Chapter 22: Gymnosperms

What are the oldest known seeds?

Late Devonian (+350 million years ago)

What significant adaptations do seeds provide for plants on land?

Protective seed coat, supply food for embryo, capability of dormancy in unfavorable environmental conditions

Which seeds are known as the first “fernlike” in appearance?

Pteridosperms (seed ferns)

What were Pteridosperms (seed ferns) reclassified as?

Gymnosperms

What does Gymnosperm refer to?

The exposed nature of the seeds

Where are (gymnosperm) seeds produced in comparison to seeds enclosed within a fruit?

On surface of sporophylls or similar structures

How are seed-bearing and pollen-bearing sporophylls often arranged in gymnosperms?

In cones

What do pollen cones in Gymnosperms produce?

Pollen grains

What is the female gametophyte produced inside of in a Gymnosperm?

An ovule that contains nucellus

What is the nucleus of a gymnosperm ovule enclosed in?

In integument

What does integument in a Gymnosperm become after fertilization?

Seed coat

Where do Gymnosperms develop (dependently)?

Within sporophyte structures

How many living phyla does a Gymnosperm Phyla contain?

Four living phyla

What does Pinophyta bear in terms of plant structure?

Bear distinct strobili (cones), needlelike leaves arranged in clusters

What is the estimated number of Pinophyta species?

About 600 species

What are examples of Pinophyta species?

Pines, furs, spruces, cedars

Ginkophyta

Notches, broad fan-shaped leaves with evenly forked veins

What are Ginkgophyta seeds described as?

Plum like seeds enclosed in fleshy covering

What is the single living species of Ginkgophyta?

Gingko biloba

What is the cycadophyta a cross between?

Between tree fern and palm, strobili in center

What is the estimated number of Cycadophyta species?

About 300 species

What is found in the xylem of a Gnetophyta?

Vessels, tracheids

What is the estimated number of Gnetophyta species?

About 70 species

What are known as the largest genus?

Pine (Pinus)

Pine (Pinus)

Dominant trees in coniferous forests of Northern Hemisphere

Which pine species is known as "the “world’s oldest known living organisms?”

Bristlecone pines

What is the leaf structure of a Phylum Pinophyta?

Needlelike and arranged in clusters of two to five leaves

Cluster

Fascicle

What type of roots are Fascicles?

Short shoots, restricted growth

Where is the hypodermis located in Pine cells?

Below the epidermis

What does a Pine cell consist of that provides a thick (outer) structure?

One or two layers of thick-walled cells, thick cuticle

What type of stomata is found in a Pine cell?

Recessed or sunken stomata

What does resin in Pine cell resin canals prevent the development of and deter?

Fungi and deters insects (antiseptic, aromatic)

What does Pine Wood consist entirely of?

Tracheids

Conifer wood

Softwood

Which type of cells are absent in Conifer wood (softwood)?

Thick-walled cells

Broadleaf tree (dicot) wood

Hardwood

What type of vessels and fibers are present in Broadleaf tree (dicot) wood?

Thick-walled

How many kinds of spores are produced in Phylum Pinophyta reproduction?

Two kinds

What do pollen cones (male strobili) in Phylum Pinophyta consist of?

Papery or membranous scales

Where are Microsporangia found (in pairs of) inside Phylum Pinophyta?

Toward bases of scales

What does Meiosis produce that develops into pollen grains?

Microspores

What does pollen grain consist of?

Four cells, a pair of air sacs

What do air sacs in the pollen grain add in wind?

Buoyancy

Where are megaspores located in seed cones?

In mesgasporangia within ovules

Where are the (pairs of) ovules found in seed cones?

At bases of seed cone scales

What are seed cones larger than in comparison?

Pollen cones

What scales are in seed cones that make it appear larger?

Woody scales with inconspicuous tracts between them

What do ovules in Megaspores contain?

A megasporangium, containing a nucellus and a single megasporocyte

What is the Megasporangium in Megaspores surrounded by?

Integument

What is the name of the pore inside of an Integument?

Micropyle

What do Megasporocytes undergo?

Meiosis

How many megaspores are produced a result of meiosis?

