Lecture 1

BIOL 225/2 Dr. S.Azam

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FORM AND FUNCTION OF ORGANISMS

(PLANT BIOLOGY ) BIOL 225/2

2012-2013

Lecture 1 Characteristics of plant cells; Types of cells & tissues

Oct 19, 2012

Dr. Sonish Azam

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PLANT FORM AND FUNCTION BIOL 225/2 2012-2013

Dr. Sonish Azam Office: •  Office: SP 437.13 •  Tel: 514-848-2424 ex 3395

•  Email: [email protected] •  Office hours: By appointment

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CLASS SCHEDULE

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Dr. Ian Ferguson & Dr. Sonish Azam Course Outline BIOL 225/2 (2012-2013) 2

of the lecture material will be covered in lecture time, and it is expected that you come prepared by reading the assigned chapters in the textbook before each lecture and any additional material that the instructors may provide or request that you read.

Class Dates Lecture Topics Chapters 5 Sept Introduction, Animal Diversity 32 7 Sept Animal Form &Function 40 12 Sept Animal Nutrition 41 14 Sept Circulation 42 17 Sept. Deadline for withdrawal with tuition refund from two-term and fall-term courses. 19 Sept Gas Exchange 42 21 Sept The Immune System 43 26 Sept Osmoregulation & Excretion 44 28 Sept Hormones & the Endocrine System 45, 11 3 Oct Animal Reproduction 46 5 Oct Animal Development 47 10 Oct Nervous Systems 48 12 Oct Sensory &Motor Mechanisms 49 17 Oct QUIZ - Animal section 19 Oct Characteristics of plant cells, Types of cells & tissues 35 24 Oct Characteristics of plant cells, Types of cells & tissues 35 26 Oct Form, function & organization of root, shoot & leaf; Transport 35, 36 28 Oct. Last day for academic withdrawal from fall-term courses. 31 Oct Form, function & organization of root, shoot & leaf; Transport 36 2 Nov Translocation & Transpiration; Plant Nutrition 37 7 Nov Translocation & Transpiration; Plant Nutrition 37 9 Nov Plant Nutrition; Photosynthesis. 37, 10 14 Nov QUIZ - Plant section 16 Nov Photosynthesis; Respiration 10, 9 21 Nov Photosynthesis; Respiration 9, 39 23 Nov Plant Growth & Development; Biotechnology 39 28 Nov Plant Growth & Development; Biotechnology 38 30 Nov Biotechnology 38

The Final Exam for the combined animal and plant sections will be scheduled during the exam period: December 6-20, 2012 3. Course Material The required textbook is available at the Concordia University Loyola Bookstore: Campbell Biology, Ninth Edition (Reece et al, 2011). The course website is available through your MyConcordia portal. It provides this course outline, some lecture note templates, exam marks when available, etc.

BIOL 225/2

•  Lecture PDF will be posted on moodle •  Please stay up to date with the information on

moodle

•  Students are expected to follow the slides and consult the book ‘Campbell Biology’ if they require additional description of the course material

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PLANTS…COMPUTER ART?

•  Romanesco grows according to a repetitive program (fractals in mathematics)

•  The development of plants depends on the environment and is highly adaptive

© 2011 Pearson Education, Inc. 5

PLANTS HAVE A HIERARCHICAL ORGANIZATION CONSISTING OF ORGANS, TISSUES, AND CELLS

•  A tissue is a group of cells consisting of one or more cell types that together perform a specialized function

•  An organ consists of several types of tissues that together carry out particular functions

•  Plants have organs composed of different tissues, which in turn are composed of different cell types



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THE THREE BASIC PLANT ORGANS: ROOTS, STEMS AND LEAVES

•  Basic morphology of vascular plants reflects their evolution as organisms that draw nutrients from below ground and above ground

•  Plants take up water and minerals from below ground

•  Plants take up CO2 and light from above ground


PARTS OF A PLANT

Reproductive shoot (flower)

Apical bud

Node

Internode

Apical bud

Vegetative shoot

Leaf Blade Petiole

Stem

Taproot

Lateral (branch) roots

Shoot system

Root system

Axillary bud

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•  Roots rely on sugar produced by photosynthesis in the shoot system, and shoots rely on water and minerals absorbed by the root system

•  Monocots and Eudicots are the two major groups of angiosperms

© 2011 Pearson Education, Inc.

