Chapter 27.127.5Plant Body
27.1aCells of all plant tissues share some general features
root and shoot systems consist of various organs
Plant organs include leaves, stems, and roots.
A tissue is a group of cells and intercellular substance that function together in one more
Plant cells differ from animal that plants; have cell wall and large central vacuole.
Central vacuole plays a role in cell elongation and maintenance of rigid tissues.
In plant tissues, the cells have a primary cell wall surrounding the plasma membrane and cell
contents(cytoplasm and organelles)
Cell walls are support for the plant
A primary cell wall is made of cellulose, a polymer of glucose, embedded in a matrix of other
Cellulose fibrils gives the cell wall strength and flexibility.
Cytoplasmic connections between cells called plasmodesmata, allows solutes such as amino acids
and sugars to move from one cell to the next.
The space between the primary cell wall of adjacent cell is filled with a polysaccharide layer called
the middle lamella.
As young plants grows, cells deposit additional cellulose and other materials inside the primary
wall, forming a strong secondary cell wall.
Secondary walls, often contain lignin a complex water insoluble polymer which makes cell walls
very strong, rigid, and impermeable to water.
The ability of almost any cell to give rise to all other parts of a plant is known as totipotency.
The advantages of totipotency allows plant to heal wounds and is also one means of asexual
reproduction. Ex. Raspberry plants, if a branch or stem comes into contact with soil for long
enough, new plant would form.
27.1b Shoot and root systems perform different but integrated functions Shoot system consist of the reproductive organs such as flowers.
A stem with its attached leaves and buds is a vegetative(nonreproductive) shoot; a bud
eventually gives ruse to an extension of the shoot.
A reproductive shoot produces flowers, which develops into fruits with seeds.
The root system usually grows below ground, it anchors the plant and supports its upright parts.
The root hairs are surface cells specialized for absorbing water and nutrients from soil.
27.1c Meristems produce New tissues throughout a plant’s life.
Determinate growth is when animals grow to a certain size and their growth slows dramatically or
Indeterminate growth is when plants can grow throughout their lives.
Leaves, flowers, and fruits exhibit determinate growth but plant hormones called meristems
produce new tissues more or less while the plant is alive.
Why do plants have indeterminate growth?
Plants are called plasticity their possible response to change.
Plasticity has a major benefit for an organisms that cannot move about.
Ex. When plants leave change direction according to the light.
Indeterminate growth allows a root system to extend and grow out of regions in which nutrients
have been depleted and forage for patches with more nutrients
Plants grow number of cells by mitotic cell division in the meristems and increase in size of cell.
When the cells divide, the daughter cells increase in size & length unlike animal cells.
27.1d Meristems are responsible for growth in both height and girth
All plants have apical meristems, clusters of selfperpetuating tissues at the tips of buds, stems and
Tissues that develop from apical meristems are called primary tissues and make up the primary
plant body. Some plants have only primary growth and some plants have both secondary growth and primary.
Secondary growth originates at cylinders of tissues called lateral meristems and increases the
diameter of older roots and stems.
Primary growth increasing the length of shoots and roots and secondary adding girth to these
27.1e Monocots and Eudicots are the two general structural forms of flowering plants
Monocot seeds have one cotyledon
Eudicot seeds have two cotyledon
Eudicots have for or five floral parts
Monocots have three floral parts
Eudicot leaf veins usually in a netlike array
Monocots leaf veins usually running parallel with one another.
Eudicot usually a main taproot(strait down/long) with smaller lateral roots
Monocots branching fibrous root system( almost everywhere)
27.1f Flowering plants can be grouped according to type of growth and lifespan.
We can distinguish between flowering plants on whether they are herbaceous or woody plants and
whether they are monocots or eudicot.
Annuals are herbaceous plants in which the life cycle is completed in one growing season.
Typically only have apical meristems
Biennials into two growing seasons. First season, root stems and leave form in second season
plant flowers seeds and dies.
Perennials, vegetative growth and reproduction continue year after years.
