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

Roots Usually underground – not visibleUsually underground – not visible Functions: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 stemVery similar to a stem Older roots of shrubs & trees have:Older roots of shrubs & trees have: –Phloem on the outside (old phloem is bark) –Cambium layer –Xylem (wood) on the inside

PhloemPhloem –Carries manufactured food down to the root for food storage XylemXylem –Carries water and minerals up to the stem

Roots on the Outside Different from a stemDifferent from a stem On a stem, theOn a stem, the terminal bud terminal bud initiates growth initiates growth On a root,On a root, the root cap the root cap initiates growth initiates growth Root cap continuously makes new cells that protect the root as it pushes into the soilRoot cap continuously makes new cells that protect the root as it pushes into the soil

Root External Structure Behind the root cap are root hairsBehind the root cap are root hairs Root hairs become side roots that branch out as the root grows olderRoot 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 stemAbsorb moisture and minerals which are conducted up to the larger roots and the stem

Roots as Crops Cash cropsCash crops –Carrots –Beets –Radishes –Sweet Potatoes

Root Propagation Plants with tuberous roots: –D–D–D–Dahlia –P–P–P–Peony –S–S–S–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:Stems have 2 main functions: –The movement of materials Movement of water and minerals from roots up towards the leavesMovement of water and minerals from roots up towards the leaves Movement of manufactured food from the leaves down to the rootsMovement of manufactured food from the leaves down to the roots –Support of the leaves and reproductive structures Flowers and fruit or seedsFlowers and fruit or seeds

Stems cont. Stems are also used for: Food storage –I–I–I–Irish Potato Reproductive methods –S–S–S–Stem cuttings or grafting Green stems manufacture food just like leaves

Stems on the Outside LenticelsLenticels –Breathing pores

Stems on the Outside cont. Bud scale scarsBud scale scars –Indicate where a terminal bud has been located –The distance between two scars represents one year of growth Leaf scarsLeaf scars –Show where leaves were attached

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

Stems on the Inside In all stems: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 xylemSap = new xylem Heartwood = old, inactive xylemHeartwood = old, inactive xylem Tree bark = old, inactive phloemTree bark = old, inactive phloem

Monocots One cotyledon (seed leaf)One cotyledon (seed leaf) Grasses, cornGrasses, corn No outside cambiumNo outside cambium Vascular bundles that contain xylem & phloemVascular bundles that contain xylem & phloem Cells don’t increase in number, they grow in size (won’t keep growing like a tree)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? FoodFood –Asparagus –Irish Potato –Celery Building MaterialsBuilding Materials –Wood

Which root system is easier to transplant? Fibrous roots or tap roots?Which root system is easier to transplant? Fibrous roots or tap roots? Answer: Fibrous rootsAnswer: Fibrous roots Why? Because when plants are dug up out of the ground, a greater % of the fibrous roots system is saved.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.If a root loses to many root hairs while being transplanted, the plant will die. Larger roots only conduct & store water, nutrients, and foodLarger roots only conduct & store water, nutrients, and food Root hairs absorb moisture from the groundRoot hairs absorb moisture from the ground

Leaves Are the food factory of the plantAre 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 animalsThey 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 leavesNeedles are actually very narrow leaves The thorns on a cactus are leavesThe thorns on a cactus are leaves Some leaves are flatSome leaves are flat Other leaves, like onion leaves, are cylindricalOther leaves, like onion leaves, are cylindrical The shape and size of leaves helps to identify plantsThe shape and size of leaves helps to identify plants

Leaf Arrangement Leaves are arranged in many different patterns and positions:Leaves are arranged in many different patterns and positions: –Alternate –Opposite –Whorled –Compound Leaf CompositionLeaf Composition –Simple –Compound PinnatePinnate Bi-PinnateBi-Pinnate PalmatePalmate

Leaves on the Outside Parts:Parts: - Petiole- Blade- Vein - Midrib- Margin 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.Leaves have specialized cells that perform very important, very specific tasks.

Leaf Cells Epidermis - skin of the leaf –S–S–S–Single layer of cells –C–C–C–Chief function: protect the leaf from loosing too much moisture –G–G–G–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. ChloroplastsChloroplasts –Food making cells –Chlorophyll - green color PhotosynthesisPhotosynthesis –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

6H 2 O + 6CO > 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 Photosynthesis LIGHT

Plant Food Food made in the leaves moves down the stem to the rootsFood 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 proteinIt 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 animalsThe plant is also used as food for people and animals The leaves are usually the most nutritious partThe leaves are usually the most nutritious part

Respiration Plants always breathePlants always breathe They consume oxygen and release carbon dioxideThey consume oxygen and release carbon dioxide Roots, stems, and leaves all need oxygen to growRoots, stems, and leaves all need oxygen to grow Plants produce more oxygen during photosynthesis than they consume while breathingPlants 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 propagationSeeds have special devices to ensure propagation Some seeds are sticky (thistles), some float in the wind (dandelions), others can survive stomach acid (cherry pits)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 partsFlowers 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 natureSeeds are the most common way plants reproduce in nature –Sexual process involving male and female parents A complete flower has both male and female partsA complete flower has both male and female parts Only one parent is needed if a plant is self- fruitful, or can pollinate itselfOnly one parent is needed if a plant is self- fruitful, or can pollinate itself

Flower Parts cont. 4 main parts4 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 openGreen, 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 partMale reproductive part Each stamen consists of:Each stamen consists of: –Filament –Anther – contains the pollen (male sex cell)

The Pistil Located in the centerLocated in the center of the flower of the flower Female partFemale part Produces female sex cells (eggs or ovules)Produces female sex cells (eggs or ovules) If fertilized, the eggs become seedsIf fertilized, the eggs become seeds

Parts of the Pistil 3 main parts: –S–S–S–Stigma – sticky, catches the pollen –S–S–S–Style – tube that leads to the ovary –O–O–O–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 legsInsects 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 stigmaAs 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 partsHas ONLY male parts or female parts Male flower – sepals, petals & stamens but no pistilMale flower – sepals, petals & stamens but no pistil Female flower – sepals, petals, & pistil, but no stamensFemale flower – sepals, petals, & pistil, but no stamens Examples: Kiwi, GinkgoExamples: Kiwi, Ginkgo

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

What is the major function of flowers?

What is a fruit? A ripened flower ovaryA ripened flower ovary Botanically, fruits = vegetables & vegetables = fruitsBotanically, fruits = vegetables & vegetables = fruits In most plants, a fruit is formed following fertilization of the ovulesIn most plants, a fruit is formed following fertilization of the ovules They contain seedsThey contain seeds

What about seedless fruit? Seedless fruit -- fruit that form without pollination or fertilizationSeedless fruit -- fruit that form without pollination or fertilization These fruit are called PARTHENOCARPICThese fruit are called PARTHENOCARPIC Examples: Banana, navel orangeExamples: Banana, navel orange

When the fruit ripens, the ovary wall thickens.When the fruit ripens, the ovary wall thickens. This is called the pericarpThis is called the pericarp The pericarp has three sections:The pericarp has three sections: The endocarpThe endocarp The mesocarpThe mesocarp The exocarpThe exocarp

Types of Fruits Aggregate fruitsAggregate fruits Multiple fruitsMultiple fruits Simple fruitsSimple fruits