Plants

Plants

The study of plants is called Botany

What is a plant?

• Multicellular eukaryote

• Produce their own food through photosynthesis

• Have thick cell walls made of cellulose

• Stems & leaves of most have a waxy waterproof coating called a cuticle to prevent water loss

Adaptations of Plants

1. Preventing water loss: Most fruits, leaves, and stems are covered with a protective, waxy layer called the cuticle

• The waxy cuticle creates a barrier that helps prevent the water in the plant’s tissues from evaporating into the atmosphere

Adaptations of Plants

2. Carrying out photosynthesis: The leaf, is a plant organ that grows from a stem and usually is where photosynthesis occurs

• Each plant species has unique leaves or leaflike structures

Adaptations of Plants

3. Putting down roots: Plants can take in water and nutrients from the soil with their roots

• In most plants, a root is a plant organ that absorbs water and minerals usually from the soil

• Roots anchor a plant usually in the ground & function as storage.

Adaptations of Plants

4. Transporting materials: Water moves from the roots of a tree to its leaves, and the sugars produced in the leaves move to the roots through the stem

• A stem is a plant organ that provides support for growth.

•Stems also can serve as organs for food storage and contain chlorophyll so they can carry out photosynthesis

Embryo

Seed Coat

Food Supply

• A seed is a plant organ that contains an embryo, along with a food supply, and is covered by a protective coat.

• It also protects the embryo from drying out and also can aid in its dispersal

Reproductive Strategies

Non-seeded Plants

• In non-seeded plants (mosses & ferns)have spores that releases directly into the environment where they can grow into haploid gametophyte plants

• These plants produce male and female gametes

Seeded Plants

• In seed plants, which include all conifers and flowering plants, sperm reach the egg without using a film of water

• This difference is one reason why non-seed plants require wetter habitats than most seed plants

Seeds• In seed plants, such as conifers

and flowering plants, spores develop inside the sporophyte and become the gametophytes.

• The gameotophytes consist of only a few cells

• Male and female gametes are produced by these gametophytes

• After fertilization, a new sporophyte develops within a seed. The seed eventually is released and the new sporophyte plant grows.

Two Main Types of Plants

1. Nonvascular Plants• Does not contain Xylem & Pholem.• Receives water from osmosis & diffusion• Must grow close to a water source• Does not have true roots, stems, or leaves

Two Main Types of Plants

2. Vascular plants have tubes and vessels to transport water and nutrients (Xylem & Phloem) Grass, trees, flowers, ferns

• Vascular plants can live farther away from water than nonvascular plants.

Xylem & Pholem

Vascular Plant are divided into:

• Seed Plants-flowers, pines, trees, grasses subdivided into: angiosperms-flowering plants gymnosperms-cone bearing plants• Seedless plants-ferns

Nonvascular Plants3 Types of Nonvascular Plants:

mosses, liverworts & hornworts

Nonvascular Plants

Moss

No true roots, stems, or leaves, must live near water or moist environment

Nonvascular Plant:Hepaticophyta: Liverworts

• Small plants commonly called liverworts because the flattened body of the plant and it resembles the lobes of an animals liver

• They grow in moist environments• They use osmosis & diffusion to

transport water• Found from Artic to Antarctic• Some found in water, others in

deserts • Most have an oily/shiny surface

2 kinds of liverworts:

1. Thallose liverwort: have broad body that looks like a lobed leaf

• The body of a thallose liverwort is called a thallus.

