plant biology Flashcards
indeterminate growth
grow forever
determinate growth
predetermined growth
adaptations to terrestrial environment
-waxy cuticle
-stomata
-vasculature
-pollen
-seeds
-support
-nutrient/water scavenging systems
-organ specialization
sporopollenin
biopolymer that resists harsh environments
challenges for land plants
-less buffered
-lack of structural support
-reproduction on land is hard
-water scarcity
-inaccessible nutrients in soil
how to deal with lack of structural support?
-already had rigid cellulosic cell walls
-already had a hydrostatic skeleton
-holdfast vs. rhizoids and then roots
-eventually can even modify stems/leaves to make tendrils
charophytes
green algae; closest relatives to land plants; contain sporopollenin
anthocyanins
uv protective pigment
hydrostatic skeleton
water pressure inside cells pushing against cellulose creating a “skeleton” to support vertical growth
liginin
very tough polymer used by plants to structurally reinforce certain cell walls (ie wood)
holdfast
a structure in algae that secures them to a particular spot
rhizoids
simple root-like structures in nonvascular plants that anchor them to a substrate but do not transport water or nutrients like true roots
key traits in plants that are absent in charophytes
-alternation of generations
-walled spores produced in sporangia
-multicellular gametangia
-multicellular, dependent embryos
-apical meristems
bryophytes
-gametophyte dominant
-waxy cuticle and in some cases stomatal pores
-lack vascular systems and structural support
-no true leaves
-flagellated sperm require a film of water to most to an egg
-no roots, just rhizoids
stomata
pores used for gas exchange
seedless vascular plants
-sporophyte dominant
-vascular tissue (xylem and phloem)
-well-developed roots and leaves
-sperm are still water-dependent
pollen grains
developed from the microspores; contain male gametophytes
pollination
the transfer of pollen to the part of a seed plant containing the ovules
evolutionary purpose for pollen
eliminates the need for a film of water; can be dispersed great distances by air or animals
germination
the pollen grain gives rise to a pollen tube that discharges sperm into the female gametophyte within the ovule
gymnosperm
cone-bearing plants; vascular seed plants that produce pollen and seeds in cones
seed
embryo and nutrients surrounded by a protective coat; produced by gymnosperms and angiosperms
angiosperm
flowering plants; vascular seed plants that produce flowers and fruit
sepal
part of a flower derived from highly modified leaves that is external to the petals; form the protective outer layer of the flower bud, but usually do not serve much purpose in the opened flower
carpel
the entire female reproductive structure of a flower
stamen
the male reproductive structure of a flower; consist of an anther where pollen is made and a stalk called the filament
petal
part of a flower derived from highly modified leaves that usually serves to visually attract animal pollinators by displaying colors
ovary
the female structure at the base of the carpal in a flower that contains the ovules and, following pollination, matures into a fruit
ovule
sac-like structures inside a flower’s ovary that hold the female gametophyte; following fertilization, they mature into seeds
anther
the meiotically-active part of the angiosperm stamen (male organ) that houses the microspores and eventually splits to release mature pollen
stigma
part of the carpal (female organ) of a flower; the wide tip at the end of the style which receives pollen and is the target site for pollination
style
part of the carpal (female organ) of a flower; a stalk extending up from the ovary and ending in a stigma; the organ that the pollen tube grows through to reach the ovules
receptacle
a swelling of the shoot at the base of a flower to which the flower parts are attached
pollen tube
the elongating cell of a pollen grain that contains the generative cell and grows down a flower’s style towards the ovules; delivers the sperm to the egg cell
embryo sac
the female gametophyte of an angiosperm located inside an ovule consisting of eight haploid cells
integument
the layered sporophyte tissue forming the outside of the ovule; within it is the megaspore and then the embryo sac; will mature into the seed coat after fertilization
micropyle
an opening in the integument of an ovule through which a pollen tube can enter and fertilize the embryo sac inside
double fertilization
the fertilization process of angiosperms where two sperm cells are formed, one fertilizing the egg cell to form the zygote and the other fertilizing the polar nuclei to form the endosperm
endosperm
triploid tissue within the angiosperm seed that stores nutrients for the developing plant embryo
cotyledon
seed leaves; embryonic structures in a seed that may be the first leaf-like structures to emerge; often play a role in nutrient storage or transport for the developing embryo
monocots
have a single cotyledon, coleoptile, and other traits; includes grasses and other relatives
dicots
have two cotyledon and other traits; eudicots
radicle
the embryonic root that germinates and gives rise to the plant’s root system
hypocotyl
embryonic shoot that emerges from a dicot seed; supports the cotyledons
coleoptile
hollow sheath-like structure found in monocots that emerges from the seed as the beginning of a shoot system, giving rise to the stem and first leaves
