Chapter 35 - Plant Structure Flashcards
From what point do the roots and shoots of vascular plants grow?
They grow from the tips (apices)
What are the functions of roots?
- anchor the plants
- penetrates soil to absorb water and minerals
- can exert huge forces as they grow
- adapted to living on land; roots are how they get water on land
What are the functions of shoots?
- stems are the scaffolding for positioning leaves
- leaves are the main site of photosynthesis; in the leaf tissues
- flowers, fruits, and seeds formed on shoot
- opposite direction of roots
What is the repeating unit of shoots?
internode, node, leaf, and axillary bud
Where is the Axillary bud located?
between the branch and the internode
Where is the Internode located?
in between branches
Where is the node located?
where the stems branch out
Name the 3 types of tissues composing roots and shoots:
- dermal tissue
- ground tissue
- vascular tissue
Dermal tissue
- epidermis
Ground tissue
- plants
- used for storage, photosynthesis, secretion, forming fibers for support and protection
Vascular tissue
conducts fluids and dissolved substances
What is a meristem?
- specialized cells in the root and shoot apices and other parts of the plant
- acts like stem cells in animals
- a meristem cell divides to give rise to a differentiating daughter cell and a cell remains as a meristem cell
Where are apical meristems located?
located at tips of roots and shoots
Apical meristems
- involved with extension of roots and shoots
- new cells are added at tips
Primary tissues
tissues derived from apical meristems; the new ones
Primary Plant body
Extension of root and stem
Root cap
protects delicate cells of root apical meristem; sloughed off and replaced as root grows through soil - produces slimy substance to help push through soil
Leaf Primordia
shelters growing shoot apical meristems from desiccation
Apical meristems give rise to what 3 tissue systems:
Protoderm, procambium, ground meristem
Protoderm
forms epidermis
Procambium
produces primary xylem (water transport) and primary phloem (nutrient transport)
Ground meristem
differentiates into more ground tissue
What is intercalary meristems and where would you find them?
found in horsetails and corns; more specifically found in the internodes and add to the length of the internodes
What type of growth is involved with lateral meristems?
increases in root and shoot diameter known as secondary growth
Lateral meristems
form from ground tissue that is derived from apical meristems (monocots are the major exception)
Secondary growth
can increase girth in non-woody plants, but the effects are most striking in woody plants
What 2 lateral meristems are in woody plants?
cork cambium and vascular cambium
Cork cambium
what makes the bark; contributes to outer bark of tree
Vascular cambium
located just beneath bark; produces vascular tissue
What is secondary xylem?
main component of wood
What is secondary phloem?
close to outer surface of woody stem
What happens if secondary phloem is damaged or removed?
remove bark of tree - damage to phloem - may eventually kill tree
Secondary tissues
most of the trunk of a tree, branches, and older roots of trees and shrubs
Secondary Plant Body
all the secondary tissues
Dermal Tissue Examples
One cell thick in most plants
- forms outer protective covering of plant
- cuticle composed of fatty cutin to protect young, exposed parts of plants
- desert succulents may also have several layers of wax to curb water loss and help block UV radiation
- sometimes dermal tissue forms tree bark
Guard cells
- example of dermal tissue forming tree bark
- paired, sausage-shaped cells that flank a stoma (opening) on the leaves, stems, and fruits of plants
- contains chloroplasts, unlike other epidermal cells
- allow passage of oxygen and carbon dioxide and diffusion of water in vapor form
- many times, stomata are more numerous on underside of leaves (minimizes water loss), but water lilies are the exception
Trichomes
- hairlike outgrowths of epidermis
- found frequently on stems, leaves, and reproductive organs
- function in keeping leaf surfaces cool, reducing water evaporation, protecting from UV radiation and highlight intensity, serving as a buffer against temperature fluctuations
- glandular trichomes may secrete sticky or toxic substances
Root Hairs
- extensions of epidermal cells, but not a separate cell
- increase surface area to maximize water and mineral uptake
What is ground tissue?
