THE PLANTKINGDOM & THEIR STRUCTURESKINGDOM & THEIR STRUCTURES Chapter 12
PLANT CLASSIFICATIONBotony, the study of plants, may not top your list ofinteresting subjects.
• First, not all green things are plants. Fungi can contain green pigments. Algae, protozoans, and even some bacteria may contain enough chlorophyll to make them green.• Second, not all plants are green. Some have other pigments which mask the green chlorophyll. Although most plants carry on photosynthesis with chlorophyll localized in plastids (autotrophic), there are thousands of heterotrophic plants. What is the difference between autotrophic and heterotrophic again?• Third, we cannot overestimate the value of plants to man. The plant kingdom provides almost all our food.• Last, plants are a source of inestimable beauty. The quiet of a lush forest and the delicacy of a soft flower demonstrate much of God’s plan and creation.
Importance of plants• Without plants life on earth would not exist
Plants: • Primary source of food for people and animals • Produce oxygen • help to keep us cool
Plants: • slow wind speed • provide a home for wildlife • beautify surroundings • perfume the air • furnish building materials and fuel
Main Groupings of Plants• Non-vascular plants: only one phylum of plants lacks vascular tissues. In this group are the mosses and similar plants.• Vascular plants without seeds: Four phyla of plants have vascular tissues but lack seeds. The best known phylum is Pterophyta, the ferns.• Vascular plants with seeds: This group is usually divided into the two following subgroups: flowering and non- flowering plants.
Non-Vascular Plants: The Mosses• Non-vascular plants are in phylum Bryophyta which contains the mosses, liverworts, and a few similar groups.
• People often think any small green thing is a moss, even though it could be grass, fungus, or anything else.• Most appear as velvety clumps in shaded areas.• In a clump there actually are many densely packed individual plants.• The most obvious part of a moss, the leafy shoot, is 1 in long and transmits water in small spaces between the cells in much the same way that a paper towel absorbs water.• On the bottom of each shoot is a tangles mass of rhizoids. They may appear rootlike, but they lack conducting tissues and therefore are not true roots.
Vascular Plants Without Seeds• Without Seeds All plants other than bryophytes have vascular tissues which conduct water and dissolved minerals through this plant• They are unusual in that they do not produce seeds. In their life cycle they produce spores, a single cell with a protective coat, which are used to spread the species.• When released, the powdery fern spores can be carried by the wind.• Under proper conditions fern spores germinate and form a heart-shaped prothallus which is one cell layer thick.
Vascular Plants with Seeds• Divided into two groups: gymnosperms (three phyla) & angiosperms (one phylum).
Conifers• Produce seeds in cones.• Largest phylum of gymnosperms• Not all cones are like the familiar pine cones and not all conifers look like pine trees, but the life cycle of a pine tree is typical.
• In spring, pine trees produce two types of cones: pollen cones and seed cones• Pollen cones: short-lived, numerous, and small are found near the tips of branches. They contain the male reproductive gametes.• Pollen lands on the open scales of the small, green, upright seed cone. Usually found on other branches of the same tree.• The scales close tightly, and in many pines the cones begins to point downward.• May not be fertilized until months later, and in some species they may not develop into seeds for several years.• When the timing is right and seeds are mature, the scales open and release the seeds.
Angiosperms: Kingdom Anthophyta: Flowering Plants• Dominant vegetation on earth today• So much diversity among the 250,000 species that they are grouped into nearly 400 different families, based primarily on floral parts.• All angiosperms have seeds enclosed in an ovary and flowers.• Many angiosperms do not produce colorful blossoms. Corn tassels and the catkins of oak trees are flowers.
Angiosperms• Divided into two classes: monocots & dicots• The basic distinction between these two is the number of cotyledons• The cotyledons has stored food to keep the embryonic plant alive while it is in the seed and to supply the sprout with energy until it can carry on photosynthesis.• The ovary of a plant is the structure which encloses the seeds; a mature ovary is a fruit. You can easily identify apples, cherries, and tomatoes as fruits, but pods of peas and kernels of corn and wheat are also fruits.