ROOT AND SHOOT

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Know the definitions and characteristics of: •  Monocots •  Eudicots •  Angiosperms •  Gymnosperms

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ROOTS

•  A root is an organ with important functions: 1.  Anchoring the plant

2.  Absorbing minerals and water 3.  Storing carbohydrates


•  Most eudicots and gymnosperms have a taproot system, which consists of: •  A taproot, the main vertical root •  Lateral roots, or branch roots, that arise from the

taproot

•  Most monocots have a fibrous root system, which consists of: •  Adventitious roots that arise from stems or leaves •  Lateral roots that arise from the adventitious roots


ROOTS IN MONOCOTS AND DICOTS

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Prop roots

Storage roots

“Strangling” aerial roots

Buttress roots

Pneumatophores

Many plants have root adaptations with specialized functions

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STEMS

A stem is an organ consisting of

•  An alternating system of nodes, the points at which leaves are attached

•  Internodes, the stem segments between nodes


http://www.uwgb.edu/biodiversity/herbarium/trees/glossary_for_trees01.htm

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•  An axillary bud is a structure that lies at the junction of the stem and petiole of a plant and has the potential to form a lateral shoot, or branch

•  An apical bud, or terminal bud, is located near the shoot tip and causes elongation of a young shoot

•  Apical dominance helps to maintain dormancy in most axillary buds


STEMS

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Rhizomes

Rhizome

Bulbs

Storage leaves

Stem Stolons

Tubers

Root

Stolon

Many plants have modified stems (e.g., rhizomes, bulbs, stolons, tubers)

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LEAVES

•  The leaf is the main photosynthetic organ of most vascular plants

•  Leaves generally consist of a flattened blade and a stalk called the petiole, which joins the leaf to a node of the stem

•  Monocots and eudicots differ in the arrangement of veins, the vascular tissue of leaves

•  Most monocots have parallel veins •  Most eudicots have branching veins

•  In classifying angiosperms, taxonomists may use leaf morphology as a criterion


Simple leaf

Axillary bud Petiole

Compound leaf Leaflet

Axillary bud Petiole

Doubly compound leaf

Axillary bud

Petiole

Leaflet

LEAVES :SIMPLE & COMPOUND

18 How would you differentiate between a leaf and a leaflet?


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Tendrils

Spines

Storage leaves

Reproductive leaves

Bracts

Some plant species have evolved modified leaves that serve various functions

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PLANT TISSUES

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DERMAL, VASCULAR AND GROUND TISSUES

•  Each plant organ has dermal, vascular, and ground tissues

•  Each of these three categories forms a tissue system

•  Each tissue system is continuous throughout the plant


Dermal tissue

Ground tissue

Vascular tissue

Three kinds of tissues

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•  In nonwoody plants, the dermal tissue system consists of the epidermis (an outer layer of tightly packed cells)

•  A waxy outer coating called the cuticle helps prevent water loss from the epidermis

•  In woody plants, protective tissues called periderm replace the epidermis in older regions of stems and roots

•  Trichomes are outgrowths of the shoot epidermis and can help with insect defense


DERMAL TISSUE SYSTEM

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Very hairy pod (10 trichomes/

mm2)

Slightly hairy pod (2 trichomes/

mm2)

Bald pod (no trichomes)

Very hairy pod: 10% damage

Slightly hairy pod: 25% damage

Bald pod: 40% damage

EXPERIMENT : Soybean pod trichomes protect against beetle damage

RESULTS

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•  The vascular tissue system carries out long-distance transport of materials between roots and shoots

•  The two vascular tissues are 1.  Xylem conveys water and dissolved minerals

upward from roots into the shoots 2.  Phloem transports organic nutrients from

where they are made to where they are needed


VASCULAR TISSUE SYSTEM

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•  The vascular tissue of a stem or root is collectively called the stele

•  In angiosperms the stele of the root is a solid central vascular cylinder where as, the stele of stems and leaves is divided into strands of xylem and phloem


VASCULAR TISSUE SYSTEM

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•  Tissues that are neither dermal nor vascular are the ground tissue system

•  Ground tissue internal to the vascular tissue is pith, ground tissue external to the vascular tissue is cortex

•  Ground tissue includes cells specialized for storage, photosynthesis, and support


GROUND TISSUE SYSTEM

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PLANT CELLS

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COMMON TYPES OF PLANT CELLS

•  Like any multicellular organism, a plant is characterized by cellular differentiation, the specialization of cells in structure and function

