Lec 19 Plant Physiology

Tissue Systems in Plants

1. Dermal tissue (epidermis)

2. Vascular tissue

3. Ground tissue

Dermal Tissue (epidermis)

• Single layer of tightly packed epidermis forming the outer layer of the plant roots, stems, leaves, flowers, fruits, seeds

• Protects the plant from injury/water loss

• No chloroplasts

Vascular Tissue

Transport system for water and nutrients in the leaves, stems, roots, fruits

Ground Tissue

• Photosynthetic tissue (not dermal or vascular), found in all plant organs

• Important for plant growth, healing after injury, produce and store food

• Provides structural support

Shoots

above-ground parts of a plant

Cuticle/Stomata/mesophyll/Bundle Sheath Parenchyma

Components of the shoots: _____, _____, _____, and _____

Cuticle

waxy layer secreted by the epidermal cells of leaf, decreases water permeability

Stomata

pores in leaf surrounded by two guard cells, regulates gas and water exchange with air

two guard cells

Stomata are surrounding by _________

Mesophyll

tissue between epidermal layers of leaf containing two types of cells

Pallisade parenchyma/Spongy mesophyll

The cell types in the mesophyll: _____ and ______

Pallisade parenchyma

Type of cell in the mesophyll that contains lots of chloroplasts, columnar and tightly packed→ primarily photosynthetic

Spongy mesophyll

Type of cell in the mesophyll that is irregularly shaped, lots of space between cells with high humidity→ primarily involved in gas exchange

Bundle Sheath Parenchyma

Conduit between mesophyll and vasculature

Stem

bridge between the roots and leaves

• Structural and transport role

• Tissue layers: epidermis → cortex → pith

Epidermis/cortex/pith

Tissue layers of the stem in outermost to innermost order?

Stoma

Term for mouth in plant context

xylem/phloem

Vascular tissue consists of _____ and _____, which occur together and transverse all plant tissues

Xylem

Types of vascular tissue involved in transport of mainly water and dissolved ions from the root to the shoot

Phloem

Type of vascular tissue involved in transport metabolites (primarily sugars, amino acids, ions) from the “source” of production (i.e. photosynthetic cells in leaves) to “sinks” (developing roots, leaves, fruits, seeds)

anchors

The root _____ the plant to the ground

water/nutrients/soil

The root absorbs _____ and ______ (mineral and metal elements) from the _____.

food/sugars

The root stores ____ and ____

Roots

Underground portion of the plant

epidermis/cortex/pericycle/endodermis

Tissue layers of root from outermost to innermost

Lateral Roots

Secondary root system that arise from the pericycle

Root Hairs

long tubular outgrowths of the root epidermal cells that increase surface area for absorption

Root cap

mass of cells covering the sensitive root tip

• Protection of root meristem, gravitropism, regularly replaced

Apical meristem

• specialized region at the tip of a plant's root, responsible for continuous growth and development of the root system

• Undifferentiated cells

gravitropism

plant's growth response to gravity, causing roots to grow downward and shoots to grow upward

cuticle

The roots have no ______ unlike the stem and shoots

Vascular cambium

undifferentiated cells that can differentiate into vascular tissue

Stem cells in plants

1. Apical meristem

2. Vascular cambium

cell wall/middle lamella/chloroplast/vacuole/tonoplast

Structures only found in plant cells: ______, _____, _____, _____, and ______

Middle lamella

layer in plant cell walls that acts as a "cement" to hold adjacent cells together

Cellulose microfibril/rigidity

Plant cells can form ________ in the cell wall similar to human myofibrils, which creates _____ in the cell wall

Pectin

Soluble dietary fiber found in the cell walls of plants, particularly in fruits and vegetables

Aquaporins

family of channel proteins, also known as water channels, that facilitate the movement of water across cell membranes (facilitated diffusion)

Plasmodesmata

Channels passing through the cells walls that connect the cytoplasm of one plant cell to the cytoplasm of the neighboring plant cells that allows for communication and controlled exchange of substances between cells

Desmotubule

continuous tube connecting the smooth ER of one cell to that of the other

gap junctions/simple/larger/substrate/PD

Plasmodesmata are:

