Plant Taxonomy: How Plants Are Named Unit 2 Plant Taxonomy: How Plants Are Named

Why are scientific names written in Latin? The early scholars always wrote in Latin or Greek Caused problems because the names were often long and difficult.

Common vs. Scientific Most plants have more than one common name. (Common names can be confusing.) The Swedish botanist, Linnaeus, developed the binomial (two name) system for naming plants. All plants having the same generic name are said to belong to the same genus and have similar characteristics. The first name is the genus (plant group name) and the second the species (or kind) The genus name is usually a noun and the species an adjective

Plant Families Related genera (plural or genus) with similar flower structures are grouped together in major units known as families.

The Taxonomist Scientist who identify and classify plants are known as taxonomists. An international set of rules drawn up to ensure that every different species has a different binomial name and that the scientific name assigned to that plant is the oldest binomial name ever used is known as the “International Code of Botanical Nomenclature”

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 - 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 Photosynthesis 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

6H2O + 6CO2 ----------> C6H12O6+ 6O2 Photosynthesis LIGHT 6H2O + 6CO2 ----------> C6H12O6+ 6O2 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 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 Reproductive methods 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 Building Materials 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

Roots on the Inside Phloem Xylem 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 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 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

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!!!