•  The major types of plant cells are: 1.  Parenchyma 2.  Collenchyma 3.  Sclerenchyma 4.  Water-conducting cells of the xylem 5.  Sugar-conducting cells of the phloem


PARENCHYMA CELLS •  Have thin and flexible

primary walls

•  Lack secondary walls •  Fleshy tissue of many

fruits

•  Perform the most metabolic functions

•  Retain the ability to divide and differentiate


Parenchyma cells in Elodea leaf, with chloroplasts (LM)

60 µm

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COLLENCHYMA CELLS

•  Are grouped in strands and help support young parts of the plant shoot

•  Have thicker and uneven primary cell walls

•  Lack secondary walls

•  Provide flexible support without restraining growth


Collenchyma cells (in Helianthus stem) (LM)

5 µm

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SCLERENCHYMA CELLS •  Are the supporting elements in plants •  Are rigid because of thick secondary walls

strengthened with lignin

•  Are dead at functional maturity (can not elongate) •  Secondary wall is produced before the protoplasm

dies

•  There are two types: 1.  Sclereids are short and irregular in shape and

have thick lignified secondary walls

2.  Fibers are long and slender and arranged in threads



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Cell wall

Sclereid cells in pear (LM)

Fiber cells (cross section from ash tree) (LM)

25 µm

5 µm

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WATER-CONDUCTING CELLS OF THE XYLEM

The two types of water-conducting cells are dead at maturity 1.  Tracheids are found in the xylem of all vascular plants

•  Thin cells with tapered ends •  Water moves from cell to cell through the pits

2.  Vessel elements are common to most angiosperms and a few gymnosperms •  Vessel elements align end to end to form long

micropipes called vessels •  End walls of vessel elements have perforation plates

that enable water to flow freely



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Vessel Tracheids 100 µm

Tracheids and vessels (colorized SEM)

Perforation plate

Vessel element

Vessel elements, with perforated end walls

Pits

Tracheids 35

SUGAR-CONDUCTING CELLS OF THE PHLOEM

•  Sieve-tube elements are cells that transport sugar in angiosperms

•  Are alive at functional maturity, though they lack organelles

•  Sieve plates are the porous end walls that allow fluid to flow between cells along the sieve tube

•  Each sieve-tube element has a companion cell whose nucleus and ribosomes serve both cells



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Sieve-tube element (left) and companion cell: cross section (TEM)

Sieve-tube elements: longitudinal view

Sieve plate

3 µm

Companion cells

Sieve-tube elements

Plasmodesma

Sieve plate

Nucleus of companion cell

Sieve-tube elements: longitudinal view (LM)

30 µm

15 µm

Sieve plate with pores (LM) 37

MERISTEMS GENERATE CELLS FOR PRIMARY AND SECONDARY GROWTH

•  A plant can grow throughout its life; this is called indeterminate growth

•  Some plant organs cease to grow at a certain size; this is called determinate growth

•  Plants are capable of Indeterminate growth because of the presence of Meristems

•  Meristems are perpetually embryonic tissue that divide when conditions permit.



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1.  Apical meristems are located at the tips of roots and shoots and at the axillary buds of shoots •  Apical meristems elongate roots and shoots, a

process called primary growth 2.  Lateral meristems add thickness to woody plants, a

process called secondary growth •  There are two lateral meristems

a)  vascular cambium adds layers of vascular tissue called secondary xylem (wood) and secondary phloem

b)  cork cambium replaces the epidermis with periderm, which is thicker and tougher


MERISTEMS ARE OF TWO TYPES :

Shoot tip (shoot apical meristem and young leaves)

Axillary bud meristem

Root apical meristems

Vascular cambium Cork cambium

Lateral meristems

Primary growth in stems Epidermis

Cortex Primary phloem Primary xylem

Pith

Secondary growth in stems Cork cambium

Cortex

Primary phloem

Secondary phloem

Vascular cambium

Secondary xylem

Primary xylem

Pith

Periderm

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Flowering plants can be categorized based on the length of their life cycle

1.  Annuals complete their life cycle in a year or less. E.g. cereals, legumes and wild flowers

2.  Biennials require two growing seasons to complete their life cycle. E.g. turnips

3.  Perennials live for many years. E.g shrubs and grass. (Buffalo grass in N.America plains had sprouted att he end of last ice age and are 10000 years old today)


