botany 101b

Warren County Master Gardener Class

Botany 101

Carol La Faver

CEA for Horticulture—Warren County

When Is a Tree a Tree?

Tree

A woody perennial plant having a single usually elongate stem generally with few or no branches on its lower part.

Shrub

A low usually several stemmed woody plant.

Herb A seed-producing,

biennial, or perennial that does not develop persistent woody tissue but dies down at the end of a growing season.

Plants Have Two Parts Sexual

Flower Buds

Flowers

Fruit

Seeds

VegetativeLeaves

Leaf Buds

Roots

Stems

Stems

Structures which support buds and leaves and serves as conduits for carrying water, minerals and sugars

Three Major Internal Parts of Stems

Xylem – conduct water and minerals

Phloem – conduct sugars

Cambium – a meristem, the site of cell division and active growth, located between the xylem and phloem

   Table 1. Comparison between monocots and dicots.

 Structure Monocot  Dicot

 Seed leaves  1  2

 Vascular system

Xylem and phloem are paired in bundles, which are dispersed throughout the stem.

Xylem and phloem inside the stem. The ring of phloem is near the bark; the xylem forms the inner ring.

 Floral parts Usually in multiples of three.

Usually in multiples of four or five.

 Leaves Often parallel-veined.

Usually net-veined

Cross-section of Stems

Pith

Node and Internode A node is the area of

stem where leaves are located.

An internode is the area of a stem between the nodes.

Modified Stems Crown – compressed stem tissue Runner – stem that grows on the soil

surface What is an example of a plant that has both

of these “stems”? Strawberry

Modified Stems (cont.) Spurs – Short stubby

side stems. Stolon – aboveground

horizontal stem Tuber – the eyes are

the nodes of the “stem”

Modified Stems (cont.) Rhizomes –

Underground horizontal stem, i.e. iris, johnsongrass.

Bulbs – Compressed underground stems surrounded by fleshy leaves, i.e. tulips, daffodils,lilies, and onions.

Modified Stems (cont.) Corms – Similar to

bulbs but do not have fleshy scales

Tuberous Stems – shortened, flattened, enlarged and underground, i.e. tuberous begonia

Tuberous Root Not a stem but an

underground storage organ

Stems have nodes but roots do not.

Stem Terminology -

Shoot - A young stem (1 year old or less) with leaves.

Twig - A young stem (1 year old or less) that is in the dormant winter stage (has no leaves).

Branch - A stem that is more than 1 year old, typically with lateral stems radiating from it.

Trunk - A woody plant's main stem.

Vines

Attach by Twining Morning glory

Vines

Attach by Aerial Roots Poison Ivy

Vines

Attach by tendrils Some wrap around and some with adhesive pads Virginia Creeper

Leaf Scar

Lenticels

Thorns

Parts of a Leaf

Blade Midrib Vein Petiole

Leaf Facts Principle function of leaves is to absorb

sunlight for photosynthesis What are leaves flat? (except conifers) Petiole is attached to the stem at a node Angle between the petiole and the stem is

the leaf axil Buds are located in the leaf axil

Leaf Facts (cont.) Epidermis –

thickened layer on top & bottom of leaf

Primary function is leaf protection

Some epidermis cells have hairs

Leaf Facts (cont.) Cuticle has a waxy

substance called cutin Protects the leaf from

dehydration and disease The amount of cutin is

direct response to sunlight

What does this have to do with hardening a plant off?

Leaf Facts (cont.) Guard cells on the

underside of leaf can open and close

The opening is a stoma

Allows for the passage of water, oxygen, and carbon dioxide

Leaf Facts (cont.) Weather determines

the opening and closing of the guard cells

Guard cells will close during darkness

Leaf Types Cotyledons or seed

leaves Spines Scale leaves Tendrils succulent storage

leaves Bracts -- Dogwood

Leaf Venation – Parallel, Pinnate, and Palmate

Shapes of Leaves – Simple, Palmate Compound, Pinnate Compound, & Double Pinnate Compound

Shape of Leaf Blade – Oblong, Lanceolate, Linear, Ovate, Elliptical, Orbicular, Cordate

Shape of Leaf Base - Hastate,

Sagittate, Peltate, Perfoliate,Terete

Leaf Margin – Entire, Serrate, Serrulate, Dentate, Undulate, Crisped, Pinnatifid

Leaf Arrangement on Stem

Alternate

Opposite

Whorled

A Bud Is an Undeveloped Shoot Leaf bud – short stem

with embryonic leaves, less plump and more pointed than flower buds

Flower bud – a short stem with embryonic flower parts

Types of Buds Terminal bud - at end

of stem Lateral bud - on the

sides of stem Axillary bud - in axis

of leaf Adventitious bud –

i.e. on root or edge of leaf

Roots Originate from lower

part of plant or cutting

Have a root cap, no nodes, and never have leaves or flowers

Principle Functions of Roots Absorb nutrients and moisture Anchor the plant in the soil Furnish physical support of the stem Serve as food storage organs May be used as a means of propagation

Types of Roots Primary (radicle) root

from embryo Taproot Lateral or secondary

root Fibrous root

Parts of a Root Meristem- area of cell

division and growth Zone of elongation –

cells increase in size, push root through soil

Maturation zone – become specific tissue, i.e. epidermis, vascular tissue

Parts of a Root

Root hairs – water & nutrient absorption

Root cap – covers and protects the meristem

What Does This Picture Tell You?

