PLANT KINGDOM EVOLUTIONARY REQUIREMENTSBy: Serena Young

PARTS OF A PLANT (FLOWER)

4 MAJOR FACTORS THAT ALLOW PLANTS TO LIVE ON LAND

• Retaining Moisture• Cuticle & stomata

• Transporting Resources• Vascular system

• Growing Upright• lignin

• Reproducing on Land• Pollen grain & seeds

RETAINING MOISTURE

• Plants retain moisture for photosynthesis

• The surface of the plant is covered with a cuticle which is a waxy, waterproof layer that helps hold in moisture

• In the cuticles, there are tiny holes called stomata which allow for gas exchange between the plant and the atmosphere

• Special cells allow the stomata to close for water retention, or to open to allow air to move in and out

• Diffusion and osmosis are taking place moving water and elemental products in or out of the cell

Cuticle

stoma

TRANSPORTING RESOURCES• While plants must get sunlight and carbon

dioxide from the air, they must also get water and nutrients from the soil

• Taller plants get more sunlight and carbon dioxide, but how will they get water and nutrient from the soil?

• The vascular system is a collection of specialized tissues in some plants that transports water and mineral nutrients up from the roots and brings sugar down from the leaves

• The vascular system allows plants to grow higher off the ground because resources are carried up and down to different parts of the plants

• The xylem carries water and mineral nutrients up from the roots

• The phloem carries sugar down from the leaves

GROWING UPRIGHT

• Plant height may also be limited by the plant’s ability to hold its own weight

• The basis of the plant is held up by the roots

• Plants need a structure to support their weight and provides space for vascular tissues

• Lignin hardens the cell walls of some vascular system and is responsible for the strength of wood and provides stiffness to the stems of other plants

• The result is a plant keeping its upright structure as they grow toward the sun

REPRODUCING ON LAND

• In all plants, eggs are fertilized within the tissue of the parent plant and develop into an embryo

• Some plants need water to reproduce and other do not

• Pollen and seeds are adaptations that allow plants to reproduce without water

• Pollen is blown by the wind or by animals, each pollen grain contains cells that will divide to form sperm

• These sperm are looking for a female egg to fertilize in the ovaries

• Seeds protect and provide nutrients for developing embryos, protecting it from wind and sunlight

• Once a seed is in the right conditions, the embryo can develop into an adult plant

Pollen

Seeds

SEED PLANTS

• Seed plants have many advantages over their ancestors:• Seed plants can reproduce without water

• Seedless plants depend on water for sperm to swim through to fertilize an egg• Seed plants use pollen which is carried by the wind or on the body of an animal pollinator such as a bee• Pollination occurs when pollen (sperm) meets female reproductive parts of the same species• Each pollen grain then divides to form sperm and fertilization occurs when the sperm reaches the egg

• Seeds nourish and protect plant embryos• Each seed has a protective coat that has a plant embryo and a food supply• A seed can survive a long time in a dormant state, during which it can withstand harsh conditions

(drought or cold) that might kill an adult plant• When conditions are favorable, the embryo will begin growing, using the food supply provided by the

seed• Seeds allow plants to disperse to new places

• Wind, water, or animals often carry seeds far from the individual plant that produced them• Many seed plants have adaptations that aid in the dispersal of seeds, such as the “wings” that carry

maple seeds in the wind• Since seeds can remain dormant, the embryo will not begin to develop until it reaches a suitable

environment

SEED PLANTS- GYMNOSPERM AND

ANGIOSPERM• Scientists believe that seed plants evolved as the earth’s climate changed from

warm ad moist to hot and dry during the Devonian period (410- 360 million years ago)

• Fossils have proved that seed plants can be grouped according o whether their seeds are enclosed in fruit

• An angiosperm is a seed plant that has seeds enclosed in some type of fruit

• A gymnosperm is a seed plant whose seeds are not enclosed in fruit• Most are cone-bearing and evergreen (example- pine tree)

