PBIO 004 Lecture Notes - Lecture 14: Sieve Tube Element, Phloem, Xylem

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OC2617651

27 Feb 2019

School

University of Vermont

Department

Plant Biology

Course

PBIO 004

Professor

Mary Lauretta Tierney

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Document Summary

Leaves are the site of photosynthesis and the production of sugars from carbon dioxide. Sugars are transferred from actively photosynthesizing (source tissue) to non- photosynthesizing (sink tissue) Mature leaves are the source tissue in plants, actively photosynthesizing and producing sugar. Sunk tissues are roots, flowers, stem, and fruit, which do not photosynthesize and produce sugar. Cambium (that produces vascular tissue) is between the xylem and the phloem cells in the vascular tissue. Phloem cells contain some organelles, but not all, so they have sieve tubes in them: these sieve tubes have companion cells that provide nutrients that the phloem cells can"t produce. Sugar from the mesophyll cells must be loaded into sieve tubes before it is transported throughout the plant: sieve tubes have small perforations for molecules to pass through. Companion cells support sieve tubes and aid in the movement of substances in and out of the phloem. Concentration gradients lead to the movement of sugar: diffusion.

Related Questions

Question 1: A slide of a terminal plant bud shows what physical characteristics demonstrating growth?

Answers:

1. an actively dividing group of cells between primordial leaves with undifferentiated vascular tissue

2. a vascular system with vascular bundles

3. spongy mesophyll tissue

4. sieve tubes, vessel elements and tracheids

Question 2: As the earth warmed and dried around 150 MYA, plants requiring _______ for fertilization were no longer dominant, but were eclipsed by plants that were ______ bearing named ___________ (literally naked seeds). These plants used _____ for fertilization freeing themselves from dependence on water. As animals of the era became terrestrial with means of terrestrial reproduction strategies, plants did the same using two different structures along with internal fertilization, the _____ being internal and fertilized by a wind carried _________ grain.

Answers:

1. water, seed, charophytya, dinosaurs, zygote, pollen

2. water, seed, gymnosperms, wind, egg, pollen

3. spores, cone, tracheids, water, pollen, embryo

4. water, flower, angiosperms, animals, spore, egg

Question 3: In the pith region of a stem the vascular system consists of two major structures;

Answers:	1. Phloem with trachieds and vessel elements and xylem with sieve-tubes and companion cells
	2. Sclerechyma fibers and parenchyma cells
	3. Phloem carrying photosynthesis products and xylem carrying water with dissolved nutrients
	4. Phloem carrying water with dissolved nutrients and xylem carrying photosynthesis products.

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The water-transporting cells of xylem tissue are tracheids and vessel members?

How is the structure of tracheids similar to the structure of vessel members?

How is the structure of tracheids different from the structure of vessel members?

How is the structure of both tracheids and vessel members related to their ability to serve as efficient water-conduction cells?

Sieve tube members are the conducting cells of phloem, specialized for the transport of metabolites within a plant. In what way do sieve tube members differ from a "typical" plant cell?

How do these differences improve the ability of sieve tube members to serve as efficient metabolite-conducting cells?

What is a companion cell, and what is its function?

To what tissue system does each of the following belong - tracheids, vessel members, sieve tube members, and companion cells?

The epidermis is a primary dermal tissue and the periderm is a secondary dermal tissue. Describe the most common cell types found in each of these tissues.

Both the epidermis and the periderm need to perform the same basic functions. What are those functions?

How does the structure of the epidermis contribute to those functions?

How does the structure of the periderm contribute to those functions?

What are guard cells?

How does the structure of guard cells differ from the structure of other epidermal cells?

What is the function of guard cells?

What are trichomes? What functions might trichomes perform?

What is a lenticel?

Describe its structure and function. Describe, in detail, the arrangement of primary tissues in a dicot stem. How does the arrangement of tissues in a monocot stem compare to that of dicot stems â how is it the same, how is it different?

The cortex region and the pith region of a dicot stem typically have different functions. What is the most common function of each region?

What type of tissue is each composed of?

In what types of plants does secondary growth occur?

In what plant organs does secondary growth occur?

Describe where lateral meristems form at the start of secondary growth in a stem.

Describe how the single layer of vascular cambium can produce both secondary xylem and secondary phloem.

What is wood?

bark?

early wood vs. late wood?

What allows the different layers of growth occurring each year to be visible to the human eye?

What is the function of mesophyll tissue?

What are the two types of mesophyll tissue in a typical dicot leaf?

How do these differ from each other with respect to location within the leaf, cell arrangement,

What is the function of the phloem? Select one: a. Phloem carries nitrogenous wastes to the roots where the waste leaves the plant. b. Phloem carries water and minerals to the rest of the plant from the roots. c. Phloem carries water from the leaves to the rest of the plant. d.

Phloem transports sugar down from the leaves to the rest of the plant. How do the cells of the xylem compare to the cells of the phloem? Select one: a. The xylem cells have thin cell walls, whereas the phloem cells have thick cell walls. b. The xylem cells are large, whereas the phloem cells are small. c. The xylem cells have chloroplasts, whereas the phloem cells do not have chloroplasts. d.

The xylem cells are square, whereas the phloem cells are round. From which part of the stem tissue is wood made? Select one: a. spongy mesophyll b. the cuticle c. old layers of xylem and phloem d. central parenchyma Flat leaves lose water to the environment more readily than pine needles do.

Which statement describes a structural characteristic of flat leaves that accounts for this difference? Select one: a. Flat leaves have a thicker coating of waterproof wax. b. Flat leaves have more surface area. c. Flat leaves have a thicker epidermis. d. The stomata of flat leaves are sunken into the leaf.

PBIO 004 Lecture Notes - Lecture 14: Sieve Tube Element, Phloem, Xylem

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