Week 5 Part 1 (Plant Form and Function)

Cortex

in plants, the tissue between the epidermis and the vascular cylinder in the roots and stems of plants

Leaf mesophyll

internal photosynthetic tissues of the leaf -Include upper, closely packed, elongate palisade parenchyma cells adapted to absorb sunlight efficiently -Spongy parenchyma, located closer to the leaf surface, contains rounder cells separated by abundant air spaces that foster CO2 absorption and O2 release by leaves

Buds

miniature shoots each having a dormant shoot apical meristem

Companion cells

the active cells found next to sieve tube elements that supply the phloem vessels with all of their metabolic needs

Leaf veins

Composed of vascular tissue and commonly occur at the junction of palisade and spongy parenchyma, or within spongy parenchyma -the xylem tissues conduct water and minerals throughout leaf tissues, fostering photosynthesis -phloem tissues carry the sugar products of photsynthesis from leaf cells to stem vascular tissues (sugar produced by leaves can be exported to other parts of the plant)

Indeterminate growth

apical meristems continuously produce new stem tissues and leaves as long as conditions remain favorable

Compare and contrast basic types of plant tissue systems with regards to their structure and function; dermal tissue system, ground tissue system, and vascular tissue system

-Dermal tissue covers and protects the plant, and controls gas exchange and water absorption (in roots). Dermal tissue of the stems and leaves is covered by a waxy cuticle that prevents evaporative water loss. Stomata are specialized pores that allow gas exchange through holes in the cuticle. Unlike the stem and leaves, the root epidermis is not covered by a waxy cuticle which would prevent absorption of water. Root hairs, which are extensions of root epidermal cells, increase the surface area of the root, greatly contributing to the absorption of water and minerals. Trichomes, or small hairlike or spikey outgrowths of epidermal tissue, may be present on the stem and leaves, and aid in defense against herbivores. -Ground tissue carries out different functions based on the cell type and location in the plant, and includes parenchyma (photosynthesis in the leaves, and storage in the roots), collenchyma (shoot support in areas of active growth), and schlerenchyma (shoot support in areas where growth has ceased)is the site of photosynthesis, provides a supporting matrix for the vascular tissue, provides structural support for the stem, and helps to store water and sugars. -Vascular tissue transports water, minerals, and sugars to different parts of the plant. Vascular tissue is made of two specialized conducting tissues: xylem and phloem. Xylem tissue transports water and nutrients from the roots to different parts of the plant, and also plays a role in structural support in the stem. Phloem tissue transports organic compounds from the site of photosynthesis to other parts of the plant. The xylem and phloem always lie adjacent to each other in a vascular bundle

Compare and contrast morphological differences between tracheids and vessel elements

1. Vessels have perforations at the end plates while tracheids do not have end plates 2. tracheids consist of individual cells while vessel elements consist of many cells 3. tracheids are found in all vascular plants while vessel elements while vessel elements are confined to angiosperms 4. tracheids are thin, vessel elements are wide

Sclerenchyma tissue

A rigid stem tissue composed of tough-walled cells that provide strength and protection to the plant stem

Vessel elements

A short, wide, water conducting cell found in the xylem of most angiosperms and a few nonflowering vascular plants. Dead at maturity, vessel elements are aligned end to form micropipes called vessels.

Determinate growth

A type of growth characteristic of most animals and some plant organs, in which growth stops after a certain size is reached.

Epidermis

Layer of outermost tissue the develops at the stem surface

Tracheids

A water-conducting and supportive element of xylem composed of long, thin cells with tapered ends and walls hardened with lignin.

Primary meristems

As the SAM grows, it leaves behind primary meristems that increase plant length and produce new organs

Axillary buds

Bear a shoot apical meristem at their tips and can produce leafy branches known as lateral shoots, or flowers

Compare and contrast the functions and structures of phloem versus xylem.

-Xylem: complex tissue containing several cell types: unspecialized parenchyma cells, stiff fibers that provide structural support, and two types of cells that facilitate water transport. Arranged in pipelike arrays, tracheids and vessel elements conduct water, along with dissolved minerals and certain organic compounds. Mature tracheids and vessel elements are no longer living cells, and the absence of cytoplasm facilitates water flow; rigid walls provide support as well. -Phloem: composed of living cells; transports organic compounds such as sugars and certain minerals in a water solution. Has sieve-tube elements, thin walled cells that are arranged end to end to form pipelines. Pores in the end walls of the sieve-tube elements allow solutions to move from one cell to another. Companion cells aid sieve-tube element metabolism, supportive fibers, and parenchyma cells

Compare and contrast three basic types of differentiated cells of the ground tissue system with regards to their structure and function.