• A woody cone is the reproductive structure of most gymnosperms

• It contains hard protective scales

• Pollen is produced in male cones, while eggs are produced in female cones

• Seeds also develop on the scales of female cones, which protect fertilized eggs

• There are 3 living phyla of gymnosperms: cycads, Ginkgo biloba, and confiers

CONIFERS

• They are gymnosperms

• Many conifers are evergreen and some lose their needles in the winter

• They are well adapted to high altitudes, sloping hillsides, and poor soil which allows them to thrive in the mountainous regions

• They tend to grow old and tall which means that they have well working vascular systems that use the phloem and xylem to move minerals, sugar, and water up and down the plants

COTYLEDONS, MONOCOTS, DICOTS, & WOOD

• Flowering plants are based on two basic kinds of seeds: seeds with one or two cotyledons

• A cotyledon is an embryonic leaf inside a seed

• As an embryo develops into a seedling, the seed leaf of some species remains inside the seed coat

• Flowering plants whose embryos have one seed leaf are called monocotyledons (monocots). Monocot plants usually have parallel veins in long, narrow leaves.

• Flowering plants whose embryos have two seed leaves are called dicotyledons (dicots). Dicots have leaves with netlike veins.

• Some flowering plants develop woody stems, while others do not.

• Wood is a fibrous material made up of dead cells that are part of the vascular system of some plants. Woody plants have lignin, making the cell wall stronger.

FLOWERING PLANTS

• They are angiosperms

• A flower is the reproductive structure of flowering plants. They protect a plant’s gametes and fertilized eggs

• A fruit is the mature ovary of a flower

PLANT CELL TYPES

• Plant cells have cell walls, plastids, and a large vacuole

• Cells are organized into tissues

• Plant tissues are made of 3 basic cell types:• Parenchyma cell• Collenchyma cell• Sclerenchyma cell

PARENCHYMA CELL

• It is the most common type of plants cell and it stores starch, oils, and water for the plant

• These cells have thin walls and large water-filled vacuoles in the middle

• Photosynthesis occurs in the chloroplasts with parenchyma cells in the leaves

• Both the chloroplasts and the colorless plastids in parenchyma cells within the roots and stems store starch

• They have the ability to divide throughout their entire lives, so they are important in healing wounds to the plants and regenerate parts

COLLENCHYMA CELL

• They have cell walls ranging from thick to thin which provide support while still allowing the plants to grow

• Flexibility is a unique feature of the collenchyma cell

• Their cells walls do not contain lignin, so they are stretchy and can change size

• As a young leaf grows, collenchyma cells can elongate and still give the leaf a structure

SCLERENCHYMA CELL

• It is the strongest of the 3 cells

• These cells have the second cell wall that is hardened by lignin, which makes these cells very tough, durable, and rigid

• Since they can’t grow with the plant, sclerenchyma cells are found in parts of the plant that aren’t lengthening anymore

• Many of these cells die when they reach maturity

• The cytoplasm and organelles of these dead cells disintegrate, but the rigid cell walls are left behind as skeletal support for the water-conducting tissues or for the plant itself

• Sclerenchyma cells form a major part of fruit pits and the hard outer shell of nuts

• They are also found in stems and leaf veins and are responsible for the gritty texture of pears

TISSUE SYSTEMS

• Plants organs are made of 3 tissue systems:• Dermal tissue• Ground tissue• Vascular tissue

• A tissue is a group of cells working together to perform a certain function

• The tissue systems of plants may consist of simple tissues from the basic cell types parenchyma, collenchyma, and sclerenchyma

• They may also be made of complex tissues that have additional types of cells

• Neighboring cells are usually connected by plasmodesmata which are strands of cytoplasm that pass through opening in cell walls and connect living cells

• Through the plasmodesmata, cells of a plant tissue can share water, nutrients, and chemical signals