• Similar to _______ in animal cells

• Small molecules (sugars, amino acids) and ions can move by _____ diffusion

• ____ molecules overcome the size exclusion limit by modifying the ________ so it can move through the PD or induce transient changes of the ___ to allow the molecule through.

diameter/callose

For plasmodesmata, the ______ of opening can be reduced / increased via the deposit of the plant polysaccharide, _____, to change movement

Functions of the Vacuole

1. Storage

2. Helps keep the chloroplasts exposed to light

3. Maintain structural integrity of the cell and plant by turgor pressure against the cell wall.

cytoplasm

Water, nutrients and other molecules are transported in and out of vacuole for storage when not needed in the ________.

chloroplasts/membrane

The vacuole elps keep the ________ exposed to light by pushing all of the contents of the cell cytoplasm up against the cell ______.

tonoplast

membrane of the vacuole

K+ pumps/aquaporin/turgor pressure

Transporters (ie. _______) in the tonoplast (membrane of the vacuole) move ions in and out of the vacuole. If ions are pumped in, this draws water into the vacuole (through _______ water channels), causing the vacuole to swell and exert more pressure against the cell wall (______) – this is essential in supporting plants in an upright position.

photons/ATP

Light-dependent reactions (_____ -> ____)

sugar

Light-independent reactions (____ synthesis)

photopigment

molecule that undergoes a chemical change when it absorbs light

Chlorophyll

main photopigment in green plants. It absorbs light at wavelengths around blue (430 nm) and red (660 nm), so green (550 nm) wavelengths are reflected.

Carotenoids

Pigment in plants that absorb light at wavelengths at 400-500 nm (blue/bluegreen), giving them an orange color (carrots). Are in thylakoid membranes. Transfer energy to chlorophyll.

yellow/orange/always/decrease

Carotenoids look ______ and _____. They are ______ present in leaves; Visible when chlorophyll levels ______

Anthocyanins

• Pigment that’s Red and Purple

• Produced in leaf during Fall

• Protect against photo-inhibitory effects of excess photons that would have been absorbed by chlorophyll

photo-inhibitory

Anthocyanins protect against _______ effects of excess photons that would’ve been absorbed by chlorophyll

Photosystem II

In the Electron and Proton Transfer in the Thylakoid Membranes of Plants, step 1 involves ______

Photosystem II

transmembrane protein complex made up of many different proteins and pigment compounds

Chlorophyll/electrons/plastoquinone

________ molecules in PSII absorb energy from light. The transfer of energy among molecules in the complex excites _______, which are donated to _________.

two/two H+/stroma

Plastoquinone picks up ____ electrons from PSII and ______ ions from the _____ and then moves through the membrane to bring electrons to the next complex.

H2O/atmosphere/lumen

The electrons that are transferred by plastquinone are replaced by splitting two _____ into O2 , H+ ions. O2 is released to the _____, H+ ions are released into the ______, generates H+ gradient across the thylakoid membrane

Cytochrome b6f

In the Electron and Proton Transfer in the Thylakoid Membranes of Plants, step 2 involves ______

Cytochrome b6f

large, multi-subunit protein complex embedded in thylakoid membrane.

cytochrome b6f

Plastoquinone transfers the two electrons it picked up from PSII to _______ and the two H+ ions are released into the lumen.

protons/electrons

Cytochrome b6f complex actively translocates _______ from the stroma into the lumen as ______ flow through it.

plastocyanin/PSI

Cytochrome b6f transfers the electrons to ________ (small peripheral membrane protein), which carries them to ___

Photosystem I

In the Electron and Proton Transfer in the Thylakoid Membranes of Plants, step 3 involves ______

Plastocyanin

________ delivers the electrons to Photosystem I

NADP/NADPH

Chlorophyll molecules from PSI absorb energy from light allowing for the donation of two electrons and the addition of H+ to _____ to produce _______

stroma/gradient

To form NADPH, H+ ions are taken from the ______, which contributes to the H+ _______ across membrane

ATP synthase

In the Electron and Proton Transfer in the Thylakoid Membranes of Plants, step 4 involves ______

stroma

The energy generated by movement of H+ ions from inside the thylakoid lumen to the stroma is harvested to combine ADP and P to make ATP. The NADPH and ATP both end up in the ________

