Plants III

Question 1

Where did angiosperm arise from?

Answer 1

gymnosperm

Question 2

when did seed plants first arrive

Answer 2

fossils found from 365 mya

Question 3

are seed plants monophyletic or polyphyletic?

Answer 3

probably polyphyletic

Question 4

Seed plant sporophyte and gametophyte

Answer 4

• sporophyte is dominant and heterosporous

- gametophyte is nutritionally dependant on sporophyte and are unisex

Question 5

What’s different about the male and female reproductive structures in seed plants vs non seed plants?

Answer 5

• air-transported microgametophyte (pollen grain)
• no water fertilization
• no antheridia
• integumented megasporangia (ovule)
• megagametophyte nourishes embryo

Question 6

What is a seed?

Answer 6

an embryo surrounded by nutritive tissue and enveloped by a seed coat

Question 7

Progymnosperms

• years that they were around?
• vasculature?
• seeds?
• example species
• what evolved from them?

Answer 7

• 370-340 mya
• 1st true trees –> made 2nd x and p (also 1st vacular bundles)
• no seeds –> reproduce like ferns (mostly homosoporous, but heterosporous ones are prob angiosperm ancestors)
• Archaeopteris = woody progymnosperm
• seed ferns and all other gymnosperm

Question 8

Seed fern example

Answer 8

medullosa

• 2 types of ferny leaves: neuropteris or alethopteris
• had seeds
• has pollen sacs

Question 9

4 types of gymnosperm

Answer 9

• conifers
• cyads
• ginkgos
• gnetophytes (derived from conifers)

Question 10

Cyads

• environment
• leaf type
• sporophyte
• stem type
• how do modern ones compare to ancient ones?
• what are sperm like?
• evolved from?

Answer 10

• tropical/subtropical
• big, stiff, compound leaves
• dioecious sporophyte, producing either male or female cones
• fleshy, parenchymatous stems
• shorter and thicker than ancient ones
• flagellated sperm in pollen tube
• probably evolved from seed ferns

Question 11

Gnetophytes

• modern or ancient?
• cone type?
• monoecious or diecious?
• how are they similar to angiosperm?
• what are the genera?

Answer 11

• ancient
• compound cone
• usually dioecious, but some ephedra are monoecious
• vessels in xylem, insect pollination, 2x fertilization, some lack archegonia
• gnetum, ephedra, welwitschia

Question 12

Gnetum

Answer 12

• dioecious tree/vine in old world wet tropics
• insect pollination
• no archegonia

Question 13

ephedra

Answer 13

• dioecious and monoecious arid plants worldwide
• vessels in xylem
• 2x fertilization
• flower-like cones
• contain ephedrine = used to be a drug, but now its an appetite suppressant–> raises BP

Question 14

Welwitschia

Answer 14

-stem is buried in desert soil
-Namib Desert in Africa
-dioecious
-cones = 2 strap-shaped leaves
-vessels in xylem
-egg tube grows toward pollen tube
no archegonia

Question 15

Ginkgos

• living species
• m/f reproductive things
• similarities with conifers and cyads

Answer 15

• Ginkgo biloba is only living species
• dioecious sporophytes
• males make pollen
• females make single seeds at end of short stalks
• fleshy seed coat
• flagellated sperm
• dates back 190 mya “living fossils”
• wood is like conifers
• reproduction is like cyads
• tolerant to pollution and pests

Question 16

Pine cones

Answer 16

femal/ovulate cones = modified long shoots

male/staminate cones = modified short shoots

Question 17

male staminate cone

Answer 17

• simple
• microsporophylls with microsporangia inserted laterally
• microspore mother cell makes microspores
• microspores mitotically divide into 4 celled male gametophyte (pollen grain) (2 veg cells, 1 tube cell, 1 generative cell)
• pollen grain lands on female cone
• eventually germinates to form pollen tube that carries generative nucleus with it towards egg
• generative nucleus gives rise to 2 daughters, one of whch divides to make 2 sperm nuclei

Question 18

female cone

Answer 18

• bigger and more complex than male
• megasporophyll = ovuliferous scales
• 2 ovules (integumented megasporangia) made in early spring on upper surface of each scale
• 1 megaspore mother cell inside megasporangium (nucellus) makes 4 megaspores, 3 of which die
• megaspore divides creating female gametophyte
• afte 1 yr of maturing, gametophyte forms 2 archegonia each with an egg at the micropyle
• fertilization
• zygote dvlps into embryo with cotelydons

Question 19

pine seed parts

Answer 19

1. seed coat (2n) develops from remains of integument and nucellus of parent sporophyte
2. female gametophyte tissue (n) serves as food supply for embryo
3. embryo (2n) is the 2nd generation sporophyte