DERMAL TISSUE

• Dermal tissue covers the outside of a plant and protects it in a variety of ways

• It is called epidermis and it is made up of live parenchyma cells in the non-woody parts of plants

• On leaves and some stems, epidermal cells may secrete a waxy-coated substance that becomes the cuticle

• Dermal tissue made of dead parenchyma cells makes up the outer bark of woody plants

GROUND TISSUE

• Dermal tissue surrounds the ground tissue

• Ground tissue makes up most of the inside of a plant

• It provides support and stores materials in roots and stems

• In leaves, ground tissue is packed with chloroplasts, where photosynthesis makes food for the plant

• Ground tissue consists of all 3 of the simple tissues: parenchyma tissue, collenchyma tissue, and sclerenchyma tissue (most common- parenchyma)

• The ground tissue of cacti has many parenchyma cells that store water

VASCULAR TISSUE

• Ground tissue surrounds the vascular tissue

• The system of vascular tissue transports water, mineral nutrients, and organic compounds to all parts of the plants

• Plants can transport necessarily fluids and nutrients throughout their systems

• A plant’s vascular system is made up of two networks of hollow tubes and each network consists of a different type of vascular tissue that works to move different resources throughout the plant

• Xylem is the vascular tissue that carries water and dissolved mineral nutrients up from the roots to the rest of the plant

• Phloem is the vascular tissue that carries the products of photosynthesis through the plant

VASCULAR SYSTEM• water and dissolve minerals move up the roots to the rest of the plant through the xylem

• One type of specialized cell in xylem is called a tracheid (long and narrow)

• Water can flow from cell to cell in tracheids through openings in the thick cell walls

• Some types of flowering plants have an additional xylem cell called a vessel element

• The cohesion-tension theory proposes that physical properties of water allow the rise of water through a plant (attracting to each other)

• However, water molecules are also attracted to the xylem wall due to adhesion (attracting to other substances)

• Transpiration is when water vapor is lost (evaporation)

• As leaves transpire, the outer flow of water lowers the pressure in the leaf’s xylem, creating a vacuum that pulls water upward

• Phloem carried sugars from photosynthesis down to the stems and roots

• Phloem is a complex tissue made mostly of cells called sieve tube elements (have holes to let the phloem fluids, or sap move through the plan)

• Phloem sap can move in any direction, depending on the plant’s need

• The pressure flow model is a theory that explains how food, or sap, moves through a plant. Phloem sap moves from a sugar source (high concentration of sugars) to a sugar sink (uses or stores sugars). The pressure changes, keeping nutrients moving.

• At a source, many plants use ATP to pump or load sugar into phloem at a high concentration (water- low and flows into phloem through osmosis). This creates high pressure at the sugar source. Sugar concentration of the sink end is lessened as sugar is unloaded into the sink.

• The overall result is higher pressure at the source end and lower at the sink end.

ROOTS AND STEMS

• Roots act as an anchor for plant support

• Roots absorb water, transport, and store nutrients

• The center of the root is the vascular cylinder (made of xylem and phloem tissues)

• Root hairs are tiny projections in cells

• The root cap covers the tip of the root and is a small cone of cells that protects the growing part of the root as it pushes through the soil

• The meristem is undifferentiated plant issue from which new cells are formed

• Apical meristems are areas of growth that lengthens the tips of roots and stems

• Roots have 2 basic forms:• Fibrous root- systems make fine branches in which most of the roots are the same size• Taproot- systems have a long, thick, vertical root with smaller branches (get water deep in ground)

• All plants require water and certain mineral nutrients for growth, development, and function

• The pattern of plant growth depends on the location of the meristem within the plants

• There is primary growth which makes stems grow taller or roots grow longer and secondary growth which adds width in the stems and roots of woody plants (tree trunk)

• The age of a tree can be determined y counting the annual ring and the climate by how thick the ring is

