Full Answer
What is the secondary phloem?
Where does phloem parenchyma occur?
How are rays produced in the secondary xylem?
What are the cell types of the vertical phloem system of conifers?
What are the secondary phloems of gymnosperms?
What is the function of the phloem?
What are alternative cell fates?
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What is Secondary Phloem? - Definition from Maximum Yield
Maximum Yield Explains Secondary Phloem. The vascular cambium growth is what forms the secondary xylem and the secondary phloem. Both are what compose the telltale rings of a tree and can be used to tell the tree’s age because each ring represents a year of the tree’s life.
Primary Phloem and Secondary Phloem | Plants - Biology Discussion
ADVERTISEMENTS: The upcoming discussion will update you about the differences between Primary Phloem and Secondary Phloem. Difference # Primary Phloem: 1. It is formed from pro-cambium of apical meristem. 2. It is found in the primary plant body of all vascular plants. ADVERTISEMENTS: 3. Primary phloem occurs in all types of organs 4. It occurs […]
secondary phloem | plant tissue | Britannica
Other articles where secondary phloem is discussed: phloem: …palms but is replaced by secondary phloem in plants that have a cambium.
Secondary Xylem and Phloem in Conifers | Botany
ADVERTISEMENTS: Let us learn about Secondary Xylem and Phloem in Conifers. Secondary Xylem (Wood): The xylem of gymnosperms is generally simpler and more homogeneous than that of angiosperms. The chief distinction between the two kinds of wood is the absence of vessels in the gymnosperms (except in Gnetales) and their presence in most angiosperms. The […]
Secondary growth in dicots and gymnosperms occurs by - Toppr Ask
Intrafascicular cambium (present between xylem and phloem) and interfascicular cambium together form a complete cambium ring, called as vascular cambium or just cambium.Vascular cambium exhibits two patterns of division i.e., multiplicative divisions and additive divisions.
Secondary Growth - University of Wisconsin–Madison
Secondary Growth. Return to Lab Page. Introduction: It is assumed that the student has achieved a proper understanding of the primary structure of the dicot stem, and specifically on an understanding of the organization of the primary tissues in the two stems we have studied (Medicago, and Coleus).It may be a good idea to review both "Cells and Tissues of the Plant Body", and "The Shoot ...
What Does Secondary Phloem Mean?
In plant biology, the secondary phloem is a part the cambium vascular growth of a tree or woody plant. It is the food-conducting tissue and is sometimes referred to as the tree’s inner bark, which is where it is located.
What is the phloem of a plant?
Phloem, in all vascular plants, is the living tissue that transports the soluble organic compounds made during photosynthesis to various parts of the plant. It consists of conducting cells, parenchyma cells, and supportive cells, such as fibers and sclereids. The secondary phloem of angiosperms consists of: 1 sieve-tube members 2 companion cells 3 scattered parenchyma 4 ray parenchyma 5 fibers (usually occurring in clusters alternating with the sieve tubes and parenchyma cells)
What is the cell that transports the soluble organic compounds made during photosynthesis?
Phloem, in all vascular plants, is the living tissue that transports the soluble organic compounds made during photosynthesis to various parts of the plant. It consists of conducting cells, parenchyma cells, and supportive cells, such as fibers and sclereids. The secondary phloem of angiosperms consists of:
What is the origin of a secondary phloem?
Secondary Phloem has the same origin as secondary xylem, namely, the vascular cambium. Cells displaced towards the outside of the vascular cambium differentiate as phloem. Secondary phloem can remain active over several growth cycles. Secondary phloem, like secondary xylem, is a complex tissue. It always has sieve elements which are analogous to tracheary elements. However, parenchyma is also present, and sclerenchyma may also be visible. There are two kinds of sieve elements, Sieve Cells and Sieve Tube Members.
Which stems show secondary phloem?
Observe commercial slides of Tilia stems that show secondary phloem.
What are densely stained cells?
The densely stained cells seen in long sections of commercial slides are phloem parenchyma. Note the presence of Amyloplasts in them. Phloem parenchyma can also contain crystals.
Which cell is more elongated, a sieve tube or a cell wall?
Sieve cells are more highly elongated than sieve tube members. The cell walls of most sieve elements are similar to those of parenchyma cells, and it is often difficult to distinguish between these in cross sections unless a sieve plate or sieve pores can be seen. Callose is preferentially stained by aniline blue .
Which phloem has rays?
Rays are present in secondary ph loem and are usually continuous with rays in the secondary xyl em. Some species develop dilated rays in their secondary phloem. Tilia americana and Hibiscus tiliaceus ( hau) are two prime examples for the presence of dilated rays. Dilated rays are principally composed by parenchyma cells which result from localized anticlinal divisions.
Does callose stain help locate sieve elements?
