Introduction to Horticulture

By Carrie Carson

The Importance of Plants

 Without plants, life on earth could not exist  Plants are the primary source of food for humans and animals

The Importance of Plants cont.

 Plants also:  Provide oxygen  Provide shade  Supply us with medicines  Renew the air  Slow down the wind  Hold soil in place  Are a home for wildlife  Furnish building materials and fuel

Parts of the Plant

 Most plants are made up of four basic parts:  Leaves  Stems  Roots  Flowers (these later become fruit or seeds)

Leaves

 Are the food factory of the plant  They produce all of the food that is used by the plant and stored for later use by the plant or by animals

Leaves Come in All Shapes and Sizes!

 Needles are actually very narrow leaves  The thorns on a cactus are leaves  Some leaves are flat  Other leaves, like onion leaves, are cylindrical  The shape and size of leaves helps to identify plants

Leaf Arrangement

 Leaves are arranged in many different patterns and positions:  Alternate  Opposite  Whorled  Simple  Pinnate  Bi-Pinnate  Palmate

Leaves on the Outside

 Parts: - Petiole - Midrib - Blade - Margin - Vein

Tip Midrib Margin

Leaf Parts cont.

 Petiole - leaf stalk  Blade - the larger, usually flat part of the leaf  Midrib - large central vein from which all other leaf veins extend  Veins - form the structural framework  Margins - edges of plant leaves

Leaves on the Inside

 Leaves have specialized cells that perform very important, very specific tasks.

Leaf Cells

 Epidermis - skin of the leaf  Single layer of cells  Chief function: protect the leaf from loosing too much moisture  Guard Cells - open and close a small space or pore on the underside of a leaf called a

stoma

to allow the leaf to breathe (exchange O2 for CO2) and

transpire

(or give off moisture)

Leaf Cells cont.

 Chloroplasts  Food making cells  Chlorophyll - green color  Photosynthesis  Process by which chloroplasts make food  The oxygen created is used directly by people and animals  Without O2 there would be no burning, rusting, or rotting

Photosynthesis

6H 2 O + 6CO 2 ----------> C 6 H 12 O 6 + 6O 2 Six molecules of water plus six molecules of carbon dioxide in the presence of light produce one molecule of sugar plus six molecules of oxygen

Plant Food

 Food made in the leaves moves down the stem to the roots  It is then used by the plant or stored in the roots or stem as sugar, starch, or protein  The plant is also used as food for people and animals  The leaves are usually the most nutritious part

Respiration

 Plants breathe 24/7  They consume O2 and release CO2  Roots, stems, and leaves all need O2 to grow  Plants produce more O2 during photosynthesis than they consume while breathing

 Stems have 2 main functions:  The movement of materials  Movement of water and minerals from roots up towards the leaves  Movement of manufactured food from the leaves down to the roots  Support of the leaves and reproductive structures  Flowers and fruit or seeds

Stems

Stems cont.

 Stems are also used for:  Food storage  Irish Potato  Reproductive methods  Stem cuttings or grafting  Green stems manufacture food just like leaves

Stems on the Outside

 Lenticels  Breathing pores

Stems on the Outside cont.

 Bud scale scars  Indicate where a terminal bud has been located  The distance between two scars represents one year of growth  Leaf scars  Show where leaves were attached

Unique Stems

 Irish Potato & Gladiolus  Very different stems  Stems are used for food storage and plant reproduction

Stems on the Inside

 In all stems:  Water and minerals travel up the XYLEM  Manufactured food travels down the PHLOEM

Dicots

 Dicots (2 cotyledons) the xylem and phloem are separated by the cambium  The cambium produces new cells  Grow continually because the cambium builds new xylem and phloem cells  Trees are a perfect example!

 Sap = new xylem  Heartwood = old, inactive xylem  Tree bark = old, inactive phloem

Monocots

 One cotyledon (seed leaf)  Grasses, corn  No outside cambium   Vascular bundles that contain xylem & phloem Cells don’t increase in number, they grow in size (won’t keep growing like a tree)

Monocots vs. Dicots

What do we do with Stems?