Parts of a Flower Sepals – leaf-like

structures at base of flower for protection

Petals – highly colored often fragrant

Petals are often used for ID of plant family

Nectar glands

Parts of a Flower (cont.) Stamen – male

reproductive organ consisting of anther and filament

Pistil – female part of the plant. It consists of stigma, style, ovary, ovules and eggs

Types of Flowers Complete flower –

has stamen, pistils, petals, and sepals

Incomplete flower- has one of these parts missing

Types of Flowers Perfect flower – has

functional stamens & pistils

Imperfect flower – if either pistil or stamen is missing

Types of Flowers Pistillate or female

flowers have no stamen

Staminate or male flowers have no pistils

Types of Plants Dioecious – has only

a male or a female flower – Holly, gingko

Monecious – plant has both separate male and female flowers - corn

Inflorescence – Spike, Panicle, Raceme, Head, Umbel

Pollination & Fertilization

Types of Fruit Simple – develop from a single ovary

Aggregate – develop from a single flower which has many ovaries

Multiple – tight cluster of individual flowers borne on a single cluster

Parts of a Seed (a Mature Ovule) Embryo – a miniature

plant in an arrested state of development

Endosperm – built in food supply

Seed Coat – hard outer covering to protect seed

Germination The resumption of

active embryo growth Radicle (root)

emerges first Hypocotyl – area

between the first leaves and root (stem)

Seed leaves encase the embryo

The Three Major Plant Functions

Photosynthesis – food production

Respiration – uses food for plant energy

Transpiration – process for moving/losing water

Photosynthesis

Carbon dioxide + Water + Sunlight = Sugar + Oxygenor

6 CO2 + 6 H20 + Energy => C6H1206 + 6 02

Photosynthesis Occurs in Chloroplasts

Factors Affecting Photosynthesis Light availability – increases as light

increases Carbon dioxide – carbon & oxygen are

used to make carbohydrates Temperature – photosynthesis highest in

the range of 65 to 85 degrees F, decreases when above and below

Factors Affecting Photosynthesis

Water – split by the sun’s energy into hydrogen and oxygen, oxygen released while hydrogen is used to make carbohydrates

Respiration

C6H12O6 + 6 O2 => 6 CO2 + 6 H2O + Energy

   Table 2. Photosynthesis and Respiration.

Photosynthesis Respiration

•produces food •stores energy •uses water •uses carbon dioxide •releases oxygen •occurs in sunlight

•uses food •releases energy •produces water •produces carbon dioxide •uses oxygen •occurs in the dark as well as light

Transpiration is responsible for:

•Transporting minerals from the soil throughout the plant. •Cooling the plant through evaporation. •Moving sugars and plant chemicals. •Maintaining turgor pressure.

Photosynthesis, Respiration and Transpiration Work Together

Environmental Factors That Affect Plant Growth

Light

Temperature

Water

Light Quantity – concentration of sunlight, varies with

season. How can you decrease it? Quality – color reaching the plant. Red & blue

have greatest effect on growth, green is reflected.

Blue light = leaf growth; Blue light + red light = flowering.

What light do you want for seedlings?

Light (cont.) Duration – Amount of time a plant is

exposed to light.

Plants flower in response to uninterrupted dark periods.

Plants are classified as either Short-day or long-day or Day-neutral.

Light (cont.) Short-day plants – form flowers when day

length is less than 12 hours in duration. Mums & Pointsettia

Long-day plants – form flowers when day length exceed 12 hours. Lettuce & Rudbekia

Day-neutral plants – form flowers regardless of day length. Petunia

Temperature If temperature is high and day length long

cool season crops will bolt. If temperatures are too low then warm

season crops may not set fruit. Adverse temperatures will cause stunted

growth and poor quality, i.e. bitter lettuce in high temperature.

Temperature Effects on Plant Growth

Photosynthesis – increase with temp to a point

Respiration – rapidly increase with temp Transpiration – increase with temp Flowering – partially triggered by temp Sugar storage – low temp reduce energy

use increase sugar storage Dormancy – warmth will break dormancy

Water

Maintains turgor pressure which regulates the opening and closing of the stoma.

Stoma are involved in the gradual evaporation of water from the leaf surface which help stabilize the plant temperature.

Relative Humidity

The water in the air divided by the amount of water the air can hold (at constant temperature and pressure).

Relative Humidity Warm air can hold more water so if water amount

remains the same and temps go up then relative humidity goes down.

Water vapor will move from an area of high humidity to one of low humidity.

Humidity inside a leaf is close to 100% When stoma opens the water vapor rushes out

causing the humidity on leaf surface to go up.

Relative Humidity (Cont.)

The “cloud” of humidity slows down transpiration and cools the leaf.

What happens to transpiration if the wind starts to blow?

Nutrients Essential for Plant GrowthAir/water Macronutrients Micronutrients

Carbon (C) Nitrogen (N) Iron (Fe)

Hydrogen (H) Potassium (P) Zinc (Zn)

Oxygen (O) Phosphorus (K) Molybdenum (Mo)

Magnesium (Mg) Manganese (Mn)

Calcium (Ca) Boron (B)

Sulfur (S) Copper (Cu)

Cobalt (Co)

Chlorine (Cl)