Transcript Basic Botany and Basic Biology

Basic Botany
Tulsa County Master Gardeners
2014
Robyn Stroup
Botany – the scientific study of plant life
Plants are essential to life on earth.
They are the primary food source for humans
and other animals.
Plants also:
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Provide fuel
Replenish the earth’s oxygen supply
Prevent soil erosion
Slow down wind movement
Cool the atmosphere
Provide wildlife habitat
Supply medicinal compounds
Beautify our surroundings
Classification
Based on shared characteristics.
Domain
Kingdom
Division or Phylum
Class
Order
Family
Genus
Species
18th century botantist
Carolus Linnaeus
Kingdom Plantae
Division Tracheophyta - vascular plants
Class Gymnosperms - naked seed plants
Class Angiosperms - enclosed seed plants
Subclass Monocots – one seed leaf
Subclass Dicots – two seed leaves
species name = genus name and specific epithet
Gaillardia aristata - common blanket flower
Our focus will be on
• Vascular plants—those that contain water-,
nutrient-, and food-conducting tissues called
xylem and phloem.
• Ferns and seed-producing plants fall into this
category.
Plant life cycles
• Annual – completes life cycle in one year.
Summer or winter annuals.
• Biennial – requires all or part of 2 years
During the first season, it produces vegetative
structures (leaves) and food storage organs.
Plant overwinters and then produces
flowers, fruit, and seeds during its second
season.
• Perennial - plants live more than 2 years
Herbaceous perennials- soft, nonwoody
stems that generally die back to the
ground each winter.
Woody perennials – woody stems that
withstand cold temperatures.
Monocots and Dicots
Need to distinguish between monocotyledonous
(monocots) and dicotyledonous (dicots) plants.
• Monocots (grasses) produce only one seed leaf
(one cotyledon).
• Dicots (broadleaf plants) have two seed leaves
(two cotyledons).
• Other differences will be discussed.
Plant Cells
• Cells – have a cell wall that provides rigidity as
long as internal water pressure exists.
– Each cell contains the DNA of the cell.
– Specialized cells carry out various functions
necessary to support entire plant.
• Meristems – cells with rapid growing
potential. Controlled by complex plant
hormones.
Functions of Roots
• Absorb nutrients and water.
• Anchor the plant in the soil.
• Support the stem.
• Store food.
Root Structure
• Meristematic zone is at the tip and manufactures
new cells - cell division and growth.
• Zone of elongation – behind the meristematic
zone. Cells increase in size. Push the root
through the soil.
• Zone of maturation - directly beneath the stem.
Cells become specific tissues such as epidermis,
cortex, or vascular tissue.
Monocot
Dicot
Root Hairs
• Root hairs are delicate, elongated epidermal cells that
occur in a small zone just behind the root’s growing tip.
• Generally appear as fine down to the naked eye.
• Increases the root’s surface area and absorptive capacity.
• Root hairs usually live 1 or 2 days.
• When a plant is transplanted, they are easily torn off or
may dry out.
Factors in root growth
• Roots in water-saturated soil do not grow well and may die due to
lack of oxygen.
• Roots penetrate much deeper in loose, well-drained soil.
• A dense, compacted soil layer can restrict or terminate root growth.
• Container plants have a restricted area for root growth, also
susceptible to cold damage due to limited amount of soil around roots.
• Roots also grow laterally and often extend well beyond a plant’s
dripline. Keep in mind when disturbing the soil around existing trees
and shrubs
Stems
• Stems support buds and leaves.
• Serve as conduits for carrying water, minerals, and food
(photosynthates).
• Vascular system inside the stem forms a continuous
pathway from the root, through the stem, and finally to
the leaves.
• It is through this system that water and food products
move.
Vascular System
• This system consists of xylem, phloem, and vascular
cambium.
• Think of as a plant’s circulatory system.
• Xylem tubes conduct water and dissolved minerals.
• Phloem tubes carry sugars (product of photosynthesis).
• Cambium is a layer of meristematic tissue that separates
the xylem and phloem.
Cambium
• Cambium continuously produces new xylem and
phloem cells thus increasing a stem’s girth.
• Important to gardeners.
– The tissues on a grafted scion and rootstock need to
line up.
