PL_LESSON 3: PLANT CELLS (pt.2)

PLANT TISSUES

Aggregation of coordinated to perform a particular function or set of functions

Parenchyma

Collenchyma

Sclerenchyma

SIMPLE (FUNDAMENTAL)

Dermal (protective covering)

Vascular (conducting tissue)

COMPLEX (CONSISTS OF TWO TYPES OF CELLS)

Apical shoot meristem (longitudinal)
Lateral meristem (girth)

MERISTEMATIC

Xylem

Phloem

Vascular (conducting tissue)

PARENCHYMA

Thin cell walls and living protoplast

PARENCHYMA

Elongate to isodiametric

PARENCHYMA

Live at full maturity and mitotic

PARENCHYMA

Photosynthetic and active metabolically

COLLENCHYMA

Cell walls of irregular thickness

COLLENCHYMA

Gives support, strength and integrity for the developing plant, leaf

SCLERENCHYMA

Evenly thick cells

SCLERENCHYMA

Usually dead at maturity

SCLERENCHYMA

With lignified secondary wall, for structural support

Fiber, Sclereid

Two Types of Sclerenchyma

Fiber

support internal structure; long and flexible

Sclereid

stone cells; short and more or less isodiametric

Fiber

Sclereid

Collenchyma

just inside the epidermis; clusters of light gray cells)

Collenchyma

is found in this area because it provides support and rigidity

Parenchyma

middle of petiole

Sclereids

thick secondary wall (lignin)

Lumen

cavity that the cell walls enclose

Pit canals

channels for transport of water and minerals

SURFACE TISSUES

Barrier of the plant and its environment

EPIDERMIS

Outermost, protoderm-derived layer of cells covering the stem, root, leaf, flower, fruit, and seed parts of a plant

EPIDERMIS

Provide a protective barrier against mechanical injury, water loss, and infection.

EPIDERMAL CELL

Primary role is to protect from a variety of harmful factors (environmental stressors) including microbes, chemical compounds as well as ultraviolet light among others

PARENCHYMA

COLLENCHYMA

SCLERENCHYMA

EPIDERMAL CELL

They also conserve moisture, secret cutin (hydrophobic) from cuticle and reduces transpiration

Cell wall, Cuticle: made of cutin

EPIDERMAL CELL Consists of:

Cell wall

Surrounds the plasma membrane of plant cells and provides tensile strength and protection against mechanical and osmotic stress

Cell wall

It also allows cells to develop turgor pressure, which is the pressure of the cell contents against the cell wall.

Cuticle

The outermost layer of plants, which covers leaves, fruits, flowers, and non-woody stems of higher plants

Cuticle

It protects plants against drought, extreme temperatures, UV radiation, chemical attack, mechanical injuries, and pathogen/pest infection.

STOMATAL APPARATUS

Tiny openings or pores in plant tissue that allow for gas exchange

Stomatal pore (stoma)

any of the microscopic openings or pores in the epidermis of leaves and young stems

Stomatal pore (stoma)

sickle shapes

Guard cells

cells surrounding each stoma. They help to regulate the rate of transpiration by opening and closing the stomata.

TRICHOMES (HAIRS)

Secrete a type of mucilage that serves to trap insects when they come in contact with the plant leaves.

TRICHOMES (HAIRS)

This substance also helps prevent excessive water loss from the leaves as well as protecting the plant from excessive moisture

GLAND CELLS

Have a primary cell wall, sometimes covered by a cuticle at the joining area with the stalk cells, and contain a cytoplasm with abundant organelles such as mitochondria, endoplasmic reticulum and Golgi cistern stacks

PERIDERM

Outer covering of woody stems and roots

PHELLEM (CORK)

Forms a series of cell layers at the outermost level of the periderm and is derived from the underlying meristematic phellogen layer (cork cambium)

PHELLOGEN (CORK CAMBIUM)

The tissue seen in several vascular plants as a portion of the epidermis.

PHELLOGEN (CORK CAMBIUM)

Found between the cork and the primary phloem, it is one of the several layers of the bark.

PHELLOGEN (CORK CAMBIUM)

It is the lateral meristem that is accountable for secondary growth substituting the epidermis in the roots and stems.