Ground tissue is all the other tissue in a plant that isn't dermal tissue or vascular tissue. Ground tissue cells include parenchyma, (photosynthesis in the leaves, and storage in the roots), collenchyma (shoot support in areas of active growth), and schlerenchyma (shoot support in areas where growth has ceased). -Parenchyma are the most abundant and versatile cell type in plants. They have primary cell walls which are thin and flexible, and most lack a secondary cell wall. Parenchyma cells are totipotent, meaning they can divide and differentiate into all cell types of the plant, and are the cells responsible for rooting a cut stem. Most of the tissue in leaves is comprised of parenchyma cells, which are the sites of photosynthesis, and parenchyma cells in the leaves contain large quantities of chloroplasts for phytosynthesis. In roots, parenchyma are sites of sugar or starch storage, and are called pith (in the root center) or cortex (in the root periphery). Parenchyma can also be associated with phloem cells in vascular tissue as parenchyma rays. -Collenchyma, like parenchyma, lack secondary cell walls but have thicker primary cells walls than parenchyma. They are long and thin cells that retain the ability to stretch and elongate; this feature helps them provide structural support in growing regions of the shoot system. They are highly abundant in elongating stems. The "stringy" bits of celery are primarily collenchyma cells. -Schlerenchyma cells have secondary cell walls composed of lignin, a tough substance that is the primary component of wood. Schelrenchyma cells therefore cannot stretch, and they provide important structural support in mature stems after growth has ceased. Interestingly, schlerenchyma cells are dead at functional maturity. Schlerenchyma give pears their gritty texture, and are also part of apple cores. We use sclerenchyma fibers to make linen and rope.

Primary growth

Growth produced by primary meristems, which lengthen stems and roots, and ultimately produce primary tissues

Primary vascular tissues

New water and food conducting tissues that develop inside young shoots and roots of all vascular plants -xylem and phloem

Fibers

Phloem fibers are tough-walled sclerenchyma cells that are long and valued for their high strength

Leaves

Plant organ consisting of flattened structures that emerge from stems and are often specialized in ways that enable photosynthesis

Stems

Plant organ that produces leaves and branches and bears the reproductive structres of mature plants

Roots

Plant organ that provides anchorage in the soil and fosters efficient uptake of water and minerals. The aggregate of a plant's roots make up the root system

Stomata

Small openings on the underside of a leaf (more common in the lower epidermis) through which oxygen and carbon dioxide can move -When open, they allow CO2 to enter and water vapor and O2 to escape leaf tissues -Closure helps to prevent excess water loss from plant surfaces

Vegetative growth

The growth of non-reproductive parts of the body

Secondary growth

The primary meristems of woody plants also give rise to secondary/lateral meristems, which increase the girth of woody plant stems and roots by producing specialized secondary tissues

Petiole

The stalk of a leaf, which joins the blade to a node of the stem-an axiliary bud occurs at this junction

Shoot

The stem and leaves of a plant

Guard cells

The two cells that flank the stomatal pore and regulate the opening and closing of the pore.

Trichomes

Tiny, spikelike projections on some leaves for protection

Collenchyma tissue

Tissue of stems composed of flexible cells

Parenchyma tissue

Tissue that makes up cortex, composed of parenchyma cells

Primary tissues

Tissues that make up the primary plant body, produced by primary meristems and made of specialized cells that occur in organs of diverse types

Stem cells

Undiffferentiated cells in plant meristems that divide to produce two cells: one that remains young and unspecialized plus another cell -the second may differentiate into various types of specialized cells, but it often retains the ability to divide

Organ systems

Vegetative growth and reproductive development in plants involve organ systems, structures that are composed of more than one organ. Branches, buds, flowers, seeds, and fruits are organ systems

Cuticle

Waxy surface coating produced by the epidermis, which reduces water loss from the plant surface and protects plants from damage by UV light, animals, and disease microorganisms

Sclereids

a reduced form of sclerenchyma cells with highly thickened, lignified cellular walls that form small bundles of durable layers of tissue in most plants

Meristems

a region of undifferentiated cells that produce new tissues by cell division -A dormant meristem occurs at the shoot and root tips of seed embryos, and these meristems become active in seedlings -In mature plants, active meristems occur at each stem and root tip (known as shoot and root apical meristems)

Sieve-tube element

phloem cell that is joined end-to-end to similar cells to form a continuous sieve tube

Vascular bundles

primary plant vascular tissues that occur in elongate clusters -appear round or oval when cross-cut

Internode

region of stem between adjacent nodes

Node

the stem region from which one or more leaves emerge

Phloem

the vascular tissue in plants that conducts sugars and other metabolic products downward from the leaves.

Blade

thin, flattened section of a plant leaf that collects sunlight

Parenchyma cells

thin-walled cells that make up parenchyma tissue of the cortex -Often store starch in plastids and therefore serve as an organic food reserve -Stem parenchyma also has the ability to undergo cell division, which aids wound healing when stems are damagec

Xylem

vascular tissue that carries water upward from the roots to every part of a plant