Upload
erik-farmer
View
215
Download
0
Embed Size (px)
Citation preview
Leaf anatomy
Leaf anatomy• Leaves start as
outgrowths from apical meristem: leaf primordia.
Leaf anatomy• 3 primary
meristems– protoderm:
becomes __________
– procambium: becomes ___________
– ground meristem: becomes ____________.
Leaf anatomy• Epidermis:
note cuticle, stomata
• Veins with vascular tissues (__________
• __________)• Supply water
& nutrients, remove sugars for transport elsewhere.
Leaf anatomy• Mesophyll
– Parenchyma tissue layers (palisade and spongy: do ____________.
Monocot vs dicot anatomy• Stem: Dicot with bundles __________. Pith
and cortex present. • Monocot: scattered vascular bundles. No
_______________.
Monocot vs dicot anatomy• Root: Dicot, < 6 phloem patches, no pith
Monocot vs dicot anatomy• Root: Monocot, many _____________, pith
present
Monocot vs dicot summary• Note root system type: dicot often with single
major root axis (taproot system), monocot lacking this (fibrous root system)
Plant Growth Phenomena• Hormones: molecules produced in small
amounts that change _________________
• _________
• Can inhibit or stimulate processes to occur
• 5 major types: – auxins– cytokinins– gibberellins– ethylene– abscisic acid
Auxins• Promote stem
elongation and growth
• Example, ___________. Bending of stem toward light
Auxins• Also involved in ______________: suppression
of lateral meristems by apical meristem
Auxins• Can stimulate production of
______________ roots (roots produced on stem or leaf)
• Useful in rooting cuttings (asexual plant reproduction)
Cytokinins• Stimulate cell division where auxin is
also present
• Acts as ____________ hormone (keeps detached leaves green).
Gibberellins• Promote stem elongation
• Mutant plants with low amounts are _________ (internode lengths short)
Ethylene• Promotes fruit ripening
• Stimulates ____________ (dropping) of leaves, flowers
Abscisic acid• Induces formation of
winter buds (bud scales, dormant meristem)
• Involved in opening and closing of _____________
• Can cause seed dormancy
Other plant growth phenomena• Gravitropism:
response of stem/root to gravity
• Stems bend away from gravity (___________ gravitropism)
• Roots bend toward gravity (_________ gravitropism)
Other plant growth phenomena• Mechanism
unclear. May involve ________ ________ called statoliths (in root cap of root, in parenchyma cells of stem)
Other plant growth phenomena• Thigmotropism: response
of plant to __________• Examples: Many tendrils
grow toward stimulus and wrap around object
Turgor movement• Not growth: involves
loss of water pressure (turgor pressure) in some cells
• Can be reversed• May involve rapid
movement (electrical signal)
• Ex, sensitive plant
QuickTime™ and aCinepak decompressorare needed to see this picture.
Flowering• Some plants use daylength as
flowering cue
• Can measure length of night (photoperiod) by pigment called ______________
Flowering• Long day plants:
flower when night is ________ than some critical time
• Short day plants: flower when night is _______ than some critical time
• Day neutral plants: don’t use photoperiod as flowering cue
Flowering• Use: Can make some plants bloom when we
want them• Ex, poinsettia. A short-day plant that growers
make flower for Christmas holidays.
Plant transport• Phloem: sugars and water (often from leaf to root)
• Xylem: water and minerals from root to shoot
• Movement driven by _____________: measure of tendency of water to move from one place to another
Plant transport• Water potential is affected by:
– solutes (high solutes = ______ tendency to move)– pressure (high pressure = ______ tendency to move)– tension (pull: high tension = ______ tendency to move).
Water transport• Xylem: water and minerals from root to shoot
• How much of water remains in plant? <____%!
Water transport• Transpiration: evaporation of water from leaves
• Driven by _______ from leaves. Water under tension. Water potential high in soil and low in air.
Water transport• Driven by pull
from leaves. Water under tension. Water potential high in soil and low in air.
Water transport• Transpiration greatly controlled by stomata
• Stomata open in ________ but can close if plant lacks sufficient water.
Stomata!
Sugar transport• Phloem: sugars and water
• Flow from ______ to _____
• Pressure flow mechanism
Sugar transport• Source: lots of sugar
dissolved in water. Generates pressure as water flows in to _______ sugar
• Sink: little sugar dissolved in water. Low pressure as water flows out
• Creates ___________ gradient that moves fluid thru sieve tubes.