– Careless weed trimming can strip the bark off a tree,
thus injuring the cambium and causing the tree to die.
Monocots & Dicots
• The vascular systems of monocots and dicots differ. These
structures are arranged differently in each.
• Monocots - xylem and phloem are paired in bundles, which
are dispersed throughout the stem.
• Dicots – the vascular system is said to be continuous because
it forms rings inside the stem.
Phloem forms the outer ring and eventually becomes
part of the bark in mature woody stems.
Xylem forms the inner ring. In woody plants, it is called
the sapwood and heartwood.
Stems, Nodes and Internode Space
• A node is an area on a stem where buds are located.
• Small buds develop into leaves, stems, or flowers.
• When pruning, it is important to locate a plant’s nodes.
Generally, you want to make a pruning cut just
above, but not too close to, a node.
This encourages the buds at that node to begin
development and ultimately form new stems or leaves.
Internodes
• The area between two nodes is called an internode.
• Its length depends on many factors, including genetics.
• Several other factors also can influence internode length:
Reduced soil fertility decreases internode length.
High-nitrogen fertilizer can greatly increase it.
Lack of light increases internode length and causes
spindly stems. Known as stretch, or etiolation. Often
occurs in seedlings started indoors and in houseplants.
Internodes contd.
• Internode length also varies with the season.
Early-season growth has long internodes.
Late-season growth generally has much
shorter internodes.
• If a stem’s energy is divided among three or four
side stems, or is diverted into fruit growth and
development, internode length is shortened.
• Plant growth regulator substances and herbicides
also can influence internode length
All stems have nodes, roots do not.
• Specialized above ground stems: stolons.
Ex. strawberry runners.
• Specialized below-ground stems: tubers
(potatoes), rhizomes (Bermuda grass), bulbs
(tulips). All store food for the plant.
Trees and Shrubs
• Trees have one main trunk. Usually are more than 12
feet tall.
• Shrubs have several main stems. Usually are less than 12
feet tall.
• Woody stems contain relatively large amounts of
hardened xylem tissue in the central core (heartwood or
sapwood).
• Herbaceous stems contain only a little xylem tissue and
usually live for only one growing season.
• Perennial plants - new herbaceous stems develop from
the crown (root–stem interface) each year.
Buds
• A bud is an undeveloped shoot from which leaves
or flower parts grow. Rest temperature may be
critical.
• Buds are named for their location on the stem.
– Terminal buds are located at the apex (tip) of a stem.
– Lateral (axillary) buds are located on the sides of a
stem and usually arise where a leaf meets a stem (an
axil).
Leaves
• Principal function of leaves is to absorb
sunlight to manufacture plant sugars through
a process called photosynthesis.
• Leaf surfaces are flattened to present a large
area for efficient light absorption.
• A leaf is held away from its stem by a petiole
attached at a node.
Leaf Structure
• A leaf blade is composed of several layers.
• Top and bottom layers are thick, tough cells called
the epidermis. Protects the other layers of leaf
tissue.
• Cuticle is part of the epidermis. Waxy cutin
protects the leaf from dehydration and disease.
Amount of cutin on a leaf increases with light
intensity. Also repels water.
Leaf Structure contd.
• Mesophyll - located between the upper and
lower epidermis.
• It is divided into a dense upper layer (palisade
mesophyll) and a lower layer that contains lots of
air space (spongy mesophyll ).
• Located within the mesophyll cells are
chloroplasts , where photosynthesis takes place
Stomata
• Stomata – openings controlled by guard cells, special
epidermal cells. Water, oxygen, and carbon dioxide passed
into and out of the leaf.
Guard cells - open and close in response to
environmental stimuli.
Close in high temperature, low humidity.
Open in mild weather.
Close in absence of light.
• The majority of the stomata are on the undersides of leaves.
Types of Leaves
• Foliage - most common and conspicuous, site of photosynthesis.
• Modified leaves:
– Scale leaves are found on rhizomes and buds. Enclose and
protect.
– Seed leaves (cotyledons) - store food for the developing
seedling.
– Spines and tendrils - protect or help support stems.
– Storage leaves - store food and water.
– Bracts - often are brightly colored. Ex. poinsettia “flowers.”
