Phyla of Gymnosperms

General Botany Lab

Gymnosperms Key Characteristics:

Seeds are unprotected

Vascular tissue with tracheids

Wood is typically soft

Resin production in certain families

Heteromorphic generations

Mostly tall, evergreen plants

Gymnosperms Anatomical Features:

Root Cross Sections

Stem Cross Section

Gymnosperms Root Cross Section:

Tilia (Angiosperm)

Pinus (Gymnosperm)

Gymnosperms Tilia (Angiosperm):

Contains vessels and tracheids

Multiseriate parenchymatic rays

No resin canals

Gymnosperms Pinus (Gymnosperm):

Contains tracheids (no vessels)

Uniseriate rays

Resin canals are present

Stem Cross Section (Young Pine):

Pith present

Resin canals are found in the cortex, secondary xylem, secondary phloem

Leaf Cross Section (Pine Needle_

Needle-like leaves in fascicles (bundles)

Leaf Cross Section (Pine Needle) Key Structures:

Epidermis and hypodermis with sunken stomata

Resin canals in the mesophyll

Mesophyll with lobed parenchyma

Vascular bundles surrounded by endodermis

Transfusion tissue transports materials between vascular bundles and mesophyll

Gymnosperms Reproductive Structures:

Pollen Cones

Seed Cones

Pine Seed

Pollen Cones (Microstrobili):

Simple Cones

Pine Pollen Grain

Pollen Cones Structure:

A sporophyll subtends the microsporangium

Microsporangium contains microsporocytes

After meiosis: Microsporocytes form pollen grains (haploid)

Pine Pollen Grain (Male Gametophyte)

Formed after mitotic divisions

Mature pollen grain contains six cells

After mitotic divisions what does the pine pollen grain form:

2 prothallial cells

1 tube cells

1 generative cell

What does the generative cell divide into:

1 sterile cell

1 spermatogenous cell

What does the spermatogenous cell divide into?

two sperm cells

Seed Cones (Megastrobili):

Compound cones

Ovule Development

Seed Cones Structure:

Sterile bract subtends an ovuliferous scale

Ovuliferous scale is a fused branch system

Seed Cones Ovule Development:

Contains a thick integument

Megasporangium (nucellus) inside the ovule

Megasporocyte undergoes meiosis → 1 viable megaspore forms

Megaspore → divides to form female gametophyte with archegonia

Archegonia contain the egg cells

Pine Seed Structure:

Embryo with several cotyledons

Thick seed coat

Life Cycle of a Pine:

1. Sporophyte produces male and female cones

2. Pollination

3. Fertilization

4. Seed Formation

Male Cones:

Microsporangia produce pollen (haploid)

Female Cones:

Ovules develop into seeds after fertilization

Pollination:

Wind carries pollen grains to female cones

Fertilization:

One sperm fertilizes the egg

Zygote develops into an Embryo

Seed Formation:

Embryo is enclosed within the seed

Seeds are dispersed for new growth