PLANTS VASCULAR SYSTEMS



Flower Dissection

Introduction Flowers, which are unique to angiosperms, function in reproduction. The flowers of many angiosperms have adapted in ways that attract pollinators (animals such as birds or insects that carry pollen between flowers). As a bird or insect feeds on a flower’s nectar or pollen, pollen sticks to the animal. When the pollinator moves on to another plant of the same species, it pollinates the second plant. Pollination may lead to fertilization and the development of a new generation of plants.

|Flower Structure |Hummingbirds |Bees |

|Shape |Hummingbirds prefer flowers with a tubular shape that fit their long, slender|Bees prefer cup-shaped flowers in which they can |

| |beaks. |nestle while gathering pollen or nectar. |

|Color |Hummingbirds as well as many other birds, are most attracted to red flowers, |Bees, as well as other insects, respond mostly to blue|

| |but will also drink nectar from flowers with colors that contain red such as |and yellow flowers. They cannot detect red. |

| |orange or pink. | |

|Pattern |Hummingbirds respond to color and shape, rather than patterns. |Bees are attracted to flowers with “runaway” lines or |

| | |dashes that lead the bee to pollen or nectar. |

|Scent |Hummingbirds have a limited sense of smell. Smell has little impact on food |Bees have a strong sense of smell and are attracted to|

| |choice. |fragrant flowers. |

1. Based on the information in the table above, use colored pencils to sketch a flower in the boxes on your sheet that you think would attract a hummingbird & a flower that would attract a bee and

answer questions 1 and 2

2. Monocots and dicots are two groups of angiosperms. One way to recognize monocots is to count the number of sepals or petals. If this number is a multiple of three, the plant is a monocot. If the number is a multiple of four or five, and if the leaves contain branched veins, the plant is a dicot. If the flower does not fit the monocot or dicot description, it likely belongs in one of other several groups of angiosperms. Observe your flower. Answer Question #3.

3. Flowers have structures with specialized shapes that allow sperm in pollen to reach the eggs in the ovaries. Follow the directions below to take the flower apart and identify its reproductive structures.

a.Gently pull off the petals and set them aside. Look for the yellow, dusty pollen.

b. Identify a stamen. A stamen consists of a stalk called the filament and a structure at the tip called the anther. Pollen is produced in the anther.

c. The stigma, style and ovary make up the pistil—the female part of a plant. Identify the style and stigma. Look for a centralized stalk (the style) with a sticky end (the stigma). In most flower species, there is only one style. Pollen at the tip of the stamen is carried by pollinators or wind sticks to the stigma and absorbs fluid. Then a tube called the pollen tube grows from the stigma through the style, toward the ovary. A cell in the pollen divides, and two sperm nuclei travel down the pollen tube toward the ovary. Answer ? 4

d. Remove the stigma and style from the flower and locate the ovary. Using forceps, or your thumbnails, pull open the ovary to observe the ovule or ovules. Each ovule contains an egg cell. If available, use a hand lens or stereomicroscope to observe the ovule(s). One sperm that travels down the pollen tube fertilizes the egg cell and forms a zygote. The other sperm fertilizes a large central cell in the ovule, which develops into a tissue called endosperm that nourishes the growing embryo. After this double fertilization takes place, the each ovule develops into one seed with the embryo and endosperm inside. Answer ? 5

Arizona wildlife rescuers save spiny residents from urban sprawl

Current Science September 21, 2007

Dawn has just broken when a small troop of volunteers arrives in the Sonoran Desert, just outside of Tucson, Ariz. Many are wearing thick welding gloves. One is carrying a bottle of typewriter correction fluid. Another is toting a jackhammer.

Why such an odd assortment of tools? The volunteers are here to save cacti. By morning's end, the group will have snatched hundreds of the prickly plants from the jaws of a developer's bulldozers. The rescue operation, repeated a dozen times around the Tucson area each year, is helping preserve Arizona's natural environment and distinctive beauty.

THE RESCUERS The wildlife rescuers belong to the Tucson Cactus and Succulent Society (TCSS). Succulents are a type of xerophyte, or plant adapted to dry climates. Their adaptations may include a thick stem that can store large amounts of water; a waxy surface that reduces water loss; and small leaves, or no leaves at all, to further limit water loss.

Cacti are the best-known succulents in North and South America. (Cacti are much less common in the rest of the world.) Their distinguishing feature isn't spines--not all cacti are prickly. But all cacti have small bumps called areoles on their surface. Areoles are highly modified branches from which the spines--or in some cases, the leaves--grow.