root functions
-anchoring the plant
-absorbing minerals and water
-storing carbohydrates
primary root
first root to emerge
lateral roots
grow laterally from the primary root; improve anchorage and water absorption; explore the soil
root hairs
small roots near the root tip which increase the surface area of the root
adapted root functions
-support
-storage
-air supply
-more
vegetative shoot
do not form flowers or reproduce; only there to perform photosynthesis and support the plant
primary growth
the development of new tissues in a plant through cell divisions that cause structures like roots and shoots to get longer and more branched
secondary growth
the development of new tissues in certain plants through cell division that cause roots and shoots to get wider and develop wood and bark
fibrous root system
a root system with manly finely divided roots and no main central taproot; usually the root system found in monocots
taproot
a root system with a large, usually thick primary root and many much smaller lateral roots branching from it; grows vertically down, deep into the soil; usually the root system found in dicots
stem
a stalk-like vascular part of the shoot system that supports leaves and flowers and can be modified for other functions; consists of nodes and internodes
nodes
the points at which leaves are attached; where vasculature comes together; may contain meristems
internodes
the stem segment between nodes
apical bud
growing shoot tip (apical meristem of the shoot); causes the elongation of a young shoot
axillary bud
(axillary meristem) structure that has the potential to form a lateral branch, thorn, or flower
axil
junction between the stem and leaf
petiole
leaf stalk by which the leaf connects to the stem
types of modified leaves
-spines
-tendrils
-reproductive (clone) leaves
-storage leaves (bulbs)
branching pattern of monocots
parallel veins
branching pattern of eudicots
branching veins
rhizome
an underground shoot that grows and branches horizontally, often helping a plant colonize an area
stolon/runner
an above-ground shoot that extends away from its parent plant, spreading horizontally over the ground with new plantlets growing along its length as an asexual reproductive strategy
tuber
an underground shoot that swells to form a storage organ; can also be used as a mean of asexual reproduction
trichome
hair-like structure on a plant’s epidermis
dermal tissue
protective, external layer of cells that functions as the barrier between the inside of the plant and the environment outside of it
ground tissue
tissue that is neither vascular nor dermal; photosynthesis, structural support, storage, etc.
vascular tissue
tube-like, rigid cells that move water and dissolves solvents
cortex
ground tissue that is external to the vasculature
pith
ground tissue that is internal to the vasculature
parenchyma cells
-have thin and flexible walls
-are the least specialized
-retain the ability to divide and differentiate
collenchyma cells
-grouped in strands and help support young parts of the plant shoot
-have thicker and uneven cell walls
provide flexible support without restraining growth
sclerenchyma cells
-rigid because of thick walls strengthened by lignin
-dead at functional maturity
xylem
conducts water and dissolved minerals upward from the roots to the shoots (only upward); dead cell walls that form tubing; wood
phloem
transports sugars from where they are made to where they are needed (up, down and horizontally); living cells
types of xylem
vessels and tracheids
sieve-tube elements
alive at functional maturity but lack organelles (only membrane and cytoplasm); transports sugars through osmosis; have companion cells
sieve plates
porous end walls that allow fluid to flow between cells along the sieve tube; connects the cytoplasm of sieve-tube cells
companion cell
nucleus and ribosomes serve both itself and its sieve-tube element
stele
vascular tissue of a root or stem
stele of the roots in angiosperms
solid cylindrical center
stele of the stems and leaves in angiosperms
divided into vascular bundles
vascular bundles in dicot stems
grouped in a ring
vascular bundles in monocot stems
sporadic
root cap
protects the apical meristem as it pushes through the soil
zone of cell division
site of primary growth of a root; includes the apical meristem
zone of elongation
growth pushes root tip into soil; fueled by water pressure within cells
zone of differentiation
mature root cells begin functioning within their role
quiescent center
part of a root’s apical meristem with inactive cell division to reduce the risk of mutations and take over the meristem’s role in case it develops serious genetic error
pericycle
layer of cells in the root lining the outside of the vascular cylinder; where lateral roots emerge
leaf primordia
part of a shoot bud; the undeveloped tissues that divide to produce new leaves; found around the apical meristem
axillary meristem
the buds located within the axil that are usually inactive but have the potential to produce a lateral shoot through primary growth
lateral meristem
regions of continuous growth in root and shoot tissue that are no longer undergoing primary growth; responsible for secondary growth, the formation of wood and bark
vascular cambium
