Major Plant Types

Plants:

·         Contain chlorophylls a and b

·         Store excess carbohydrates as starch

·         Have cellulose in cell walls

·         Differ from green algae because plants produce multiceullular embryos protected within the female plant

·         Have alternation of generations life cycles:

 

Terms to know below:

 

o   Sporophyte

o   Spore

o   Sporangium

o   Gametophyte

 

o   In nonvascular plants, the gametophyte is the dominant generation.

o   In vascular plants, the sporophyte is the dominant generation=adaptation to life on land. (Other land adaptations include vascular tissues for water and nutrient transport, waxy cuticle covering leaves and stems for water conservation, stomata in leaves that regulate gas and water exchange.)

 

There are four major groupings of plants, each group representing an evolutionary event causing the division.

o   Nonvascular: lack true roots, stems, and leaves

o   Seedless Vascular: have transport tissues for conducting water, minerals, sucrose, and hormones; do not produce seeds

o   Gymnosperms: have vascular tissue and produce seeds but no fruit

o   Angiosperms: have vascular tissue and produce flowers and fruit derived from ovaries

 

Group 1: The Nonvascular Plants: low-lying plants, leafy in appearance         

·         Evolutionary History:

·         Reproduction

o   Asexual via regeneration

o   Most reproduction is done sexually.

·         Gametes develop in protective jackets

·         Male: antheridium

·         Female: archegonium

·         Alternation of generations: in nonvascular plants, dominant generation is gametophyte; sporophyte is smaller and short-lived

·         Sperm swims to archegonium to fertilize egg

·         Diploid zygote divides by mitosis into sporophyte

·         Sporophyte grows into long stalk capped with a sporangium

·         Cells inside sporangium undergo meiosis to produce haploid spores

·         Sporangium bursts, spores scatter

·         Spores undergo mitosis to form haploid gametophytes

·         Mature gametophytes form gametes

·         Physical:

o   Sperm need water, which limits height of nonvascular plants.

·         Bryophytes: Mosses

o   Prefer damp, shaded areas

o   Multicellular rhizoids are used for attachment and water absorption

o   Asexual reproduction is by fragmentation.

o   Have complex sporophytes, each covered by an operculum.

o   Sphagnum

 

o   Don’t get caught laying low!  Some mosses aren’t mosses at all.  Ex: Irish moss, Spanish moss, Reindeer moss, Club moss

·         Hepatpophytes: Liverworts

o   Some are flat, some leafy to resemble moss

o   Rhizoids anchor plant

o   Asexual reproduction involves gemmae.

o   Marchantia

 

·         Anthocerophytes: Hornworts

o   Photosynthetic but may associate with cyanobacteria

·         Possess one single large chloroplast

o   Sporophytes appear like small green broom handles

·         Cells at the base of the horn divide continuously

 

Group 2: The Seedless Vascular Plants: have transport mechanisms

·         Evolution:

o   Xylem

o   Phloem

o   Leaves

·         Reproduction:

o   Diploid sporophyte is dominant generation.

o   Homosporous spores:

·         Psilophyta: Whisk Ferns

o   Most have no leaves or roots; however, a few have true leaves that are microphylls.

o   Instead of roots: has underground stems that associate with a mycorrhizal fungus

o   Above ground stems fork repeatedly and contain sporangia at ends of branches.

·         Lycophyta: Club Mosses: ground pines/spike mosses: common in temperate woodlands; most epiphytic

o   Rhizomes branch and send up small aerial stems.

·         Microphylls cover stems and branches, each containing one strand of vascular tissue

o   Specialized leaves grouped into club-shaped stroboli.  Spores produced here germinate into independent gametophytes.

o   Lycopodium

·         Sphenophyta: Horesetails: only one genera

o   Rhizome produces tall aerial stems.

o   Stroboli are found at tips of stems. Spores are produced that germinate into independent gametophytes.

o   Equisetum

·         Pterophyta: Ferns: widespread; range in size

o   Fronds:

o   Archegonia and antheridia are involved in reproduction.

·         Flagellated sperm must swim to archegonia in film of water.

o   Sporophytes produce independent gametophytes.

 

Group 3: The Vascular Gymnosperms: Seed Plants

·         Evolution:

·         Reproduction:

o   Heterosporous:

o   Male and female gametophytes exist. (pollen in males, ovules in females)

o   No external water needed for fertilization

o   After fertilization, the seed develops (embryonic plant).

§  Seeds:

·         Gymnosperm: “naked seed”=not completely enclosed by sporophyte tissue at pollination

·         Four groups:

o   Conifers: many evergreens; produce naked seeds in cones

§  Monoecious

 

o   Cycads

§  Resemble palms or ferns

§  In danger of extinction

§  Often dioescious

§  Coontie: (Zamia pumila)

 

o   Ginkgoes: only one species survives

§  Ginkgo biloba

 

§  Dioecious

o   Gnetophytes: trees and climbing vines with broad leaves

§  Most closely related to angiosperms; no archegonia

§  Some produce nectar to attract insects

§  Ephedra

 

Group 4: The Vascular Angiosperms: Flowering plants

·         Evolution:

·         Reproduction:

o   Flowers:

o   Ovules are always enclosed within diploid tissues and the ovary develops into a fruit

o   Alternation of Generations with sporophyte as dominant phase

·         “Double fertilization” occurs.

·         Physical Forms: 2 primary types

o   Monocots

·         Have only one seed leaf (cotyledon) in their seeds

·         Typically have fibrous roots

·         Flower parts are mostly in threes or multiples of threes

·         Ex: corn, tulips, pineapples, bamboos, sugarcane

o   Dicots

·         Have two cotyledons in seeds

·         Typically have a taproot system

·         Flower parts are mostly in fours or fives, or multiples of these

·         Cacti, strawberries, dandelions, beans