module 6 (stem)

stem

it is the aerial part of the plant

stem

mechanical support

stem

site where leaves and reproductive shoots get attached

pollinators, dispersal agents

a stem exposes the leaves for photosynthesis and positions the reproductive shoots for optimal access to ______ and _________

photosynthesis

a stem exposes the leaves for _________ and positions the reproductive shoots for optimal access to pollinators and dispersal agents

water and minerals

stem conducts ____ and ______ from roots to the leaves and solutes from leaves to storage and use sites

• support

• conduction

• growth

• storage

• stem as food

stem functions

asparagus, broccoli, potato, cauliflower

stem as food

shoot

a young stem (1 year old or less) with leaves

twig

a young stem (1 year old or less) that is in the dormant winter stage (no leaves)

branch

a stem that is more than 1 year old typically with lateral stems radiating from it

trunk

a woody plant’s main stem

Herbaceous stems

thin, soft and green in color except those that grow underground

Woody stems

taller, thicker, and harder than herbaceous stems

1. bud'

2. terminal bud

3. bud scales

4. terminal bud scale scars

5. lateral buds/ axillary buds

6. leaf scar

7. petiole

8. lenticel

9. node

10. internode

11. bundle scar

external parts of stem

bud

stem’s primary growing point

terminal bud

single bud found at the apex of the stem

bud scales

protects lateral & terminal bud

terminal bud scale scars

marks left on the stem from the previous years which serve as external measure of annual growth

lateral buds/axillary buds

buds that occur in the leaf axils on the side of a stem

leaf scar

mark that leaves on the stem after the leaf falls

petiole

stalk that extends from the stem to the base of the leaf

lenticel

pores that allow for gas exchange

petiole

stalk that extends from the stem to the base of the leaf

lenticel

pores that allow for gas exchange

lenticel

if stomata is the gas exchange of leaves, ano yung sa stem

Node

segment of stem where leaves and lateral buds are attached. (above or below ground)

Internode

section of a stem between two nodes

Bundle scar

used in the identification of the woody plants and it is a mark left in the leaf scar from the vascular tissue attachment

bundle scar

tiny bumps in leaf scar where vascular tissue enter the leaf from the stem.

because they mark the places where bundles of vascular tissue were located

why are they called bundle scars

• primary growth

• secondary growth

two types of growth in stems

primary growth

this growth increases length of the stem

secondary growth

this growth increases the thickness of the stem

Herbaceous plants

these plants mostly undergo primary growth

woody stem

secondary growth builds _____

terminal bud

the apical meristem is located in a bud, called a _________, at the tip of the stem.

epidermis

protoderm»»

primary xylem and primary phloem

procambium»»

pith and cortex

ground meristem »»

primordium (primodia)

developing leaves

lateral meristems

controls secondary growth

axillary buds

where is lateral meristems located

phellogen

cork cambium is also called

phelloderm (inside) and phellem (outside)

cork cambium produces what

phellem

cork cell is also known as

lenticels

it develops beneath the stomata

suberin

cork cells are impregnated with _______ »» protection

annual plants

complete their entire life cycle from germination to death within one year

Perennial plants

they live multiple years

stele

vascular cylinder is also called

stele

composed of primary xylem, primary phloem, and pith

protostele

the simplest form of stele

protostele

consists of a solid core of conducting tissues in which the phloem usually around surrounds the xylem

Siphonosteles

tubular with pith in the center. common in ferns

eusteles

most present-day flowering plants and conifers have this

eusteles

the primary xylem and primary phloem are in discrete vascular bundles

primary tissue

vascular cambium and cork cambium both develop from _____ in the stem as a stem enters into secondary growth

spring wood

vascular cambium active during the spring produces a xylem called

summer wood

xylem with smaller or fewer vessel elements & large number of tracheids. this produced after spring wood

annual rings

indicates the age of tree, but it also denotes the climate

annual ring

one years growth of xylem is called

vascular rays

lighter streaks seen on transverse or cross section of tree trunk

vascular rays

consist of parenchyma cells that may be alive > 10 years

vascular rays

functions by lateral conduction of nutrients & water from the stele (thru xylem & phloem) to the cortex

protoplast

cell without cell wall

pits in the walls

the protoplasts of some of the parenchyma cells that surround the vessels and tracheids grow through the

cavity of the vessel

as the protoplasm continues to expand, much of the _________ or tracheid becomes filled

tylosis (tyloses)

protrusions filled with resins, gums, or tannins: that prevent conduction of water & dissolved substance

tylosis

results to accumulation of resins, gums and tannins as well as pigments that darken the color of the wood

heartwood

older darker wood at the center.

heartwood

helps strengthen the tree

sapwood

lighter; still functioning xylem closest to the cambium

heartwood

it is not of much use to the tree, because it no longer conduct materials

softwood

no fibers or vessel elements; only tracheid

softwood

pines and cone-bearing trees

hardwood

wood of woody dicots

bark

all tissues outside the vascular cambium, including the phloem

inner bark

consist of primary and secondary phloem

outerbark

(periderm) consist of cork tissue and cork cambium

lacticifiers

specialized cells of ducts

lacticifiers

form extensive branched networks of latex-secreting cells

lacticifiers

found in woody flowering plants

lacticifiers

most common in the phloem but present throughout all parts of plantla

latex

where morphine (from opium poppy) is extracted

latex

a thick fluid that is white, yellow, orange, or red in color and consists of gums, proteins, sugar, oils, salts, alkaloid drugs, enzymes, and other substances

latex

function: aids in closing wounds

rhizomes

an underground stem

rhizomes

usually grows horizontally

rhizomes

capable of producing new shoots and roots

ginger

Zingler officinale

Asparagus

Asparagus officinalis

bamboo

Bambusa vulgaris

runners

aboveground stems that “run” across he soil surface

internodes

runners also have long __________

adventitious buds

____ appear at alternate nodes along the runners

stolons

similar to runners but are produced beneath the surface of the ground and tend to grow in different directions but usually not horizontally

Tendrils

modified to wrap around and cling to thing for support

tendrils

modified stem in grape & Boston ivy

tendrils

leaf parts in peas and cucumber