• Found growing on damp soil

2 kinds of liverworts:

2. Leafy Liverwort: are creeping plants with 3 rows of thin leaves attached to a stem

• Leafy liverworts grow close to the ground and usually are common in tropical jungles and areas with persistent fog

• Their stems have flat, thin leaves arranged in three rows—a row along each side of the stem and a row of smaller leaves on the stem’s lower surface

Nonvascular Plant:Anthocerophyta: Hornwort

• Small Plants• Sporophytes

resembles the horns of an animal

• Nonvascular plant-grows in damp, shady habitats

• Relies on osmosis & diffusion to transport nutrients

•Currently consisting of only about 100 species•are similar to liverworts in several respects

Nonvascular Plants:Bryophyta: Mosses

• Nonvascular plants• Rely on osmosis and

diffusion to transport materials

• Habitats include close to streams, rivers or humid tropical forest

• Limited in size (less than 5 cm tall)

• Cannot compete with vascular plants

Mosses

Mosses are:• More familiar than

liverworts• Small plant w/ leafy

stems• Grow in dense carpets

or turfs• Mosses have rhizoids,

which help anchor the stem to the soil.

• Some have upright stems; others have creeping stems that lie along the ground or hang from steep banks or tree branches

Mosses

• Some mosses form extensive mats that help retard erosion on exposed rocky slopes

• Moses grow in a wide variety of habitats, even in the arctic during the brief growing season where sufficient moisture is present

• A well-known moss is Sphagnum, also known as peat moss. – This plant thrives in acidic bogs in northern regions

of the world. It is harvested for use as fuel and is a commonly used soil additive

Non-seed Plants

•Non-seed plants are vascular plants

Psilophyta: Wisk Ferns

• Consist of thin, green stems.

• Are unique vascular plants because they have neither roots nor leaves

• Small scales that are flat, rigid, overlapping structures cover each stem. •The two known genera of

psilophytes are tropical or subtropical, only 1 found in U.S.

Lycophyta: Club Mosses

• Vascular plants adapted primarily to moist environments

• Have stems, roots, and leaves• Their leaves, although very

small, contain vascular tissue• Ancestors grew as tall as 30 m

and formed a large part of the vegetation of Paleozoic forests

• The plants of these ancient forests have become part of the coal that is now used by people for fuel.

Club Moss

• The club moss, Lycopodium, is commonly called ground pine because it is evergreen and resembles a miniature pine tree

• Some species of ground pine have been collected for decorative uses in such numbers that the plants have become endangered

Arthrophyta: Horsetails

• Vascular plants• They have hollow,

jointed stems surrounded by whorls of scalelike leaves

• The cells covering the stems contain large deposits of silica

• About 15 species of arthrophytes exist today

Horsetail• Early horsetails were tree-sized members of the

forest community. Today’s arthrophytes are much smaller than their ancestors

• There are only about 15 species in existence, all of the genus Equisetum

• These plants also are called scouring rushes because they contain silica, an abrasive substance

• Most horsetails are found in marshes, in shallow ponds, on stream banks, and other areas with damp soil

Pterophyta: Ferns

• The most well-known and diverse group of non-seed vascular plants.

• They have leaves called fronds that vary in length from 1 cm to 500 cm

• The large size of fronds is one difference between pterophytes and other groups of seedless vascular plants

Although ferns are found nearly everywhere, most grow in the tropics

Ferns

• According to fossil records, ferns—division Pterophyta—first appeared nearly 375 million years ago

• Ancient ferns grew tall and treelike and formed vast forests

• In most ferns, the main stem is underground. This thick, underground stem is called a rhizome.

Fronds

Root

Rhizome

Fern Structures

• The leaves of a fern are called fronds and grow upward from the rhizome.

• The fronds are often divided into leaflets called pinnae, which are attached to a central rachis.

• The branched veins in ferns transport water and food to and from all the cells.

• Fern spores are produced in structures called sporangia

Fern Structures

Sorus

• Clusters of sporangia form a structure called a sorus (plural, sori). Sori are usually found on the underside of fronds but in some ferns, spores are borne on modified fronds

Seeded Plants

Cycadophyta: Cycads• Were abundant during

the Mesozoic Era. • Today, there are about

100 species of cycads• They are palmlike trees

with scaly trunks and can be short or more than 20 m in height

• Cycads produce male and female cones on separate trees

Cones

• Cones are woody strobili scaly structures that support male or female reproductive structures

• Seeds are produced in female cones.

