WHAT IS A STEM ?
A STEM IS CONSIDERED TO BE THE
CENTRAL AXIS OF THE PLANT.
IT SUPPORTS THE LEAVES AND FLOWERS
OF THE PLANT.
IT HAS NODES FROM WHICH NEW SHOOT
OR SOMETIMES NEW ROOTS CAN ARISE.
USUALLY FOUND ABOVE THE GROUND BUT
CAN BE MODIFIED AND FOUND BELOW
THE GROUND AS WELL.
FUNCTIONS OF STEM
 SUPPORTS LEAVES AND
FLOWERS.
 TRANSPORTS WATER AND
SOLUTE FOR ROOTS TO
LEAVES.
 STEMS IN SOME PLANTS
ARE PHOTOSYNTHETIC.
 IT MAY STORE SOME
MATERIALS NECESSARY
FOR LIFE. [ EG: WATER,
STARCH, SUGAR, ETC]
 IN SOME PLANTS STEMS
HAVE ADAPTATIONS FOR
SPECIALIZED FUNCTIONS.
MODIFIED AND SPECIALIZED
STEMS
UNDERGROUND MODIFICATION
BULB
 BULBS – LARGE BUDS
WITH SMALL STEM AT
THE LOWER END
SURROUNDED BY
NUMEROUS FLESHY
LEAVES AND
ADVENTITIOUS ROOTS
AT THE BASE.
 EXAMPLES – ONION,
TULIP AND LILY
RHIZOMES
 RHIZOMES -HORIZONTAL STEM
THAT GROWS BELOW
THE GROUND WITH
ADVENTITIOUS ROOTS.
 EXAMPLES – IRISES,
GRASSES AND FERNS
OTHER PLANTS
LIKE GINGER
PRODUCES
LARGE, THICK
RHIZOMES
CALLED
PACHYMORPHS.
A PACHYMORPH
RHIZOME OF GINGER
TUBER
TUBER –
ACCUMULATION OF
FOOD AT THE TIPS
OF UNDERGROUND
STOLONS.
THE “EYES” OF THE
POTATO ARE THE
NODES OF STARCH
LADENED STEM.
CORMS
A CORM IS A
SWALLON,
VERTICAL STEM
WITH A PAPERY
COVERING.
GLADIOLUS AND
CROCUS ARE
EXAMPLES OF
PLANTS THAT
FORM CORMS.
CROCUS CORMS
AERIAL MODIFICATION
THORNS
 HONEY LOCUST
[ MODIFIED STEM ]
 BLACK LOCUST
[ MODIFIED LEAF
STIPULE ]
TENDRILS
GRAPE TENDRIL
PHYLLOCLADES
CACTI IS THE BEST
EXAMPLE OF
PHYLLOCLADE.
THE STEM OF
CACTI IS FLESHY
THAT ARE
MODIFIED ALSO
FOR FOOD, WATER
STORAGE AND
PHOTOSYNTHESIS.
CLADODES
 CLADODE IS A
MODIFIED
PHOTOSYNTHESIS
ORGAN, INSTEAD OF A
FLAT GREEN LEAF IT IS
A FLAT GREEN STEM
THAT PLAYS THE
ROLE.
 A CLADODE ARISES IN
THE AXIL OF A MUCH
REDUCED SCALE LEAF.
 EXAMPLES INCLUDE
RUSCUS AND
ASPARAGAUS.
SUB-AERIAL MODIFICATION
OFFSETS
 SUB AERIAL STEMS
WHICH ARE SHORT,
SLENDER
BRANCHES OF ONE
INTERMODAL
LENGTH ARE
CALLED OFFSETS.
 EXAMPLES – PISTIA,
EICHHORNIA, ETC.
STOLONS
 STOLONS OR
RUNNERS –
HORIZONTAL STEM
THAT GROWS
ABOVE THE
GROUND WITH
LONG INTERNODES.
 EXAMPLES –
AIRPLANTS, ETC.
SUCKERS
 IT ARISES FROM THE
BASAL, UNDERGROUND
PART OF THE MAIN STEM.
 IT DEVELOPS A LEAFY
SHOOT AND
ADVENTITIOUS ROOTS
BEFORE SEPARATING
FROM THE MOTHER
PLANT.
 EXAMPLES INCLUDE
CHRYSANTHEMUM, MINT,
ETC.