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24.1 Cells and Tissues of Flowering Plants
The tree is important in agriculture and pest control.
In India and Pakistan, neem leaves can be mixed with stored grains or placed in drawers with clothing, keeping insects at bay.
In this chapter, we look at the structure of roots, stems, and leaves and discuss the specialized cells and tissues that make up these organs.
There are three types of tissue in angiosperms.
There are differences in the location, structure, and function of angiosperm tissues.
The body of a plant is similar to that of an animal.
You learned about cell features common to both plant and animal cells in Section 4.3.
The first cells of a plant embryo are called cells.
Like animal stem cells, plant meristem cells can divide indefinitely and give rise to many different types of differentiated cells.
New cells are small and boxlike, with a large nucleus and small vacuoles.
As these cells mature, they assume many different shapes and sizes, each related to the cell's ultimate function.
There are new and developing parts of a plant.
A differentiating daughter cell and a meristem cell are formed when stem cells divide.
The grass continues to grow despite the fact that you can cut it.
Plants grow from their apices and can grow wide as well.
A plant increases in size due to secondary growth.
The entire body of both nonwoody and young plants has skin cells.
The walls of cells that are exposed to air are covered with a skin.
The cuticle protects against organisms that can cause disease.
In roots, some cells have long, slender projections.
The root hairs absorb water.
There are hairlike extensions on fruit, leaves, or stems that can protect from herbivory.
The leaf is used for gas exchange.
cork and cork cambium are included in the periderm.
In gas exchange, Lenticels in cork are important.
Sometimes glandular trichomes help protect a plant from herbivores by producing a toxic substance.
Hypodermic needles are formed when the stiff trichomes of the stinging nettle lose their tips.
Some of the defenses that have evolved in angiosperms are discussed.
Gas exchange and water loss occur when the stomata is open.
In plants with wood, the stem is replaced by cork cells.
cork cells can be removed at maturity.
cork cambium is a meristem that makes new cork cells.
This is the entire cork area of the plant.
As the new cork cells mature, they increase in volume, and their walls become encrusted with suberin, a lipid material, so that they are waterproof.
The plant is protected by non living cells that help it resist attacks.
The cork cambium overproduces cork in certain areas of the stem surface, causing ridges and cracks to appear.
Gas is exchanged between the interior of a stem and the air in Lenticels.
Parenchyma cells are the most abundant and correspond best to plant cells.
These are the least specialized of the cell types and are found in the plant's organs.
They can either contain the chloroplasts and carry on the process of photosynthesis, or they can contain the plastids that store the products of the process.
Storage parenchyma cells can be found in a juicy bite from an apple.
The air spaces of water lilies and other aquatic plants are connected by Parenchyma cells.
Parenchyma cells can give rise to more specialized cells when roots are placed in water.
The plant cells are the most specialized of the Parenchyma cells.
The walls are thicker and irregular compared to parenchyma cells.
The only function of scleroenchyma cells is to give strong support.
They have evolved a wide variety of mechanisms in order to survive and have established the base of the ecosystems.
Some plants use defensive strategies in an attempt to protect themselves.
A defensive strategy is a mechanism that has arisen through a process of natural selection in which the members of a group that possess the strategy compete better than those without it.
The more successful competitors have more chances to pass on their genes.
If a tree becomes injured, the xylem vessels plug up with chemicals that block them off above and below the site of the injury.
The damage will not spread to other locations on the tree.
Other plants make toxins in an attempt to deter pests.
Anyone who has come in contact with poison ivy or the pine tree knows how effective this defense mechanism is.
The polysaccharide found in the cell walls of plants is called Cellulose.
It's difficult for many predator to get the nutrition they need from eating the leaves because of the indigestible substance.
Plants can survive in environments that don't allow yearround growth.
Deciduous trees shed their leaves in response to the decrease in light, temperature, and humidity that occurs during the fall.
Seed dormancy allows the next generation to wait before germinating and competing for resources.
Many plant life cycles are timed so that the seeds are produced during the summer, and the following spring, so that they can grow.
Some plants only start to grow when they have undergone some form of physical trauma or seed scarification.
Many species of plants found in chaparral regions, which are hot and dry, can grow in an environment that has little competition for resources.
Evolutionary success is measured by the passing of one's genes to the next generation.
Plants have evolved the ability to reproduce both sexually and asexually.
Sexual methods of reproduction include stoons, rhizomes, and tubers.
Plants will be present on Earth for a long time because of the wide variety of survival mechanisms.
Plants have many mechanisms to ensure their survival.
There is a toxin in the leaves of poison ivy.
The thickness is usually involved in the corners of the cell.
The conochyma cells form bundles just beneath the skin and give support to the immature parts of the plant.
The strands in the stalks are mostly collenchyma cells.
The primary function of most sclerenchyma cells is to support the mature regions of a plant.
Most of the fibers found in ground tissue are in the veins.
Fibers are long and slender and may be grouped in bundles.
There are fibers that can be used to make rope and linen.
Linen is soft due to the fact that Flax fibers are not lignified.
Seed coats and nutshells contain sclereids, which are shorter than fibers and more varied in shape.
The Page 437 hard texture of pears and nuts is caused by stone cells.
There are two types of blood vessels.
The xylem and phloem are considered to be complex tissues because they are composed of two or more cells.
Both types of conducting cells are hollow and dead, but the vessel elements are larger and are arranged to form a continuous vessel for water and mineral transport.
The xylem tissue has a photomicrograph and a drawing.
The two types of vessels are composed of vessel elements.
A drawing of animals.
In addition to vessel elements and tracheids, xylem can also lend additional support as well as store various substances.
The parenchyma cells are located between rows of tracheids, conwater and minerals across the width of a plant.
The Sieve-tube members have no nucleus.
A nucleus is contained in the companion cell of each sieve-tube member.
The nucleus of the companion cell may control and maintain the life of both cells.
The companion cells are thought to be involved in the transport function of phloem.
Sclerenchyma fibers support phloem.
The phloem tissue has a photomicrograph and a drawing.
A drawing of sieve tube and companion cells.
The cells that make up these tissues are listed.
The transport functions of xylem and phloem are compared.
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