PL SCI 221 MIDTERM EXAM QUESTIONS AND
ANSWERS LATEST UPDATE
Some advantages of graphing
Precocity- ability to induce fruitfulness without need for completing the juvenile phase of
plant
Dwarfing- reduce size of scion
Ease of propagation- when scion is difficult to colonial propagate
Provide specific root characteristics- (ie root stock of tart cherry)
Provide disease/pest resistance
Stem modification
Above ground-
stolons, tendrils, thorns, crowns
Stem modification
Below ground-
rhizomes, bulbs, tubers, corms
Stolons-
horizontal stem that grows above ground. Their function is vegetative reproduction as
new plants are produced where nodes touch the ground
Tendrils-
a branch that is capable of clinging or coiling around structures to provide additional
support
Rhizomes-
horizontal stem that grows below ground roots and shoots develop from the nodes.
Store food for renewing shoot growth following periods of stress
Bulbs-
compressed stem surrounded by fleshy leaf life structures called scales which enclose
shoot or flower buds. Outer scale leaves protect the bulb, while the inner scale leaves
store the food reserves
Stems and roots of woody pants become wider by accumulation of
Wood (secondary xylem)
Inner bark (secondary phloem)
Outer bark (periderm)
Secondary xylem and phloem both originate from the
vascular cambium
Only dicot gymnosperms produce
wood
Cambia of gymnosperms and angiosperms are thought to be
homologous
True secondary growth occurs in
Most dicots
All gymnosperms
Not in angiosperms or ferns
, Dicot stems-
vascular bundles arranged in a circle around the pith, required for forming continuous
cambium
Promeristem-
meristematic zone, below the apical dome with the true meristem
How does vascular cambium produce growth in stem thickness-
cells expand, the cambium cell divides again, this time forming a new xylem cell
Tropical tree rings are regulated by the
wet and dry seasons, instead of the summer and winter seasons
Tree rings larger when young-
tree must grow faster when young. Also there is a geometrical constraint of adding a
volume of wood to a stem of increasing radius
Cork cambium (phellogen)-
produces cork (phellem) & phelloderm (sometimes)
Lenticels for
gas exchange
Three functions of wood
1- structural support
2- Storage
3- Water transport
Axial wood elements-
transport water with dissolved mineral nutrients up from the soil to the leaves,
radial (ray) wood elements are used to
transport nutrients between growth rings and storage of metabolites
Three plains of cut wood
Cross section- perpendicular to the axis
Tangential longitudinal- parallel to growth rings
Radial longitudinal- perpendicular to growth rings
Both conifers and angiosperms have rays
which serve in storage and connect the phloem and xylem radially
In conifers, tracheids provide both
transport and structural support
In angiosperms, there is a division of labor between
vessels (transport) and structural support (fibers)
Many angiosperms have
tracheids in addition to vessels and fibers
Resin ducts (canals)-
present in wood of some conifers and can also be formed in other trees in response to
injury, living cells lining these ducts produce resin which is transported by the ducts to
fight insect or pathogen invasion or to cover wounds
Tracheids-
narrow, spindle shaped elements with closed ends, water is transported up from one
tracheid to another is through small structures in radial walls called bordered pits
Vessels
for transport
fibers
ANSWERS LATEST UPDATE
Some advantages of graphing
Precocity- ability to induce fruitfulness without need for completing the juvenile phase of
plant
Dwarfing- reduce size of scion
Ease of propagation- when scion is difficult to colonial propagate
Provide specific root characteristics- (ie root stock of tart cherry)
Provide disease/pest resistance
Stem modification
Above ground-
stolons, tendrils, thorns, crowns
Stem modification
Below ground-
rhizomes, bulbs, tubers, corms
Stolons-
horizontal stem that grows above ground. Their function is vegetative reproduction as
new plants are produced where nodes touch the ground
Tendrils-
a branch that is capable of clinging or coiling around structures to provide additional
support
Rhizomes-
horizontal stem that grows below ground roots and shoots develop from the nodes.
Store food for renewing shoot growth following periods of stress
Bulbs-
compressed stem surrounded by fleshy leaf life structures called scales which enclose
shoot or flower buds. Outer scale leaves protect the bulb, while the inner scale leaves
store the food reserves
Stems and roots of woody pants become wider by accumulation of
Wood (secondary xylem)
Inner bark (secondary phloem)
Outer bark (periderm)
Secondary xylem and phloem both originate from the
vascular cambium
Only dicot gymnosperms produce
wood
Cambia of gymnosperms and angiosperms are thought to be
homologous
True secondary growth occurs in
Most dicots
All gymnosperms
Not in angiosperms or ferns
, Dicot stems-
vascular bundles arranged in a circle around the pith, required for forming continuous
cambium
Promeristem-
meristematic zone, below the apical dome with the true meristem
How does vascular cambium produce growth in stem thickness-
cells expand, the cambium cell divides again, this time forming a new xylem cell
Tropical tree rings are regulated by the
wet and dry seasons, instead of the summer and winter seasons
Tree rings larger when young-
tree must grow faster when young. Also there is a geometrical constraint of adding a
volume of wood to a stem of increasing radius
Cork cambium (phellogen)-
produces cork (phellem) & phelloderm (sometimes)
Lenticels for
gas exchange
Three functions of wood
1- structural support
2- Storage
3- Water transport
Axial wood elements-
transport water with dissolved mineral nutrients up from the soil to the leaves,
radial (ray) wood elements are used to
transport nutrients between growth rings and storage of metabolites
Three plains of cut wood
Cross section- perpendicular to the axis
Tangential longitudinal- parallel to growth rings
Radial longitudinal- perpendicular to growth rings
Both conifers and angiosperms have rays
which serve in storage and connect the phloem and xylem radially
In conifers, tracheids provide both
transport and structural support
In angiosperms, there is a division of labor between
vessels (transport) and structural support (fibers)
Many angiosperms have
tracheids in addition to vessels and fibers
Resin ducts (canals)-
present in wood of some conifers and can also be formed in other trees in response to
injury, living cells lining these ducts produce resin which is transported by the ducts to
fight insect or pathogen invasion or to cover wounds
Tracheids-
narrow, spindle shaped elements with closed ends, water is transported up from one
tracheid to another is through small structures in radial walls called bordered pits
Vessels
for transport
fibers
