CPSC 112 Lectures #5-8(?)

Root general notes

organ of vascular plants that grow underground usually and serve to anchor the plant, absorb water/minerals, translocate water/minerals to other parts of the plant, sometimes food storage (usually associated with taproots)

Taproot system roots

Primary root with secondary roots growing out of it, tertiary roots grow from the secondary roots

Which root system is better for drought tolerance?

taproot system

Root system associated with food storage?

taproot system

Plant tropism

biological phenomenon indicating growth toward/away a stimulus (plants turn towards positive environmental stimuli and turn away from negative stimuli)

Examples of plant tropisms

responses to gravity, light, moisture, and root/shoot branching

Does gravity play a large role in influencing growth/development in plants?

yes

Gravitropic

response of a plant to the force of gravity

How do roots/shoots respond to gravity?

shoots respond negatively, roots respond positively (shoots grow away from gravity's pull, roots give in to gravity)

What triggers root bending with gravitropism?

an asymmetrical flow of auxin

3 zones of roots?

zone of maturation, elongation, cell division, and also the root cap

Root cap functions

tissue at the tip of the root that protects the growing root tip, contains statocytes (cells involved in gravity perception - statoliths), secretes mucilage to facilitate movement in the roots, and interacts with soil microbiota

Cell division zone notes

behind the root cap, tissue of actively dividing cells (undifferentiated), smaller than other root cells, provides cells for future growth (some go to root cap, most go to elongation zone)

Elongation zone notes

behind root apical meristem, cells initiate cell elongation gradually

Maturation zone

behind the elongation zone, cells initiate differentiation and attain their final purpose/size, form root hairs, where the vascular system is formed

Outer layer of cells on the root is called?

epidermis

Extension of the epidermis?

root hairs

What does the epidermis surround?

the cortex, pith, and vascular bundles

What do the cortex and pith store?

photosynthetic products

What surrounds the vascular system?

endodermis

What does xylem do?

transports water/nutrients from the soil to the plant

What does phloem do?

moves sugar/other metabolic products

xylem/phloem formation in dicot ROOTS?

arranged in an x shape

xylem/phloem formation in monocot ROOTS?

arranged in a ring shape

What direction does xylem transport water/minerals?

from the root to the stem to the leaves (unidirectional)

is xylem made of living or nonliving cells?

composed of nonliving cells

What direction does phloem move in?

Phloem is biodirectional and transports manufactured food (from the leaves to the rest of the plant)

Roots create new cells that expand/differentiate to give?

support to the plant and absorb water/minerals

Why does root growth follow the path of least resistance?

to save energy

What is needed for root growth?

moisture for elongation and moving down, oxygen for respiration

What do roots explore for?

water/nutrients (potassium/phosphorous)

Where does the inital radicle of the root come from?

the seed's energy

What kind of soil do roots grow into?

moist soil, they can't go through dense/dry soil

what direction do roots grow?

down/sideways

What can wheel tracks across fields cause?

soil compaction

How does soil compaction affect root growth?

roots can't grow through compacted soil, restricts their growth

Example of an abiotic stressor?

soil acidity (lower pH is acidic and has higher concentration of hydrogen ions)

Example of a biotic stressor?

pests (bugs feed on the roots of plants and can cause lodging due to weakened roots)

2 steps in corn root system development (and monocots in general)

seminal root develops and comes out during germination, after that the nodal root system develops

Seminal root system notes for corn (monocot)?

2-5 roots emerge from the seed, anchor and provide nutrients for 2-3, after 4-6 weeks they die

Nodal root system notes

critical for growth/establishment, come from the nodes on the stem belowground

Brace roots

same as nodal roots but aboveground, they proliferate surface soil/ support the stalk, scavenge for water/nutrients

Soybean root system (dicot) notes

taproot system, seminal roots remain alive/active, lateral roots branch from seminal root

Soybeans have symbiotic relationship with

rhizobia (bacteria that fixes nitrogen)

Early growth concerns of plants

seedlings are vunerable, too dry/too much water affects root seedlings

Small shoot system is evidence of

bad root system

rate of nutrient/water uptake is much greater when?

early in the season

possible causes of slow growth?

cold temps (40s-50s are usually bad), soil compaction, nutrient deficinies in the root zone, insect/disease pressure, drought stress, also excess soil moisture is bad (bc it limits respiration)

How to manage water level?

irrigation/drainage

How to manage deep vs shallow root systems?

tillage

How to manage weeds?

cultivation

fertilizer is used to?

avoid root injury EDIT THIS

What drives water/nutrient uptake?

concentration gradients

how does xylem move?

one way only

Are there end walls between cells for xylem?

no

How does phloem move?

