Flowers, Fruits, and Seeds Chapter 8

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

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

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

Dicots Monocots 2 cotyledons 1 cotyledon Flower parts in multiples of 4 or f5 Flower parts in multiples of 3 Leaves with distinct network of veins Leaves with parallel 1° veins Vascular cambium and cork cambium present Vascular cambium and cork cambium absent Vascular bundles of stem in ring Vascular bundles of stem scattered Pollen grains with 3 apertures Pollen grains with 1 aperture

Structure of Flowers Flowers begin as embryonic primordium that 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

Structure of Flowers

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

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

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

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

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

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

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

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

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

Fruits Dry Fruits - mesocarp dry 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

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

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

Inside of sunflower achene 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

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

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

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 Osage orange multiple fruit Multiple Fruits Derived from several to many individual flowers in single inflorescence Mulberries, Osage orange, pineapples, figs

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

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

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

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

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

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

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

Vivipary in red mangrove 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

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