- all vascular and epidermal tissue
- makes up the bulk of the plant
Parenchyma
- type of ground tissue
- most common type of plant cell
- function is storage of food and water, photosynthesis, and secretion
- cells may live for many years (over 100 years in some cacti)
- ## most of the cells in fruits such as apple are parenchyma
Chlorenchyma
- a photosynthetic parenchyma
- found in leaves and out parts of herbaceous systems
Collenchym
- example is celery strings
- tough, but flexible cells support plant organs allowing them to bend without breaking
- found in stems and leaf petioles
- have living protoplasm just like parenchyma and can live for many years
Sclerenchyma
- cells have tough, thick walls
- mature cells don’t have living protoplasm
- cells contain lignin that make cell walls more rigid
Two forms of Sclerenchyma
1) fibers forming long, slender strands; linen woven from sclerenchyma fibers of flax plant
2) sclereids vary in shape and are often branched; gritty texture of a pear is from groups of sclereids in soft flesh of fruit
Vascular Tissue
xylem, phloem
Xylem
principal water-conducting tissue made up of vessels and tracheids
How does water move through the xylem?
water moves in an unbroken stream through the xylem from roots to shoots to the leaves
Transpiration
diffusion of water vapor from a plant
Phloem
principal food-conducting tissue in vascular plants; is composed of sieve cells and sieve tube members
Roots adapted for..
growing underground and absorbing water and solutes
What are the four regions of roots?
- root cap
- zone of cell division
- zone of elongation
- zone of maturation
Root cap
protects the root and functions in perception of gravity; can tell up from down
Zone of cell division
contains apical meristem
Zone of elongation
extends root through soil
Zone of maturation
cells become differentiated
Modified roots
1) taproots
2) fibrous root
3) adventitious roots
Adventitious roots
roots that arise from the stem or some place other than the root of the plant
- can function in support, stability, acquisition of oxygen, storage of water and food, or parasitism of a host plant
Taproots
consist of single large root w/ smaller branching roots
Fibrous roots
systems are made up of many small roots of similar size
What are the function of stems?
they carry leaves and flowers and support the plant’s weight
Where are the leaves attached?
they are attached to the stems at the node
What are the types of leaf arrangements?
alternate, opposite, and whorled
What is the most common leaf arrangement?
most often the leaves are arranged spirally around the stem 137.5 degrees apart - this angle relates to the golden mean.
Golden mean
a mathematical ratio found in nature
What is the significance of the 137.5 degrees apart?
May maximize the exposure of leaves to the sun
Arrangement of vascular bundles in Monocots
vascular bundles are scattered throughout the ground tissue of the stem
Arrangement of vascular bundles in Eudicots
vascular bundles are arranged in a ring around the outside of the stem - the interior of the stem is pithy
Secondary growth in Monocots
does not have secondary growth
Secondary growth in Eudicots
exhibits secondary growth as the vascular cambium produces secondary growth; this shows up as annual growth rings
What do modified stems do?
they carry out vegetative propagation and store nutrients
What are some examples of modified stems?
Bulbs, corms, rhizomes, runners and stolons, tubers, and tendrils
Bulbs
swollen underground stem consisting of fleshy leaves attached to small knob-like stems with adventitious roots at the base
EX. onions, lilies, and tulips
Corms
sort of look like bulbs, but when cut, there are no fleshy leaves - they are stems with some brown, papery nonfunctional leaves on the outside and some adventitious roots
EX. Crocus, gladiolus
Rhizomes
Horizontal stems that grow underground - adventitious roots grow from the lower surface
EX. ferns, bearded iris, perennial grasses
Runners and stolons
Horizontal stems with long internodes that grow just above the surface of the ground
EX. Strawberries
Tubers
tips of rhizomes swell and become tubers - the “eye” of the potato is evidence where a leaf is formed when the tuber started to grow - the eye is an axillary bud and will grow into a new potato plant
Tendrils
twining stems that aid in climbing
EX. English Ivy, grapes
What are some modified leaves
tendrils of peas and pumpkins
What is the primary function of leaves?
is the primary site for photosynthesis
Leaves are determinate structures, what does this mean?
they stop growing at maturity
Leaf anatomy
most leaves have dorso-ventral symmetry resulting in more surface area for photosynthesis
Blade
main part of leaf
Petiole
stalk that attaches leaf to main stem of plant
Veins
vascular bundles made of xylem and phloem
Veins in Monocots
have parallel leaf veins
Veins in Eudicots
have netted or reticulate veins
Simple leaves
blades are not divided
Compound leaves
blades divided into leaflets
What are the three types of tissues in leaves?
a) epidermis with guard cells
b) vascular tissue
c) mesophyll (site of photosynthesis)
Modified leaves include:
floral leaves, spines, reproductive leaves, insectivorous leaves
Floral leaves
(bracts) surround the true flowers (which can be quite small) and act as showy petals
EX. poinsettia, dogwood
Spines
(not the same thorns or prickles) are modified leaves on cacti and some other plants - they can reduce water loss and can deter predators
Reproductive leaves
little plant-lets growing along margins that when separated can grow into a full-sized plant (kalanchoe)
insectivorous leaves
traps insects to provide supplemental nutrition - these plants often live in acid swamps that do not provide all the nutrients the plant requires
EX. sundews, Venus flytrap, pitcher plants
