans, lentils, peanuts Milkweed follicle Legumes

18. Fruits • Dehiscent fruits cont’d. • Siliques andSilicles-split along 2 sides, but seeds on central partition, which is exposed when 2 halves separate • Silique -more than 3 times longer than wide • Silicle -less than 3 times longer than wide • Mustard family: broccoli, cabbage Silicle Silique

19. Fruits • Dehiscent fruits cont’d. • Capsules -consist of at least 2 carpels, and split invariety of ways • Irises, poppies, violets, snapdragons Capsules

20. Fruits • Indehiscent Fruits – don’t split at maturity • Single seed united with pericarp • Achene -base of seed attached to pericarp • Sunflower seed, buttercup, buckwheat Inside of sunflower achene

21. Fruits • Indehiscent Fruits cont’d. • Nut -similar to achene, but larger, with harder and thicker pericarp, and cluster of bracts at base • Acorns, hazelnuts, hickory nuts Acorn

22. Fruits • Indehiscent Fruits cont’d. • Grain (Caryopsis) -pericarptightly united with seed • Grasses: corn, wheat, rice, oats • Samara -pericarpextends as wings for dispersal. • Maples, ashes, elms Corn section • Schizocarp -twin fruit that breaks into one-seeded segments called mericarps Samaras • Parsley family: carrots, anise, dill Schizocarp of mericarps

23. Fruits • Aggregate Fruits • Derived from single flower with several to many pistils • Individual pistils mature as clustered unit on single receptacle. • Raspberries, blackberries, strawberries Blackberry aggregate fruits • Multiple Fruits • Derived from several to many individual flowers in single inflorescence • Mulberries, Osage orange, pineapples, figs Osage orange multiple fruit

24. Fruit and Seed Dispersal • Dispersal by Wind • Fruits: Samaras, plumes or hairs on fruit • Seeds: Small and lightweight, or with wings

25. Fruit and Seed Dispersal • Dispersal by Animals • Seeds pass through digestive tract • Fruits and seeds adhere to fur or feathers • Oils attract ants • Elaiosomes on bleeding hearts used as food by ants Seeds from bleeding hearts. Elaiosome is white. • Water Dispersal • Some fruits contain trapped air for floatation

26. Seeds • Structure • Ovules develop into seeds • Cotyledons -food storage organs that function as “seed leaves” • Embryo -cotyledons and plantlet • Plumule - embryo shoot Bean seed

27. Seeds • Structure cont’d. • Epicotyl- stem above cotyledon attachment • Hypocotyl - stem below cotyledon attachment • Radicle - tip of embryo that develops into root Bean seed

28. Seeds • Epigeous germination • Hypocotyl lengthens, bends and becomes hook-shaped • Top of hook emerges from ground, pulling cotyledons above ground Epigeous germination • Hypogeous germination • Hypocotyl remains short and cotyledons don’t emerge above surface

29. Germination • Germination - beginning or resumption of seed growth • Some require period of dormancy • Brought about by mechanical or physiological factors, including growth-inhibiting substances present in seed coat or fruit • Break dormancy by mechanical abrasion, thawing and freezing, bacterial action, or soaking rains • Scarification - artificially breaking dormancy • After ripening -embryo composed of only a few cells when fruit ripens; seeds won’t germinate until embryo develops

30. Germination • Favorable environmental factors needed for germination • H2O and O2 • Light or its absence • Proper temperature range • Enzymes in cytoplasm begin to function after H2O imbibed

31. Longevity • Seed viability varies, depending on species and storage conditions • Viability extended: • At low temperatures • When kept dry • Vivipary -no period of dormancy; embryo continues to grow while fruit still on parent Vivipary in red mangrove

32. Review • Introduction • Differences Between Dicots and Monocots • Structure of Flowers • Fruits • Fruit and Seed Dispersal • Seeds