Callose stained with aniline blue fluoresces under near ultra violet and violet light. This provides a more certain method to locate sieve elements . Callose is also present in their cytoplasm and its fluorescence aids in the location of sieve elements.
Is a secondary phloem a trachea?
Secondary phloem, like secondary xylem, is a complex tissue. It always has sieve elements which are analogous to tracheary elements. However, parenchyma is also present, and sclerenchyma may also be visible. There are two kinds of sieve elements, Sieve Cells and Sieve Tube Members. Sieve Tube Members are highly specialized for translocation.
What is secondary phloem?
1. Secondary phloem develops from a lateral meristem called vascular cambium. 2. It is found only during secondary growth of dicots and gymnosperms with the exception of annuals. 3. Secondary phloem is restricted to stems and roots of perennial dicots and gymnosperms. 4. It is formed inner to the primary phloem. 5.
Where is the primary phloem found?
Difference # Primary Phloem: 1. It is formed from pro-cambium of apical meristem. 2. It is found in the primary plant body of all vascular plants. 3. Primary phloem occurs in all types of organs. 4. It occurs towards the periphery.
Where are sciereids formed?
13. Sciereids are formed in the secondary phloem of several plants.
What is the secondary phloem?
Secondary phloem, the tissue produced to the outside of the vascular cambium, is also a complex tissue that includes an axial and a ray system. Like the xylem, the axial system in secondary phloem includes conducting cells, either sieve cells in conifers or sieve tube members in the angiosperms, which conduct solutes from the sites of photosynthesis to other parts of the plant. Phloem parenchyma occurs in the axial system, as well as companion cells (angiosperms) and albuminous cells (conifers). Fibers are very common in the secondary phloem of both conifers and angiosperms (FIG. 7.31), and the pattern of fiber production by the cambium can sometimes be used to identify secondary phloem and bark tissue taxonomically. Although some conifers can produce regular, repeating bands of sieve cells, fibers, and parenchyma, they do not seem to produce these on an annual cycle, so it is not possible to determine the age of bark as it is to date wood by counting the tree rings.
Where does phloem parenchyma occur?
Phloem parenchyma occurs in the axial system , as well as companion cells (angiosperms) and albuminous cells (conifers). Fibers are very common in the secondary phloem of both conifers and angiosperms (FIG. 7.31 ), and the pattern of fiber production by the cambium can sometimes be used to identify secondary phloem and bark tissue taxonomically.
How are rays produced in the secondary xylem?
The rays in the secondary xylem and phloem are produced by periclinal divisions of ray cell initials of the cambium. Ray development involves periodic changes in their number, height, and width as the tree grows. Most new rays form in very young trees when peripheral expansion of the cambium is maximal.
What are the cell types of the vertical phloem system of conifers?
The main cell types of the vertical phloem system of conifers are sieve cells, parenchyma cells, and fibers. In dicotyledons, the cell types are sieve tube members, companion cells, parenchyma cells, and fibers. The problem to be addressed now is how the cells of these two vertical phloem systems come to be distinctively distributed within ...
What are the secondary phloems of gymnosperms?
Secondary phloem tissues of both gymnosperms and dicotyledonous angiosperms are concerned mainly with the basipetal transport of sugars. Just as the structure of secondary xylem tissue shows relative simplicity in conifers but is more complex in dicotyledons, so the same is true of the secondary phloem (Srivastava, 1963; Esau, 1969). The main cell types of the vertical phloem system of conifers are sieve cells, parenchyma cells, and fibers. In dicotyledons, the cell types are sieve tube members, companion cells, parenchyma cells, and fibers. The problem to be addressed now is how the cells of these two vertical phloem systems come to be distinctively distributed within the radial files of phloem. The cell divisions that accompany phloem cell differentiation seem to be quite distinctive (Esau and Cheadle, 1955 ), suggesting that this feature can be taken as a starting point in a discussion of phloem cell arrangements.
What is the function of the phloem?
Usually only a narrow band of phloem close to the cambium is actively involved in conduction—the functional phloem or inner bark . As the older phloem becomes nonfunctional, there are many histological changes in the tissue, including the collapse of sieve elements, the development of sclereids from parenchyma cells, and/or the deposition of ergastic substances in parenchyma cells. These changes have also been identified in fossil phloem (Smoot, 1984c). It is in the nonfunctional phloem that subsequent cork cambia may arise in older axes.
What are alternative cell fates?
Alternative cell fates might be associated with different cell division patterns in different locations around the cambial perimeter. For example, Zee (1968) deduced two principal sequences of periclinal and radial divisions, in secondary phloem of pea ( Pisum sativum) epicotyl, as well as an occasional third pathway. Whether a given radial file of the phloem consistently divides according to one or other of the first two pathways, or whether the pathways alternate within a single radial file, is not known.
