TOPIC 4: Tissues and Primary Growth of Stems

Stems

It support leaves and
branches.

Stems

It transports water and
solutes between roots and
leaves.

Stems

In some plants, ______ have
become adapted for specialized
functions.

Stems

May be vegetative (leaf bearing) or reproductive (flower bearing)

Node

Area of stem where leaf is born

Internodes

Stem area between nodes

Buds

Stem elongation.
Embryotic tissue of leaves and stem (not flower bud)

Terminal bud

Located at tip of stems or branches

Axillary bud

Gives rise to branches

Apical dominance

Prevention of branch formation by terminal bud

- Epidermis
- Cortex
- Pith
- Xylem
- Phloem
- Vascular Cambium

Parts of the stem

Xylem

Water and minerals travel up to other plant parts

Phloem

Manufactured food travels down to other plant parts

Cambium

Separates xylem and phloem

- Dermal Tissue System
- Vascular Tissue System
- Ground Tissue System

Three (3) types of Plant Tissues

Dermal Tissue System

- Outer covering
- Protection

Vascular Tissue System

- "Vessels" throughout plant
- Transport materials

Ground Tissue System

- Body of plant
- Photosynthesis; Storage; Support

Stems

They grow by division at meristems

- Stolons
- Rhizomes
- Tubers
- Bulbs

These shoots are often mistakes for roots

Stolons

They grow on the surface and enable a plant to colonize large areas asexually when a parent a plant fragments into many smaller offspring

Rhizomes

These are horizontal stems that grow underground

Tubers

These are the swollen ends of rhizomes specialized for food storage

Bulbs

These are vertical, underground shoots consisting mostly of the swollen bases of leaves that store food

Ground Tissue

This type of tissue is neither dermal or vascular

Pith

Ground tissue internal to the vascular tissue

Cortex

Ground tissue external tot the vascular tissue

Parenchyma

- Least specialized cell type
- Only thin primary cell wall is present
- Possess large central vacuole
- Generally alizve at functional maturity

Parenchyma

- Make up most of the ground tissues of the plant
- Storage
- Photosynthesis
- Can help repair and replace damage organs by proliferation

Collenchyma

- Possess thicker primary cell walls than that of parenchyma
- No secondary cell wall present
- Generally alive at functional maturity

Collenchyma

Provides support without restraining growth

Sclerenchyma

- Have secondary cell walls strengthened by lignin

fibers and sclereids

Two forms of sclerenchyma

Sclerenchyma

Rigid cells providing support and strength to tissues

Fibers

There are long, slender and tapered, and usually occur in groups

Sclereids

Shorter than fibers and irregular in shape

Vascular Tissue

runs continuously throughout the plant; transports materials between shoots and roots

Xylem

Main water-conducting tissue of vascular plants

- Sieve elements
- companion cells

2 main components of the phloem

Sieve elements

It has no nucleus and only a sparse collection of other organelles

Phloem

Conducts sugars and amino acids from the leaves to the rest of the plant

Pores

____ in sieve plate between sieve tube elements are open channels for transport

Companion cells

it has a role in transport of photosynthesis of products from producing cells in mature leaves

Companion cells

Contains many, many mitochondria for cellular respiration to provide the cellular energy required for active transport

Cotyledons

Have one cotyledon (seed leaf) in the embryo.

Cotyledons

Have two cotyledons in the embryo.

Scattered

In most monocot stems, the vascular bundles are __________ throughout the ground tissue

Ring

In dicots, instead of being scattered, the vascular bundles form a ______

Primary growth

Apical meristems: Mitotic cells at "tips" of roots / stems

Secondary growth

Lateral Meristems:
Mitotic cells "hips" of plant

Secondary growth

It is responsible for the increase in stem/root diameter

- Meristem cells
- Differentiated cells

Growth patterns in plant:

Meristem cells

A growth pattern; Dividing cells

Differentiated cells

Cells are specialized in structure and role

Meristems

The tissue in most plants consisting of undifferentiated cells

Analogous

Meristematic cells are ____________ in function to stem cells in animals

(L1) epiderma
(L2) subepidermal
(L3) corpus

Layer 1
Layer 2
Layer 3
of Tunica-Corpus Model

- Vascular cambium
- Cork cambium

Two lateral meristems:

Vascular cambium

It is a lateral meristem in the vascular tissue of plants

Vascular cambium

It is a cylinder of unspecialized meristematic cells that divide to give rise to cells that further divide

- Fusiform initials
- Ray initials

2 types of cells found in vascular cambium

Vascular cambium

A type of meristem - tissue consisting of embryonic (incompletely differentiated) cells from with other plant tissues originate

Cork cambium

This lateral meristem produces cork, part of the bark

The secondary vascular tissues and periderm

This make up the secondary plant body

Vascular cambium

In wood, it is the obvious line separating the bark and wood

Cork cambium

Responsible for secondary growth that replaces the epidermis in roots and stems