Modified leaf - bract
Modified leaf - tendril
Leaf Venation
• Veins - vascular bundles of xylem and phloem extend from
the stem, through the petiole, and into the leaf blade.
• Two principal types of venation:
Parallel-veined leaves - numerous veins run essentially
parallel to each other. Monocots.
Net-veined leaves - veins branch from the main rib or
ribs and subdivide into finer veinlets. Allows for
resistance to tearing. Dicots.
Leaf as Plant Identification
Two types of leaves:
• Simple - the leaf blade is a single, continuous unit.
• Compound - several separate leaflets arising from the
same petiole.
Leaf type can be confusing because a deeply lobed simple leaf
may look like a compound leaf.
Leaf Arrangement
• Opposite - leaves are positioned across the
stem from each other, leaves at each node.
• Alternate -(spiral) leaves are arranged in
alternate steps along the stem, only one leaf
at each node.
• Whorled - leaves are arranged in circles along
the stem
Leaf Edge
Flowers
• Sexual reproduction as their sole function.
• Fragrance and color attract pollinators (insects or birds).
• Stamen (male flower part) - anther (pollen sac) and supported by a
filament.
• Pistil (female flower part) - stigma supported by the style. Ovary contains
eggs, which reside in ovules. If pollination occurs, the ovule develops into
a seed.
• Accessory parts such as sepals, petals, and nectar glands
Sepals are small, green, leaf-like structures located at the base of a
flower - protect the flower bud. Collectively - the calyx.
• Petals - may contain perfume.
• Collectively – a corolla
• The number of petals on a flower often is used
to help identify plant families and genera.
– Dicots - multiples of four or five sepals and/or
petals.
– Monocots - multiples of threes.
Often forgotten!
• Monoecious plants - separate male and
female flowers on the same plant. Usually
self-pollinating
• Dioecious species - separate male and female
plants. Male and female plants must be
planted close enough together for pollination
to occur.
Important pollinator!!!!
Pollination
• Transfer of pollen from an anther to a stigma, by wind or by
pollinators.
• Pollen will grow a long tube down the style to the ovules inside the
ovary. When pollen tube reaches the ovules, it releases sperm, and
fertilization typically occurs.
• Fertilization is the union of a male sperm nucleus from a pollen grain
with a female egg. The ovule develops into a seed.
• Pollination is no guarantee that fertilization will occur.
• Cross-fertilization combines genetic material from two parent plants.
• The resulting seed has a broader genetic base. Usually are more
successful.
Fruits
• Fertilized, mature ovules (seeds) plus the
ovary wall.
Some seeds are enclosed within the ovary
(ex. apples).
Some seeds are situated on the outside of
fruit tissue (ex. strawberries).
Seeds
Contain all of the genetic information needed to develop into an entire plant.
• Embryo is a miniature plant in an arrested state of development.
• Endosperm is a built-in food supply.
• Seed coat - protects the seed from disease and insects. Also prevents water from
entering the seed and initiating germination before the proper time.
Scarification is used to break or soften the seed coat. Heat of a forest fire, digestion
of the seed by a bird or mammal, or partial breakdown of the seed coat by fungi or
insects.
Embryo dormancy is common. Seeds must go through a chilling period before
germinating. Stratification - storing seeds in a moist medium (potting soil or paper
towels) at temperatures between 32 ° and 50 °F. Required length of time varies by
species.
• Seed’s age greatly affects its ability to germinate.
• Older seed is less viable. If it does germinate, the
seedlings are less vigorous and grow more slowly.
• The seedbed must be properly prepared and made up
of loose, fine-textured soil.
• Seeds must be planted at the proper depth. Too
shallow, may wash away. Too deep, won’t be able to
push through the soil.
• Seeds must have a continual supply of moisture;
however, if over-watered, they will rot.
Photosynthesis
• A plant requires energy from the sun, carbon dioxide from the air,
and water from the soil.
Carbon dioxide + Water + Sunlight => Sugar + Oxygen
• Photosynthesis occurs only in the chloroplasts.
• Chloroplasts are incredibly small. One square millimeter, about the
size of a period on a page, would contain 400,000 chloroplasts.