LEAVES

• Most leaves share similar structures

• The blade is usually broad and flat, and it collects the sunlight for plants

• The blade connects to the stem by a thin stalk called a petiole

• A bud that grows between the petiole ad the stem of a plant, called an axillary bud, marks where a leaf ends

• Leaves have an outer covering of dermal tissue and internal system of vascular tissue surrounded by ground tissue

• The dermal tissue is covered by a waxy cuticle (water resistant covering)

• The cuticle protects the inner tissues and limits evaporation from the plant

• Between the 2 dermal layers of a leaf is parenchyma tissue called mesophyll (veins made up by the vascular tissues of phloem and xylem)

LEAVES CONTINUED

• Upper portion of the mesophyll has chloroplasts that are useful for photosynthesis

• Lower portions has the stomata and it is the site of transpiration and gas exchange

• A pair f guard cells surround each stoma, and can open and close

• During the day, stomata of most plants open, allowing CO2 necessary for photosynthesis to enter

• Potassium ions from nearby cells accumulate in the guard cells, which causes water to flow into the guard cells, opening the stoma

• When the stoma is open, water evaporates from the leaves

• When the plant is losing water faster than gaining it, the guard cells deflate ad close the stomata, causing the plant to run low on CO2 for photosynthesis

LEAF CHARACTERISTICS

• Certain leaf structures can be used to identify plants

PLANT LIFE CYCLES

• Plants complete their life cycle by alternating between 2 phases that allow the plants to reproduce sexually and disperse to new areas

• Sporophyte phase involves a diploid plant body that produces spores

• Gametophyte phase involves a haploid plant body that produces gametes

• Alternation of generations is the type of life cycle which alternates between haploid and diploid phases

• Life cycle of moss has a dominate gametophyte phase. The capsule at the tip of the moss sporophyte contains spore-producing sacs called sporangia. When the pores are mature, the capsule opens and releases them. A moss gametophyte produced gametes in special reproductive structures. Males produce sperm and females produce an egg. A sperm swims through water to reach an egg and when it fertilizes it, the sporophyte phase begins again.

PLANT LIFE CYCLES CONTINUED

• The life cycle of ferns has a dominant sporophytic phase for all vascular plants. Sori are clusters of sporangia. Spores are released from sporangia when they are mature. A fern gametophyte is often called a prothallus (plant body). It anchors itself to the soil using rhizoids (thread-like structures). When water is present, male structures release sperm which swim toward an egg. When the egg is fertilized, a zygote grows above the prothallus. The mature sporophyte is the familiar fern plant. Newly forming fronds (underside of a fern leaf) are called fiddleheads which produce spores on the underside of each frond, and the cycle repeats.

• The life cycle of conifers has a familiar form for all seed plants, sporophytes. Seed plants produce 2 spores which develop into a female and male gametophytes. Female cones are larger and more scaly than male cones. Each female pine cone has 2 ovules that produce spores. One spore of each ovule will develop into a microscopic female gametophyte, and the rest will die. Male spores are produces inside male cones, which only live for a few weeks. Male spores develop into pollen grains. Male cones release pollen which can stick onto a female cone. After pollination, eggs are produced inside the ovule and a pollen tube begins to grow from the pollen grain toward an egg. 2 sperm also develop inside the pollen grain. The sperm travel down the pollen tube which will fertilize an egg, forming a zygote, and then an embryo. At the same time, the ovule develops into a protective pine seed. Each scale of a female pine cone can be home to 2 developing pine seeds. Once the seeds are mature, the scales open up and release them. The life cycle begins again with a new sporophyte.

REPRODUCTION IN FLOWERING PLANTS

• The outer-most layer of a flower is made of sepals (modified leaves that protect the developing flower)

• The layer just inside the sepals is made up of petals (modified leaves)

• A stamen is the male structure of a flower and a carpel is the female one. Female gametophytes are produced inside the ovary (found at base of flower)

• When a pollen grain reaches the stigma (tip) of the same plant species, the flower has been pollinated

• In flowering and vascular plants, the sporophyte is the dominant phase

• Fertilization in the flower starts with production of male and female gametophytes and then double fertilization.

