STEM Stems are adapted to different environments. Underground stems Modified for food storage ex:...

STEMStems are adapted to different environments.

Underground stems

Modified for food storage

ex: white potato (tuber)

Climbing stems (tendrils)

ex: strangler fig tree

Runner stems

Runs along the surface of the ground and reproduce quickly by asexual reproduction

ex: strawberry

Cladophyll

Modified for water storage and photosynthesis

ex: cactus

STEMUnderground

stems

Climbing stems (tendrils)

Runner stems

Cladophyll

Types of Stems

Herbaceous stems

are soft, green and juicy

usually live for 1-2 years

is seen in two groups of

plants

Woody stems

are made up of thick and though tissue called wood

normally live more than 2 years

almost all of them are dicots

ex: oak tree, maple treemonocots

no vascular cambium

vascular tissue is scattered irregularly

ex: corn

dicots

has vascular cambium

vascular tissue is arranged in a circle

ex: bean, sunflower

Types of Stems

Herbaceous stems Woody stems

monocots dicots

Monocot and Dicot Stems Flowering plants seeds have at least one seed leaf called

cotyledon, that stores food.

Some seeds have one cotyledon and the plants that grow from these seeds are called dicots.

Some seeds have one cotyledon and the plants that grow from these seeds are called dicots.

ex: corn monocot bean dicot

Monocot and Dicot Stems

Monocot stems Dicot stems

fundemental tissue vascular cambium

Monocot and Dicot Stems Monocot stems Dicot stems

Monocot and Dicot Stems

Epidermis: protects the stem of herbaceous monocot and dicot plants. Cork protects the stem of woody (dicot) plants.

Cortex: made up of parenchyma cells to support the stem and store food in dicot plants.

Fundamental tissue: composed of parenchyma cells. In monocots, the fundamental tissue is not separated into pith and cortex.

Vascular cambium: produces new xylem at the inner side and new phloem at the outer side in dicot plants.

Monocot and Dicot Stems

*** In a woody dicot stem, xylem produced by vascular cambium builds up as the new xylem is added and these compose annual rings of a tree. In this way plant grow wider. But phloem doesn’t build up as new phloem is formed. Because older phloem break off as layers when new ones are added.

*** Because monocots don’t have vascular cambium, they don’t show secondary growth.

*** In woody stems lenticels which are unsuberized permits gas exchange. In herbaceous stems, stomata permit gas exchange.

Monocot and Dicot Stems

LEAF

Internal Structure of the Leaf

Mesophyll (Photosynthethic Tissue)

Upper portion of mesophyll

It’s one or two cell layers thick

Composed of tall, tightly packed cells filled with chloroplast

It’s the main site of photosynthesis

It’s below palisade layer

It’s made up of irregularly shaped cells

Between it’s cells there are large air spaces.

It’s cells have fever chloroplasts.

It’s main function is to allow diffusion of gases into the leaf.

PALISADE SPONGY

Internal Structure of the Leaf

TYPES OF LEAF

TYPES OF LEAF

Differences between Monocot and Dicot Plants

Seed leaves:

Monocots Dicots

Differences between Monocot and Dicot Plants

Flowers:

Monocots Dicots

Differences between Monocot and Dicot Plants

Leaves:

Monocots Dicots

Differences between Monocot and Dicot Plants

Stems:

Monocots Dicots

Differences between Monocot and Dicot Plants

Stems:

Monocots Dicots

Differences between Monocot and Dicot Plants

Roots:

Monocots Dicots

Differences between Monocot and Dicot Plants