Biology Exam 3 Review Botany Part 2

True or False? Plants need a variety of nutrients in order to survive, grow and reproduce.

True

Essential Elements

are nutrients that are needed in relatively large quantities

Plants need a lot of…

• Carbon

• Oxygen

• Hydrogen

Macronutrients

other nutrients that are needed in relatively large quantities (approx. 1g/1kg)

Six Macronutrients

• Nitrogen

• Phosphorous

• Potassium

• Sulfur

• Calcium

• Magnesium

Eight Micronutrients

• Iron

• Chlorine

• Manganese

• Zinc

• Copper

• Nickle

• Boron

• Molybdenum

True or False? Nutritional needs of plants were determined by studying plants in hydroponic culture.

True

True or False? Most nutrients are obtained from the soil.

True

Soil

a mixture of several components, both living and non-living

Living Components of Soil

• plant roots

• fungi

• bacteria

• protists

• animals

  • worms

  • insects

  • crustaceans

  • mammals

Non living components of soil

• air

• water

• decomposing organic matter

• dissolved minerals

• clay particles

• silt and sand grains

• rocks

A Horizon / Topsoil

contains the living and dead organic matter, along with mineral nutrients. A think one of these is a characteristic of fertile grasslands

B horizon / Subsoil

• “mixing zone”

• contains organic material from the topsol and fragments of rocks and minerals from bedrock below

C horizon / Parent Rock

the source of the inorganic mineral nutrients needed by plants

Cation Exchange

• makes many nutrients available in plants

• Chemical weathering of parent rock causes clay particles to become negatively charged

  • causes positively charged ions to be attracted to the clay

Clay

is important to retain mineral nutrients in soils

Plant roots

pump protons into the soil and the protons change places with the mineral ions and enter the root hairs

Symplastic Pathway

allows nutrients to travel from cell to cell via the plasmodesmata

Apoplastic Pathways

allows nutrients to travel to the vascular tissue via cell walls

Casparian Strip

• layer of suberin in endodermis that is impermeable to water

• prevents water and mineral from crossing endodermis between cell walls

• must cross plasma membrane via cytoplasm - cells cen monitor minerals entering vascular tissue

• Water cant flow backwards out of the root vascular tissue

The uptake of Nutrients via Roots

• some nutrients are obtained via symbiosis

• symbiotic mycorrhizae (fungus roots) fungi provide a number of mineral nutrients to plants the fungi extend special hyphae into the roots of the plants that allow the fungi to direct nutrients into the root

Plants can attract symbiotic nitrogen

• fixing bacteria to aggregate around a root hair. The root hair will then extend and curl around the bacterial, forming a nodule

  • this nodule creates an anoxic environment for nitrogen fixation

Xylem Sap Movement

• plants need lots of water to prevent desicatio

Mature Maple Tree

200L water per hour in summer

Actively transpiring leaf

replaces all water every hour

Xylem Sap

can ascend 100m in height against gravity

Two mechanisms to move xylem sap

• root pressure

• Transpiration cohesion

Root Pressure

push from below

Transpiration Cohesion

pulls from above

Water Evaporates from Leaves

generates negative pressure (suction)

Transpiration

suction due to evaporation provides most of the force to move water up through the stem

Adhesion

sticks to other things

Cohesion

sticking to itself

Movement into roots and up stems is driven by

water potential

Asexual reproduction

• produces genetically identical clones

• regenerative propagation is a common form

Stolons

(runners) are horizontal stems that form adventitious roots at certain intervals, which can then give rise to independent plants

Tuber

is an underground stem that can generate new plants at each eye

Stolons, Bulbs and Plantlets..

all methods of asexual reproduction that will produce genetically identical offspring

Apromixis

• (‘above mixing’)

• when diploid cells in the carpel divide to form embryos without meiosis or fertilization

• dandelions, blackberries, and some citrus

Parthenocarpy

• is the generation of fruit without fertilization

  • creates seedless fruits

    • bananas and watermelons

Sexual reproduction

increases genetic diversity

Plant Hormones

• produced in one part of the plant, transported to other parts where it trigger responses in target cells and tissues

