travismulthaupt.com Chapter 35 Plant Structure and Growth Essential Idea: Plants adapt their growth to environmental conditions. TOK: Plants communicate chemically both internally and externally. To what extent can plants be said to have language?

travismulthaupt.com Cell Organization Tissues are groups of cells with a common function. Tissues (or many different types) comprise organs--they carry out particular functions. Tissues are groups of cells with a common function. Tissues (or many different types) comprise organs--they carry out particular functions.

travismulthaupt.com 3 Basic Organs Three basic organs evolved to take advantage of this –1. Roots –2. Stems –3. Leaves They are organized into a root system and a shoot system. Three basic organs evolved to take advantage of this –1. Roots –2. Stems –3. Leaves They are organized into a root system and a shoot system.

travismulthaupt.com Plant Tissue Plants have 3 tissue systems: –1. Dermal –2. Vascular –3. Ground Each plant organ has the three tissue types. Plants have 3 tissue systems: –1. Dermal –2. Vascular –3. Ground Each plant organ has the three tissue types.

travismulthaupt.com 1. The Dermal Tissue System It is the outer protective covering, it’s the first line of defense against physical damage and pathogens. Non-woody plants consist of a tightly packed tissue called the epidermis. Woody plants consist of protective tissues called periderm (eventually forming bark). It is the outer protective covering, it’s the first line of defense against physical damage and pathogens. Non-woody plants consist of a tightly packed tissue called the epidermis. Woody plants consist of protective tissues called periderm (eventually forming bark).

travismulthaupt.com 1. The Dermal Tissue System The epidermis also forms the cuticle which assists in protection, disease prevention, and prevention of water loss.

travismulthaupt.com 2. The Vascular Tissue System Vascular tissue starts in the root system. The root system provides a large surface area for mineral ion and water uptake. The roots are modified with root hairs. Vascular tissue starts in the root system. The root system provides a large surface area for mineral ion and water uptake. The roots are modified with root hairs.

travismulthaupt.com The root hairs dramatically increase the surface area of the plant for mineral and water uptake. 2. The Vascular Tissue System

travismulthaupt.com 2. The Vascular Tissue System Carries out long-distance transport of materials between roots and shoots. The 2 tissues are: –A. Xylem –B. Phloem Together, they’re the stele Carries out long-distance transport of materials between roots and shoots. The 2 tissues are: –A. Xylem –B. Phloem Together, they’re the stele

travismulthaupt.com Stele The vascular tissue of a root or stem is called the stele. –In angiosperms, the stele of the root is in the form of a solid vascular cylinder. –The stele of the stem and leaves is arranged into a vascular bundle--strands consisting of xylem and phloem. The vascular tissue of a root or stem is called the stele. –In angiosperms, the stele of the root is in the form of a solid vascular cylinder. –The stele of the stem and leaves is arranged into a vascular bundle--strands consisting of xylem and phloem.

travismulthaupt.com A. Xylem Xylem conveys water and dissolved minerals upward from roots to shoots.

travismulthaupt.com A. Xylem The two types of water conducting cells of xylem. –A. Tracheids –B. Vessel Elements: These are dead at functional maturity. The two types of water conducting cells of xylem. –A. Tracheids –B. Vessel Elements: These are dead at functional maturity.

travismulthaupt.com A. Tracheids Are found in the xylem of all vascular plants. Most angiosperms, a few gymnosperms, and a few seedless vascular plants have vessels. When the cell dies, a non- living conduit remains through which water flows. The secondary cell walls contain lignin. Are found in the xylem of all vascular plants. Most angiosperms, a few gymnosperms, and a few seedless vascular plants have vessels. When the cell dies, a non- living conduit remains through which water flows. The secondary cell walls contain lignin.

travismulthaupt.com B. Vessel Elements Usually wider, shorter and thinner than tracheids. They are relatively long micropipes and are aligned end to end. Usually wider, shorter and thinner than tracheids. They are relatively long micropipes and are aligned end to end.

travismulthaupt.com B. Phloem Phloem transports organic nutrients from where they are made to where they are needed (from leaves to root tips, developing leaves and fruits).

travismulthaupt.com B. Phloem and Sieve Tubes The sugar conducting cells of phloem are alive at maturity. The sugar and other organic nutrients flows through sieve tubes. The end walls of sieve tubes have sieve plates which have pores that allow fluid to move from tube to tube. The sugar conducting cells of phloem are alive at maturity. The sugar and other organic nutrients flows through sieve tubes. The end walls of sieve tubes have sieve plates which have pores that allow fluid to move from tube to tube.