• Chlorophyll, the pigment that makes leaves green, is found in the
chloroplasts. It traps light energy from the sun.
• If any light, water, and carbon dioxide—is lacking, photosynthesis
stops.
Photosynthesis contd.
• Carbon dioxide enters a plant through its stomata.
• Photosynthesis fluctuates throughout the day as
stomata open and close.
Typically, they open in the morning, close at
midday, reopen in late afternoon, and close in the
evening.
• Temperature - occurs at its highest rate between
65°and 85°F and decreases at higher or lower
temperatures.
Respiration
• Carbohydrates made during photosynthesis are converted
to energy. This energy is used for cell growth and building
new tissues. The chemical process by which sugars are
converted to energy is called respiration.
Sugar + Oxygen => Carbon dioxide + Water + Energy
• Essentially the opposite of photosynthesis. Photosynthesis
is a building process, while respiration is a breaking-down
process.
• Respiration not dependent on light. Occurs 24/7.
• Respiration occurs in all life forms and in all cells.
Transpiration
• When guard cells shrink, its stomata open, and water vapor
is lost.
• In turn, more water is pulled through the plant from the
roots.
• Rate of transpiration directly related to stomata being open
or closed.
• Stomata account for only 1 percent of a leaf’s surface but
90 percent of the water transpired.
• Transpiration is a necessary process and uses about 90
percent of the water that enters a plant’s roots.
• The other 10 percent is used in chemical reactions and in
plant tissues.
• Water moving via the transpiration stream is responsible
for several things:
- Transporting minerals from the soil throughout the
plant.
- Cooling the plant through evaporation.
- Moving sugars and plant chemicals.
- Maintaining cell turgor.
• Amount and rate of water loss depends on factors such as
temperature, humidity, and wind or air movement.
• Greatest in hot, dry, windy weather.
Environmental Factors
Light: quantity, quality and duration
Quantity - intensity or concentration of sunlight.
Quality - wave-length of light.
Sunlight supplies the complete range of
wavelengths.
Blue light is responsible primarily for leaf growth.
Red light, combined with blue light, encourages
flowering
Duration - photoperiod - to the amount of time a plant
is exposed to light. Controls flowering in many
plants.
• It’s actually the length of uninterrupted darkness
that is critical to floral development!
• Short-day plants (long night) form flowers only
when day length is less than about 12 hours.
• Long-day plants (short night) form flowers only
when day length exceeds 12 hours.
• Day-neutral plants form flowers regardless of day
length.
Temperature
• Influences most plant processes - photosynthesis,
transpiration, respiration, germination, and
flowering.
• As temperature increases (up to a point),
photosynthesis, transpiration, and respiration
increase.
• When combined with day length, temperature
also affects the change from vegetative (leafy) to
reproductive (flowering) growth.
• Depending on the situation and the specific plant.
Water
• Growing plants contain about 90 percent water.
• Primary component in photosynthesis and respiration.
• Responsible for turgor pressure in cells.
• Carries minerals and carbohydrates throughout the
plant.
• Responsible for cooling leaves as it evaporates during
transpiration.
• Regulator of stomatal opening and closing, thus
controlling transpiration, and, to some degree,
photosynthesis.
• Source of pressure to move roots through the soil.
• Medium in which most biochemical reactions take
place.
Plant Hormones
Produced naturally by plants. Plant growth regulators
applied by humans – may be natural or synthetic.
5 groups:
Auxin:
• Bending toward a light source (phototropism)
• Downward root growth in response to gravity
(geotropism)
• Promotion of apical dominance
• Flower formation
• Fruit set and growth
• Formation of adventitious roots
Gibberellins:
• stimulate cell division and elongation
• break seed dormancy
• speed germination
Cytokinins:
• found in both plants and animals
• stimulate cell division
• used in media for tissue culture
Ethylene Gas
• induces ripening
• causes leaves to droop and drop (abscission)
• promotes senescence
• part of the reason leaves fall off of trees
• used to artifically ripen fruit
Abscisic acid (ABA)
• general plant-growth inhibitor
• induces dormancy
• prevents seeds from germinating
• causes abscission of leaves, fruits, and flowers
• causes stomata to close
Any Questions?
Thank you!