BIO410 Secondary Growth

what are residual procambium cells

a region of dividing cells in between the xylem and phloem

how is secondary growth initiated

auxin is drained from buds as plant gets older

what do the residual procambium cells and the pith ray parenchyma cells divide to form into

a ring of vascular cambium VC

what are residual procambium cells

area of dividing cells in between xylem and phloem

what are pith ray cells

large parenchyma cells in between the bundles

what is the vascular cambium

a lateral meristem, a ring of meristematic cells

what does the vascular cambium differentiate/specialize from

residual procambium and the pith ray parenchyma

where is 2º xylem and 2º phloem produced from the VC

2º xylem to the inside - conducts water and nutrients

2º phloem to the outside - conducts sugars

why are the 2º xylem and 2º phloem produced in a ring

because the VC is in a ring

tissues that develop from the vascular cambium are

secondary

tissues that develop from the apical meristem are

primary

what are the sugar conducting cells in the 1º and 2º phloem

STM and CC

what are the water/ion conducting cells in the 2º xylem for a flowering plant? conifer?

flowering plant - xvm and tracheids

conifers - tracheids

what is 2º xylem (wood) conducting

water and minerals

what is heartwood

the dark center of the tree

what compound is the dark color in heartwood due to

tannin

what is tannin and what are its functions

secondary metabolite

anti predation, fire retardant

what is dendrochronology

the science or technique of dating events, environmental change, and archeological artifacts by using characteristics patterns of annual growth rings in timber and tree trunks

what are significant uses of dendrochronology

look at climate change over time with the help of annual rings, also helpful in observing changes in water uptake

how do scientists use tree rings to study climate change

bigger rings indicate larger XVMs/tracheids due to increased water uptake. smaller rings indicate smaller XVMs/tracheids due to decreased water uptake. water levels can indicate climate change.

how does the VC increase in diameter every year

dividing by mitosis

why does the VC need to increase its diameter

the wood (2º xylem) pushes against the VC, which stimulates it to enlarge

how can you count the annual rings in trees

each annual ring has a spring and summer season, so one spring and one summer represents 1 year

can monocots make rings of wood

no because the vascular bundles do not form a ring, they are scattered all over the stem

palm trees are monocots, so how do they get so tall without making wood for support

the scattered vascular bundles and prop roots (fibrous roots) support palm trees

hardwoods

flowering trees/shrubs that make wood

wood contains XVMs and tracheids

softwoods

conifers

tracheids only, no XVMs

what evolved first, softwoods or hardwoods

softwoods because they have more ancestral traits

are tracheids a derived or ancestral trait, relative to XVMs

ancestral trait

do all trees make annual rings

no

do trees have well developed annual rings in tropical environments

no because it is wet all the time, difficult to age trees

when does bark form

after wood forms

what is the cork cambium

a meristem that forms in the cortex parenchyma (right below the epidermis)

where does cork cambium form cork cells

to the outside of the tree, replacing the epidermis and protecting the tree

are the cork cambium cells alive or dead

alive because they are meristematic

are cork cells alive or dead

dead because they are made of suberin, they are completely impermeable

what are rays

cells that run horizontally through the wood, made by the VC

what is the function of rays

transport tannins to the tree center, makes pine needles/bark appear orange or red

does the heartwood coduct water and nutrients

no

what are lenticels

organs for gas exchange, allows bark to breathe

where are cork tress native to and what commercial product is harvested from them

native to Portugal, Spain, and Italy

product - cork (wine stoppers, flooring, insulation)

how is the bark in cork trees removed and processed

through a sustainable process called stripping, the bark along the tree’s trunk is cut to take out large, flat sheets without penetrating the inner bark. these sheets are then left to dry for 6 months, then it is boiled

where are bristle cone pine trees found

utah, nevada, colorado, giza

what are bristle cone pine trees known for

making cork

how old is the oldest living bristle cone pine tree today

over 5000 years old

what happened to the oldest bristle cone pine tree

accidentally cut down by a graduate student

what did scientists discover at the very tops of coast redwood forest unexpectedly

they discovered a canopy system with a very unique environment

name an important tree that requires fire to open its cones

giant sequoia

what is the benefit of fire to plants

giant sequoia has serotinous cones or seeds that only open and disperse after being exposed to high temperatures, ensuring regeneration after a fire

what is a prescribed/control burn

fire management technique used intentionally to reduce excess vegetation (fuel buildup) encouraging the growth of trees that require fire to open its cones, and decrease the risk of uncontrolled wildfires

describe how prescribed/control burns are a return to indegenous land practices

many Indigenous cultures historically employed fire as a tool for land stewardship, and their practices have been recognized for their ecological benefits

what is the danger in letting fuel build up

increased wildfire risk, higher fire intensity, long-term ecological damage, and water pollution

what is cultural burn

a form of prescribed burning that Indigenous peoples and local communities have used for generations to manage the land and promote ecological health

california fan palm

the only native palm tree to california, grows near waterways and arid regions

which animals survive due to california fan palms

birds (woodpeckers, hawks, eagles)

mammals (bats and rodents)

insects (pollinators and palm weevils)

reptiles and amphibians (snakes, lizards, frogs)

temperate deciduous forest

forests that are dominated by broad leaf trees that are deciduous in cold winters

ex. sugar maple

desert biomes

less than 25 cm of rain per year

ex. joshua tree and the mojave desert

african savanna

large expanses of grasslands by trees with water saving features

ex. boabab trees