Flowers and Reproduction

Reproduction

• Produce offspring that have identical copies of the parental genes.

• Generate new individuals that are genetically different from the parents.

• Stable environment creates adaptability

• Diverse species survive better genetically than homogenous species

• Asexual reproduction – reproduce easily but not good for dispersal.

• Sexual reproduction requires 2 individuals with diverse genes and maybe fit some may be not fit

Flowering Plant Life Cycle

Sporophyte (2N)

Mitosis Carpel Stamen Zygote (2N) Meiosis Fertilization Megaspore Microspore Megagamete (egg) (N) Megagemetophyte (N) Mitosis Microgamete (sperm) (N) Microgametophyte (N)

• S is diploid in their flowers, meiosis gives rise to haploid.

• Spores, megaspore and microspore then undergo mitosis to haploid gametophyte (plant) then produce gametes megagamete (egg) and microgamete (sperm) then fertilization to form zygote (2N) grow into sporophyte

• Oogamy Microgametophyte (male) – sperm – smaller

Megagametophyte (female) – egg – large • Heterospory – has 2 types of spores

microspores and megaspore • Alternation of Generation – has S and G in

the life cycle alternation of heteromorphic generation – 2 different organisms (alternants) S and G

Flower Structure

Flower – a stem with leaflike structures

1. Appendages: sepals – calyx, petals – corolla, stamens – androecium, carpels gynoecium, pedicel – flower stalk, receptacle – for attachment

• Complete flower – all four floral parts are present

• Incomplete flower – when 1 or 2 parts are lacking

2. Sepals - outermost modified leaves , protect the bud from bacteria and fungi, maintains humidity and protects the nectar; petalloid – colored sepals for attraction

3. Petals – inner whorl, together with sepals is called the perianth, leaf – like pigmented, no fibers, thin, for attraction.

4. Stamens – male, produce pollen from the anther (2N) of 4 long columns of tissue containingthe mmc or microscope mother cells or microsporocytes that will undergo meiosis producing 4 microspores (N). Tapetum as nurse cells of microspore development, tetrad microspore also called pollen with intine (inner) wall and exine(outer) wall and of sporopollenin – waterproof, resistant to chemicals and for protection from drying. It has germination pore with patterns (ridges, bumps, spines) all contribute to fossilize strength of the pollen.

5. Carpels – female • Stigma – catches the pollen • Style – elevates the stigma • Ovary – produce the megaspore • Ovary wall, placenta, ovule – funniculus, integument,

micropyle, nucellus (megasporangium) as mmc or megasporocytes will undergo meiosis producing 4 megapores 3 degenarates 1 remains inside the carpel or ovule.

A. Gametophyte Development

1. Microgametophyte Microsporocyte – meiosis 4 microspores – mitosis - vegetative cell – pollen tube

Generative cell – mitosis – 2 sperm cells Pollen tube penetrates the stigma absorb Nutrients from the style 2. Megagametophyte

Megasporocyte – meiosis 1 megaspore – 3x mitosis – 8 nuclei as the megagametophyte 3 small degenarates 3 antipodals first 8 – nucleate coenocyte 2 polar 2 synergid – egg apparatus 1 egg cell – egg apparatus

B. Fertilization

Syngamy – pinsmogamy – fusion of protoplasm Kayogamy – fusion of nuclei Pollen tube (3 nuclei) – style – ovule – micropyle – 1 synergid pollen breaks releasing 2 sperm cells, 1 sperm nucleus + 1 egg = zygote (2N) – only nuclear genes, 1 sperm + polar nuclei = endosperm (3N) – mitosis without cytokinesis resulting to thousand of nuclei later cytokinesis that nourishes the zygote.

C. Embryo and Seed Development

Zygote – embryo – mitosis – globule – heart shaped – torpedo shaped – suspensor – stalk push the embryo to endosperm The embryo forms 2 primordia that grow into cotyledons after becoming elongate cylinder, axis of radicle, hypocotyl and epicotyl and vascular tissue differentiate in the embryo with small leaves, lateral roots, then matures and becomes quiescent Dehydrates furniculus breaks forming a scar the hilum In dicots cotyledons store nutrients of oil, starch and protein which may be used during and after germination and embryo development, endosperm shrinks. In monocots, cotyledon does not become thick the endosperm remains, during germination, the cotyledons acts as digestive / absorptive tissue transferring endosperm nutrients to the embryo

D. Seed

• Matured ovule

• Seed as to endosperm

1. Albuminous – endosperm present e.g. monocot

2. Exalbuminous – no endosperm e.g. dicot seeds

E. Fate of the Megagametophyte

1 sperm + egg = zygote (2N) 1 sperm + 2 polar nuclei (3N) endosperm Synergids and antipodals – breaks down Nucellus – expands then crushed Integuments – seed coats or testa – tough and sclerenchymatous

F. Fruit Development

- Matured ovary Parts; Exocarp – outer layer (skin or peel) Mesocarp – middle layer (fleshy, fibrous) Endocarp – innermost layer (tough, potir stony, or thin) Pericarp – entire fruit wall

G. Pollination

• Transfer of one pollen from one stigma to another

a. Cross pollination – pollination of a carpel by pollen from a different flower b. Self pollination – pollination of a carpel by pollen from the same flower or another flower on

the same plant. Pollen incompatibility Self pollination is inhibited by compatibility barriers chemical reactions between pollen and carpels that prevent pollen growth.