• Male cones produce clouds of pollen

Diversity of Cone Bearing Trees

• Trees that bear cones are called gymnosperms

• Characteristics: produce seeds in cones

(pines, firs, cedars) needle-like leaves

Male cones: produce pollen

Female cones: contain seeds

Adaptations in Coniferophyta• The reproductive structures of most conifers are

produced in cones.

Male cones

Female cone

Wing

Pollen grain

SporesPollen

sac

Ovule

Two seeds

Wing

• Evergreen confiers: trees that are green year round & photosynthesize when conditions are right

• Deciduous trees: lose their leaves each fall to conserve water through winter conditions

Gnetophyta: Gnetophytes

• There are three genera of gnetophytes (NEE toh fites) and each has distinct characteristics

1. Gnetum (Nee tum) includes about 30 species of tropical trees and climbing vines

Gnetophyta: Gnetophytes

• There are about 35 Ephedra (eh FEH dra) species that grow as shrubby plants in desert and arid regions

Gnetophyta: Gnetophytes

• Welwitschia (wel WITCH ee uh) has only one species, which is found in the deserts of southwest Africa

• Its leaves grow from the base of a short stem that resembles a large, shallow cap

Ginkogophyta: Ginko biloba

• This division has only one living species, Ginkgo biloba, a distinctive tree with small, fan-shaped leaves

• All ginkgoes are cultivated trees, and they are not known to exist in the wild

Ginkos

• Ginkgoes (GING kohs) have male and female reproductive structures on separate trees.

• The seeds produced on female trees have an unpleasant smell, so ginkgoes planted in city parks are usually male trees

• Ginkgoes are hardy and resistant to insects and to air pollution

Coniferophyta: Cone-Bearing Trees

• These are the conifers (KAH nuh furz), cone-bearing trees such as pine, fir, cypress, and redwood

• vascular seed plants that produce seeds in cones

• Species of conifers can be identified by the characteristics of their cones or leaves that are needlelike or scaly.

• Bristlecone pines, the oldest known living trees in the world, are members of this plant division.

• Another type of conifer, the Pacific yew, is a source of cancer-fighting drugs.

Bristlecone Pine

Anthophyta: The Flowering Plants

• Commonly called the flowering plants, are the largest, most diverse group of seed plants living on Earth

• There are approximately 250 000 species

• Unlike conifers, anthophytes produce flowers from which fruits develop

Diversity of flowering plants

• Flowering plants, also called angiosperms, produce seeds enclosed within a fruit.

• A fruit includes the ripened ovary of a flower.

Anthophyta

• Monocotyledons (mah nuh kah tul EE dunz) include grasses, orchids, lilies, and palms

• Dicotyledons (di kah tul EE dunz).

• A fruit usually contains one or more seeds.• Division has 2 classes

Monocot Characteristics

Dicot Characteristics

• An embryo is an early stage of development of an organism

• Embryos of seed plants include one or more cotyledons

• Cotyledons usually store or absorb food for the developing embryo.

Seed coat

Cotyledon

Cotyledons

Cotyledons

Life span of anthophyta

1. Annual plants live for only a year or less. They sprout from seeds, grow, reproduce, and die in a single growing season.

• Annuals form drought-resistant seeds that survive the winter.

Life span of anthophyta

2. Biennial plants have life spans that last two years -1st year: grow many leaves and develop a strong root

system-Over the winter, the aboveground portion of the plant

dies back, but the roots remain alive-2nd year: food stored in the root is used to produce new

shoots that produce flowers and seeds.

Life span of anthophyta

3. Perennials live for several years, producing flowers and seeds periodically—usually once each year

They survive harsh conditions by dropping their leaves or dying back to soil level, while their woody stems or underground storage organs remain intact and dormant