SHOOT SYSTEM OF PLANTS: THE STEM

_________ - part of sporophyte of vascular plants that typically appears above the ground

• appendages: leaves, buds, flowers, fruit

• either branched or unbranched aerial stem axis

SHOOT SYTEM

__________ - functioning for support of aerial parts and transport of materials between roots and leave

stem

stems is in an alternating system of _______ ( points where leaves and branches originate) and _____ (segments between them)

nodes, internodes

The apex of the stem is where the ________ - responsible for the increase in plant height

apical meristem

responsible for plant height??

apical meristem

what is the shape of the shoot apex and is composed of what type of cells?

dome-shaped, meristematic

the apical meristem gives rise to the ________ meristems which are?

primary meristems

• procambium

• ground meristem

• protoderm

____________ responsible for primary growth and gives rise to primary tissues

primary meristems (procambium, ground meristem, protoderm)

if primary tissues are retained up to maturity, plant growth is described as

open or intermediate

in gymnosperms and most dicots, INCREASE IN DIAMAETER of the plant body is due to the activity of the _______________

secondary/lateral meristem

___________ responsible for the increase in diameter of the plant body

secondary/lateral meristem

what are the components of secondary/lateral meristem

• vascular cambium

• cork cambium

which are responsible for the production of the secondary tissues of the plant body?

secondary/lateral meristem

_________________: primary tissue; _______________: secondary tissue

primary meristem, secondary/lateral meristem

plant height: _________________; plant diameter:__________________

apical meristem: secondary/lateral meristem

_______________: primary growth; ___________: secondary growth

primary meristem, secondary meristem

if monocots exhibit secondary growth, they would not have _______________

vascular cambium

a monocot exhibiting secondary growth, but absent vascular cambium is called what?

anomalous secondary growth (not following the pattern of secondary growth of a ring of vascular cambium)

can anomalous secondary growth be seen in some gymnosperms and dicots?

YES

__________________ - have soft and green stems that does not exhibit secondary growth

herbaceous plants

this type of plants have hard stems

woody plants

Are nodes and internodes clearly seen in a dicot or monocot plant?

in a dicot plant - nodes and internodes are clearly seen

at the extreme tips of the main stem and its branches is where _______________ are located

terminal buds

angles between leaves and internodes, ___________ are located

axillary buds

__________________: angles between leaves and internodes; _____________: extreme tips of the main stem

axillary buds, terminal buds

can you clearly see the nodes and internodes in a monocot plant?

No, because of the presence of a leaf sheath that covers the nodes and internodes

what is the flattened base of the leaf clasping the stem - covers the nodes and internodes (found in monocot plant only!)

leaf sheath

____________________ - region of an internode immediately above the node which consists of actively dividing cells

intercalary meristem

what is the significance of the intercalary meristem?

helps in the regeneration of the lawn grass which are removed by grazing herbivores

• enables plant to survive and rapidly regenerate leaves

what are the whitish pores in the surface of a woody plant?

lenticels

what is the function of lenticels?

gas exchange

in young stems, the ________ located in the epidermis, site for gas exchange, but as woody stems age, lenticels develop beneath the ______________

stomata

lenticels develop where in a stomata?

beneath the stomata

area of detachment of a leaf is called what?

leaf scar

at the tip of each stem there is an

apical meristem

_______________ - responsible foe the increase in the length of the stem

apical meristem

the outer layer of the apical meristem is called _______________

tunica

____________ - is made up of one or more layers of cells that divide anticlinally (planes perpendicular to the surface of the shoot apex)

tunica

this lies below the tunica

corpus

__________ - made up of cells that divide in various planes, thus adding volume to the apical meristem

corpus

cells of ______________ sustain their continuity over the enlarging mass through surface growth

tunica

does the concept of tunica and corpus apical organization apply yo vascular cryptogams and gymnosperms?

no, it only applies to angiosperms

________________ - ear-like structures from the activity of tunica and corpus

leaf primordia

_______________ arising from the periphery of the shoot apical meristem

leaf primordia

apical meristems gives rise to primary meristem - procambium, ground meristem, protoderm - that differentiates into _________________

primary tissues

apical meristem —→ primary meristem —> primary tissues

true

______________ - differentiates into epidermis, thus outermost layer

protoderm

__________ - produces the ground tissues cortex and pith; in the middle (below apical meristem)

ground meristem

____________ differentiates into primary vascular tissues - sandwiched between layers of ground meristem

procambium

outermost tissue of the stem; followed by the _____ comprising several layers of cell

epidermis, cortex

Helianthus annuus stem has a pith in the center, thus the stele is called

siphonostele

Helianthus annuus - has vascular tissues that are in discrete bundles w/parenchymatous tissues between two adjacent bundles. what type of stele?

siphonostele, specifically eustele (typical in gymnosperms and dicots)

_____________ - in a dicot stem, this is position near the cortex

primary phloem

what is the cluster of thick-walled cells?

