PLANT DIVISIONS

Plants NOTE: We use the term Divisions instead of the term Phyla when referring to plants. Characteristics of plant kingdom members –Alternation of generations with the diploid sporophyte generation dominant except in bryophytes

Evolution of plants from green algae A certain group of green algae known as the charophytes have the following in common with plants. –Chloroplasts of both have thylakoids stacked as grana and chlorophyll b and carotene to act as accessory pigments for chlorophyll a. –The % of cellulose in both is around 25% –Similar mitosis and cytokinesis mechanisms –Similar sperm structure for sperm –DNA evidence backs this up. –Body of some charophytes is haploid, but fertilized egg is retained in the organism and grows and then does meiosis: clue to how alternation of generations started.

Vascular tissue –Most division (all except bryophytes) have vascular tissue of xylem (water and minerals) and phloem (nutrients). –Picture shows vascular tissue in a leaf in a bundle known as a vein. These are the lines you can see in the leaf.

Carbon dioxide Plants lowered the levels of carbon dioxide from 25X current levels to current levels over a period of 100 million years as they adapted to and spread on land.

Invasion of land Stomata Cuticle Lignin: bonds to cell wall cellulose to add strength and waterproofing Vascular tissue: xylem and phloem Roots: absorb nutrients and water vs. rhizoids of moss and holdfasts of algae that don’t. Seeds: dormancy Fruit: spreading seeds Flowers: cross pollination

Cuticle –A waxy cuticle covers parts exposed to air to prevent dessication. Openings in the cuticle (stomata) allow for gas exchange and are controlled by the guard cells. Guard cells

Cuticle, Dermal tissue, ground tissue, and vascular tissue

Flagellated sperm vs. pollen The more primitive plants have flagellated sperm that allow them to swim to the egg. This means that the mosses, ferns, and other primitive plants require water to have fertilization. Fern sperm Types of pollen

Plant Divisions: Bryophyta MOSSES Dominant gametophtye generation (green) Also includes liverworts and hornworts Need sperm to fertilize egg NO vascular tissue limits height of the plant and therefore have no true roots, stems, or leaves. haploid spores are made by meiosis in the sporangium of the sporophyte. Moss sporophyte

Other Bryophytes Liverworts Hornwort

Gametophytes AntheridiumArchegonium Male gametophyte Female gametophyte Makes sperm makes egg

Lycophyta: club mosses,lycopods They have vascular tissue. Inconspicuous gametophyte can live underground for ten years. LycopodiumClub mosses

Sphenophyta: horsetails Once occupied the niche of trees before conifers and flowering plants existed They are homosporous

Pterophyta Homosporous: create one spore that is bisexual. Vascular tissue but no seeds: allows them to get taller, but limits them to shady moist areas for reproduction. Fronds: big “leaf like” arrangement Fiddlehead: emerging sporophyte Spore making sporangium on underside of fronds when reproducing.

Ferns Fiddlehead Sporangia on underside of frond Fronds Bisexual gametophyte

Gymnosperms (naked seeds) have no flowers: gingko, cycad, and conifers

Coniferophyta Redwoods, firs, pines, yews, cypresses Naked seeds: not enclosed in fruits Wind pollination (NEEDS A LOT) Seeds, vascular tissue No flowers Often needles thick with cuticle and small in size to limit transpiration.

Seed cones vs. pollen cones Seed cones seeds Pollen cones

Oldest and largest Redwoods (400 feet tall) bristlecone pine (4600 years old)

Anthophyta Flowering plants Flower will develop into fruit that is used for seed dispersal via wind, water, or animal. Pollination can be by wind, bird, bat, insect. Most advanced (recent) Gametophyte is reduced and within the flower. Most diverse: grasses to trees

Seed dispersal

Flower structure: reproduction organ of some plants

Double Fertilization Generative nucleus becomes two “sperm” through mitosis. First sperm fertilizes egg in the ovule and second sperm fertilizes polar nuclei to become triploid endosperm. Endosperm will become “food” for seed.

Prefixes for plants Mega and Arche are female Micro and Anther are male Microgametophyte = pollen (becomes sperm) Megagametophyte = makes eggs Atheridium: anthers make male gametes Archegonium: place where eggs are made

Monoecious (one house) flower Name the parts Dioecious: Two houses/ male and female flowers

Parts: functions Female (carpel/pistil) –Stigma is sticky “top” that collects pollen –Style is connection between stigma and ovary. –Ovary is where eggs are made in the ovules Male (stamen) –Anther makes the pollen –Filament holds anther away from female part to allow for wind/insect to carry pollen away Petals (collectively called corona): attracts pollinators Sepals (collectively called calyx); protects the bud before blooming

Fruit The ripened ovary becomes the fruit after the fertilization of the egg and formation of the seed. Single fruit: one flower with one pistil Aggregate fruit: one flower with mutliple pistils Multiple fruit: multiple flowers fuse to make one fruit

Fruit types Simpleaggregatemultiple

Review What division of plants has no vascular tissue? What is made by the archegonium? What part of the flower “catches the pollen? What is one gymnosperm other than coniferophyta? What part of a flower becomes the fruit? Where do you find the sporangium on a fern?

More review What process makes the gametes in a plant? What division of plants includes the tallest trees? What is the purpose of the fruit? What is the food of a seed called? What group of green algae are the closest relatives to plants? What does the cuticle prevent? How many flowers lead to an aggregate fruit? What is true of plants that are heterosporous?