Introduction to Horticulture

Introduction to Horticulture Importance of Plants Plant Parts & Their Functions

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)

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 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

Stems 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 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 - seed leafs) 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

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

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 Compound Leaf Composition Simple Compound Pinnate Bi-Pinnate Palmate

Leaves on the Outside Parts: - Petiole - Blade - Vein - Midrib - Margin Tip Margin Midrib

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 oxygen there would be no burning, rusting, or rotting

6H2O + 6CO2 ----------> C6H12O6+ 6O2 Photosynthesis LIGHT 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 always breathe They consume oxygen and release carbon dioxide Roots, stems, and leaves all need oxygen to grow Plants produce more oxygen during photosynthesis than they consume while breathing

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

Introduction to Horticulture