Lecture 17: vascular plant innovations and seedless vascular plant lineages

Gametophytes

multicellular haploid gamete plant that produces gametes by mitosis in gametangia

gametangia

multicellular sex organs of the gametoephyte that produces gametes by mitosis

archegonia

female sex organ that produces the female gametes; egg cells

antheridia

male sex organ that produces the male gametes: sperm cell

homosporous

male and female gametangia may occur on a single individual plant: homosporous gametophytes are hermaphroditic

heterosporous

male or female gametangia occur on separate individuals plant

unisexual either male or female

megagemetophytes

female haploid plant that produces female gametes egg cell

microgametophytes:

male haploid plant produces male gametes sperm cell

sporophyte

multicellular diploid spores plant that produces spores by meiosis in sporangia

sporangia

multicellular organs that produce spores by meiosis

spores

single haploid cells that give rise to the gametophyte generation coated in sporopollenin

megasporangium

contains megasporocytes diploid cell that divide by meiosis to produces haploid megaspores that become the multicellular female haploid megagametophytes

microsporangium

contains microsporocyte diploid cells that divide by meiosis to produces haploid microspores that becomes the multicellular male haploid microgametophytes

Adaptive value of heterospory: genetic diversty

genetic diversity separate, unisexual male and female gametophytes reduce the probability of self fertilization which maintains genetic diversity in the population via outcrossing

Adaptive value of heterospory: door opener

separate unisexual male and female gametophytes facilitated the evolution of important novelties

Seedless vascular plants: lycophytes

club mosses, spikes mosses and quilworts

Seedless vascular plants: monilophytes

whisk ferns, horsetails ferns and leptosporangiate ferns

Diagnostic features of lycophytes

lateral sporangia microphyll leaves

simple roots

lateral sporangia

(sometimes clustered in apical "cones", called stroboli), this is anothersolution to increasing the number of sporangia on a given sporophyte

microphyll leaves

(simple leaves with a singular vascular strand derived from sterile lateral sporangia)

simple roots

(simple roots derived from dichotomously branching underground stems withrootlets that evolved from microphyll leaves)

Diagnostic features of Euphyllophytes True-leaved plants comprising monilophytes and seed plants

Overtopping growth

Megaphyll leaves

Complex roots

Diagnostic features of Euphyllophytes overtopping growth

sporophytes has a dominant axis and side branches

Diagnostic features of Euphyllophytes megaphyll leaves

"true" leaves with more complex vascularization that evolved from side branches

Diagnostic features of Euphyllophytes complex root

with complex branching and root hairs that evolved from dermis

overtopping growth

involves the asymmetric division of the apical meristem, such that there is a main stem and side branches

adaptive value of overtopping growth to plant bc

taller growth and enhanced competitions for sunlight

taller growth: more disperal

allowed elaboration of novel organs from side branches such as megaphyllous leaves and complex root.

Evolution of major features of seedless vascular plant and Euphyllophytes

lycophytes:

- club mosses

-spikes mosses

-quillworts

Monilophytes

- whisk ferns

-horsetail ferns

-lepto ferns

seed plant

Evolution of major features of seedless vascular plant and Euphyllophytes: LATERAL SPORANGIA

YES: lycophyteS

NO: moilophgyteS and seed plants

Evolution of major features of seedless vascular plant and Euphyllophytes: LEAVES

all of them

lycophytes: microphyll

monilophytes and seed plants :megaphylls

Evolution of major features of seedless vascular plant and Euphyllophytes:ROOTS

all of them

lycophytes: simple

monilophytes and seed plants :complex

Evolution of major features of seedless vascular plant and Euphyllophytes: OVERTOPPING GROWTH

NO; lycophytes

yes: monilophytes and seed plants

Evolution of major features of seedless vascular plant and Euphyllophytes: HETEROSPORY

No: lycophytes: club mosses and quillworts

monilophytes: whisk ferns and horsetails

yes:

SOME lycophytes: spikes mosses

SOME monilophytes: lept ferns

seed plants

Evolution of major features of seedless vascular plant and Euphyllophytes:SEED

none besides seed plants