Seeded Plants

General Definitions

• Monoecious: female and male reproductive structures on the same plant

• Dioecious: female and male reproductive structures on separate plants

• Synoecious: having male and female organs in the same flower or receptacle

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• Zygomorphic: bilaterally symmetric

• Circinate vernation: the unrolling of leaves are plants mature, found in ferns and cycads

• Cotleydon: seed leaves

• Dichotomous venation: Veins fork by twos extending from a common point forming a “y” pattern fanning put in leaves

• Tunica: the organization of the shoot apex consisting of one or more peripheral layers of cells and interior. Tunica layers undergo surface growth (anticlinal divisions)

• Reticulate Venatation

Introduction

• Arise in the Late Carboniferous period

• Gymnosperms

  • Naked seed

  • About 1079 species

• Angiosperms: seeds inside additional structure

  • Retention of the megaspore

• All seed plants are heterosporous

What is a seed

• A fertilized reproductive structure consisting of three parts of a plant life cycle

  • Mother sporophyte covering/integument (2n)

  • Nutritive megagametophyte (n) -> at first, the megaspore

  • Zygote (2n)

    • In flowering plants, also contains 2 polar nuclei that form an endospore (3n)

• Nonferitlzied unit: ovule

• Integument: protecting the covering of the seed

  • Micropyle: little opening in the integument to the megasporangium

• Gymnosperm seed:

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• Angiosperm Seed:

  • Unfertilized megasporangium: called an ovule

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  • Mother sporophyte covering/integument (2n)

  • Nutritive megagametophyte (n) -> at first, the megaspore

  • Zygote (2n)

    • In flowering plants, also contains 2 polar nuclei that form an endospore (3n) during double fertilization

  • Double Layer integuments

Gymnosperms

Phylum Cycadophyta

• 337 species

• Common in the Mesozoic period

• DIoecious

• Pinnately divided leaves w/ circinate vernation

• Vascular tissue:

  • Located in Eustele: separate bundles mostly around the edge

• Reproduction:

  • Located in cones

  • Female Plants: round cones

  • Male cones: Long cylindrical cones

  • Microspores:

    • Microspore (n)-> microgametophyte(3 cells) begins while grains are still in the microsporangium

    • monosulcate: pollen with one furrow through which the germinating pollen tube develops

  • Pollen: (microgametophyte)

    • Monosulcate

    • Dispred by insects

    • Pollen lands on a pollination roplet (exuding from the micropyle)

      • A spermatogenous cell divides to form 2 multi-flagellated sperm, fertiliztion occurs

    • Fertilization can take up to 4-6 months

  • Female gametophyte

    • 2-6 archegonia form at the micropylar end each with a larg egg cell

    • Pollen tube ruptures in a pollen chamber to release the two sperm which swim into the archegonial chambers

  • Seeds:

    • 2 cotyledons

    • Root emergers first from the seed through the micropyle

    • 2 cotyledons remain in the seed

    • True leaves emerge from the ruptured seed coat

Phylum Ginkgophyta

• Many fossil species

• Single extant species: Ginkgo biloba

• Dioecious

• Leaves (sometimes bilobed)

• Dichotomous venation

• Male sporangia in loose cone structures

• Ovules/seeds in stalked pairs

• Shoots and Leaves:

  • Long shoots: with distinct nodes and internodes

  • Short shoots: spur shoots with short, crowded internodes

  • Loose wood (secondary growth(

  • The degree of lobing of the leaf depends on position and hormones

• Sperm is flagellated

• Pollination occurs before fertilization

Phylum Gnetophyta

• Male and female cones associate with one another

  • Flower-like cones when both cones are together

• Ring of male sporangia at the top of stalk

• Vessels present in wood

  • Vessel: big water transport pipes

  • Also contain tracheads

• Mostly dioecious (few monoecious)

• DNA Diadvamntges

  • Plants copy a lot of chromosomes

  • Differences can be repeated leading to confusing results and false associations

Genus Ephedra

• Source of ephedrine, pseudoephedrine and other stimulats

• Leaves are opposite or whorls

• Misty dioecious (gew monoecious)

• Bracts under microsporangia and megasporangia

• Pollen germinates directly onto gametophyte

  • Pollination and fertilization lasts 10 hours

Genus Gnetum

• Leaves opposite, with net like (reticulate) venation

• Cone/strobilus divided into conspicuous nodes and internodes

• Moropohloigcally similar to angiosperms

Genus Welwitschia

• 1 species in the Namib Desert of Angola and Namibia

• Produces two leaves which grow indefinitely

  • Leaf veins parallel, connected by small oblique veins

  • Apical meristem dies early: plant without its head

• Dioecious

  • Cones on branches stalks

Anthophyte Hypothesis

• Hypthesis that proposes that gnetophytes are the sister group of Angiosperms

• Evidence: (mostly morphological)