Parts Flowers of a Stemsplant• Four basic parts Roots• leaves• stems• roots• flowers Leaves
Let’s Look at a Plant…flower leafstem What important part cannot be seen?
Did you say “Roots”?What’s the job of theroots?• They hold the plant inplace.• They take in waterfrom the soil.• They take in food fromthe soil.
What does the stem do?The stem’s jobs:• The stem standsthe plant up.• The stem is theelevator that takesthe food and waterto the rest of theplant.
The leaf’s job:• The leaf breathes Why do plants havein air called carbon leaves?dioxide andbreathes outoxygen.• The leaf takes inenergy from thesun and turns itinto energy for the This is called photosynthesis.plant.
The Flower What does the flower do?• The flower attracts insects by its color and smell so insects can pollinate the flower.• After being pollinated, the flower makes the seeds.
Leaf • Important function-manufactures food for the plant by using light energy • Can turn to catch the sunlight
Leaf Margin • Plants may be identified by the edges, shape and arrangement of the leaves. • The leaf edges are known as the margin
• A simple leaf is a single leaf arising from a stem• Two or more leaves arising from a common point on the stem is a compound leaf
• A leaf consists of two familiar parts: petiole and blade• The petiole is the stem of the leaf• The blade is the wide portion
THE BASICS OF PHOTOSYNTHESIS • Almost all plants are photosynthetic autotrophs, as are some bacteria and protists – Autotrophs generate their own organic matter through photosynthesis – Sunlight energy is transformed to energy stored in the(b) Kelp form of chemical bonds 31 (c) Euglena (d) Cyanobacteria (a) Mosses, ferns, and flowering plants
AN OVERVIEW OF PHOTOSYNTHESIS• Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water 32 Carbon Water Glucose Oxygen dioxide gas PHOTOSYNTHESIS
Leaf Structure vascular bundle (vein) xylem (water) cuticle phloem (sugar) epidermispalisadeslayer spongy layerepidermis cuticle stomate guard cells Copy this to turn in and use
Roots• Roots can go down 6, 8, 10 feet• Not all roots are below ground• Most roots serve to anchor the plants• They absorb water• Transport these absorbed substances to where they are needed in plants.• Also function as food storage as with carrots, radishes, and beets.
Zone of Maturation - cell differentiation Protoderm Ground Meristem Provascular Zone of Cell Elongation - cell expansionNotice how the growing zone hasno root hairs or lateral roots!Growth among soil particles wouldresult in shear forces.Zone of Cell Division - new cells by mitosis Root Cap - penetration, padding
Roots• Plants such as Poison Ivy and English Ivy have roots that help them climb trees, walls and sides of buildings• These are called adventitious roots which appear where roots are not normally expected.
Roots Notes• Taproot is the main root of a plant and generally grows straight down from the stem
Roots Notes• Fibrous roots are generally thin, somewhat hairlike, and numerous. The Fibrous root system is normally shallow.
But shrubs also generally have some compromise for uprooting forces… feeder roots extending laterally.In shrubs like thistea plant (Camelliasinensis), the rootsystem will be moretap root than fibrousroot.Notice the diameterof this tap rootcompared to thisman’s waist!
Tropical soils are nutrientpoor.Roots must traverse thesurface for minerals, soroots grow on the surface(not tap root).So, to keep this tall baobabtree standing upright, theroots grow in diameter butonly in the verticaldimensions to form ridgeroots…called buttress roots.My wife here is as large as Iam so you can see theseroots are a meter tall!These roots inspired gothiccathedral architects todesign buttress walls.
• Stems-support the leaves, flowers, and fruit.
Woody Stems• Are tough and winter hardy. They often have bark around them.
Herbaceous Stems• Succulent, often green, and will not survive winter in cold climates
Modified Stems- bulbs, corms, rhizomes, tubers bulbs, corms, rhizomes, tubers• Not all stems are erect, above ground structure. Some grow along the ground or even underground. Some stems have specialized jobs to perform.
Bulbs• Short stems that are surrounded by modified leaves called scales.• Examples: Easter lilies and onions