2 way flow

Do cells for phloem have end walls?

yes

vascular bundle pattern in dicot STEMS?

ring shape pattern

vascular bundle pattern in monocot STEMS?

vascular bundles arranged randomly

Functions of xylem?

transports water/minerals from the roots up. can ONLY move up, forms vascular bundles with phloem

Xylem structures

lignin in the walls gives extra strength, matures then dies, hollow structure

is phloem living tissue?

yes

Phloem functions?

food/nutrient transport, able to move up/down, transports sugars and amino acids

Is phloem located outside of vascular bundles?

yes (making it more exposed)

Does xylem or phloem provide extra support to the plant?

xylem (bc lignin is present)

Is energy from the plant needed to transport xylem?

no. water moves up in repsonse to tension caused by transpiration

is water a polar molecule?

yes

How does xylem work?

water moves up in response to tension due to transpiration through capillary tubes, no energy needed from the plant

Does phloem carry sugars?

yes, glucose and sucrose

Do all organisms need energy for metabolic reactions?

.yes

Autotroph

organism that can form nutritional organic substances from simple inorganic substances (like CO2 or light)

Carbon sequestration

plants with long lifespans store up carbon over long periods of time

Photosynthesis

process driven by light energy in which sugars (glucose) are constructed from water and carbon dioxide and oxygen is released as a byproduct

Photosynthesis equation

6CO2 + 6H2O --> light energy --> C6H12O6 + 6O2

Where do plants get energy to fuel the metabolic pathway of photosynthesis?

sunlight

Leaf anatomy parts

Cuticle, epidermis, mesophyll, leaf veins, palisade layer

Cuticle

prevents water loss in leaves

Epidermis

covers the upper/lower surfaces of the leaf, allows sunlight for photosynthesis, mediates exchanges between the plant and its environment

Mesophyll

builds most of the interior of the leaf, where photosynthesis happens

Palisade

layer that captures sunlight (lower layer allows CO2, H2O, and O2 to diffuse out)

What do leaf veins do?

bring water to the leaf

3 steps of photosynthesis?

Diffusion of CO2 into the leaf, then light-dependant reactions, then light-independant reactions

Stomata

microscopic pores surrounded by 2 guard cells

Functions of the stomata?

regulates gas exchange between the plant and atmosphere and is major pathway for diffusion of CO2, O2 and water vapor

When do the stomata open?

when light strikes the leaf (turgid cells are open, flaccid cells are closed)

Do the stomata need to be open for photosynthesis?

yes, but water loss is a side effect when they're open

How much water that the plant takes up is lost through transpiration?

~90%

Transpiration

exhalation of water vapor through the stomata

Things that affect stomata density?

temperature, humidity, light intensity around the plant

When the concentration of CO2 goes up, the number of stomata produced ___

goes down (inverse relationship)

Light-dependant reactions

energy from sunlight is absorbed by the chlorophyll and converted into chemical energy

Light-independant reactions

Calcin Cycle (carbohydrate molecules are assembled from CO2 using the chemical energy from the previous step)

Chloroplast

organelle that conducts photosynthesis. enclosed in double membrane, thylakoid membrane contains chlorophyll pigments (which absorb light energy), the space between the inner and thylakoid membrane is filled with stroma (fluid)

Chlorophyll pigment is green to absorb?

red/blue lights and reflect green light

What regulates the size/number of chloroplasts per cell?

genetics and environmental factors (number of chloroplasts increases with high CO2 levels, decreases with high temps)

Cyclosis

movement of chloroplasts around the cell based on light conditions

What does too much light cause?

photoinhibition

What does photoinhibition do?

damages photosynthetic machinery and interferes with cellular activity

Energy from the sun is absorbed by chlorophyll and

converted and stored as chemical energy, idk EDIT THIS, happens in thylakoid membrane

Molecules that store chemical energy obtained from sunlight?

NADPH (electron carrier molecule) and ATP (energy currency molecule)