H+ gradient/ATP synthase

In both ETCs (chloroplasts vs mitochondria), electron flow is coupled to the generation of a _______, which is used by _______ to generate ATP

thylakoid membranes/ATP/NADPH

Light-dependent reactions occur in the _______ producing ___ and _______

stroma/CO2/H2O

Light-independent reactions occur in the _______. Uses ATP and NADPH from light-driven reaction as well as ___ and ___ to produce carbohydrates (glucose)

synthesis/breakdown

In plants, sucrose is made both during the day (______) and night (_______ of stored starches)

Sucrose

disaccharide formed of glucose and fructose

Maltose

disaccharide formed of two glucose

Triose phosphates

3 carbon molecules that can be combined to form 6 carbon sugars

Hexose

General term for a 6 carbon sugar (e.g. fructose & glucose)

triose phosphates/hexose phosphates

When producing sucrose during the day, ________ are converted to ________, which then make sucrose

starch/maltose/glucose/hexose phosphates

When producing sucrose during the night, ______ is broken down to _____ and _____. Then ______ are made, which can then be turned into sucrose.

small/solar

Only _____ amount of _____ energy is converted to carbohydrates

upwards/vascular/xylem

Water and minerals move ______ in plant through ______ tissue called _______

hydrostatic pressure/surface tension/evaporation

The movement of water up a plant is due to ________, _______, and ________, and may be up a “column” several hundred feet tall

Water is pulled from the xylem into the cells walls of the mesophyll, where is evaporates into the air spaces within the leaf. Water evaporates then diffuses through the leaf air space, through the stomata.

xylem/mesophyll/air spaces/diffuses/stomata

Water is pulled up from the plant's roots through the _____ vessels.

Once in the leaf, water moves into the _______ cells where it evaporates into the _______ within the leaf and ______ through the leaf's internal air spaces, eventually leaving through the _______

stomata/cuticle

• 95% Water Loss: The majority (95%) of water loss occurs through the _____, which are tiny pores found on the lower epidermis of the leaf.

• The _______, which covers the leaf's surface, serves as a barrier against water loss. However, only about 5% of total water loss happens through the ______

• Guard Cells: The stomata are controlled by guard cells, which regulate their opening and closing, thereby controlling water loss and gas exchange (CO₂ in, water vapor out).

negative hydrostatic pressure/evaporation/surface tension

due to ________ (negative tension) from _______ occurring in the leaves, water is drawn upwards by ________.

Guard cells features

• Thicker Cell Walls: The cell walls of guard cells are thicker near the stomatal pore. This thickness makes the area inflexible, affecting how the guard cells swell and change shape.

• Inelastic Fibers: Bands of inelastic fibers run around the guard cells, which also influence how the cells deform.

Thicker cell walls/inelastic fibers

____ and _____ determine how guard cells will change shape when they swell

water/away/pore/guard cells/buckle

When _______ is taken up by the guard cells, they expand. However, the expansion is limited to the sides of the cells _____ from the _____ (due to the thick walls and fibers).

This limited expansion causes the _______ to _______ and open the pore between them, allowing gas exchange (such as CO₂ in and water vapor out) and water loss through transpiration.

morning/afternoon/K+/sucrose

Stomata are open in _______ and _______: pump ___ and ______ into guard cells, this causes water to enter, cells swell and buckle, pore opens. Cells shrink and stomata are closed at night.

Endodermal

In the root, the _______ layer contains the Casparian strip

Casparian strip

A band of radial cell wall that is impregnated with a wax-like hydrophobic substance called SUBERIN

apoplast/transmembrane

The casparian strip prevents water movement through the _______ pathway and forces water across the cell membranes (___________ pathway)

SYMPLAST Pathway

a network of cell cytoplasm connected by plasmodesmata

APOPLAST pathway

a system of cell walls and intercellular spaces: it is the predominant pathway

TRANSMEMBRANE pathway

move across cell membranes

open

Under normal conditions, aquaporin channels are ____

close/serines

During drought, aquaporin channels ____ when ______ dephosphorylated