Biology 11 Reviewer

2nd Long Exam

Roots
Germination
o Epigeal cotyledons and shoot apex emerge
while hypocotyl elongates
o Hypogeal cotyledons remain within testa
and hypocotyl elongates only slightly or not at
all
Types of root system
o Taproot system
o Fibrous root system
o Adventitious roots (cassava, sweet potato)

pericycle origin of phloem and xylem

xylem differentiation in primary roots
o from periphery inwards (centripetal)
o exarch
protoxylem first before metaxylem

Casparian strips
o in endodermis
o impermeable to small molecules to prevent
diffusion of ions from the apoplast within the
vascular column
Lateral root primordial
o continue to develop and grow out through the
cortex and ruptures through the epidermis
o becomes a fully developed root by the time it
emerges

As cells enlarge, they begin to show

1. differences in wall thickening
2. cell shape, cell contents
3. differences in activity and function
Rates of pattern formation
o rapidly-growing seedlings (corn or pea) fully
matured primary tissues 10-15 mm behind the Secondary growth
tip. o occurs when cells in the residual procambium
o slow-growing roots mature tissues may be and later parts of the pericycle begin to make
found within a few mm of the apex periclinal divisions.
 o Only the pericyle cells opposite the xylem
points start to make periclinal divisions.
o inner layer: vascular cambium.
o outer layer: pericycle.

Formation of vascular cambium

o Layers (from outermost):
Cortex
secondary phloem
vascular cambium
secondary xylem
Formation of periderm
o periderm replaces the epidermis.
o develops from the activity of the phellogen or
cork cambium
NOTE: cork cambium originates from the division of
the pericyle
Stems Primary tissues in the stem
Leaves can drop off, leaving a scar but there will o Origin: protoderm, procambium and ground
still be a bud or shoot into which it has developed meristem
As shoot apex grows, older leaf primordia are left Epidermis; ordinary epidermal cells, guard
behind. cells, idioblasts, trichomes
New primordia are continuously borne above Cortex: parenchyma, collenchyma may be
existing ones continuous or separated
strips). In others may contain
sclereids, secretory cells, laticifers.
Endodermis: conspicuous in stems of
lower vascular plants`
Primary vascular system

o In gymnosperms and dicotyledons it is a

continuous or split cylinder. If split, each
Specialized stems strand is called vascular bundle.
o Rhizomes horizontally growing Collateral bundle: phloem is external to
o Bulbs vertically-growing underground roots xylem
with fleshy leaves and short stem
Bicollateral bundle: phloem on the inner
o Stolons horizontally growing with plantlets
along nodes side of xylem.
o Tubers enlarged tips of rhizomes Vascular cambium - a cylinder of meristematic
o Runners cells that forms secondary vascular tissue.
in grasses; horizontal o The accumulation of this tissue increases the
when these branches touch the soil they diameter of a woody plant.
produce adventitious roots.
o Secondary xylem - forms to the interior
o Taro (gabi) corm
vertically growing enlarged stem o Secondary phloem forms to the exterior of
Primary growth the VC
o Apical meristem -> Primary meristem
Protoderm -> epidermis
Procambium -> stele, vascular cambium
Ground -> cortex

NOTE: trees do not need a heartwood to survive

In temperate countries:
o Activity of the cambium is commonly
periodic. The xylem produced during one
 growth period constitutes a growth layer
(growth or annual rings).
Parts of the periderm
o Phellogen
cork cambium, a lateral meristem
arise from epidermis, cortex or phloem
o phellem
in compact rows with no intercellular
spaces
Primary wall with cellulose, sometimes
with lignin or suberin
Suberin layer is impermeable to water and
gases and can resist action of acids.
Are dead cells
o Phelloderm
living cells with non-suberized walls
may store starch, in others contain
chloroplasts and photosynthetic
Sclereids may be present.

