Plant Development - Unit 2 BSCI207

Plants are composed of 3 primary parts

• Leaf

• Stem

• Root

Leaf

Where photosynthesis occurs

Stem

Everything above the bottom of the plant that helps hold it up

Roots

Allow for plant to absorb nutrients and water

3 primary plant tissues

• Dermal tissue

• Ground tissue

• Vascular tissue

Dermal tissue

• Outside covering of plant

• Protective layer

• Can be part of absorbing stuff from roots

Ground tissue

• Cells of the plant that are helping to support it

• Or leaves that are performing photosynthesis

Vascular tissue

• Includes Xylem and Phloem

• How plants get water and other minerals, and sap

• “Conducts water and solutes throughout plants”

A plant normally grows through/using ______

Meristems

Two different kinds of Stem Cells

1. Cells that make up stem

2. The Zygote that forms (all the different types of cells in body STEM from zygote)

Stem cells are _______

Pluripotent

Pluripotent

• Can be come different types of cells

• Not just one specific cell (ex. skin cell divides into two more skin cells)

Shoot apical meristem

• Stem cells at the top of the plant

• Can become different tissues within the plant stem

• Can become one of the three plant tissue types

Root apical meristem

• Can become different tissues within the plant root

• Can become one of the three plant tissue types

Within the stem there are multiple tissue types…

• Cork Cambium

• Vascular Cambium (xylem and phloem)

Plant primary growth

• Growth of the stem

• Including phloem and xylem

• Mainly upwards growth (less outwards)

• Primary xylem and phloem occur

Phloem carries ____ and xylem carries ____

• Phloem: Sugar and water

• Xylem: Water

Small plants (like grasses) only undergo ____ growth

Primary

Secondary plant growth

• Adding additional tissues

• Increases diameter of plant

• Secondary xylem and phloem occur

(Wood Plant Stems Layers) Outer layer is ____

Bark

Bark is composed of _____

• Cork

• Cork Cambium

• Phloem

Cork

Protects inner layer

Why do trees form rings?

• Throughout season, Xylem cells are either larger or smaller

• Less photosynthesis during winter = less growth = smaller cells

What is between secondary xylem and secondary phloem?

Vascular Cambium

Vascular tissues is made up of three major tissues types

• Trachei’s (Xylem)

• Vessel Elements (Xylem)

• Sieve Tube Elements (Phloem)

Primary body of plant is formed by ______ (3)

• Apical meristems in terminal buds

• Axillary buds

• root tips

Stem cells during primary growth are ______

• Vascular Cambium

• Separating into Xylem and Phloem

Stem cell that produces cork ____

Cork Cambium

Growth at plant tips of roots and shoots produces the _____ body

Primary

Secondary growth is caused by ___ (2)

• Precisely oriented cell division in vascular cambium

• Precisely oriented cell division in cork cambium

• ^Two lateral meristems

Vascular cambium and cork cambium add _____ (3)

• Secondary xylem (wood)

• Secondary Phloem

• Cork

Additional Growth Type

• Vegetative Growth

• Reproductive Growth

Plant Vegetative Growth

Stem and leaf production

Reproductive growth causes ____ production

Flower production

What steps to go from Apical meristems to flowers (5 total)

apical meristems —> leaves, stems —> inflorescence meristems —> floral meristems —> flowers

Flower is made of four organs

• Sepals

• Petals

• Stamens

• Carpels

Sepals

Protective layer

Petals

Attracts pollinators

Stamen is _____ and includes _____ (2)

• Anther and Filament

• Male reproductive parts

Carpel

• Stigma, Style, Ovary

• Female reproductive part

Homeotic genes =

Hox genes

Hox gene

Master regulator gene that will turn on a bunch of other genes

Coen and Meyerowitz Model

ABC Model

ABC Model has ____ genes and determines _____

• 3 floral hox genes

• Determine the four different tissue types

A Gene

Sepals

AB Genes

Petals

CB

Stamens

C

Carpels

Actual expression of genes into whorls (4 combinations)

1. A - Sepals

2. AB - Petals

3. BC - Stamens

4. C - Carpels

(Looking from above)

A and C genes _____ each other

repress/inhibit

Homeotic Mutants called _____ in plants

Mads Box Genes

Primary growth affects _____ while secondary growth affects ______

• growth of roots and stems in length (primary)

• increase in girth (secondary)