Arizona is the fastest growing state in the country. New subdivisions, shopping malls, and golf courses are sprouting up and competing with the local succulents for space. Because damaging or destroying native plants is illegal in the Tucson area, the TCSS volunteers play a vital role. Since 1999, they have staged 175 rescue missions in cooperation with local developers and found new homes for more than 34,000 succulents.

THE BIG DIG How is a plant as spiny and untouchable as a cactus rescued? Thick gloves are a must, says Richard Wiedhopf, president of TCSS. So is a shovel. In some cases, a jackhammer is handy if the soil around the roots is crusty or rocky. "We also have a sling that we carry the larger cacti in," Wiedhopf told Current Science. "Two to four people can use a handhold on the sling to make transportation easier."

Another necessity is white correction fluid to protect the cacti from sunburn. Sunburn? "That's right," says Matthew Johnson, a researcher at the Boyce Thompson Arboretum. An

arboretum is a garden with a large collection of trees and shrubs cultivated for scientific or

educational purposes. High temperatures and intense light can break down the chlorophyll (the green pigment that enables a plant to conduct photosynthesis) and destroy the cells in a cactus's

epidermis (surface layer). Unlike a human's red sunburn, a cactus's sunburn is white. A sunburn can not only disfigure the plant but in severe cases can even kill it.

When a cactus is transplanted, the south-facing side of the plant should be well marked with the correction fluid, says Johnson. The marking indicates the direction in which the cactus must be oriented when replanted. If the north-facing side is turned south or west toward the sun, especially during hot times of the year, the cactus could develop a sunburn. "The north side won't have the thicker surface layers found on the portions of the plant that normally receive more intense sunlight," says Johnson. "All succulents are potentially vulnerable to sunburn damage."

QUEEN OF THE NIGHT The Tucson area is native ground to 32 species of cacti and 11 other succulents. One of the most unusual cacti is the queen of the night, or night-blooming cereus. Its stem resembles a dead stick, camouflaging it among the debris of the desert floor. Unlike most flowering plants, which bloom during the day, the queen's large white flowers open at night to attract nocturnal pollinators, such as hawk moths. Each flower blooms for only one night, though one plant may have several flowers that open on different evenings.

For some unknown reason, the queens in a large area often flower at the same time. Tohono Chul Park in Tucson holds an annual Night-looming Cereus Night, which is announced when many of the plants are forecast to bloom.

Another Arizona native is the stately saguaro, a tall, columnar cactus with uplifted arms. The spines on a cactus protect it against thirsty and hungry animals. One Arizona saguaro exacted a unique form of payback against an enemy. In 1982, a man named David Grundman headed into the Arizona desert with a rifle. He shot a small saguaro in the trunk so many times, it fell to the ground. Then, taking aim at an 8-meter (26-foot) saguaro, he blasted off one of its huge arms, which landed on Grundman and crushed him to death.

TCSS sells most of the succulents it digs up to businesses and home owners at a small cost. It donates the rest to schools and botanical gardens. "There is nothing better than being out in the desert in the early morning," says Wiedhopf. "Everyone enjoys the three to four-hour rescue. People might be tired and dirty, but they really feel that they have accomplished something positive."

The Australian cycad plant is like a dude who douses himself in too much AXE.

It’s a real turn off.

Cycads are gymnosperms – cone-bearing plants – and more than 300 species exist around the world. The male cycad produces pollen that must be carried to the female cycad to fertilize the eggs. For years scientists thought that the wind performed that job. But a team of U.S. and Australian scientists recently found that for one species of cycad (Macrozamia lucida) that grows in Australia, the pollination process is trickier than that.

The trunk of the cycad is located largely in the soil. Above ground, the plant looks like a palm tree with a crown of large leaves. And perched atop the crown is a large cone.

For several weeks once a year or every few years, the male Australian cycad tree exudes a scent like turpentine and attracts tiny flying insects called thrips. The thrips crawl into the male’s cone and consume some of the pollen, getting covered in the stuff as they eat.

Each day at about 11 a.m., the male cycad uses its stores of sugar, starch, and fats to crank up its temperature by about 14 degrees Celsius (25 degrees Fahrenheit), becoming as hot as 38 degrees C (100 degrees F). At the same time the tree pumps out so much scent it starts to stink. “It’s a harsh, overwhelming odor like nothing you ever smelled before,” says Irene Terry, a biology professor at the University of Utah.

