10 1 Sexual Reproduction in Flowering Plants Review

10. 1 Sexual Reproduction in Flowering Plants

Review from 29. 4! Sepals: surround unopened flower bud; whorl around petals when open Petals: size, shape, colour, odor used to attract pollinators

Stamen: composed of anther (sac-like container) and filament (slender stalk) � Male reproductive parts Pistil: female reproductive parts; vase-like shape � Stigma (enlarged, sticky knob), Style (slender stalk), and Ovary (enlarged base, contains ovules)

Perfect Flower (Bisexual): has all parts (sepals, petals, stamens, and a pistil) Imperfect Flower (Unisexual): missing some parts � Staminate Flowers: only have stamens � Pistillate Flowers: only have pistils Monoceious: staminate and pistillate flower on one plant Diocecious: staminate and pistillate flower on separate plants

Involves 2 generations: sporophytes and gametophytes � Diploid sporophytes produce haploid spores through meiosis

Heterosporous – ovules (pistil) produce megaspores; anthers (stamen) produce microspores Microspores pollen grains (spermcontaining microgametophyte or male gametophyte) Megaspores egg-containing embryo sac (megagametophyte or female gametophyte) Fertilization Zygote Embryo within seed Germination Growth of new sporophyte plant!

In ovules. . . megaspore undergoes meiosis produces 4 haploid megaspores v 3 megaspores disappear, remaining 1 undergoes mitosis v Results in megagametophyte (embryo sac) v cytoplasm differentiates and produces polar nuclei (2 nuclei in centre, 3 at each opposite end) v

In anthers. . . Pollen sacs contain microspores undergoes meiosis and produces 4 haploid microspores v microspores separate, each one produces a pollen grain v. Nucleus undergoes mitosis, creating 2 nuclei called tube cell and generative cell v

� When pollen is windblown or carried to the stigma of the same type of plant � Pollen grain germinates and develops a long pollen tube �Grows within style, reaching ovule in ovary � mitosis of generative cell produces 2 sperm (no flagella)

Double fertilization occurs. . . �One fertilizes egg, forming a zygote �Other fertilizes polar nuclei, forming endosperm nucleus

� Endosperm nucleus divides, forming endosperm (food for developing plant) � zygote develops into multicellular embryo � Ovule wall hardens, forming seed coat Seed consists of sporophyte embryo, stored food, and seed coat. � Ovary (and sometimes other floral parts) develops into fruit

Involves cell division, cellular elongation, and cell differentiation into tissues then organs. Development: set series of stages from a simpler to more complex form Cellular Differentiation: specialization of structure and function

� single-celled zygote under endosperm nucleus � endosperm nucleus divide by mitosis, producing mass of endosperm tissue � zygote divides upper part = embryo, lower part = suspensor (anchors embryo and transfers nutrient)

Cotyledons (seed leaves) develop � embryo goes from heart-shaped to torpedo shaped Shoot apex: shoot apical meristem = above ground growth � Root apex: root apical meristem = underground growth � Endosperm is taken up by 2 cotyledons � Epicotyl is above cotyledon, contributes to shoot development � Hypocotyl is below cotyledon, contributes to stem development � Radiclecontributes to root devleopment Result: Embryo + stored food now contained in seed

� � � monocots = 1 cotyledon monocot cotyledon rarely stores food � absorbs food from endosperm and passes it to embryo dicot cotyledon usually stores food

Fruit: a mature ovary that usually contains seeds � Ovary wall thickens to become pericarp (fleshy) � apple, tomatoes, peaches � dry fruits have dry pericarps � legumes (peas and beans) split along 2 sides or seams

� Aggregate fruits develop from individual ovaries (blackberries, strawberries)

� adaptations to be carried by animals � clover has hooks to attach to fur � eaten by animals, then deposited in stool � buried by animals � ocean currents – ex. carry coconuts � wind – wooly hairs, plumes and wings

Germination: when an embryo grows into a seedling Dormancy: time during which no growth occurs, even when conditions are favourable Growth affected by presence of water and oxygen, temperature, dormancy period, etc.

Growth requires regulation (inhibitors and stimulators) � fleshy fruits – inhibitors that prevent growth until seeds are removed/washed � stimulators may include mechanical actions (ex. fire making seed coat permeable to water) Water uptake causes seed coat to burst!

Dicot � 2 cotyledons (seed leaves) shrivel up Plumule: epicotyl bears young leaves Dicot seedling breaks through ground. . . � Shoot is hook shaped � hypocotyl becomes part of stem � radicle develops into roots

Can also grow in the dark � Etiolation: stem elongates, roots/leaves are small, plant lacks colour � resumes normal growth when light becomes normal

Monocot � endosperm is food storage tissue (cotyledon has no storage role) � plumule and radicle covered in protective sheaths (coleoptile and coleorhiza) � burst through coverings when germination occurs