Four megaspores

How many megaspores degenerate after undergoing meiosis?

Three megaspores

What do the remaining megaspores develop into after undergoing meiosis?

Female gametophytes with archegonia at micropyle end

How many years do seed cones take to mature?

Two years

What do pollen grains in seed cones catch onto during the first year of maturation?

Sticky pollen drops oozing out of micropyle

What do pollen grains produce in seed cones during the first year of maturation?

Pollen tube, growing through nucellus

What is the number of sperm produced in seed cone pollen tubes during the first year of maturation?

Two sperms

Mature male gametophyte (seed cones)

Germinated pollen grain with pollen tube, two sperm

The produced sperm in pollen tubes (seed cones) have:

No flagella, no formed antheridium

What develops as a result of seed cone maturation?

Megaspore

Which two generations mature in the second year of seed cone maturation?

Female gametophyte, archegonium

Where do the pollen tubes in seed cones arrive at during the second year of maturation?

Archegonium

What do the sperm unite with to form zygotes during the second year of seed cone maturation?

One sperm unites with egg

What happens to the other sperm after uniting with egg during the second year of seed cone maturation?

Other sperm degenerates

What is the embryo in a seed cone nourished by?

Female gametophyte

What does the seed coat of a seed cone become during the second year of maturation?

Integument

What are the other, lesser-known (than conifers) gymnosperms?

Ginkgos, cycads, gnetophytes

What are examples of other conifers?

Yew (Taxus), California nutmeg (Torreya), Podocarpus, Junipers

What do the two conifers, Yew and California Nutmeg, produce (singly) at tips of shoots?

Ovules

What is each ovule partially surrounded by in both Yew and California Nutmeg conifers?

Fleshy, cupcake aril

Where are Podocarpus (conifer) located?

Southern hemisphere

What are the Podocarpus seeds described as?

Fleshy-coated seeds with large appendage at base

What are Juniper (conifer) seed cones like?

Fleshy

How many living species of Phylum Ginkgophyta (Ginkgo) are there?

Only one living species, existing in cultivation

What is the leaf structure of Ginkgo (maidenhair trees)?

Notches, broad, fan-shaped leaves (No midrib, prominent veins) on short, slow-growing spurs

What type of veins are found in the Ginkgo (maidenhair trees)?

Hair-like veins, branching dichotomously

What is a characteristic of the Gingko (maidenhair trees) that involves natural shedding of leaves?

Deciduous

What is the life cycle of a Ginkgo similar to?

Pines

How many of the Gingko species are considered living?

Only one living species

Dioecious

Male and female structures on separate trees

What is a characteristic of the Gingko that involves two distinct, separate female and male individuals?

Dioecious

What are Gingko seeds enclosed in?

Fleshy seed coat with nauseating odor

What type of plants are Phylum Cycadophyta (the Cycads)?

Slow-growing plants of tropics and subtropics

What is the plant structure of the Cycads?

Tall, unbranched trunks with a crown of large pinnately divided leaves

What is the life cycle of the Cycads similar to?

Conifers

Which insects (sometimes) perform pollination on the Cycads?

Beetles

What is a characteristic of the Cycads that involves two distinct, separate female and male individuals?

Dioecious

Which two strobili do the Cycads contains?

Pollen and seed strobili

Which unique gymnosperm contains vessels in the xylem?

The Gnetophytes

Which species makes up more than half of the Gnetophytes?

Join firs (Ephedra)

Joint firs (Ephedra)

Shrubby plants of drier regions of southwestern North America, South America, Asia, and Europe

Which genus contains most of the remaining gnetophyte species?

Gnetum

What type of plant structure does Gnetum have?

Vine-like plants with broad leaves

Where are Gnetum usually located?

In tropics of South America, Africa, and Southeast Asia

Which species is the only one confined to the deserts of southwestern Africa?

Welwitschia

What is the plant structure of the Welwitschia?

Short stem, large taproot, two traplike leaves that become tatters and split

What is a characteristic of the Welwitschita that involves two distinct, separate female and male individuals?

Dioecious

Which two type of strobili do Welwitschia contain?

Male and female strobili