27.2 The three plant tissue systems Plants have three types of ground tissue systems:
Parenchyma cells have air space between them, which facilitate the movement of oxygen to
submerged parts of plant and help the leaves float upward toward the light of aquatic plants
Parenchyma make up the roots, stems, leaves, flowers and fruits
Function of tissue: photosynthesis, respiration, storage secretion, solute transportation
Function of tissue: flexible strength for growing plant parts
Ex. Strings in celery are example of the flexible ground tissue
The primary cell walls of collenchyma cells are built of layers of cellulose and pectin and are
Function of tissue: Rigid support, deterring herbivores
Some regions of the cell wall lack secondary wall material, forming a pit where the cell wall is more
porous than elsewhere.
Water can flow through these pits.
Two types of sclerenchyma cells
Sclereids and fibbers
27.2dVascular Tissues are specialized for conducting fluids
Vascular tissue systems consist of complex tissues composed of specialized conducting cells,
parenchyma cells, and fibres
Xylem and phloem are the two kinds of vascular tissues in flowering plants.
Xylem: Transporting water and minerals Soil upward from a plant roots to the shoot.
Xylem contains two types of conducting cells: tracheids and vessel members.
Tracheids are elongated with tapered, overlapped ends.
Vessel members are shorter wider cells joined end to end in tubelike columns celled vessels.
Like tracheids, vessel membranes have pits
As vessel membranes mature, enzymes break down portions of their end walls producing
perforations(a hole made or bigger in diameter, so can easily move).
Vessel membranes allow water to move more rapidly but do not prevent air bubbles, and if air
bubbles form there would be a blockage of the whole vessel
Tracheids, the pits are impermeable to air bubbles, and a bubble the forms in one tracheids stays
there but continues to move water.
Phloem: Transporting sugars and other solutes
The main conducting cells of phloem are sieve tube members, which are connected end to end
forming a sieve tube.
Sieve plates are studded with pores.
Phloem tissue often contains fibers and sclereids in addition to conducting cells; these
sclerenchyma cells strengthen stems.
Companion cells are connected to mature sieve tube members by plasmodesmata.
Companion cells retain their nuclei when mature
Companion cells assist sieve tube members with uptake of sugars and unloading of sugars.
24.2c The Dermal Tissue system protects plant surface
A complex tissue called epidermis covers the primary plant body in a layers.
The external surface of the tissue is coated with a waxes called cuticle, which resists water loss
and protect attacks by microbes.
Guard cells contain chloroplasts and so can carry out photosynthesis.
The pore between a pair of guard cells is called a stoma( gas exchange) Trichomes gives the stems or leaves of some plants a hairy appearance.
Root hairs extensions of the outer wall of root epidermal cells, are also trichmoes.
Root hairs absorb much of a plant’s water and minerals from the soil.
27.3a Stems are adapted to provide support, routes for vascular tissues, storage, and new growth.
Stems four main functions:
Stems provide mechanical support, such as growth, photosynthesis, and reproduction. These parts
include meristematic tissues, leaves, and flowers.
Stems house the vascular tissues(xylem &phloem) which transport products throughout the plant
Stems store water and food
Give rise to new cells of the shoot
A plant stem develops in a pattern that divides the stem into modules each consisting of a node
and an internode.
Node is where one or more leaves are attached the region between the two nodes is internode.
Primary growth occurs in budsa terminal bud at the apex of the main shoot and axillary buds,
which produce branches where leaves and stems meet.
Meristematic tissue in buds give rise to leaves, flowers, or both.
Internode cells nearest the apex are most active, so the most visible new growth occurs at the ends
The stems of grass(ex.) elongate as the internodes are pushed up by the growth of such meristems
This adaption allows grasses to grow back readily after grazing because the meristem is not
Terminal buds release a hormone(auxin) that inhibits the growth of nearby lateral buds, a
phenomenon called apical dominance.
Gardeners who want bushier plant can stimulate axillary bud growth by cutting off the terminal bud.
Primary growth begins when a cell of this meristem divides, one of its daughter cell remains part of
the meristem, where as the other begins to follow a path.
The differentiating cells give rise to three primary meristems: protoderm, procambium, and ground
meristem These primary meristems are unspecialized tissue that eventually turn into specialized cells.
In eudicots, the primary meristems are responsible for elongation of the plant body.
The protoderm, a meristem that gives rise to the stem’s epidermis, the outermost layer of the shoot