PHELLODERM

The secondary cortex, which is formed on the inner side of phellogen

PHELLODERM

It mainly consists of living cells, including chloroplast, which is mainly involved in synthesizing and storage of food.

Monocot

Has a sclerenchymatous bundle sheath on the outside of a vascular bundle

Monocot

No trichomes

Monocot

Vessels are rounded in shape or oval and are arranged in a Y-shaped formation

Monocot

Vascular bundles are closed

Eudicot

No bundle sheath on the outside of a vascular bundle.

Eudicot

Has trichomes

Eudicot

Vessels are of a polygonal shape and are arranged in rows or chains

Eudicot

Vascular bundles always remain open due to the presence of cambium within phloem and xylem, and the phloem fiber cap.

GROUND TISSUES

Can either be parenchyma, collenchyma oR sclerenchyma

GROUND TISSUES

Depends on the plant structure involved and its perceived function

PRIMARY XYLEM (ENDARCH XYLEM)

Distributes water and dissolved minerals upward through the plant, from the roots to the leaves.

Conducting cells

treachery elements which are the constituents of tracheids and vessels. These are typically involved in the transportation of water and also in structural assistance

Tracheids

lateral pit pairs; narrow, tapered ends

Primitive element of xylem

fluid-conducting tissues

PRIMARY XYLEM (ENDARCH XYLEM)

Consisting of a single elongated cell with pointed ends and a secondary, cellulosic wall thickened with lignin (a chemical binding substance)

PRIMARY XYLEM (ENDARCH XYLEM)

Containing numerous pits but having no perforations in the primary cell wall.

Vessel elements

One of the cell types found in xylem, the water conducting tissue of plants

Vessel elements

They are typically found in angiosperms (flowering plants) but absent from most gymnosperms such as conifers

PRIMARY PHLOEM

Carries food downward from the leaves to the roots

PRIMARY PHLOEM

Sieve cells and albuminous cells (gymnosperms)

gymnosperms

Elongated living cells of the phloem, the nuclei of which have fragmented and disappeared and the transverse end walls of which are pierced by sievelike groups of pores plates

Sieve cells and albuminous cells (gymnosperms)

They are the conduits of food (mostly sugar) transported from the leaves to the rest of the plant.

Sieve tube members and companion cells (angiosperms)

Living cells (which do not contain a nucleus) that are responsible for transporting carbohydrates throughout the plant.

PRIMARY PHLOEM

They are associated with companion cells, which are cells that combine with sieve tubes to create the sieve element-companion cell complex.

METAPHLOEM

They are much smaller compared to metaxylem

METAPHLOEM

Even though they have undergone long periods of expansion before differentiation.

Metaxylem

Largest tracheary elements

metaphloem

Cells closest to the metaxylem become

air space

is where the first xylem elements formed

bundle sheath

The entire bundle is enclosed in a ___ of sclerenchyma for additional support

MERISTEMS

Source of all other tissues

MERISTEMS

Regions of undifferentiated, embryonic cells

Totipotent cells

can develop into any type of cell

Pluripotent cells

can develop into many, but not all different types of cells

Multipotent cells

can develop into multiple types of cells, but not as many types as pluripotent cells

SHOOT APICAL MERISTEMS

Divide by mitosis and cytokinesis

SHOOT APICAL MERISTEMS

Responsible for longitudinal growth (increase in height of stem)

Apical buds

at the tips of roots and shoots

Apical buds

primary growing point located at the apex (tip) of the stem.

Axillary buds

located in the leaf axils

Axillary buds

an embryonic or organogenic shoot located in the axil of a leaf.

SUBAPICAL MERISTEM

• Visible differentiation begins;

  • Certain cells stop dividing

  • Start elongating

  • Differentiating into the first tracheids or vessel elements of the vascular bundle

Protoderm

develops into epidermis

Ground Meristem:

Develops into cortex and pith (fundamental tissues)

Procambium

Develop into primary vascular tissues

LEAF TRACE

A vascular bundle that extends from the stem vascular bundles through the cortex and enters a leaf.

LEAF TRACE

Connection of the vascular tissues of stem to the leaf

LEAF GAP

Break in the vascular tissues of a stem above the point of attachment of a leaf trace.