  • very small concentrations needed for this effect

Auxin

• plant hormone

• any chemical which promotes cell elongation in shoots, produced in apical meristem

• Phototropism mechanism

• used in herbicides

Phototropism mechanisms

• how auxin was discovered

• response to light; stems bend toward light source

• membrane protein asymmetry - carrier proteins for auxin are located only in the basal end of the cell

Gibberellic Acid (GA) or Gibberellins

• Produced in leaves and stems; stimulate cell elongation and division

• can cause ‘bolting’ in plants in normally compact plants

• sprayed to get larger fruits

• required for seed germination

  • high concentration in seeds

Ethylene

• Gaseous hormone

• numerous effects on plants

• Interacts with auxin

• fruit ripening

• inhibits stem elongation, promotes lateral swelling of stems

Fruit ripening

• caused by ethylene

• stimulates loss of chlorophyll in fruit, softening of cell walls

• produced and released rapidly

Apical hook

of eudicot seedlings is maintains by asymmetrical production of ethylene, which inhibits elongation of cells on the inner surface

Abscisic Acid (ABA)

• produced in bud - induced dormancy

• involved in seed dormancy

• helps plants cope with stress

Why do leaves fall?

interaction between auxin and ethylene

During dry conditions, ABA

collects in leaves - induces stomatal closure - regulates guard cells

Nitrogen

• macronutrient

  • used in nucleic acids and amino acids

Phosphorous

• macronutrient

  • used in nucleic acids, membrane lipids, and ATP

Potassium

• macronutrient

  • numerous uses in cell

Sulfer

• macronutrient

  • used in amino acids, in coenzymes and defense

Calcium

• macronutrient

  • used in plant cell walls and cell signaling

Magnesium

• macronutrient

  • essential component of chlorophyll and enzymes

Growth and Differentiation

the two development processes from a single-celled zygote to a mature plant

Growth

is an increase in the size of individual cells that contributes to an increase in size of the entire plant

• adding more cells via cell division can also increase the size of a plant

Differentiation

• the process through which different cell types arise from pre-existing, primordial cells (stem cells)

  • as this continues cells become more “fixed” in terms of their identity and function; can only give rise to certain types of cells

    • caused by gene expression

Totipotent

• early embryonic cells

• can give rise to any type of cell

‘Master’ Transcription Factors

• stimulated by a variety of exogenous and endogenous signals

  • then promote this in different cells

    • if different embryonic cells express different proteins, they will develop into different types of cells

PLETHORA (PLT)

• important in the normal development of roots

  • causes normal roots to grow

  • when interfered with produced unusually small roots

  • these expressed in apical meristems will trigger the development of roots at the top of the shoot

• transcription factor

Turgor Pressure

Plant cells grow as ______________ ( from the water in the vacuole and the cytosol) pushes outward of the cell wall

• this causes the cell wall to relax and expand and add cellulose microfibrils to reinforce the cell wall

  • without more cellulose the cell wall would lose its shape

Meristems

• Plants can grow by adding more cells at the _______

  • cell division in the _______ is controlled by a small protein, CLAVATA3, amd a transcription factor, WUSCHEL

CLAVATA3

• small protein

• when there are enough cells in the meristem ______, migrates to the target cells and suppresses the production of WUSCHEL

• if defective the meristem will produce fascinated flowers with a folded head and excess petals

WUSCHEL

• Is produced in cells below the meristems

  • if defective the meristem will produce fascinated flowers with a folded head and excess petals

How do cells ‘decide’ what they will become in the adult plant?

• the egg cell, before fertilization, is polar

  • distinct top and bottom ends, defined by attachment to parent plant

    • after first division, top of the cell becomes smaller apical daughter cell, where auxins accumulate and stimulate the development of cotyledons

    • the bottom of the cell becomes the longer basal daughter, which supports embryo and keeps it attached to parent

Apical Daughter Cell

after the first division, the top of the cell becomes the smaller _______ , where auxins accumulate and stimulate the development of the cotyledons

Basal daughter cell

the bottom of the cell becomes the longer ______ , which supports the embryo and keeps it attached to the parent

Asymmetrical cell division

• can lead to the unequal division of various proteins, nucleic acids and transcription factors

Tropisms

• growth responses resulting in curvature or growth towards or away from a stimulus

• causes by differential elongation of cells on each side of the stem, leaf, root, etc.