The stench is offensive not only to people but to the thrips too. They hightail it for the gentler scent of the female cycad and crawl inside her cone. As they do, some of the pollen on their bodies falls off and pollinates the female’s eggs. By midafternoon, the male cools off and eases back on the odor. The thrips return to him and the cycle begins again.

“People think of plants as just sitting there and looking pretty and sending out some odors to attract pollinators,” says Terry. “but these cycads have a specific sexual behavior timed to repel attract and deceive the thrips.”

PLANTS VASCULAR SYSTEMS

Xylem and phloem make up the big transportation system of vascular plants. As you get bigger, it is more difficult to transport nutrients, water, and sugars around your body. You have a circulatory system if you want to keep growing. As plants evolved to be larger, they also developed their own kind of circulatory systems. The main parts you will hear a lot about are called xylem and phloem.

It all starts with a top and a bottom. Logically, it makes sense. Trees and other vascular plants have a top and a bottom. The top has a trunk, branches, leaves, or needles. The bottom is a system of roots. Each needs the other to survive. The roots hold the plant steady and grab moisture and nutrients from the soil. The top is in the light, conducting photosynthesis and helping the plant reproduce. You have to connect the two parts. That's where xylem and phloem come in.

ZIPPY XYLEM

The xylem of a plant is the system of tubes and transports water and dissolved minerals. As a plant, you have roots to help you absorb water. If your leaves need water and they are 100 feet above the ground, it is time to put the xylem into action! Xylem is made of vessels that are connected end to end for the maximum speed to move water around. They also have a secondary function of support. When someone cuts an old tree down, they reveal a set of rings. Those rings are the remains of old xylem tissue, one ring for every year the tree was alive.

PHLOEM FUN

The fun never stops in the plant's circulatory system. Most plants have green leaves, where the photosynthesis happens. When those sugars are made, they need to be given to every cell in the plant for energy. Enter phloem. The phloem cells are laid out end-to-end throughout the entire plant, transporting the sugars and other molecules created by the plant. Phloem is always alive. Xylem tissue dies after one year and then develops anew (rings in the tree trunk). What is the best way to think about phloem? Think about sap coming out of a tree. That dripping sap usually comes from the phloem

1. Observe the prepared slide of a cross section of a Dicot Stem under low power of the microscope (it is the picture on the bottom of the slide. Draw the cross section as observed under low power in one of the circles provided.

A vascular bundle is the xylem and phloem put together. You can see a picture of a single bundle on the right. The vascular bundles are arranged in a ring toward the outside of a dicot stem. Switch to the high-power objective and focus on a single vascular bundle. Observe the thick-walled xylem (label all underlined words on your drawing) cells. Notice the smaller, thinner-walled phloem cells within the bundle.

2. Switch back to the low-power objective and observe the arrangement of cells within the stem cross section. The pith is the large area in the middle of the ring of vascular bundles. Surrounding the ring is the cortex. The cells on the outside rim are the epidermis. Label the xylem, phloem, pith, cortex, and epidermis in your drawing.

3. Observe the prepared slide of a cross section of a monocot stem under the low-power objective of the microscope (It is the picture on the top of the slide). Draw the cross section as observed under low power in one of the circles provided. Note the general arrangement of the cell and position of the xylem and phloem.

4. Examine the epidermis, cortex, and pith in the monocot stem cross section. Label the xylem, phloem, epidermis, cortex, and pith in your drawing.

1. Observe the prepared slide of a cross section of a dicot stem under low power of the microscope (it is the picture on the bottom of the slide. Draw the cross section as observed under low power in one of the circles provided.

A vascular bundle is the xylem and phloem put together. You can see a picture of a single bundle on the right. The vascular bundles are arranged in a ring toward the outside of a dicot stem. Switch to the high-power objective and focus on a single vascular bundle. Observe the thick-walled xylem cells. Notice the smaller, thinner-walled phloem cells within the bundle.

2. Switch back to the low-power objective and observe the arrangement of cells within the stem cross section. The pith is the large area in the middle of the ring of vascular bundles. Surrounding the ring is the cortex. The cells on the outside rim are the epidermis. Label the xylem, phloem, pith, cortex, and epidermis in your drawing.

3. Observe the prepared slide of a cross section of a monocot stem under the low-power objective of the microscope (it is the picture on the top of the slide). Draw the cross section as observed under low power in one of the circles provided.

