Made by-V.V.S.S.PREETISr. MEDICON -1Roll no- 33

ROOT & STEM MORPHOLOGY

(INCLUDING MODIFICATIONS)

WHAT IS MORPHOLOGY?

Morphology is the study of –External features of plants,Arrangement,RelationshipOf organs.

The underground part of flowering plant is the root system while the portion above the ground forms the shoot system.

Plant has vegetative and reproductive organs

Vegetative Organs

RootsStemsLeaves

THE ROOTLOCATION- grows underground

TYPES OF ROOTS-

1) Primary- formed directly from axis of embryo plant.

2) Lateral- arises from primary.

TYPES OF ROOT SYSTEMS

G

TAP ROOTS FIBROUS ROOTS ADVENTIOUS ROOTS

•Prominent in dicot •Prominent in monocots

•They develop from organs

•Primary roots grow & becomes stout.

•Roots develop from lower nodes

Of shoot system

•Secondary & tertiary grow from primary root

•They have same length & diameter

Function of roots

Anchor the plant

Absorb water and minerals from soil

Storage

Fig. 38.21

STORAGE ROOTS

SWOLLEN TAP ROOTS FUSIFORM-eg:raddish NAPIFORM-

eg:beetroot CONICAL -eg;carrot

SWOLLEN ADVENTIOUS ROOTS

FASICULATED-eg asparagusNODULATED -eg: gingerMONILIFORM-eg: grassesSweet potato

PROP ROOTS

IN BANYAN TREE,Branches give off roots that grow into the soil & support the branches

STILT ROOTS

IN SCREWPINE short roots grow obliquely downward from near base of stem

CLIMBING ROOTS

IN climbers like PEPPER & BETEL NUT,adventitious roots are formed at nodes which help in climbing.

EPIPHYTIC ROOTS

IN VANDA,Base of tissue grows spongy tissue termed velamen that absorbs moisture from the air

CONTRAC TILE ROOTS

IN COLACASIA,They posses roots that contract so underground roots are kept at proper levels.

FLOATING ROOTS

IN JUSSIAEAroots are white, spongy filled with air.Help plants to float

BREATHING ROOTS

IN AVICENNIA,Roots grow into vertical branches that have openings called Pneumetaphores for root aeration.

REORODUCTIVE ROOTS

Exposed roots of MURRAYAHave adventitious buds which grow into new plants.

PARASITIC ROOTS

IN CUSCUTAHaustoria Penetrate into host stem & enter vascular bundles which absorb materials.

ASSIMILATORY ROOTS

IN TRAPA,Adventious roots with chlorophyllous tissue capable of photosynthesis.

FOLIAR ROOTS

INBRYOPHYLLUMRoots arise from lamina, petiole,veins

TUBERCULAR ROOTS

IN SWEET POTATOLateral roots are swollen &Without definite shape.

THE STEMThe stem grows erect& lifts the leaves , exposing them to sunlight.it also conducts materials from roots to leaves. Based on nature of stem,plants are divided into herbs,shrubs & trees

Function of Stems support

leaves to maximize light absorption

part of conduit for transport of water, minerals, and organic solutes

storage

UNDERGROUND MODIFICATIONS OF STEM

•BULBDry scale leaves,Tunicated,Stem is small reduced & disk shaped.

•RHIZOMESGrows horizontally,Elongated.stem nature is evident from CATAPHYLLS.

AMORPHOPHYLLUS

•STEM TUBERIn potato,An aerial branch grows downward &stores food

• CORMIn amorphophyllusStem is massive,swollen,Held in position by contractile roots

POTATO

SUBARIEL MODIFICATIONS FOR VEGETATIVE PROPOGATION

•RUNNERIn StrawberryAxillary buds from lowest leaves give rise to modified branches.

•STOLONThey grow upwardsLike ordinary branches & arch down to meet soil.

STOLON

•SUCKERIn menthaIt goes up & forms a daughter plant after striking root

•OFFSETIt is shorter & thickerFound in aquatic plants

EICHHORNIAMENTHA arvensis

SUCKER OFFSET

ARIEL MODIFICATIONS OF STEM

•TENDRILSIN grapesAxillary bud is modified into tendrils.

•CLADOPHYLL /PHYLLOCLADEThe entire shoot is flattend & leaf like.

•CLADODEBranch of a single internode which is flattened to stimulate a leaf like.

•BULBILIN DIOSCOREA It is a modified floral bud which becomes vegetative.

CLADODE

ACACIA

BULBIL

DIOSCOREA

THE END

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