33. Plant Anatomy

Growth

Mechanisms of Plant Growth

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil, and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions. How does acid rain affect plant growth?

Beyond primary and secondary growth, what other aspects of plant growth might be negatively affected when plants are exposed to environmental stress?

Which statement best characterizes primary growth?
a. It does not occur in roots, only in shoots.
b. It leads to the development of cork tissue.
c. It produces the dermal, ground, and vascular tissues.
d. It produces rings of xylem, phloem, and cork tissue.

Growth in Plants Intro (2016)

Plant Structure

SECONDARY GROWTH

Which statement concerning grafting is correct?
a. Stocks and scions refer to twigs of different species.
b. Stocks and scions must come from unrelated species.
c. Stocks provide root systems for grafting.
d. Grafting creates new species.

 No. Annuals complete their life cycle in a single year. 

 No. Biennials generally live for two years. 

 No. Most plants have indeterminate growth and continue growing until they die. 

 None of the listed responses is correct. 

What does "perennial" mean?

If you wanted to plant a flowering plant in your yard that would bloom every spring, which of the following should you choose?

Dicotyledon Root Structure | Plant Biology

Primary and Secondary Growth

 Primary growth increases the diameter of the plant. 

 No. Primary growth increases the length of the plant. 

 Stems that only experience primary growth are called woody plants. 

 Herbaceous plants have stems that exhibit only secondary growth. 

 Secondary growth, a feature of herbaceous plants, extends the length of the plant. 

 No. Primary growth extends the length of the plant. Secondary growth is not a feature of herbaceous plants. 

 Primary and secondary growth are required to produce woody plants. 

Consider the directions of growth.

Some plants grow by primary and secondary mechanisms. Choose the correct description of a mechanism and its result.

Animation: Embryo and Endosperm Development

Vascular plants = Winning! | Crash Course biology| Khan Academy

 No. Apical meristem is responsible for primary growth. 

 No. Periderm is an external protective tissue and is not responsible for secondary growth. 

 No. Pith is ground tissue near the center of a stem. 

Consider which of these answers gives rise to secondary xylem and secondary phloem.

Annual rings in wood are evidence that in climates with a single annual growing season, the __________ divides actively when water is plentiful and temperatures are suitable for growth and ceases to divide when water is scarce and the weather is cold.

BioFlix: From Soil Into Roots

Animation: Primary and Secondary Growth

 No. The meristem is the source of new cells. 

 No. Cell division in the vascular cambium, which produces secondary xylem and secondary phloem, causes an increase in the diameter of a stem. 

 differentiation (specialization) of root cells 

 No. Differentiation is the process by which cells become specialized to perform specific functions. 

 No. Root hairs are structures that increase the surface area of a root, thereby increasing the rate of nutrient absorption. 

How do roots lengthen quickly?

Root tips are pushed farther into the soil mainly by __________.

Short Video: Root Growth in a Radish Seed

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil, and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions. How does acid rain affect plant growth?

Which meristem was likely affected in the chinaberry tree?

BioFlix: Water Transport in Plants

 No. Although primary growth does occur at the axillary buds, such growth results in branching, not an increase in height. 

 No. Bud scales are protective structures. 

 No. Lateral meristems play a role in secondary growth. 

 No. These are stem regions to which leaves are attached. 

Primary growth must occur in a region of cell division.

Which example below is the site of primary growth that results in the plant’s increasing in height?

 More than 1 meter off the ground and more deeply embedded in the tree 

 No. Consider apical meristems; they elongate shoots through primary growth, and thus the tree grows from the top. 

 1 meter off the ground and the same depth in the tree 

 No. Consider lateral meristems; they add girth to woody plants through secondary growth. 

 More than 1 meter off the ground and the same depth in the tree 

 No. You are not considering apical and lateral meristems. Apical meristems elongate shoots through primary growth, and thus growth occurs from the top. Lateral meristems add girth through secondary growth, and thus the tree will increase in diameter. 

 No. One of the other choices is correct. 

 1 meter off the ground and more deeply embedded in the tree 

Where does growth occur in a tree?

If you pound a nail into a tree 1 meter off the ground and come back to find it in 20 years, what will it be?

Trees can be killed by girdling—the removal of bark and vascular cambium in a ring all the way around the tree. Explain why.

 No. The division of the cells of the apical meristem of a root provides the cells for primary growth. 