PRIMARY GROWTH LENGTHENS ROOTS AND SHOOTS

Primary growth lengthens the parts of the root and shoot systems produced by apical meristems



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PRIMARY GROWTH OF ROOTS

•  The root tip is covered by a root cap, which protects the apical meristem as the root pushes through soil

•  Growth occurs just behind the root tip, in three zones of cells:

1.  Zone of cell division

2.  Zone of elongation 3.  Zone of differentiation, or maturation


Epidermis

Cortex

Root hair

Vascular cylinder

Zone of differentiation

Zone of elongation

Zone of cell division (including apical meristem)

Key to labels

Root cap

Dermal Ground Vascular

Mitotic cells

100 µm 44


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•  The primary growth of roots produces the epidermis, ground tissue, and vascular tissue

•  In angiosperm roots, the stele is a vascular cylinder o  In most eudicots, the xylem is starlike in

appearance with phloem between the “arms” o  In many monocots, a core of parenchyma

cells is surrounded by rings of xylem then phloem


Epidermis Cortex Endodermis Vascular cylinder Pericycle Core of parenchyma cells Xylem

Phloem

Endodermis Pericycle

Xylem

Phloem


Key to labels

50 µm

100 µm 100 µm

(a) (b) Root with parenchyma in the

center (typical of monocots)

Root with xylem and phloem in the center (typical of eudicots)

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•  The ground tissue, mostly parenchyma cells, fills the cortex, the region between the vascular cylinder and epidermis

•  The innermost layer of the cortex is called the endodermis

•  The endodermis regulates passage of substances from the soil into the vascular cylinder


Emerging lateral root

Cortex

Vascular cylinder

Pericycle

100 µm Epidermis Lateral root

3 2 1

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•  Lateral roots arise from within the pericycle, the outermost cell layer in the vascular cylinder


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PRIMARY GROWTH OF SHOOTS

•  A shoot apical meristem is a dome-shaped mass of dividing cells at the shoot tip

•  Leaves develop from leaf primordia along the sides of the apical meristem

•  Axillary buds develop from meristematic cells left at the bases of leaf primordia


Shoot apical meristem Leaf primordia

Young leaf

Developing vascular strand

Axillary bud meristems

0.25 mm 50


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TISSUE ORGANIZATION OF STEMS

•  Lateral shoots develop from axillary buds on the stems surface and disrupt no other tissues

•  In most eudicots, the vascular tissue consists of vascular bundles arranged in a ring

•  In most monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a ring


Sclerenchyma (fiber cells)

Phloem Xylem

Ground tissue connecting pith to cortex

Pith

Cortex Vascular bundle

Epidermis

1 mm 1 mm

Vascular bundles

Epidermis

Ground tissue


Key to labels

(a) (b) Cross section of stem with vascular bundles forming a ring (typical of eudicots)

Cross section of stem with scattered vascular bundles (typical of monocots)

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TISSUE ORGANIZATION OF LEAVES

•  The epidermis in leaves is interrupted by stomata, which allow CO2 and O2 exchange between the air and the photosynthetic cells in a leaf

•  Each stomatal pore is flanked by two guard cells, which regulate its opening and closing

•  The ground tissue in a leaf, called mesophyll, sandwiched between the upper and lower epidermis


The mesophyll of eudicots has two layers: 1.  The palisade mesophyll in the upper part of the leaf

2.  The spongy mesophyll in the lower part of the leaf; the loose arrangement allows for gas exchange




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FIGURE 35.18

Key to labels


Cuticle

Bundle- sheath cell

Xylem Phloem

Sclerenchyma fibers

Stoma

Upper epidermis Palisade mesophyll Spongy mesophyll Lower epidermis

Cuticle Vein Guard cells

(a) Cutaway drawing of leaf tissues

(b)

(c) Cross section of a lilac (Syringa) leaf (LM)

Surface view of a spiderwort (Tradescantia) leaf (LM)

Guard cells

Stomatal pore

Epidermal cell

Vein Air spaces Guard cells

50 µ

m

100 µ

m

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•  The vascular tissue of each leaf is continuous with the vascular tissue of the stem

•  Veins are the leaf’s vascular bundles and function as the leaf’s skeleton

•  Each vein in a leaf is enclosed by a protective bundle sheath



Lecture 1

Documents

biol 2252

shoot apical

vascular tissue

tissue system

apical meristems

hairy pod

axillary bud

vascular tissue