Note the general arrangement of the cell and position of the xylem and phloem.

4. Examine the epidermis, cortex, and pith in the monocot stem cross section. Label the xylem, phloem, epidermis, cortex, and pith in your drawing.

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Coloring Flowers!

Coloring the Main Flower The receptacle is the part of the branch on which a flower forms. Color the receptacle (B) brown. Sepals are leaf like structures that surround and protect the flower before it blooms. Color the sepals green. Petals are the colorful part of the flower that attracts insects and even other small animals, such as mice, birds, and bats. Color the petals a bright color of your choice. All flowering plants have flowers, but some are not brightly colored. The petals of these flowers are reduced or absent and the plant relies on the wind or water for pollination. The

flower has both male and female reproductive parts. The female reproductive structures are called carpels. In most flowers, the carpels are fused together to form a pistil. Color the pistil in the flowers pink. The male reproductive structures are called the stamens. Color the stamens of the flowers blue. Coloring the Pistil & Stamen The pistil has three parts. The stigma at the top is often sticky and is where the pollen attaches. Color the stigma purple. The style is the long tube that attaches the stigma to the ovary. Sperm from the pollen will travel down this tube to the ovules. The ovules, or eggs, are stored in the ovary until they are fertilized. Plants can only fertilize eggs of the same species. Special chemicals prevent sperm from fertilizing the eggs of flowers that are not the same kind. Color the style red, and the ovary pink. Color the ovules black.

Each stamen consists of an anther , which produces pollen, and a filament, which supports the anther. In the stamen off to the left side (the one next to the pistil) color the anther dark blue, and the filament light blue. Pollen produced by the anther is carried by insects or other animals to the pistil of another flower where it may fertilize the eggs.

Plant Reproduction

Sexual reproduction in plants occurs when the pollen from an anther is transferred to the stigma. Plants can fertilize themselves: called self-fertilization. Self-fertilization occurs when the pollen from an anther fertilizes the eggs on the same flower. Cross-fertilization occurs when the pollen is transferred to the stigma of an entirely different plant.

When the ovules are fertilized, they will develop into seeds. The petals of the flower fall off leaving only the ovary behind, which will develop into a fruit. There are many different kinds of fruits, including apples and oranges and peaches. A fruit is any structure that encloses and protects a seed, so fruits are also "helicopters" and acorns, and bean pods. When you eat a fruit, you are actually eating the ovary of the flower.

Use the following information to identify the 6 roots at this station.

The first structures to appear on a germinating seed are the roots.

In a taproot system, the primary root grows longer and thicker than the secondary roots. Due to the greater mass & volume than the other roots the taproot is more likely to be a food source.

In a fibrous root system, the secondary roots continue to grow, and eventually all the roots are of equal or nearly equal size.

Adventitious roots grow from parts of the plant other than the roots.

Aerial roots are roots that are suspended in the air.

Roots anchor the plant in place, absorb water containing dissolved minerals from the environment, and act as storage areas for excess food.

Plant structures that grow between the roots and leaves are called stems. Although stems usually grow above the ground in vertical positions, they can also grow under the ground in horizontal positions. All stems begin growing as soft, tubelike structures. If the stem remains soft, and usually green, for the entire life of the plant, it is a herbaceous stem. A woody stem becomes bark.

Stems conduct water and dissolved minerals from the roots to the leaves, and food from the leaves to the rest of the plant. Stems may also functions as food storage areas, supporting structures, and places for the growth of new plants.

Current Science Jan. 4, 2008 Issue 9 pg13

x 100 = Percent Water

How much Water is in a Plant?

All living organisms consist mostly of water.

The adult human body is about 60% water, by weight, and 75% by volume.

As much as 95% of the weight of some plants is due to the water they contain.

1. We already weighed each of the plants. Then we set the plants on a newspaper to dry overnight. The Fresh weights were:

Grass___________g Grapes___________g Carrots___________g

Record the Fresh weights in your table.

2. Find the Dried (g) weight of the grass, grapes, and carrots. Record the data in your table

3. To calculate Total Water Lost subtract the Fresh column from the Dried Column

Fresh (g) – Dried (g) = Total Water Lost

Do this for each plant and record the number in the table.

5. To calculate Percent Water divide Total Water Lost by Fresh then take that number and multiply it by 100.

Total Water Lost (g) Fresh (g)

Do this for each plant and record

the number in the table.

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