Flower as to component parts Incomplete flowers – flowers that lack either or both essential organs. They are also imperfect flowers. a. Pistillate flower – female flower b. Staminate flower – male flower Perfecft flowers – if both essential organs are present even if sepals or petals or both are lacking. Sexuality of Plants – Dioecy 1. Monoecious – having both staminate and carpellate flower in the same plant

e.g. cucurbits, corn plant 2. Dioecious - having separate flowers in different plant; staminate flower and pistrelatye

flower in separate plants e.g. papaya, marijuana, dates, willows

Agents of Pollination: Animals – zoophillous – fleshy and edible Insects – entomophillous – color, shape, fragrance, size Water – hydrophillous – buoyant impermeable Wind – anemophillous – dust like pollen feathery stigmas Flower as to Symmetry 1. Actinomorphic or regular – radially symmetrical – any longitudinal cut through the center

produces the same. e.g. gumamela 2. Zygomorphic or bilateral symmetry – the cut is at the center producing halves which are

exactly a mirror of it. E.g. bean flower

Ovary Position 1. Superior Ovary / hypogenous – ovary is above the other flower parts 2. Inferior Ovary / epigynous – when ovary is located below the other floral organs 3. Half inferior / perigynous – intermediate or partially buried ovaries

Inflorescence – flowers grouped together a. Determinate inflorescence – limited growth due to its apex is converted to flower. Terminal

flower opens first with a bract and an axillary flower b. Indeterminate inflorescence – the lowest, outermost flower opens first and new flowers are

continuous by coming from the apex e.g. raceme, catkins (imperfect flowers) 1. Spike – florets are sessile 2. Raceme – with axis and florets pedicillate 3. Umbel – pedicels end in small rounded portion 4. Head or capitate – flowers sessile ray flowers, disk flowers 5. Catlein – flowers imperfect 6. Spadix – spike like inflorescence with imperfect flowers but both types occur in the

same and enclosed by bract – spathe 7. Panicle – branced raceme with several flowers

Fruit – matured ovary of the flower after fertilization, are adaptations that results in the protection and distribution of seeds Kinds of Fruit 1. True fruit – contain only ovarian tissues

a. Simple fruit – fruit develops from a single ovary or the fused ovaries of 1 flower b. Aggregate fruit – when separate carpels of one gynoecium fuse during development c. Multiple fruit – during development all the individual fruits of an inflorescence fuse into

1 fruit. E.g. figs, mulberries, pineapple, jackfruit. Some various flower parts the receptacle, bracts, inflorescence, axis will join the mature fruit

Classification of Fruit Types 1. Fleshy fruit – are indehiscent, edible and digestible 2. Dry fruit – not edible

- Dehiscent – break open and release the seed - Indehiscent fruit – do not break open at maturity

Fruit Types 1. Fleshy fruit

Berry – all three layers, exocarp, mesocarp, endocarp are soft e.g. tomato, grape Pome – endocarp is papery, receptacle is edible Drupe – endocarp is hard, sclerenchymatous, e.g. stone fruits: peach, cherry, plum, apricot

Fibrous drupe – mesocarp is fibrous e.g. coconut Fleshy drupe – mesocarp is fleshy e.g. mango

Pepo – exocarp is tough, hard rind, the inner parts not differentiated into distinct layers, e.g. pumpkin, water melon, squash, cantelope Hesperidium – exocarp is leathery, all citrus fruits

2. Dry Fruits – a. Indehiscent

1. Developing from a single carpel Caryopsis – one seeded and testa fused to the fruit wall e.g. grass fruits, grains, rice, oats, corn Achene – seed and fruit remain distinct, fruit wall thin and papery e.g. sunflower Samara – one seeded fruit with wing like outgrowth of the ovary wall e.g. narra, apitong, maple

2. Developing from a compound gynoecium Nut – gynoecium originally consists of several carpels and ovules, all degenerate except one ovule during development, pericarp hard at maturity, e.g. walnut, almond

b. Dehiscent fruit 1. Developing from a single carpel

Legume or pod – fruit breaks open along both sides of sutures e.g. beans Follicle – fruit breaks open only on one side e.g. milkweeds, pandacaqui, kalachuchi

2. Developing from a conmpound gynoecium Capsule – opens in many ways

a. Loculicidal – splitting between lines of fusion e.g. b. Septicidal – along lines of fusion e.g. c. Circumscissile – splitting into a top and bottom half e.g. primrose d. Poricidal – opening by small pores e.g. poppy

Schizocarp – compound ovary breaks into individual carpels called mericarps e.g. anise

3. Compound Fruits a. aggregate fruit – carpels of flowers not fused but grow together during fruit maturation e.g. atis, raspberry

b. multiple fruit – all fruits of an inflorescence grow together during fruit maturation e.g. pineapple, jackfruit Dispersal – When fruits and seeds travel through same agents: Animals – Zoochory Endozoochory – when eaten by animals Epizoochory – when attached to animals Ornithocory – birds Mammaliochory – mammals Chiroptechory – bats Myrmechory – ants Wind – anemochory Water – Hydrochory Plant itself - Autochory