Sugar transport• Result: sugar flows to
wherever demand is high
Secondary Growth
Secondary Growth• Two types of growth• Primary growth: up and
down. Generated by apical meristems. Form _________ tissues
• Secondary growth: growth in girth. Generated by lateral (secondary meristems). Form __________ tissues.
• All plants do primary growth• Woody plants do __________
growth
Secondary Growth• Lateral meristems
– 1) ______________: makes new phloem and xylem
– Called ________ phloem and xylem tissues (vs. primary phloem and xylem made directly from procambium)
– Function: xylem takes water + minerals to leaves, phloem takes sugars to roots
Secondary Growth• Lateral meristems
– 2) ___________: makes new cell type, cork cell. Cork cells with primary wall impregnated with waxy material (_______). Dead at maturity. Forms waterproof layer on outside of body to replace epidermis.
– _________: Tissue composed of cork cells and made by cork cambium. Also is a secondary tissue.
Secondary Growth• Stem cross section
Secondary Growth• Vascular bundles contain __________________
• Located between primary xylem and phloem
• Meristematic: can still do _______________
Secondary Growth• Residual procambium cells start to divide• Produce new cells ______________
Secondary Growth• Parenchyma cells between bundles also start to divide• Together form solid ring of cells, all dividing laterally• This is __________________
Secondary Growth• Vascular cambium makes secondary xylem on
__________, secondary phloem on __________
• Note how cambium moves outward over time
Secondary Growth• Note arrangement of primary phloem and secondary
phloem, primary xylem and secondary xylem
Secondary Growth• Secondary xylem may contain:
– 1) Vessel elements
– 2) Tracheids
– 3) ____________
– 4) Fibers
• Secondary phloem may contain:– 1) Sieve tube elements
– 2) Companion cells
– 3) Parenchyma
– 4) ___________
Secondary Growth• Two
Secondary Growth• Later secondary growth
Secondary Growth• First cork cambium: Forms under ___________
Secondary Growth• Cork cambium: Makes files of cork cells to
outside. Forms first __________. Epidermis cut off from rest of stem and dies.
Secondary Growth• Problem: cork cells are
dead at maturity. Cork layer cannot _________ as vascular cambium continues to grow.
• Solution: form new ______ ______ in cortex under old one
• After time, several __________ build up (yellow lines). Newest (inner) one cuts off water to layers beyond it and they _______.
Secondary Growth• Periderm replaces epidermis. How get _______
into stem?
Secondary Growth• Lenticels: Loosely packed __________.
Allow oxygen to diffuse into stem to support living cells there.
Secondary Growth• Note ____ made by
vascular cambium: Form ________ transport system (often parenchyma cells)
• In phloem: phloem ray
• In xylem: xylem ray (wood ray)
Secondary Growth• In temperate zone, cambium activity varies
between _____ and ______ in growing season• Spring: big cells (_______ wood). • Summer: small cells (_______ wood).• Form growth ring (tree ring): one season’s growth• Ex, pine (mostly tracheids)
Secondary Growth
• Ex, oak (note vessels, thick-walled _________)
Secondary Growth• Young tree section: Note rays here (phloem and
xylem)
• Also note growth rings: early and late wood
• How old was this stem when cut?
Secondary Growth• In older tree: wood
is secondary xylem
• Heartwood: old non-functional xylem
• ________: younger often functional xylem
Secondary Growth• Bark: From vascular
cambium outward• ___________: From
current cork cambium outward (all is dead)
• __________: From vascular cambium to current cork cambium. Contains functional secondary phloem
Secondary Growth• Removing inner bark
is deadly: girdling tree often will kill it
• Why? Roots ______• Why? No ________
from leaves.
Secondary Growth
• Flow chart, showing how primary and secondary tissues develop in stem
Secondary Growth• Note that roots of woody plants also do secondary
growth
• Vascular cambium forms from __________
• First cork cambium forms in _____________.
Secondary Growth• So outer cortex and epidermis are sloughed off
and lost
Uses of Growth Rings
• 1) Fire frequency
• Break in bark (_________) allows fire to burn through vascular cambium into wood
• Leaves burned layer
• If tree survives, can have record of fires in wood.
Ponderosa pine, WY
Uses of Growth Rings
• 1) Fire frequency
• Helpful information when trying to determine “natural” frequency of fires for managing forests.
Uses of Growth Rings• 2) Climate patterns (___________________)
• Width of rings can indicate growth conditions for tree (rainfall, etc.)
• Can reconstruct climate information
• Oldest reconstructions go back 8,000 yr B.C.
Uses of Growth Rings• 2) Climate patterns
• Oldest reconstructions from bristlecone pine wood go back as far as ________ yr B.C.