From Zygotes to Seeds and Fruits AP Biology Spring 2011

 Making a lateral cut through an ovary of different flowering plants shows variation  Some are divided into more than one chamber, with more than one ovule attached to the ovary wall  Part of the wall may become a tissue mass in the center of the ovary  Figure on page 532

 Variation in embryo sporophyte development  Ex. Shepherd’s purse- eudicot Two cotyledons which develop from 2 lobes of meristematic tissue Embryos absorbs nutrients from endosperm and stores them in cotyledons

 Ex. Monocots: Monocots have one cotyledon Most monocot embryos do not tap into nutritive tissue until after germination

 Until embryo sporophyte fully formed, parent plants transfer nutrients to ovule’s tissue  Food accumulates in endosperm or in coyledons

 Ovule will eventually pull away from ovary wall  Seed coat forms  Embryo, food reserves, and coat = seed Seed = mature ovule

 Only flowering plants make seeds in ovaries, and only they make fruits  Several ways to categorize fruit Origin Composition Appearance

 Simple fruits: one flower, originate in a single or fused carpel Ex. Cherries, apples

 Aggregate fruits: one flower, originate in several unfused carpels and become a cluster of several fruits Ex. Strawberries, raspberries

 Multiple fruits: start out as a cluster of individually pollinated flowers that grow together and fuse into a single body Ex. Figs, pineapples

 True fruit: only the ovarian wall and its contents

 Accessory fruit: other floral parts, such as the receptacle, expand right along with the ovary Ex. Watermelons, apples

 Dry fruit: Dehiscent: fruit wall splits along definite seams to release the seeds inside  Ex. Capsella pods and pea pods Indehiscent: wall does not split open, seeds are dispersed inside intact fruit wall  Ex. Acorns, grains (corn), sunflowers, maples, strawberries

 Fleshy fruit: Drupe: have a pit (stone hard jacket around one seed; sometime more), and fleshy fruit that encloses the pit  Ex. Cheeries, peaches, apricots, almonds, olives

 Fleshy Fruit: Berry: has one to many seeds, no pit, and fleshy fruit Ex. Grapes, tomatoes, lemons, oranges, grapefruit Pepo: hard rind on ovary wall (pumpkins, watermelons, cucumbers) Hesperidium: leathery rind on ovary wall (citrus fruits)

 Pome: has seeds in a somewhat elastic core tissue and fleshy accessory tissues that encloses its core Ex. Apples, pears

 To categorize an apple: Simple fruit: originates from one flower Accessory fruit: fleshy receptacle expands around five carpels Pome: carpels form an elastic core in fleshy accessory tisue