BOT3015L Biology of Flowering Plants Anatomy Seedlings, Meristems, Stems, and Roots Presentation created by Danielle Sherdan All photos from Raven et al.

BOT3015LBiology of Flowering Plants

AnatomySeedlings, Meristems, Stems,

and Roots

Presentation created by Danielle Sherdan

All photos from Raven et al. Biology of Plants except when otherwise noted

Today

•Review seeds and the life cycle of plants

•Seed germination

•Roots and root meristem

•The three primary tissues

•Specialized cells in primary root tissues

•Interesting examples of root function and adaptations

•Shoot and shoot meristem

•Review seeds and the life cycle of plants

•Seed germination

•Roots and root meristem

•The three primary tissues

•Specialized cells in primary root tissues

•Interesting examples of root function and adaptations

•Shoot and shoot meristem

Life cycles

From Outlaw’s lecture series

Angiosperm life cycle

From Outlaw’s lecture series

Floral structure

Gametophytes

Today

Monocot seed development

typical monocot (maize)

seed with ovary wall (pericarp)

Monocots have one cotyledon (scutellum in grasses) that matures

during germination

Source of nutrition for seed germination: endosperm

(compare to dicot) Maize fruit and seed

Dicot seed developmentmaturedicot - two cotyledonsimmature

Three tissue systems:

Dermal

Vascular

Cortex or GroundAll cells of the primary growth in dicots are part of these three systems and originate at meristems

. . . A reminder that endosperm is formed in all angiosperms, but does not persist in dicots. In dicots, cotyledons are the primary source of nutrients for germination.

Today

•Review seeds and the life cycle of plants

•Seed germination

•Roots and root meristem

•The three primary tissues

•Specialized cells in primary root tissues

•Interesting examples of root function and adaptations

•Shoot and root meristem

Seed germination

What causes a seed to resume growth?

What observations did you make while germinating seeds?

What is growth?

Plants-In-MotionTime-lapse videos of plant growth and response

Broadly, where do the energy and basic elements required for growth come from?

Dicot germination and seedling

An example of epigeous (epi=above, geo=earth) germination

Dicot germination and seedling

An example of hypogeous (hypo=below, geo=earth) germination

Monocot germination and seedling

Today

•Review seeds and the life cycle of plants

•Seed germination

•Roots and root meristem

•The three primary tissues

•Specialized cells in primary root tissues

•Interesting examples of root function and adaptations

•Shoot and shoot meristem

Rootthe first structure to emerge from the

germinating seed

Typical dicotTaproot persists and grows deep into the ground

Typical monocotTaproot does not persist and adventitious roots originate from the shoot

Notice the high surface volume: area ratio

Typical of a

dicotTypical of a

monocot

Tap Root vs. Fibrous Root

From Outlaw lecture

What are the functions of roots?

Organization of the plant body

Apical = at the tip (of the root, the shoot, including laterals)

Meristem = group of perpetually “embryonic” cells

Root apical meristem

The rootcap and mucigel protect the root apical meristem as it pushes

through the soil

Mucigel

Today

•Review seeds and the life cycle of plants

•Seed germination

•Roots and root meristem

•The three primary tissues

•Specialized cells in primary root tissues

•Interesting examples of root function and adaptations

•Shoot and shoot meristem

All cells of primary growth are from one of three primary tissues

Diagram of major parts of primary dicot

plant body

Ground tissue is throughout the plant body

Ground tissue of typical dicot root and shoot

RootButtercup (Ranunculus)

ShootAlfalfa (Medicago)

All cells are from one of three primary tissues

Diagram of major parts of primary dicot

plant body

Vascular tissue is throughout the plant body

Vascular tissue of typical dicot root

RootButtercup (Ranunculus)

Vascular tissue of typical dicot shoot

ShootAlfalfa (Medicago)

All cells of primary growth are from one of three primary tissues

Diagram of major parts of primary dicot

plant body

Dermal tissue is throughout the plant body

Ground tissue of typical dicot root and shoot

RootButtercup (Ranunculus)