first cork cambium may form as epidermal cells

o Inner cells cork cambium
o Outer cells cork
Lenticel- protrude above surrounding periderm
because of bigger size and loose arrangement of
the cells
Leaves o Betalains contain nitrogen
o Anthocyanins no nitrogen
Primary growth of shoots Tendrils (cadena de amor, grape, pisum)
o As shoot apex grows, older leaf primordia are o is a specialized stem, leaf or petiole with a
left behind. threadlike shape that is used by climbing
o New primordia are continuously borne above plants for support and attachment, generally by
existing ones. twining around whatever it touches.
o In angiosperms specially, as young o Can photosynthesize
primordium develops from SAM, preparations o Can be formed from modified shoots,
are under way for emergence of the next modified leaves
primordium Nepenthes
Types of leaves o An epiascidiate leaf
o Palmately compound leaf o If meristematic activity continues the lamina
o Pinnately compound leaf (rachis, leaflets) can become funnel-shaped forming a container
o Simple leaf - blade consists of only one piece FROM EXERCISE 7:
o Parallel monocotyledon leaf (blade, auricle, o Phyllotaxy system of leaf arrangement on
sheath) the stem
Gymnosperm (pine leaf) Alternate or spiral one leaf per node
o Epidermis- heavily cuticularized & with thick Opposite two leaves per node
walls Whorled three or more leaves per node
o Hypodermis (beneath epidermis) fiberlike o Blade/Lamina thin, flattened, green structure
cells with thick walls. o Petiole holds the blade upright
o Lobed mesophyll cells Petiolules stalk of each leaflet
o Resin ducts o Stipules outgrowths in pairs found at the
o Sunken stomata base of some dicot leaves
o Transfusion tissue Stipulate and exstipulate
Dicots Stipels outgrowths in pairs at the base of
o Netted venation the petiolule
o palisade layer occurs adaxially (upper), Venation
spongy layer occurs abaxially (underside) o Netted veins branch profusely and form a
NOTE: Isobilateral leaf- A leaf in which the palisade network over the blade (dicot except plantain)
o Parallel veins do not form a network
parenchyma occurs adaxially and abaxially beneath
the epidermis of the leaf (monocot except gabi and ube)
Internal structure of leaves
Monocot o Epidermis outermost layer, with cuticle, with
o Bundle sheath or border parenchyma stomata and guard cells, more stomata on
o Bulliform cells thin-walled, highly lower epidermis than upper epidermis
vacuolated water-containing cells o Mesophyll photosynthetic parenchymatous
Rapid expansion of leaf: expansion tissues region between upper and lower epidermis
Changes in turgor in opening/closing of o Palisade layer elongated and closely
leaves: motor cells arranged (perpendicular to upper epidermis)
Modified leaves o Spongy layer loosely arranged and
o Spines irregularly-shaped (for gas exchange)
o Storage leaves o Vascular tissues form vascular bundles in
o Reproductive leaves leaves
o Bracts Border parenchyma thin-walled cells
Bougainvillea colored bracts (get their Bundle sheath thick-walled cells
color from betalains) o Bulliform cells large thin-walled cells in
Flowers monocot for rolling in of leaves
o Pigments present are called betalains
o Betalains and anthocyanins are water-soluble
pigments found in the vacuoles of plant cells
 Border parenchyma (thin-walled cells in dicots)
Bundle sheath (thick-walled cells)
Transpiration
o Evaporation of water from from aerial parts of
the plant
Stomatal transpiration
Cuticular transpiration
Lenticular transpiration
o Factors
Light intensity*
Wind velocity *
Temperature
Humidity
Soil Water Supply
Guttation
o Secretion of water to the surface of leaves
through specialized pores called
HYDATHODES

Pine needle
After boiling, only sclerenchyma and vascular
tissues remain (petiole, leaf veins, and midrib)
Leaf
o Epidermis
Cuticle
Stomata and guard cells
Bulliform cells in monocots
o Mesophyll
Palisade layer
Spongy layer
Vascular tissues