Plant Physiology Flashcards
name the systems in the plant organization
root system and shoot system
name the organs in the plant organization
roots, stems, leaves
what is so special about tissue systems?
they are unique to plants
- each organ consists of ALL 3 systems
- continuous throughout plant
shoot system
above ground (stems, leaves, flowers, fruit)
root system
below ground (root)
what are the functions for the root system?
- anchor to ground
- absorb minerals and water
- store carbs (and other reserves)
root hairs
- thin, finger-like extensions of root epidermal cells
- primarily near tip of elongated roots
stems
- plant organs bearing leaves and buds
- elongate and orient shoot to maximize photosynthesis
- elevate reproductive structures-increase pollen and seed dispersal
- green stems- limited photosynthesis
leaves
- main photosynthetic organ in vascular plants
- capture light, gas exchange
dermal tissue system
- outer protective covering
- 1st line of defense against physical damage, pathogens
what do herbaceous (nonwoody) plants have?
epidermis - single layer of tightly packed cells
cuticle - waxy coating - helps prevent water loss
what do woody plants have?
periderm (bark) replaces epidermis
what are the functions of dermal tissue?
- reduce water loss
- defend against insects
- root hairs: absorb water and minerals
- guard cells
what are guard cells?
- specialized cells in leaves
- regulate gas exchange
- open close stomata
ground tissue system
- most of plant
- includes cells specialized for: storage, photosynthesis, support, short distance transport
vascular tissue system
- transport materials throughout plant body
- mechanical support
- xylem and phloem
xylem
conducts water and dissolved minerals upward from roots
phloem
transports sugars from where made (mostly leaves) to where needed (usually roots ands sites of growth)
cohesion-tension hypothesis
when stomata open, water evaporates out of leaves = transpiration
cohesion creates tension (within the xylem) - like a soda straw
- water in stem xylem is pulled into leaves
- water in root xylem is pulled into stem
sequence water movement through xylem
soil -> root tissue -> root xylem -> stem xylem -> leaf xylem -> leaf ground tissue -> stomata -> atmosphere
how does phloem conduct dissolved sugar
translocation - bidirectional movement
- moves source -> sink
- made in leaves -> stored in root
- stored in roots-> throughout plant for growth and maintenance
source
area w/ excess sugar (e.g. leaf)
sink
area of storage or metabolism (e.g. roots)
pressure-flow hypothesis
- explanation for movements of sugars in phloem
- suggests translocation occurs via pressure gradient
how does pressure-flow hypothesis explain movement at source?
at source - high pressure - sugar loaded/pushed into phloem
how does pressure-flow hypothesis explain movement at sink?
at sink - low pressure - sugar pushed out of phloem
plasmodesmata
- cytoplasmic connections between plant cells
- allows molecules and ions to pass between cells
indeterminate growth
- occurs throughout life of plant
- continuous expect for dormant periods
- keep growing due to perpetually dividing, unspecialized tissue
- growth at meristem
primary growth
- all plants
- increase length by adding more cells
secondary growth
- only woody plants
- increase girth (circumference) of plant
hormones
organic compounds, act as chemical messengers
- control specific physiological responses in plants
- aka plant growth regulators
- hormones interact - hard to tell the cause (s) of one effect
tropisms
directional growth response to an environmental stimulus - often due to hormones
directional (postive)
grows toward stimulus
direction (negative)
grows away stimulus
what is the difference between taxis and tropism?
taxis - movement in response to stimulus
tropism - growth in response to stimulus
auxins
- 1st plant hormone discovered
- causes directional growth towards light
- group of natural and artificial hormones (many synthetic)
- triggers cell elongation
- main site of production: shoot -> root
sequence phototropism
light exposure -> auxin produced at tip -> auxin moves to shaded side, then down stem -> shaded side elongates -> plant bends towards light
what are some practical applications for auxins?
- herbicides
(1) synthetic auxins: 2, 4-D, 2, 4, 5-T
(2) Agent Orange: 50/50 mix
-can be sprayed to induce fruit development
cytokinins
- control of cell division and differentiation
- produced in actively growing tissue (roots, embryos, fruit …)
- stimulate cytokinesis (where they got their name0 but only WITH AUXIN
explain the experiment done with Auxin
cultured ground tissue
- no cytokinin -> cells got bigger
- cytokinin -> cells got bigger
- cytokinin and auxin - cells divided
abscisic acid (ABA)
- not related to abscission (falling of leaves)
- maintains seed dormancy
- increases likelihood that seed only germinates under suitable conditions
- spring rainstorm -> ABA washed out -> seed germinates
ethylene (C2H4)
- unique among plant hormones
- promotes fruit ripening
- also causes triple response to mechanical stress
- produced when growing shoot encounters obstacle
triple response
behavior to avoid obstacles
what are the three components to ethylene
- slow elongation
- thicken stem
- curve, grow horizontally
