1. Arrangement of tissues in plant organs (stems, leaves, roots)
- arrangement of tissues is related to organ function
Stems:
functions
a) support and positioning of leaves
to maximize photosynthesis
b) transport
- from roots to leaves, leaves to roots, etc.
2. shoot apical meristem multiple functions
a) increase stem length
b) form leaf primordia
c) form bud primordia
nodes
internodes
bud primordia develop into axillary buds
4. - in monocots:
- vascular bundles “scattered”
- ground tissue = ground parenchyma
no pith and cortex
5. secondary growth in stems:
- occurs in some dicots
- requires lateral meristems
vascular cambium
cork cambium
- process begins when lateral meristems develop
- vascular cambium develops as a single layer of
cells;
- in ring passing through and between vascular
bundles
7. cork cambium develops as a ring within the cortex
- cells divide, producing cork cells
at stem surface
8. resulting stem structure:
- periderm at surface
- cortex
- continuous layer of secondary phloem
- vascular cambium
- continuous layer of secondary xylem
- pith
9. lateral meristems continue to function;
new layers of periderm, secondary phloem, and secondary xylem
are formed
– adds to stem width
wood
bark
hardwood
softwood
12. Leaves:
major function = photosynthesis
- structure designed to optimize photosynthesis
attached to stems at nodes
generally consist of
1) blade
2) petiole
sessile leaves
have no petiole
- may also have leaf sheath
13. leaf blade may be undivided (simple leaf)
or
the leaf blade may be divided into leaf segments (compound leaf)
palmately compound leaf
pinnately compound leaf
14. leaf phyllotaxy = arrangement of leaves on the stem
- can influence the ability of leaves to absorb light
spiral phyllotaxy –
opposite phyllotaxy –
16. Leaf Anatomy:
each leaf consists of:
epidermis
mesophyll
veins
epidermis - upper epidermis and a lower epidermis, covered with cuticle
- single layer of epidermal cells,
some guard cells,
possibly some trichomes
17. the mesophyll is photosynthetic ground tissue
- must absorb light energy and CO2
- light energy absorbed as it passes through leaf
- CO2 enters at stomate, diffuses to mesophyll cells
in dicots, leaf mesophyll in two layers:
palisade mesophyll
- specialized for light absorption
20. vascular tissue - in veins
- each vein contains some xylem and some phloem
veins – a few large veins and many smaller veins
large veins create “venation pattern”
e.g., netted venation
- typical of dicots
22. in each vein,
xylem on upper side;
phloem on lower side
each vein surrounded by a bundle sheath
veins required to
1) bring in water and minerals
2) collect metabolites for transport in phloem
24. two common root systems:
1) a taproot system
- one major root (= the taproot) with many lateral roots
(root branches)
- the taproot originates from the radicle (in the embryo)
- seen in most dicots
- advantages
25. 2) fibrous root system
- many adventitious roots
, plus many lateral roots
- often spreads horizontally; does not grow deeply into soil
- common in monocots
advantages:
26. for either type of root system,
continued new growth is essential to function
1) to reach new sources of water & minerals
2) to balance increases in shoot size
3) compensates for the loss of absorptive ability in older
roots
- most absorption occurs at root tips
(where root hairs are)
27. Root growth:
- occurs at root tip
- every root tip has a
1) root cap
2) region of cell division
3) a region of elongation
4) a region of maturation
28. in dicots, the mature root includes:
epidermis
cortex
vascular tissue, in central cylinder
in monocots,
- pith is present in the center of the
vascular tissue