FRST 200 exam

Xylem

-One direction

-water and minerals

-has tracheids, vessel elements, and xylarly fibers

Tracheids

-Dead at maturity

-within xylem

-thinner than vessels

-capillary action

-found in every secondary growth plant

-secondary cell walls for support

Vessel elements

-Secondary cell walls for support

-dead at maturity

-ONLY FOUND IN ANGIOSPERMS

-stacked atop each other to create vessels

-has perforation plate

Xylarly fibres

-No cell membrane, just cell walls

-FOUND IN ANGIOSPERMS

Phloem tissue

-Transports sugars, hormones, proteins, etc.

-Multidirectional, from source to sink.

-Has sieve cells, sieve tube elements, albuminous cells, companion cells, and phloem fibres

Sieve cells

-Like tracheids

-alive at maturity but NO NUCLEUS

-no pits but has sieve spots for sugars to go in and out

Albuminous cells

Acts to load and unload sugars from sieve cells,

Sieve tube elements

-Alive at maturity

-NO NUCLEUS

-ONLY IN ANGIOSPERMS

-stacked to create sieve tubes which are more efficient and can start and stop sugar flow themselves

Companion cells

Do basically the same as albuminous cells

Phloem fibres

-Thick cell walls

-dead at maturity

-ONLY IN ANGIOSPERMS

-provide support

Secondary growth

-Increases girth of plant

-creates wood

-needs vascular cambium to be continuous

Hardwood

Angiosperms, complex, has holes for water + air,

Softwood

Gymnosperms, less complex

Vascular cambium

- Developed from procambium

- wedged between the xylem and phloem

- needs to be continuous for secondary growth

- interfascicular cambium bridges gaps between facicular cambium - why damage to tree can inhibit secondary growth, a lateral meristem

Fusiform + ray initials

- Ray initial through xylem + phloem

- divide inwards (XYLEM) and outwards (PHLOEM)

- called periclinal division - parallel to stem growth

Secondary phloem

- Produces inner bark

- gets pushed to outer edges from fusiform + ray initials so needs to be replaced in annual growth

Secondary xylem

- grows inwards

- differs based on tree type

- angiosperms : tracheids, vessel elements(pores), fibers, ray parenchyma

- gymnosperms : tracheids, rays, sometimes resin canals

Annual growth

- Can be seen in the rings - categorized by early wood and late wood

- needs time of little to no growth

Early wood

- formed early in the growth year

- xylem formed early

- tracheids and vessel elements (lumens) long to maximize water transport

Late wood

- smaller lumens (tracheids + vessel elements)

Sapwood

- xylem that is actively transporting water

- closest to surface

- ray parenchyma still alive (xylem dead tho womp womp, think cheeky quirky little living mole inside husk of dead xylem)

Heartwood

- not transporting water actively

- ray parenchyma dead

- stores compounds to drive off fungi, virus, etc

Reaction wood

- uneven vascular cambium growth in response to gravitropism

- 2 types - tension wood (angiosperms) and compression wood (gymnosperms)

Tension wood

- Angiosperms

- pulls the stem up, on upper side of tree

- tension strength high

Compression wood

- Gymnosperms

- on lower side to push stem upright

Root secondary growth

- no rings

- pericycle cells complete vascular cambium

Taproot system

- One main vertical root that grows more lateral roots off it

- primary flow

- big ol anchor

- goes deep

- will take a taproot in me to pass this

Flatroot system

- slow taproot growth, lateral roots go brrr

- shallow roots

- adapted for shallow or poor soils

Heartroot system

- mix of taproot and flatroot

- all moderately deep

Root buttressing (ha)

- if vascular cambium not even around root and root not stable, can make i - beam looking construct to limit horizontal motion

Bark

- epidermis from primary growth not ****ing good enough get your shit together epidermis more like epidernotgonnamis it when its gone

- needs more support, tree makes second better child with the cork cambium

Cork cambium

- shoved in just below epidermis

- divides inward AND outward

- when inwards - makes phelloderm

- when outwards makes cork / phellem

- divides sideways

- makes more cork to keep up with stem girth (i wish haha am i right haha)

Cork / phellem

- cells filled with wax to prevent water loss

- dead at maturity

- trees such as the cork oak have single periderm with extra thick cock i mean cock i mean cock i mean cork so taking layers off does not kill the tree

