Plant Structure and Growth

Horticulture

Plant Taxonomy:How Plants Are Named

• Uses Latin Names (Example- Red Maple)• Kingdom- (Plant)• Phylum- (Spermatophyta)• Class- (Angiospermae)• Order- (Acerales)• Family- (Aceraceae• Genus- (Acer)• Species- (Rubrum)• Variety or cultivar- (October Glory)

• Scientific Name is usually listed as Genus Species• Example- (Acer Rubrum)

Major Parts of a Plant

• Leaves– Where photosynthesis occurs

• Seeds– Method of sexual reproduction

• Flower– Site where reproduction occurs

• Stem– Transports nutrients and supports the plant

• Root– Take in nutrients and anchor plant

Parts of a Leaf

• Petiole– Stalk of the leaf

• Blade– Large, flat part of the leaf

• Midrib– Center vein from which all other veins extend

• Vein– Distribute nutrients and water from xylem– Collect food and take to phloem

• Margin– Edges of plant leaves

Seeds

• Method of sexual plant reproduction

Parts of a Seed

• Cotyledon– The first leaves of a plant

• Seed Coat– Outside covering of a seed

• Endosperm– Food storage tissue that nourishes the embryo

• Embryo– New plant developed after fertilization

Types of Seeds

• Monocots– A seed with only one cotyledon– All grasses are monocots

• Dicots– A seed with two cotyledons– All broadleaf plants are dicots

Flower

• Site for pollination/fertilization• Beauty is used to attract insects• Has both male and female parts

• Complete flower– Has both male and female parts– Can pollinate itself

• Incomplete flower– Has only male or only female parts– Must have another flower to pollinate

General Parts of the Flower

• Sepals– Green leaf-like parts that cover and protect the

flower bud

• Petals– Are actually leaves– Brightly colored to attract insects for

pollination

Male Parts of the Flower

• Stamen– Makes up all male parts

• Pollen– Male sex cell, similar to sperm

• Anther– Sac-like structure on top of the filament

• Filament– Short stalk that holds the anther

Female Parts of the Flower

• Pistil– Makes up all female parts

• Ovules– Female sex cell, similar to the egg

• Stigma– Sticky part of the system, catches pollen

• Style– Tube that leads from the stigma to the ovary

• Ovary– Place where ovule is fertilized by the pollen– Turns into a fruit or seed coat

Stems

• Transports food, water, and nutrients

• Supports the leaves and flowers

Parts of the Stem

• Xylem– Water and minerals travel up to other plant

parts

• Phloem– Manufactured food travels down to other plant

parts

• Cambium– Separates xylem and phloem

Major Parts of a Plant

• Roots– Take in water and nutrients– Anchor the plant and hold it upright– Store large quantities of plant food– Used to propagate or reproduce some plants

Types of Root Systems

• Fibrous Roots– Easier to transplant

– Short, small, compact roots

• Tap Root– Difficult to transplant, since most of the tap root is

cut-off

– Tap root is primarily used for storage of food

• In both types, most nutrients and water are absorbed by root hair

Plant Processes

• Photosynthesis– Mixes light, water, and carbon dioxide in the presence

of chlorophyll to produce sugar and oxygen

• Respiration– Combines sugars and oxygen to give off water and

heat

• Transpiration– Loss of water through the leaves or stems

– Causes wilting when soil is dry

Photosynthesis

• Process by which Carbon Dioxide and Water in the presence of Light are converted to Sugar and Oxygen

• Takes place in the Chloroplasts

• Carbon Dioxide + Water + Light + Chlorophyll = Glucose (sugar) + Oxygen

Respiration

• Process of sugars and oxygen combining to give off heat/energy, water, and carbon dioxide

• Takes place mostly at night• Due to over-watering and poor soil

drainage, roots often die due to not being able to take in oxygen

• Plants give off more oxygen than they use

Transpiration

• Release of water vapor from plants. Most transpiration occurs through the stomates of plants on the underside of the leaves. Air also passes in and out during this process.

• Process is used to cool or maintain heat within the plant.

Nutrient Needs

• All plants need certain nutrients to survive

• Macro-nutirents- needed in large quantity

• Micro-nutrients- needed in smaller quantities

Macronutrients

• Expressed as N-P-K, as a % of of weight

• N- Nitrogen

• P- Phosphorus

• K- Potassium or Potash

Micronutrients

• Ca (Calcium)• Mg (Magnesium)• S (Sulfur)• Fe (Iron)• B (Boron)• Mn (Manganese)• Cu (Copper)• Zn (Zinc)• Mo (Molybdenum)• Cl (Chlorine)

Diseases

• Powdery Mildew caused by a fungusLooks like a white powdery growth on the plant

Botrytis Blight caused by a fungus

Gray fuzzy growth

Pythium dark brown, rotted roots

Damping –Off caused by a fungus and kills seedlings

Insect Pests

• Aphids- small green, round bodied insects– Excrete honey-dew– Cause yellow spots on leaves

• Fungus gnats- thin, gray colored flies– Damage is caused by the larvae, which are

white worms with a black head

• Mealy bugs- oval shaped insects, covered with a white powder

Insect Pests

• Spider Mites- small yellow/red, 8 legs– leave a web on the plant– Leave yellow spots and strings on the leaves

• Thrips- very small insects, 2 pairs of wings– Transmit diseases between plants– Feed on leaves and petals

• White Flies- white insects, 4 wings– Live on the underside of leaves– Cause yellow spots on leaves

Biological Control of Pests

• Integrated Pest Management-– The use of other beneficial insects to control insects

that are harmful to greenhouse crops

– Example- The chalcidoid wasp is used as a control for whiteflies. It lays eggs in the pupa of whiteflies. The adult wasp emerges from the dead whitefly carcass and begins to look for more pupa to lay eggs in, which restarts the process.