Plant Cells and Growth

Shoot System

Usually above ground

- Vegetative organs

- Reproductive organs

Vegetative organs

leaves and stems

Reproductive organs

flowers and fruits

Root system

usually underground

- only one organ: roots

Determinate growth

Maximum size genetically determined

- growth stops after a time

- usually cannot heal/regrow

- maximum size rarely achieved in nature

- leaves, flowers, fruits

Indeterminate growth

No maximum size genetically

- able to keep growing through life

- usually can heal/regrow

- limited by resources and environmental factors

- roots and stems

cell theory

1665 - Robert Hooke sees 'chambers' on cork tissue under microscope - ca;;s them "cells"

1838 - Schleidern and Swann stated that:

1. All plants and animals are made of cells

2. Cell is the basic unit of life

1858 - Virchow added that:

3. Cells arise by reproduction from previous cells - "Omnis cellula e cellula"

All cells have the same 4 components

Plasma (cell) membrane

Cytoplasm

DNA

Ribosomes

Plasma membrane

A phospholipid bilayer with embedded proteins

Serves as a barrier between the cell and the environment

Controls the passage of organic molecules, ions, water, oxygen, and cellular waste (carbon dioxide and ammonia)

Cytoplasm

Entire region of the cell between the plasma membrane and the nuclear envelope

Comprised of organelles suspended in the cytosol and the cytoskeleton

Provides the structure for different components of the cell

Cytosol

Gel-like material in the cytoplasm

Cytoskeleton

Protein threads in the cytoplasm

DNA - the nucleus

In eukaryotic cells, DNA is typically housed in the nucleus

Directs the synthesis of ribosomes and proteins

Stores chromatin and the nucleolus

Separated from the rest of the cell by the nuclear envelope

Nucleolus

Where ribosomes are made

Nuclear envelope

A double membrane

Ribosomes

Structures responsible for protein synthesis

They are NOT organelles

Can either float free in the cytoplasm or be embedded in the endoplasmic reticulum

Receives instructions from nucleus in the form of mRNA on the specific order of amino acids to build a given protein

Eukaryotic cell unique components

Endomembrane system

Endoplasmic reticulum

Golgi aparatus

Mitochondria

Endomembrane system

Modify, package and transport lipids and proteins

Vesicles and peroxisomes

bud off from the endomembrane and serve as transport units for diverse materials

During cellular replication, DNA is visible in the form of _____

Chromosomes, linear in eukaryotes

Chromatin

During cellular growth and maintenance, proteins attach to chromosomes, making them resemble jumbled threads

DNA + proteins

Endoplasmic reticulum (ER)

A series of interconnected sacs and tubules that

- modify proteins

- synthesize lipids

Golgi apparatus

A series of flattened membranes that receives proteins and lipids from the ER, which it then sorts, tags, packages and distributes

Mitochondria

The 'powerhouse' of the cell

The site of cellular respiration

Contains its own DNA and ribosomes

Cellular respiration

Makes ATP from glucose and other nutrients

Uses oxygen and produces carbon dioxide as waste product

ATP

The cell's main energy-carrying molecule

Plant cell unique components

Cell wall

Central vacuole

Plastids (such as chloroplast)

Central vacuole

A large, membrane-bound structure which stores water and can fill much of the cell

- plays a key roles in regulating water concentration in the cell

- stores also nutrients, ions, and waste products

- surrounded by tonoplast

Osmosis

releasing water under dry conditions and absorbing water under wet conditions

Tonoplast

Membrane

Chloroplast

A type of plastid that stores chlorophyll and other pigments for photosynthesis

Contains its own DNA and ribosomes

Pigments are stored in interconnected sacs (tylakoids), often found in stacks (grana)

Other plastids in plant cells

Chromoplast: stores orange/yellow pigments

Amyloplast: stores starch

Middle lamella

A thin layer of pectin binding adjacent cells

Primary cell wall

Occurs on the surface of all plant cells - initially deposited on the surface of middle lamella

- composed of cellulose microfibrils bundle together

- rather thin and elastic, allowing for cell enargement

- only cell wall present in some cells

Secondary cell wall

Made of layers deposited inner to the primary wall

- occurs as cell reaches mature size

- lignin is deposited together with cellulose (adding rigidity)

- thicker than primary wall (as it grows, it pushes the cell membrane in - can lead to cell death)

Plasmodesmata

Pores which allow for communication between cells

Meristem

Regions of continuous cell division and growth located in different points of the plant

Three types:

-Apical

-Lateral

-Intercalary

Apical meristem

Located at very end of stems (shoot apical meristems) and roots (root apical meristems)

Primary meristematic tissue

protoderm, ground meristem, procambium

Protoderm

Gives rise to epidermis

Ground meristem

Gives rise to ground tissue (photosynthetic, storage, support)

Procambium

Gives rise to vascular tissue (transport)

Lateral meristem

Responsible for secondary growth

Located in two regions:

- Vascular cambium

-Cork cambium

Vascular cambium

Arises from procambium

Gives rise to vascular tissue

Cork cambium

Which arises from the pericycle and the cortex

Produces periderm (secondary dermal tissue)

Meristems in a seed

All three types of primary meristematic tissue are observed in the embryo of a seed