a tissue of the lateral meristem that produces new xylem and phloem in secondary growth, creating wood; connects vascular bundles using ground cells and turning them into meristem cells
cork cambium
a tissue of the lateral meristem that produces more epidermis in secondary growth, creating bark
secondary phloem
accumulates outside of the vascular cambium
secondary xylem
accumulates inside the vascular cambium
water potential
Ψs + Ψp
Ψp
-positive if pumped
-negative if sucked
Ψs
-negative
-gets more negative as solute levels rise
-Ψs is 0 in pure water
pressure and osmosis
-water always moves from more positive to more negative Ψ
-the more dissolved solutes, the more negative Ψs
-the more dissolved solutes, the more water wants to move into an area by osmosis
transpiration
the movement of water up the xylem and into the atmosphere, driven by the evaporation of water through the stomata
translocation
the directed movement of water and dissolved sugars through the phloem
how the stomata controls transpiration
-transpiration is controlled by the plant opening and closing its stomatal pores
-guard cells on either side of the pore regulates whether it is open or closed
-opening and closing is controlled by the turgor pressure within the guard cells
-guard cells turgid: stomata open
-guard cells flaccid: stomata closed
-potassium ions play a role in
stomatal opening and closing
abscisic acid
a plant hormone produced in response to drought and other stress that causes stomatal closure
apoplast
outside the plant cell; cell wall space and the inside of the dead xylem vessels
apoplastic route
a pathway water and dissolved solutes can take into the root system by moving through interconnected cell walls, as opposed to the cytoplasm
symplast
inside the plant cell; the cytoplasm through the plasma membrane
symplastic route
a pathway water and dissolved solutes can take into the root system by moving through the shared cytoplasm of adjacent cells via the plasmodesmata
plasmodesmata
pores in the plant cell walls that allow the cytoplasm and cell membranes of neighboring cells to be continuous and joined together so that molecules can easily pass between cells
endodermis
a ring of cells in the root between the cortex and vascular bundle (stele) that acts as a barrier for molecules entering the xylem from the cortex
casparian strip
a ring of waterproof waxy material that encircles the cell walls of a root’s endodermis, thus blocking the apoplastic route
source
a part of a plant at a given time that has sugar to be exported to other parts of the plant, either because sugar is stored or produced there
sink
a part of a plant at a given time that requires sugar to be transported in, either because sugar is being accumulated or consumed there
sucrose-proton symporter
an active transport protein in sieve-tube cell membrane that co-transports sucrose into the cell against its concentration gradient and protons down their concentration gradient
uptake of mineral nutrients
-the endodermis regulates and transports needed minerals from the soil into the xylem
-water and minerals move from the protoplasts of endodermal cells into their own cell walls
-diffusion and active transport are involved in this movement from symplast to apoplast
-water and minerals now enter the xylem tracheids and vessel elements
chemiosmosis
powering something by coupling it to H+ movement across a membrane
bulk flow by positive pressure
in the sieve tube (phloem)
1) loading of sugar
2) uptake of water
3) unloading of sugar
4) recycling of water
9 essential macronutrients
-carbon
-oxygen
-hydrogen
-nitrogen
-phosphorus
-sulfur
-potassium
-calcium
-magnesium
8 essential micronutrients
-chlorine
-iron
-manganese
-boron
-zinc
-copper
-nickel
-molybdenum
rhizosphere
a sphere of influence in the soil created and maintained by a plant’s roots that hosts a specific community of beneficial microbes
rhizobacteria
free-living, root-associated bacteria living in a plant’s rhizosphere
endophyte
nonpathogenic bacteria that live between the cells of host plant tissues; mutualistic beneficial relationship
how endophytes and rhizobacteria help enhance plant growth
-produce chemicals that stimulate plant growth
-produce antibiotics that protect roots from disease
-absorb toxic metals or increase nutrient availability
root nodule
round, knobby swellings on the roots of legume plants that house nitrogen-fixing rhizobium bacteria
mycorrhizae
a type of mutualistic relationship between plants and certain root-associated fungi
-the plant provides the fungus with
carbohydrates manufactured
through photosynthesis
-fungus provides mineral nutrients
like nitrogen and phosphorus
-the fungus increases surface area
for water uptake and mineral
absorption
-the fungus secrete growth factors
that stimulate root growth and
branching
mesophyll
the ground tissue within a leaf that does most of a plant’s photosynthesis
spongey mesophyll
the type of mesophyll between the palisade mesophyll and the lower epidermis which has cells packed less densely with many air spaces in between
palisade mesophyll
the type of mesophyll just under a leaf’s upper epidermis which has rectangular and closely packed cells
coevolution
two types of organism both evolving traits over time that make them better participants in mutually beneficial behavior, often leading to an exclusive partnership
fruit
mature ovary of a flower; protects the enclosed seeds and aids in the dispersal by wind or animals
