1 travismulthaupt.com Chapter 35 Plant Structure and Growth

travismulthaupt.com Monocots Vs. Dicots (Eudicots) Formerly, angiosperms were divided into two groups:Formerly, angiosperms were divided into two groups: –Monocots-one cotyledon. –Dicots-two cotyledons. There were also many other features that distinguished the two groups.There were also many other features that distinguished the two groups. Formerly, angiosperms were divided into two groups:Formerly, angiosperms were divided into two groups: –Monocots-one cotyledon. –Dicots-two cotyledons. There were also many other features that distinguished the two groups.There were also many other features that distinguished the two groups.

travismulthaupt.com Current Research on the Topic Current research suggests that monocots form their own clade.Current research suggests that monocots form their own clade. The remaining angiosperms are divided among many lineagesThe remaining angiosperms are divided among many lineages –Most of which are known as eudicots. Current research suggests that monocots form their own clade.Current research suggests that monocots form their own clade. The remaining angiosperms are divided among many lineagesThe remaining angiosperms are divided among many lineages –Most of which are known as eudicots.

travismulthaupt.com Monocots Vs. Eudicots One cotyledonOne cotyledon Parallel veinsParallel veins Scattered vascular tissueScattered vascular tissue Fibrous rootsFibrous roots Floral organs in multiples of threeFloral organs in multiples of three One cotyledonOne cotyledon Parallel veinsParallel veins Scattered vascular tissueScattered vascular tissue Fibrous rootsFibrous roots Floral organs in multiples of threeFloral organs in multiples of three Two cotyledons Two cotyledons Webbed veins Webbed veins Vascular tissue in a ring Vascular tissue in a ring Taproot present Taproot present Floral organs in multiples of 4 or 5 Floral organs in multiples of 4 or 5 Two cotyledons Two cotyledons Webbed veins Webbed veins Vascular tissue in a ring Vascular tissue in a ring Taproot present Taproot present Floral organs in multiples of 4 or 5 Floral organs in multiples of 4 or 5

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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 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 long micropipes and are aligned end to end. Usually wider, shorter and thinner than tracheids. They are 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 systems 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 systems 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 Contain perpetually embryonic cells. There are two main types: –1. Apical –2. Lateral Contain perpetually embryonic cells. There are two main types: –1. Apical –2. Lateral

travismulthaupt.com 1. Apical Meristem These are located at the tips of roots and in the buds of shoots. These enable primary growth (length). These are located at the tips of roots and in the buds of shoots. These enable primary growth (length).

travismulthaupt.com 2. Lateral Meristem After the primary growth from the apical meristem has stopped, the remaining growth is mostly all secondary (girth). It increases 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). It increases 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 Viewing a transverse section of a woody plant: –The vascular cambium appears as a ring with interspersed regions of fusiform initials and ray initials. Viewing a transverse section of a woody plant: –The vascular cambium appears as a ring with interspersed regions of fusiform initials and ray initials.

travismulthaupt.com Fusiform Initials Produce elongated cells--tracheids, vessel elements, fibers of xylem, sieve tube members, companion cells, parenchyma and fibers of phloem. These run parallel to the root axis. Produce elongated cells--tracheids, vessel elements, fibers of xylem, sieve tube members, companion cells, parenchyma and fibers of phloem. These run parallel to the root axis.

travismulthaupt.com Ray Initials These are shorter and run perpendicular to the stem/root axis. These consist of parenchyma cells and provide a way for H 2 O and nutrients to flow between secondary xylem and secondary phloem. These are shorter and run perpendicular to the stem/root axis. These consist of parenchyma cells and provide a way for H 2 O and nutrients to flow between secondary xylem and secondary phloem.

travismulthaupt.com B. Cork Cambium Replaces the epidermis with periderm which is thicker and tougher.

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

travismulthaupt.com Primary and Secondary Growth There are interspersed regions of fusiform initials and ray initials. When these initials divide they increase the circumference of the cambium. There are interspersed regions of fusiform initials and ray initials. When these initials divide they increase the circumference of the cambium.

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 They have thick, lignified cell walls that give wood its hardness.