Phototropism

• cells on darker side of shoot elongate more than cells of lighter side

• illuminating one side causes auxin to migrate across the tip of the un-illuminated aside

• sensing light - specific to light spectrum

• plants ‘see’ light by exposure to blue light which stimulates phototropin

Phototropin

a receptor protein in the cell membrane

Experiment by Darwin Conclusions

• The chemical is produced in the coleoptile tip

• the chemical stimulates growth in coleoptile cells

• the coleoptile curves to the light because of higher concentrations (and more growth) on the shaded side

Roots display ______ gravitropism

• Positive

  • (grow down)

Shoots display _____ gravitropism

• Negative

  • (grow up)

Thigmotropism, Thigmomorphogenesis, Turgor Movements

respond to mechanical stimuli

Thigmotropism

• trophic response to touch

• vines - wind around objects

• touch causes cells on opposite side of stem to elongate and shoot bends towards support object

Thigmorphogensis

• change in form which results from mechanical vibrations or wind

• shaking and vibration causes sharter, sturdier plants

• increase in hormone ethylene inhibits cell elongation - results in a shorter, sturdier stem

Turgor movements

• sensitive plant respond to touch by folding / dropping leaf

• Changes in turgot pressure in specialized cells allows plants to orient (or move) their leaves

• loss of turgor pressure in the leaf pulvini results in wilting

Venus fly-traps

• use action potentials to stimulate rapid tugor - induced movement

• mechanical stimulation on receptor hairs

• electrical signal propagated - action potential due to ion movement

• effector cells on outside of trap swell (increased turgor pressure) forcing trap shut

Phytochrome

• discovered in 1959

• photoactive compound in plants which sense light and dark

• responses of plants to red (660nm) and ‘far-red’ light (730nm)

Pr

• inactive form

• far - red light induced

Pfr

• active form

• red light induced

• tells seed to germinate

Photoperiodism (How do plants know it is spring?)

• day length - regulates sprouting and flowering

• temperature

• interaction of temperature and change in day length - accounts for variability between years

• responses vary between plants

Physiological responses to day length

seed germination, flowering, leaf abscission

Short - Day plants

require long night period (chrysanthemums, poinsettias); flower in fall, winter

Long day plants

require short dark period (spinach, radish, iris, grasses); late spring or summer flowering

Day neutral plants

unaffected by day length, depends on plant maturity (tomatoes, peas, rice, dandelions)

Can plants tell time?

• Circadian ‘endogenous’ rhythm

• plant can ‘ tell the time’ independent of light -internal ‘clock’ proteins

Phloem

Which tissue transports photosynthetic products, like sugats, to the places where they are needed?

Auxins

Name a hormone that encourages cell elongation in plants

b) clay

The component of soil that is most important for holding positively charged nutrients is:

a) Humus

b) clay

c) Parent rock

d) water

e) air

a) vegetative propagation

A form of asexual reproduction that involves a genetically identical identical clone growing from a fragment (e.g. a stem, a leaf, a root) of a parent plant is:

a) vegetative propagation

b) apomixis

c) parthenocarpy

d) self fertilization
e) cross pollination

d) ethylene

Which hormone is responsible for causing fruit to ripen?

a) abscisic acid

b) indoleacetic acid

c) gibberellins

d) ethylene

e) auxin

d) all of these

Which of the following are ways that plants can avoid self-fertilization?

a) genetic incompatibility

b) having distinct male and female flowers

c) having distinct male and female plants

d) all of these

e) b and c only

False

True or False? Self fertilization is a form of asexual reproduction.

True

True or False? The A horizon of soils contains decaying organic matter.

True

True or False? Macronutrient are nutrients that are needed in concentrations equivalent to 1 gram of nutrient to 1 kg of plants mass.