BIO151 UNIT 3 CH. 35 FROM HAZEL

bud

an underdeveloped/embryonic shoot

normally occurs in the axil of a leaf or at the tip of a stem

guard cells

specialized epidermal cells involved in gas exchange

2 of these flank the stomatal pore & regulate the opening/closing of the pore

periderm

(in woody plants!)

protective tissues that replace the epidermis in older regions of the stem & roots

cuticle

a waxy epidermal coating that helps prevent water loss in leaves & most stems

region of elongation

location: a few mm behind the tip of the root

where most of the growth occurs as root cells elongate, sometimes more than 10x the original length

cell elongation in this zone pushes the tip father into the soil; root apical meristem keeps adding cells to the younger end of the zone of elongation

zone of differentiation/maturation

cells complete their differentiation & become distinct cell types

late/summer wood

in temperate regions, wood that’s produced later in the growing season

has thick-walled cells that don’t transport as much water but provide more support

early/spring wood

in temperate regions, wood that develops early in the spring

usually has secondary xylem cells w. large diameters + thin cell walls

structure maximizes delivery of water to leaves

lignin

an indigestible strengthening polymer that accounts for more than 1/4th of dry mass of wood

present in all vascular plants but not bryophytes

internodes

the stem segments between nodes

sieve plates

refers to the end walls between sieve-tube elements

has pores that facilitate the flow of fluid from cell-to-cell along the sieve tube

mesophyll

refers to the leaves ground tissue

sandwiched between upper & lower epidermal layers

consists of parenchyma cells specialized for photosynthesis

in many dicot leaves, found in layers palisade & spongey

petiole

stem that attaches the blade of the leaf to the rest of the plant

blade

flat, photosynthetic part of the blade

taproot system

facilitates anchorage of plant in the soil

prevents toppling, allowing the plant to grow taller & access more favorable light conditions, may provide advantages for seed/pollen disposal

can be specialized for food storage

root hairs

thin, finger-like extensions of root epidermal cells that emerge from the tips of elongating roots, where absorption of water & minerals take place

nodes

points at which leaves are attached, each stem consists of an alternating system of these points

3 types of tissue in plants

ground, dermal, vascular

rhizome

a horizontal shoot that grows just below the surface

vertical shoots emerge from axillary buds

pneumatophores (air roots)

produced by trees that inhabit tidal swamps

projects above the water’s surface at low tides, which enable the root system to obtain oxygen (which lacks in thick, waterlogged mud)

lateral roots

first roots to branch off from the primary root

these can also branch, increasing surface area of the roots & increasing ability to acquire resources such as water & minerals

primary root

originating in the seed embryo, the first root to emerge from a seed,

branches to form lateral roots

apical bud

refers to the growing shoot tip

most of the growth of a young shoot is concentrated near this area

stele

collectively refers to the vascular tissue of a root or stem

“strangling” aerial roots

some seed germinate in the crevices of tall trees

these roots grow to the ground, wrapping around the host tree & objects

shoots grow upward & shade out the host tree, killing it

sapwood

refers to the newest, outermost layers of secondary xylem that still transport xylem sap

allows a large tree to survive even if the center of the trunk is hollow

palisade mesophyll

located beneath the upper epidermis

consists of 1 or more layers of elongated, chloroplast-rich cells that are specialized for light capture

companion cell

found alongside each sieve-tube element, connected via numerous plasmodesmata

the nucleus & ribosomes serve itself and adjacent sieve-tube element

in some plants, these cells help load sugars into the sieve-tube element, which then transport the sugars to other parts of the plant

dendrochronology

science of analyzing tree growth ring patterns

growth ring

appears as cross sections of most tree trunks & roots

vary in thickness, depending on seasonal growth

trees typically grow in wet & warm weather; growth halts in the cold & dry weather

purpose of the stomata

allows exchange of CO2 & O2 between the surrounding air & the photosynthetic cells inside the leaf

regulates CO2 uptake for photosynthesis

are major avenues for the evaporative loss of water

perrenials

refers to plants that live for many years,

shrubs, trees, and some grasses

stoma

refers to the stomatal pore or to the entire stomatal complex

consisting of a pore flanked by the 2 specialized epidermal cells (guard cells)

adventitous

a plant organ that grows in an unusual location, such as roots arising from stem or leaves

tubers

enlarged ends of rhizomes or stolons, specialized for storing food

what parts of the plant display determinate growth?

leaves, thorns, & flowers

secondary growth

woody plants also grow in circumference in the parts of stems & roots that no longer grow in length

refers to growth in thickness & made possible by lateral meristems

biennials

requires 2 growing seasons (2 years) to complete their life cycle

flowering & fruiting only in the second year

annuals

completes life cycle in a single year or less, includes most stable food crops & wildflowers

dies after producing seeds & fruits, enabling the plant to transfer the maximum amount of energy to reproduce

stolons

horizontal shoots that grow along the surface

these “runners” enable a plant to reproduce asexually as plantlets grow from axillary buds/along each runner

determinate growth

growth stops after a certain size is reached

functions of the stem

elongate & orient the shoot in a way that maximizes photosynthesis by the leaves

elevates reproductive structures, facilitating the dispersal of pollen & fruit

green ones may also perform a limited amount of photosynthesis

root cap

thimble-like structure that protects the apical meristem as the root pushes through soil

is produced by the root apical meristem

secretes a polysaccharide slime that lubricates the soil around the tip of the root

types of vascular tissue

xylem & phloem

indeterminate growth

plant growth isn’t limited to an embryonic or juvenile period, instead occurring throughout the plant’s life

what information can be obtained from the growth rings?

by counting them, age can be determined

thick rings indicate a warm year, thin rings indicate a cold year

this can be used to study climate change

trichomes

specialized epidermal cells found in shoots, composed of outgrowths (cacti spikes)

reduces water loss & reflects excess light

can defend against insects through shapes that hinder movement or glands that secrete sticky fluids or toxic compounds

primary growth

refers to growth in length

allows root to extend throughout the soil & shoots to increase exposure to light

in non-woody plants, it produces all or most of the plant body

meristems

undifferentiated tissues found in plants

contain cells that can divide, leading to new cells that elongate & become differentiated

allows growth to occur throughout the plant’s life (indeterminate growth)

bundle sheath

each vein of a leaf is enclosed by this protective layer of cells

regulates the movement of substances between the vascular tissue & mesophyll

compound leaf

the blade consists of multiple leaflets

leaflet has no axillary bud at its base

in some plants, each leaflet is further divided into smaller leaflets

may help confine invading pathogens to a single leaflet, rather than allowing them to spread to the entire leaf

simple leaf

has a single, undivided blade

some are deeply lobed

heart wood

as a tree/woody shrub ages, older layers of secondary xylem no longer transports water & minerals (xylem sap)

these layers are closer to the center of a stem or root

generally darker than sapwood bc of resin & other compounds that permeate the cell cavities & help protect the core of the tree from fungi + wood-bearing insects

dermal tissue

serves as the outer protective covering of the plant, first line of defense against physical damage & pathogens

types: epidermis, cuticle, periderm, guard cells, trichomes