ShootAlfalfa (Medicago)

Specialized dermal cells in the shoot

The structure of the leaf and aspects of stomatal physiology will be topics of study next week

Specialized epidermal cellsVenus flytrap

Today

•Review seeds and the life cycle of plants

•Seed germination

•Roots and root meristem

•The three primary tissues

•Specialized cells in primary root tissues

•Interesting examples of root function and adaptations

•Shoot and shoot meristem

Root Hairs—a special feature of roots (a)

Radish (Raphanus) Bentgrass (Agrostis)

Root Hairs—a special feature of roots (b)

Cell Division

Cell Elongation

Root Hairs—a special feature of roots (c)

More than with shoots, elongation growth is restricted to very near (~1.5 mm) the root tip; otherwise, elongation would tear off lateral appendages.

Root hairs increase surface area.

Typical dicot root

RootButtercup (Ranunculus)

The endodermis

Casparian Strip—a band of hydrophobic material (mostly suberin) that is impregnated in the wall, preventing apoplastic transport.

From Outlaw’s lecture

The endodermis

Pathways for entry into xylem transport: all require that the solute be transported into the symplast (because the apoplast is discontinuous at the endodermis). Then, solutes are excreted into the apoplast interior to the endodermis.

Apoplast

Symplast

From Outlaw’s lecture

Typical dicot root

RootButtercup (Ranunculus)

Secondary Growth (root)

Example cross section of the dicot root in primary growth

The cambium (perpetually meristematic layer between xylem and phloem) divides mitotically, producing either:

A secondary xylem cell to the inside and a replacement cambial cell.

ORA secondary phloem cell to the outside and a replacement cambial cell. Secondary growth rare in monocots

From Outlaw’s lecture

Ordinarily, lateral roots arise in the pericycle.

But roots can arise adventitiously, too. (Adventitious simply means arising in an unusual location.)

The pericycle

Salix (Salicaceae family)From Outlaw’s lecture

Today

•Review seeds and the life cycle of plants

•Seed germination

•Roots and root meristem

•The three primary tissues

•Specialized cells in primary root tissues

•Interesting examples of root function and adaptations

•Shoot and shoot meristem

Support roots in the marsh

habitat.

Mangrove (a dicot) Interesting Examples

From Outlaw’s lecture

Aerial roots absorb water from the air and have a

multi-layered epidermis for

protection and reduced water

loss

Orchid (a monocot) Interesting Examples

Epidermal layers

Cross section of root

Modified leaves form hollow containers that roots grow into and that collect rainwater and debris. Many ants associate

with these plants, likely adding to nitrogen supply

Flower pot plant (an epiphyte)

Interesting Examples

Today

•Review seeds and the life cycle of plants

•Seed germination

•Roots and root meristem

•The three primary tissues

•Specialized cells in primary root tissues

•Interesting examples of root function and adaptations

•Shoot and shoot meristem

The shoot

What are the functions of the

shoot?

Primary tissues differently organized in angiosperm shoots

Typical of dicots Typical of monocots

Example dicot stem cross sectionvascular bundles in ring with defined pith and cortex

Primary tissues differently organized in angiosperm shoots

ShootAlfalfa (Medicago)

Example monocot stem cross sectionvascular bundles scattered

Primary tissues differently organized in angiosperm shoots

Maize (Zea)

Apical Meristems both have the three primary tissues

ShootRoot

Lilac (Syringa)Radish (Rafarus)

Block Diagram of

Typical Shoot Apical

Meristem

Primary meristems give rise to primary tissuesModified from Outlaw’s lecture

Lilac (Syringa)

Example cross section of the dicot shoot in primary growth

Secondary Growth (shoot)

The cambium (perpetually meristematic layer between xylem and phloem) divides mitotically, producing either:

A secondary xylem cell to the inside and a replacement cambial cell.

ORA secondary phloem cell to the outside and a replacement cambial cell.

From Outlaw’s lecture

The main idea