Phelloderm

- made of parenchyma cells

- alive at maturity

Lenticel development

- cork cambium divides enough to create bulges underneath stomata

- growth causes bulge to split

- allows for passive gas exchange

- maintained throughout life cycle of the plant

Bark development

- made of periderm and secondary phloem

In young trees

- smooth bark - periderm continuous, bark stretching with annual growth

In mature trees

- periderm splits, can be discontinuous

- cork cambium arising continuously from old secondary phloem

- flakey or scaly

Girdling

- kills trees cause cuts off phloem + sugar transport

- prevents new cork cambium

Root grafting

- friction between roots of same species can damage root vascular cambium, graft the two roots together

Active growing season

- Shoot apical meristem produces phytomers, increases height

- axillary meristems create branches

Syllaptic branches

- buds that grow in SAME season they were produced

- if you can see a leaf below the branch it is a syllaptic branch

Proleptic branches

- from lateral buds

- branches NOT grown in same season ie no leaf underneath

- has bud scale scars

Lateral buds

- follow leaf arrangement - grown at nodes

- can remain for multiple growing seasons

- can take over should damage occur to canopy

Determinate growth

- bud set occurs early

- creates all the growth for the following season

- cue for bud set is developmental

Indeterminate growth

- bud set later

- creates only some of the growth for the next season

- cue for bud set is environmental

Growing season order ++++++++COME BACK TO+++++++++

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- bud set

- cold hardiness develops

- leaf senescence

- chilling requirement

- quiescence

- heat sum requirement

Environmental cues that cause bud set

- extreme heat

- drought

- nutrient stress

- cold

- pathogen/herbivory

- changing daylength ie CRITICAL PHOTOPERIOD

Phytochrome in bud set role

- Pfr = active phytochrome, under high quality red light

- Pr = inactive, under far red or darkness

- sets threshold of critical photoperiod

Critical photoperiod

- determined genetically

- the amount of daytime vs CONTINUOUS nighttime a plant needs to realize its gotta set that bud

- also differs based on latitude

- plants in north / high elevations set bud early

- generally tracks timing of frost, highly selective

Lammas growth

- a second growth after bud set before full dormancy if conditions are insanely good

- adds itty bitty little smidge of more growth as a treat

- both terminal and lateral buds can undergo Lammas growth, can create forking by making another leader

Leaf senescence

- deciduous canopy would lose too much water in winter so the tree axes it

- induced by long nights too BUT critical photoperiod for this is shorter ie happens later in the year

- controlled via hormones

- nutrients like nitrogen and chlorophyll broken down in leaf and reabsorbed into inner bark by phloem

Colour change in leaf cause

- senescence causes chlorophyll to stop getting produced and get yoinked back up

- carotenoids are unmasked, thats what the point of the mask is, shows the yellows and oranges

- anthocyanin, the red, is produced

Anthocyanin

- the red pigment

- like sunblock

- produced in exposed canopy

Abscission zone

- base of petiole

- split into two layers - the separation layer and the protective layer

Separation layer

- starts outside, progresses inwards, girdling leaf

- cuts off tissues ending with the xylem

Protective layer

- on the tree

- suberin / wax seals off tissues

- forms waterproof barrier to keep innards in, plugging xylem

Abscission process

- middle lamella (gunk made of pectin) between separation and protective layers is digested

- cells in separation layer expand

- zone is weakened so gravity or wind or anything can yank that shit off

Cladoptosis

Whole branch abscission, tree just says **** this whole ass thing

- when a branch is no longer considered useful, ever look up and see where branches were on a tall tree but aren't anymore? Yea its this

Cold hardiness

- resistance to damage from freezing

- develops right after bud set pre leaf senescence

- induced by photoperiod

- begins with sugar content in bud GOING UP

- highly selective cause only plants that survive winter can reproduce

LT50

- the measurement for cold hardiness

- lethal temp at which 50% of tissue is injured or 50% of species dies

- LT50 decreases as cold hardiness increases (ie can withstand colder temps)

- max LT50 through Jan - Feb

Extraorgan freezing

- ice created around bud by bud scales + stem tissue

- protective ice

- keeps tissues inside from freezing

Deep supercooling

- most common in milder areas

- functional down to -40 degrees C

- water remains in cell below freezing point

- plant INCREASES solute concentration in cell, isolating cell from cell nucleating agents

Freeze dehydration

- water yoinked out of cells

- makes ice in controlled way between cells outside cell walls

- means no ice can be made within cell

- most common in areas with severe winters

Chilling requirement

- amount of time at cool temps, approx 1.5 C

- differs by species / population

- goes into quiescence (like the snooze button)

Heat sum requirement

- ends quiescence

- certain number of days above about 5 degrees C

Interaction of chilling + heat sum

- buds need both + respond to both

- warmer winters means longer time taken to hit chilling req so therefore higher heat sum req needed