Chapter One: What is Plant Biology?

Introduction Plants make up more than 98% of total

biomass on Earth

They produce oxygen, produce food for all living things, and remove large amounts of CO2 from atmosphere

Life would not exist without plants

If all plants on Earth were wiped out, the oxygen in our atmosphere would run out within 11 years

Introduction Plants belong to Kingdom Plantae

Multicellular eukaryotes

Cell walls made of cellulose

Carry out photosynthesis using green pigments chlorophyll a and b

Include trees, shrubs, grasses, mosses, and ferns

Most are autotrophs

Plant Survival Needs Because plants are stationary, living on

land can be challenging

Plants must have:

Sunlight (photosynthesis)

Water and Minerals (photosynthesis and growth)

Gas exchange (bring in oxygen, dispose of CO2)

Transport of water and nutrients

Early Plants The first plants evolved from an organism

much like the multicellular green algae living today.

Green algae are protists not plants

DNA sequences show that plants came from these green algaes

Oldest plant fossils ~ 450 mya

Similar to today’s mosses

Simple and grew in damp places

Divisions Four main groups:

Bryophytes (mosses and relatives)

Seedless Vascular Plants (ferns and relatives)

Cone-bearing plants (gymnosperms)

Flowering plants (angiosperms)

Groups based on three important features:

Water-conducting tissues?

Seeds?

Flowers?

Relationship of Humans with their Environment

Human and Animal Dependence on Plants

Oxygen production

Food products

Lumber, paper, clothing

Coal, oil

Methane gas from decomposed plants and animal manures

Gasohol

Plants and the Future Cultivation of food plants

Use of plants in cleaning polluted water

Algae and space exploration

Identification and preservation of medicinal plants

Botany as a Science Botany: the study of plants

Science: “a search for knowledge of the natural world”

Botanists: scientists who study plants

Scientific Method:

Observations and testing hypotheses

Principles and theories

Botany as a Science Hypothesis: tentative, unproven

explanation for something that has been observed

Controlled experiment: an experiment in which only one variable is changed

Variable: specific aspect of an experiment

Independent: variable that you control

Dependent: variable that changes in response to independent (what you measure)

Microscopes Anton van Leeuwenhoek (1632-1723)

Development of primitive microscopes

First to describe bacteria, sperm, and other microbes

Primitive microscopes

Led to the discovery of plant cells (1665)

Botanical Disciplines Plant Anatomy: internal structure of plants

Marcello Malpighi (1628-1694)

Discovered various tissues in stems and roots

Nehemiah Grew (1628-1711)

Structure of wood

Botanical Disciplines Plant Physiology: plant function

J. B. van Helmont (1577-1644)

Flemish physician and chemist

Famous willow branch experiment

Botanical Disciplines Plant Taxonomy: identifying, naming, and

classifying plants

Oldest branch of plant study

Carolus Linnaeus (1707-1778)

Wrote Species Plantarum (1753)

Pteridologists: study ferns

Bryologists: study mosses and other similar plants

Botanical Disciplines Plant Geography: how and why plants are

distributed, 19th century

Sir Joseph Hooker

Charles Darwin

Botanical Disciplines Plant Ecology: interactions of plants with

one another and with their environments

Rachel Carson

Wrote Silent Spring (1962)

Increased public awareness of ecology with her publication

Botanical Disciplines Plant Morphology: form and structure of

plants, 19th century

Botanical Disciplines Other related sciences:

Genetics: heredity studied with plants, plant breeding for crops, genetic engineering for food, medicine, etc.

Cell biology: study of cell structure and function

Electron microscopy

Economic botany and ethnobotany: practical uses of plants and plant products (herbal medicine)