  • Presence of vessels in xylem

    • Take less energy than trachedis, which use adhesion

  • Compound nature of both male and female cones with enveloping brats

  • Net veined leaves

• Commonalities in Gnetophytes and flowering plants:

  • Shoot apical meristems with a protective layer (tunica)

  • Double fertilization

  • No archegonia

  • Vessels in wood

  • Each megasporangium, surrounded by two parts, could be two integuments

Phylum Confierophyta

• Dominant plants in the largest forests of the world (Taiga)

• Presence in the Upper Carboniferous

• Cedars, Yews, Douglas firs, cypress, firs, jumpers, pines

• Woody plants

• Leaves-needle like

  • Some exhibit broader leaves

• Mostly monoecious

• Reproduction:

  • Male and Female Sporangia

  • Microsporangiate: pollen cones

    • Small

    • Sporangia below and are paired on a branch

    • Male Gaemets lack flagella

  • Megasporangiate (seed) cones

    • Female cones are above and are paired on a reduced branch with another brat

    • Seeds are pointed to the inside of the cone

    • Two brackets per egg

  • Life Cycle:

    • Megaspore division to form gametophytes occurs within the sporangia

• Oldest individual: Pinus longaeva

  • bristlecone pine

• Tallest individual: Sequoia sempervirens

  • Coast redwoods

• Most VOluminous Individual: Sequoiadendron giganteum

  • Giant sequoia

Angiosperms

Flowering plants

Rapid appearance in the Cretaceous period

General Characteristics

• Flower: male female sporangia arranged together within a single structure subtended by two sterile whorls (sepals and whorls)

• Pistil/Fruit: seeds enclosed within a protective structure

  • Fruit: mature pistils

• Vessels

• Embryo Sac: reduction of female gametophyte to 7 cells and 8 nucleic

• Double Fertilization: one sperm fertilizes egg; the other sperm fertilizes two polar nucleic and forms a 3n nutritive tissue (Endosperm)

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  • Divides rapidly

• Abominable Mystery:

  • Rapid appearance and divsersification in the Cretaceous (

  • Plants not have fossilized easily

• Perfect (bisexual): majoirty of flowers include both stamens and carpels

• Imperfect (unisexual) stamen or carpel is missing

  • Staimante and carpellate flowers on the same plant: monoecious

  • Flowers on different plants: dioecious

Three Main groups of Angiosperms

• Cotelydon: seed leaf

• Monocots:

  • Flowering parts in 3s

  • # of cotyledons: 1

  • Benetation: parallel

  • Scattered vascular bundles

  • Herbaceous

  • Pollen morph: monocolplate

    • Pollen grains that have a single germinal furrow

• Eudicots (tricolplate)

  • # of cotyledons: 2

  • Flower parts: 4s or 5s

  • Vascular bundles: outer ring

  • Venatation: reticulate(netlike)

  • Smaller flowers and fusing of parts

  • Pollen: tricolpate

    • Pollen with three apertures, equally spaced and parallel to the polar axis

• Magnoliids (older plants)

  • Flower parts: spirals or 3s

  • # of cotelydons: 2

  • Vascular bundles: outring

  • Venatation: reticulate

  • Has ethereal oils

• Shoots and stems

  • Typically has a tunica (like gnetophytes)

  • Dicots:

    • Vascular tissues arranged in eusteles

      • Eusteles: vascular bundles of phloem and xylem strands with parenchyma cells between bundles

    • Placed in a ring on the outer edge

  • Monocots:

    • Scatted throughout the stem in monocots

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General Structure of angiosperm:

• Stamen(microsporangium): anther and filament

  • 4 microsporangia in total

  • In older (fossil plants) males are held on a petal-like structure instead of a filament called a LAMINA

  • Life cycle:

    • Microspores (N)-> division-> 2 pollen cells -> mitosis-> form 2 non flagellated sperm

    • Monocolplate pollen:

      • Gymnosperm (not pines), monocots, magnoliids

    • Tricoplate:

      • Eudicots

• Pistil (megasporangium): stigma, style, ovary

  • Carpel: female units of symmetry

    • Pistils that fused together, creating 1 symmetrical pistil

  • APOCARPOUS:

    • Multiple free pistils

    • Cross section Marginal pistils

    • Many females in 1 flower

    • Typically found in early plants

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  • SYNCARPOUS

    • 1 pistil, made of multiple parts

    • Pistils are fused together

    • Depends on placement:

      • Pariental: pistils are found in the side of the wall

      • Axile: central walls

      • Free central: attached to a flagpole(middle) inside

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  • Pistils Evolution:

    • Began as modified leaves w/ sporangia on leaflets (similar to cycads)

    • Leaf edges curled inwards and fused_> 3 carpels have fused to form a large chambered ovary

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  • Megasporgangium:

    • Ovules oriented with the pistils

    • Two integuments on the megasporangium ovule may be erect or turned back against the funiculus (most common form)

• Floral and Ovary Organization:

  • Ovary Superior: ovary attached to the receptacle above the attachment of other floral parts

  • Flower hypogynous: sepals, petals, stamens are attached to the receptacle below the ovary

  • Flower perigynous: sepals, petals and stamen are attached to the margin of a cup-shaped extension of the receptacle (hypanthium)

    • It appears to be on the ovary

  • Overy Inferior: an ovary sits below the point of attachment for the other parts of the flower

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Ex: bananas, apples. Blueberries

• Flower epigynous: sepals, petals, and stamens grow from the top of the ovary

  • Found in the inferior ovary

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  • Hypanthium: floral cup

• Microgametophyte: pollen

  • Consists of only two cells:

    • Generative and vegetative cell

Upon germinating on the stigma, the generative cell of the pollen will divide to form two sperm nuclei

Life Cycle of an Angiosperm

• Alternation of Generations:

  • POLLINATIONS always occurs BEFORE fertilization

  • Ovule (female): Megasporocyte within sporangium (2n)-> Meiosis-> 4 Megaspores (n)-> 1 megaspore survives-> mitosis x3-> Megagametophyte forms

    • Female megagametophyte consists of egg cells and two polar nuclei

    • Eggs generated at the tip of the seed

    • Unfertilized: ovule

  • Anther (male): Microsporocyte (2n)-> meiosis-> microspores (n)-> mitosis-> pollen grains (n)-> lands on pollen tube(stigma) for POLLINATION-> pollen grain divided to form sperm (2)

  • Double fertilization-> one sperm fertilzies the two polar nucelic-> endospore

    • 1 sperm-> ovary-> zygote (2n)

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• Pollination: transfer of pollen from an anther to a stigma (in angioseprms)

  • Indirect: pollen reaches the stigma of pistils

  • Abiotic:uses wind, water, or gravity

  • Biotic: pollen is transferred by bees, wasps, butterflies, beetles etc.

    • Plants offer attractants to animals

      • Pollen is rich in protein and fats

      • Nectar: water, sugars, amino acids

  • Surface proteins interact between pollen and determine whether pollen will germinate and move through the transmitting tissue

• Methods of Attracting Pollinators:

  • Flowers: visually attractive

    • Sometimes seductive (wasps example)

    • Nectar for food

  • Fruit and seed dispersal

    • Fruit. seed flesh is rich in sugar in vitamins, promoting animal consumption

• Pollination Syndromes

  • Syndrome: a pattern that commontly exists

  • Bees and Wasps: yellows and blue, often UV lines *Most frequent pollinators*

  • Flies and Beetles: bad smells (rotting, dead, manure)

  • Butterflies: bright flowers (reds, yellows, whites) and landing platform

  • Moths: dusk or night blooms w/ heavy sweet scent

  • Bats: broad flowers w/ lots of stamen. DUsk or night blooming

  • Birds: red, tubular for lots of nectar, no or little odor

  • Other animals: lizards, mice, lemurs, and humans

  • Wind: oaks, hicokires, cottonwoods, grasses

  • Water pollination: found in eelgrass

    • Pollen floats to the top of water and floats until it finds a blooming flowers

• Fruit/Seed Dispersal

  • Animals:

    • Fleshy fruits: for eating, then seeds are deposited in manure

    • Sticky fruits: for catching a ride on animal to be deposited elsewate

  • Wind: winged fruits/seeds

    • Very light seeds

    • Ex: orchids

  • Water: coconuts

Special Families

• Orchidaceae:

  • Monocots

  • 20,000-28.00 species

  • Inferior ovary

  • Zygomorphic (bilaterally symmtertirc)

  • Lottery pollination:

    • Millions of tiny seeds

  • One unique pollinator

• Asteraceae:

  • Sunflower family

  • Eudicot

  • 23,000-32,000 species (largest flowering family)

  • Inferior ovary

  • Partially radially symmetric, partly bilateral

  • Flowers clustered into heads/landing pads

  • Sepals modified into pappus -> for dispersal