• Double fertilization is when one sperm fertilizes the egg and the other combines with the polar nuclei in the embryo sac. The cell now has a tripoid (3n). It will become the endosperm (food supply for the developing embryo).

• After fertilization, the next sporophyte generation begins. The ovule becomes a seed (contains embryo and endosperm with a seed coat). Using the nutrients provided by the endosperm, the embryo develops 1 or 2 cotyledons (seed leaves). While the seed develops, the ovary grows into a fruit.

SEED DISPERSAL & GERMINATION

• Animals, wind, and water can spread seeds

• Seeds begin to grow when environmental conditions are favorable• Dormancy- state of inactivity during which an organism or embryo is not growing

• Inside the seed coat, an embryo can withstand extremes that would kill a young seedling

• Germination- when the embryo breaks out of the seed coat and begins to grow into a seedling• The embryo starts to take up water, which causes the seed to swell and the coat to

crack• Then the embryonic root called a radicle breaks through the cracks• A young shoot called a plumule eventually breaks through the surface of the soil• Some species of dicots have cotyledons of other dicots emerge above ground with the

growing shoot, when the leaves emerge from the shoot, they begin to make food through photosynthesis, then the plant is called a seedling

ASEXUAL REPRODUCTION

• Sexual reproduction produces genetic diversity and asexual reproduction allows a well adapted plant to make many copies of itself

• Regeneration is the process by which a new plant can grow from a fragment of a non-reproductive structure, such as a root, stem, or leaf

• Vegetative reproduction is a type of asexual reproduction in which stems, leaves, or roots attached to the parent plant reproduce new individuals

• Many plants have structures that are specifically adapted for vegetative reproduction:• Stolons (stems that grow horizontal to the ground)• Rhizomes (horizontal underground stems)• Tubers (underground stem modified for storage)• Bulbs (underground stems surrounded by modified leaves adapted for storage,

covered with a protective, papery skin)

HORMONES

• Plant hormones regulate plant functions

• A hormone is a chemical messenger produced in one part of an organism that stimulates or suppresses the activity of cells in another part

• Some hormones in plants are:• Gibberellins• Ethylene • Cytokinins • Auxins

GIBBERELLINS & ETHYLENE

• Gibberellins produce dramatic increases in size

• They are involved in ending seed dormancy, starting germination, and promoting the rapid growth of young seedlings

• They are responsible for the large size of many fruits and rapid upward growth of some flower stalks

• Ethylene causes ripening and is naturally produced by plants

• Fruits or vegetables, such as tomatoes, are shipped to far away places and when they arrive, they are exposed to ethylene gas to ripen before they are sold

CYTOKININS & AUXINS

• Cytokinins stimulate cytokinesis (final stage if cell division)

• They are produced in growing roots and developing seeds and fruits and are involved in the growth of side branches

• A property of cytokinins are used to slow the aging of plant organs

• Auxins are involved of the lengthening of plant cells produced in the apical meristem (growing tip)

• Auxins stimulate growth of the primary stem, preventing growth of new branches

• Gardeners use the property of auxins to control branching patterns by cutting off the tip of the growing stem (less auxin in stem, and side branches are encouraged to grow)

• The lengthening of cells triggered by auxins also controls some forms of tropism, the movement of a plant in response to an environmental stimulus

• If a stimulus (sun) hits one side of a stem, auxins will build up in the cells on the shaded side of the stem…the cells elongate and grow/bend toward the light

PLANT RESPONSES

• Phototropism is the tendency of a plant to grow toward the light

• Thigmotropism is the plant’s response to touch

• Gravitropism is the up and down growth of a plant

• Photoperiodism is signals from the changing lengths od day and night through the year

• Rapid responses do not involve growth and are often adaptations that help to protect plants from predators