 Food  Asparagus  Irish Potato  Celery  Building Materials  Wood

Roots

 Usually underground – not visible  Functions:  Anchor the plant and hold it upright*  Absorb water and minerals from the soil & conduct them to the stem*  Store large quantities of plant food*  Propagate or reproduce in some plants * = essential to all plants

Roots on the Inside

 Very similar to a stem  Older roots of shrubs & trees have:  Phloem on the outside (old phloem is bark)  Cambium layer  Xylem (wood) on the inside

 Phloem  Carries manufactured food down to the root for food storage  Xylem  Carries water and minerals up to the stem

Roots on the Outside

 Different from a stem  On a stem, the terminal bud initiates growth  On a root, the root cap initiates growth  Root cap continuously makes new cells that protect the root as it pushes into the soil

Root External Structure

 Behind the root cap are root hairs  Root hairs become side roots that branch out as the root grows older  Absorb moisture and minerals which are conducted up to the larger roots and the stem

Roots as Crops

 Cash crops  Carrots  Beets  Sugar Beets - Sugar  Radishes  Sweet Potatoes

Root Propagation

 Plants with tuberous roots:  Dahlia  Peony  Sweet Potato  Are propagated by separating the root clump or by rooting spouts from the root

Types of Root Systems

Fibrous Root System vs. Tap Root System

 Which root system is easier to transplant? Fibrous roots or tap roots?

 Answer: Fibrous roots  Why? Because when plants are dug up out of the ground, a greater % of the fibrous roots system is saved.

 If a root loses to many root hairs while being transplanted, the plant will die.  Larger roots only conduct & store water, nutrients, and food  Root hairs absorb moisture from the ground

Flowers, Fruits, & Seeds

 Flowers are pretty & contain nectar in order to attract insects  These insects fertilize the flower by pollination  Pollination begins fruit and seed formation

Fruits & Seeds

 Fruits and seeds are eaten, collected, and spread out by animals and people  This reproduces the plant

Seeds

 Seeds have special devices to ensure propagation  Some seeds are sticky (thistles), some float in the wind (dandelions), others can survive stomach acid (cherry pits)

Flower Parts

 Flowers differ in shape, size, and color, but all have relatively the same parts

Flower Parts cont.

 Seeds are the most common way plants reproduce in nature  Sexual process involving male and female parents  A complete flower has both male and female parts  Only one parent is needed if a plant is self fruitful, or can pollinate itself

Flower Parts cont.

 4 main parts  Sepals  Petals  Stamens  Pistil

The Sepals

 Green, leaf like parts of the flower that cover and protect the flower bud before it is open

Petals

 Are actually leaves  Generally the most striking part of the flower  Bright colors are used to attract insects for pollination

The Stamens

 Male reproductive part  Each stamen consists of:  Filament  Anther – contains the pollen (male sex cell)

The Pistil

 Located in the center of the flower  Female part  Produces female sex cells (eggs or ovules)  If fertilized, the eggs become seeds

Parts of the Pistil

 3 main parts:  Stigma – sticky, catches the pollen  Style – tube that leads to the ovary  Ovary – eggs develop here, after fertilization the ovary grows to become a fruit or seed coat

Flower Construction

 Insects looking for nectar have to climb over the anther and brush pollen on their legs  As they climb towards the center looking for food, they deposit pollen on the stigma

Fertilization

 After an insect deposits pollen, fertilization begins!

 The pollen grain sprouts and sends a long stalk (pollen tube) down the style to the ovary

Fertilization cont.

 The pollen sperm cell can then fertilize the female egg cells and seeds begin to develop  The ovary enlarges into a seed coat or fruit

Pollen

Incomplete Flower

 Has ONLY male parts or female parts  Male flower – sepals, petals & stamens but no pistil  Female flower – sepals, petals, & pistil, but no stamens  Examples: Kiwi, Ginkgo

Flowers are Important!

 Many plants are grown only for their flowers  Floriculture industry in a multimillion dollar business!!!