phloem cap

_______________ which xylem is positioned next to the pith in a dicot stem?

protoxylem

in a dicot stem

_____________: positioned next to the pith (toward center); _____________ positioned closer to the cortex (oriented outwards)

protoxylem, metaxylem

what type of xylem maturation is exhibited when the protoxylem is closer to the pith (oriented towards the center), while metaxylem is closer to the cortex (oriented outwards)

endarch

_________________ this is found between primary xylem and primary phloem

fascicular cambium

_________ this is found between two adjacent vascular bundles

interfascicular cambium

fascicular cambia and interfascicular cambia together forms a ring of _______________, when the stem starts to undergo secondary growth

vascular cambium

types of tissues in a stem

• ____________ - wood harvested

• ____________ - inner bark

xylem, phloem

cross section of Tillia sp.

__________ - composed of the phellem (cork), phellogen (cork cambium), phelloderm (cork parenchyma)

periderm

_____________ - the outermost layer which is made up of suberized cork cells.

phellem

the layer next to phellem; arises from either epidermis or cortex

phellogen (cork cambium)

when the cells in a lateral meristem divide - produces 2 layers of cells

• inner layer: _________

• outer layer differentiate into _______

• cork cambium/ phellogen

• cork cells/phellem

in woody plants, cork cambium (phellogen) may produce one or two layers of cell that becomes the _________

phelloderm/ cork parenchyma

loosely packed parenchymatous cells found in the periderm are called

lenticels

this is considered as a temporary outer layer in woody plants

epidermis

when secondary growth (increase in diameter/thickness) occurs, ___________ eventually disappear due to expansion, thus replace by _______

epidermis, periderm

region inner to periderm is made of tissues resulting from the meristematic activity of the vascular cambium which produces;

• ______________ to the outside

• _______________ to the inside

secondary phloem

secondary xylem

ring of brick-like cells

vascular cambium

in most woody plants - with regular growth - both the _______ cambium and _______ cambium exhibit meristematic activity only near the beginning of the growing season

vascular, cork

what happens to primary xylem and primary phloem, as lateral meristems continue to produce secondary tissues?

• primary xylem - pushed closer to the pith (center)

• primary phloem - pushed towards cortex (outward) - destroyed eventually

where can you find newly formed secondary xylem and secondary phloem?

they can be found adjacent to the vascular cambium

all tissues outer to the vascular cambium comprise the ______; while the tissues inner to it comprise the _______

bark, wood

what tissues are included in the bark (outer)?

• secondary phloem

• primary phloem

• peridem (phellem, phellogen, phelloderm)

what tissues are included in the wood (inner)

• primary xylem

• secondary xylem

• pith

in a tree trunk:

• darker portion is the ______

• lighter portion is the ______

• bark

• wood

_____________ - comprising xylem elements that cease to function in water conduction; dark region in the center

heartwood

_______________ - light region close to the bark

sapwood

which layer contains newer xylem has newer xylem elements?

sapwood

type of stele exhibited by corn is?

atactostele

_________ - type of stele in which is common to monocot stems, but some dicots too like pepper have this.

atactostele

TRUE OR FALSE

• No monocot has a true vascular cambium that gives rise to secondary vascular tissues

TRUE

modified stems

• bulb

• corm

• rhizome

• tuber

• runner

• cladophyll

• stem tendril

• thorn

___________ - consists of small stem tissue to which fleshy storage leaves are attached (ex. onion)

bulb

• Serves as a nutrient storage organ which enables rapid regrowth and flowering. (onion)

______________ - globose stem tissue surrounded by few-scale-like leaves (ex. Colocasia esculenta) - taro

corm

• Serves as a nutrient storage organ that stores large amounts of carbohydrates (energy reserve)

___________ - horizontal stem growing underground (aboveground in some ferns) usually having short internodes and scale-like leaves (ex. Zingiber officinale)

rhizome

• Allows the plant to survive underground and it allows it to produce new shoots.

__________ - thick undergound storage stem usually having outer buds and lacking storage leaves and scales (Solanum tuberosum)

tuber

• Serves as a storage organ for food which is mainly starch.

__________________ - horizontal stem with long internodes growing aboveground (Cynodon dactylon)

runner

• It enables the plant for rapid vegetative expansion and enables quick recovery from damage when the root at nodes touches the soil.

____________ - flattened stem resembling leaves (Homalocladium platycladum)

cladophyll

• It serves the primary site for photosynthesis as there are no leaves. Reduces water loss

_________ long and slender coiling branch usually found in vines having weak stems (Coccinia grandis)

stem tendril

• It supports the plant by coiling itself around fences or other plants. This allows vertical growth for more sunlight.

____________ - sharp-pointed stem, not to be confused with spine (modified leaf/leaf part) and prickle (outgrowth from plant surface)

• (x Citrofortunella microcarpa)

thorn

• Serves as a defense mechanism against herbivores.