 No. Cork cambium is meristematic tissue that produces new cork by cell division and differentiation. 

 No. Vascular cambium is meristematic tissue that produces new xylem and phloem by cell division and differentiation. 

 No. The apical meristem consists of actively dividing cells found at the tip of a terminal bud. 

Consider which one of these is not a type of actively dividing, undifferentiated tissue.

Cell division would occur least frequently in which of these tissues?

The phase change of an apical meristem from the juvenile to the mature vegetative phase is often revealed by
a. a change in the morphology of the leaves produced.
b. the initiation of secondary growth.
c. the formation of lateral roots.
d. the activation of floral meristem identity genes.

Heartwood and sapwood consist of
a. bark.
b. periderm.
c. secondary xylem.
d. secondary phloem.

The vascular cambium gives rise to 
(A) all xylem. 
(B) all phloem. 
(C) primary xylem and phloem. 
(D) secondary xylem and phloem

Plant Root Structure

Plant Anatomy and Morphology

Suppose a flower had normal expression of genes A and C and expression of gene B in all four whorls. Based on the ABC hypothesis, what would be the structure of that flower, starting at the outermost whorl?
a. carpel-petal-petal-carpel
b. petal-petal-stamen-stamen
c. sepal-carpel-carpel-sepal
d. sepal-sepal-carpel-carpel

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil, and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions. How does acid rain affect plant growth?

Based on the results presented here, predict the impact of acid rain on the vascular cambium in the two species. How would that effect be apparent in the amount of wood produced in the tree trunks?

What are Meristematic Tissues? | Don't Memorise

Root Growth

 No. Ground tissue does not contribute to intermediate growth. 

 No. Dermal tissue is the outer covering of the plant. 

 No. Periderm is the outer covering of woody stems. 

Consider which type of tissue is undifferentiated.

A region of dividing cells in a plant is called a __________.

You attached a birdfeeder to a tree 5 years ago at a position 6 feet above the ground. The tree has grown since at a rate of 1 foot per year. What is the current height of the birdfeeder?

Animation: Secondary Growth

 No. Nodes are places in the stem at which leaves are attached. 

 No. Leaf primordia are finger-like projections along the sides of apical meristems from which leaves develop. 

 No. Axillary buds form at leaf nodes. They are a type of dormant apical meristem. 

 No. Bundle sheaths are layers of cells that enclose and protect the vascular tissue in leaves. 

Where is girth added to a plant?

Which of the following is a lateral meristem?

 Removing the apical meristem stimulates growth in the lateral meristem, thus making the plant bushier. 

 No. The lateral meristem increases the girth of stems and roots. It does not make a plant bushier. 

 Removal of a node stimulates the internodes to grow and make the plant bushier. 

 No. Nodes are the places on the stems where leaves attach, and internodes are the stems between nodes. They are not the places where growth occurs. 

 Removing the apical meristem causes the plant to change from its vegetative phase to its reproductive phase. The reproductive phase is bushier. 

 No. Removal of the apical meristem is not the signal that causes the plant to go from vegetative to reproductive growth. Also, reproductive growth is not necessarily bushier. 

 Removing plant stems always leads to the plant producing more leaves. 

 Removing the apical meristem stimulates growth in the axillary buds, thus making the plant bushier. 

Where else does the plant have meristem?

Why does pinching off the top of a plant make it bushier?

 No. Vascular cambium gives rise to secondary xylem and secondary phloem. 

 No. The endodermis separates vascular tissue from ground tissue. 

 No. The cortex is a ground tissue region. 

Consider the tissue that is characteristic of roots.

Lateral roots in seed plants are initiated by cell divisions in the __________.

Internal Structure of Roots

Primary Growth in Plants

Which of the following arise(s), directly or indirectly, from meristematic activity?
a. secondary xylem
b. leaves
c. dermal tissue
d. all of the above

Most of the growth of a plant body is the result of
a. cell differentiation.
b. morphogenesis.
c. cell division.
d.cell elongation.

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil, and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions. How does acid rain affect plant growth?

Give a plausible explanation for the differential effect of acid rain on height in camphor and chinaberry trees (i.e., what structural features might offer more protection from acid rain in one species versus another?).

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil, and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions. How does acid rain affect plant growth?

Develop a hypothesis on the likely effects of acid rain on primary growth in trees. Based on your hypothesis, make some predictions about the impact of acid rain on the height of tree trunks.

Primary Meristems

Secondary Growth

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