travismulthaupt.com Companion Cells Sieve tubes have companion cells that help to load sugars into sieve tube members.

travismulthaupt.com 3. Ground Tissue The ground tissue system provides for storage, photosynthesis and support. The ground tissue system comprises tissues that are neither dermal nor vascular. Pith is ground tissue internal to the vascular tissue. The cortex is ground tissue external to the vascular tissue. The ground tissue system provides for storage, photosynthesis and support. The ground tissue system comprises tissues that are neither dermal nor vascular. Pith is ground tissue internal to the vascular tissue. The cortex is ground tissue external to the vascular tissue.

travismulthaupt.com Meristems Dicotyledonous plants have apical and lateral meristems. Meristems contain perpetually embryonic cells. There are two main types: –1. Apical –2. Lateral Dicotyledonous plants have apical and lateral meristems. Meristems contain perpetually embryonic cells. There are two main types: –1. Apical –2. Lateral

travismulthaupt.com 1. Apical Meristem The apical meristem is located at the tips of roots and in the buds of shoots. Mitosis in this area enables primary growth, extension of the stem and development of leaves. (length). The apical meristem is located at the tips of roots and in the buds of shoots. Mitosis in this area enables primary growth, extension of the stem and development of leaves. (length).

travismulthaupt.com Hormones Plant hormones control the growth in the shoot apex. –Auxins-initiates growth of roots and development of fruits and leaf development. –IAA-controls growth of shoot apex, promotes elongation in stem cells. IAA is synthesized in the apical meristem and is transported down for stem growth. –Cytokines-produced in root, promotes axillary growth. –Gibberellins-contributes to stem elongation. Plant hormones control the growth in the shoot apex. –Auxins-initiates growth of roots and development of fruits and leaf development. –IAA-controls growth of shoot apex, promotes elongation in stem cells. IAA is synthesized in the apical meristem and is transported down for stem growth. –Cytokines-produced in root, promotes axillary growth. –Gibberellins-contributes to stem elongation.

travismulthaupt.com Tropisms Plant shoots also respond to the environment by tropisms. –Phototropism-growth towards light. The absorption of light by photoreceptors can control the transcription of specific genes. –Gravitropism-growth in response to gravitational force. Plant shoots also respond to the environment by tropisms. –Phototropism-growth towards light. The absorption of light by photoreceptors can control the transcription of specific genes. –Gravitropism-growth in response to gravitational force.

travismulthaupt.com 2. Lateral Meristem After the primary growth from the apical meristem has stopped, the remaining growth is mostly all secondary (girth). There are two main types of lateral meristems that increase the girth of the plant. –A. Vascular cambium –B. Cork cambium After the primary growth from the apical meristem has stopped, the remaining growth is mostly all secondary (girth). There are two main types of lateral meristems that increase the girth of the plant. –A. Vascular cambium –B. Cork cambium

travismulthaupt.com A. Vascular Cambium Adds layers of vascular tissue to the woody plant. Secondary xylem (wood) Secondary phloem Adds layers of vascular tissue to the woody plant. Secondary xylem (wood) Secondary phloem

travismulthaupt.com A. Vascular Cambium From year to year the vascular cambium can be seen as rings on a transverse section of a woody plant.

travismulthaupt.com B. Cork Cambium Replaces the epidermis with periderm which is thicker and tougher. Produces cork and provides a protective tissue layer for the plant. Replaces the epidermis with periderm which is thicker and tougher. Produces cork and provides a protective tissue layer for the plant.

travismulthaupt.com Primary and Secondary Growth Viewing a transverse section, the vascular cambium appears as a ring.

travismulthaupt.com Primary Growth Recall, primary growth produces the main plant body.

travismulthaupt.com Secondary Growth Secondary growth continues over the years and layers of wood accumulate (secondary xylem- tracheids, vessel elements and fibers.)

travismulthaupt.com Secondary Growth This secondary growth increases the diameter of the tree each year. Counting these layers tells you the age of the tree. This secondary growth increases the diameter of the tree each year. Counting these layers tells you the age of the tree.

travismulthaupt.com Secondary Growth Secondary growth is due to the division of the vascular cambium. The vascular cambium produces 2° xylem to the inside, and 2° phloem to the outside. Secondary growth is due to the division of the vascular cambium. The vascular cambium produces 2° xylem to the inside, and 2° phloem to the outside.

travismulthaupt.com Secondary Growth Secondary growth is also due to the division of the cork cambium. The cork cambium produces some cells that grow inward, and a lot of cells that grow outward. Secondary growth is also due to the division of the cork cambium. The cork cambium produces some cells that grow inward, and a lot of cells that grow outward.