Lecture 4 Plant Structure Growth And Development Image

Lecture #4 – Plant Structure, Growth And Development Image – the Angel Oak 1

Key Concepts: • • What is a kingdom? Why study plants? What makes a plant? The hierarchy of structure – plant cells, tissues and organs Growth Primary growth – elongation Secondary growth – diameter expansion Morphogenesis occurs during growth 2

Carolus Linnaeus (1707 -1778) Image – Linnaeus The founder of modern taxonomy defined kingdoms by morphological similarity 3

Linnaeus’ Taxonomic Hierarchy Taxonomic Category Example (taxon) Kingdom Plantae, also Metaphyta = all plants Division (phylum) Magnoliophyta = all angiosperms Class Liliopsida = all monocots Order Asparagales = related families (Orchidaceae, Iridaceae, etc) Family Orchidaceae = related genera (Platanthera, Spiranthes, etc) Genus Platanthera = related species (P. ciliaris, P. integra, etc) Specific name/epithet ciliaris = one species 4

Linnaeus’ Taxonomic Hierarchy Taxonomic Category Example (taxon) Kingdom Plantae, also Metaphyta = all plants Division (phylum) Magnoliophyta = all angiosperms Class Liliopsida = all monocots Order Asparagales = related families (Orchidaceae, Iridaceae, etc) Family Orchidaceae = related genera (Platanthera, Spiranthes, etc) Genus Platanthera = related species (P. ciliaris, P. integra, etc) Specific name/epithet ciliaris = one species 5

Images – the yellow fringed orchid Platanthera ciliaris 6

Linnaeus recognized only 2 kingdoms • If it moved – animal; if it didn’t – plant • Fungi were lumped with plants • The microscopic world was largely unknown Images – the 3 multicellular kingdoms, animals, fungi and plants 7

The 5 kingdom system – developed in the 1960’s and used until recently Diagram – the 5 kingdom system 8

Molecular data supports 3 domain classification scheme Diagram – 3 domain system of classification Kingdoms are defined by monophyletic lineage 9

Classification is Dynamic! Diagram – transition from 5 kingdom to 3 domain system indicating dynamic nature of classification Multicellular eukaryotes remain fairly well defined – the plants, fungi and animals. Classification of single celled organisms is still underway. 10

Current Taxonomic Hierarchy Taxonomic Category Example (taxon) Domain Eukarya = all eukaryotic organisms Kingdom Plantae, also Metaphyta = all plants Division (phylum) Magnoliophyta = all angiosperms Class Liliopsida = all monocots Order Asparagales = related families (Orchidaceae, Iridaceae, etc) Family Orchidaceae = related genera (Platanthera, Spiranthes, etc) Genus Platanthera = related species (P. ciliaris, P. integra, etc) Specific name/epithet ciliaris = one species 11

Why Plants? 12

Why Plants? Image – shooting stars 13

What makes a plant? ? ? 14

Images and diagrams – characteristics that separate plants from other kingdoms 15

What makes a plant? ? ? • Multicellular, eukaryotic organisms with extensive specialization • Almost all are photosynthetic, with chloroplasts (= green) Ø Some obtain additional nutrition through parasitism or carnivory Ø Some are saprophytic, entirely without chlorophyll (absorb dead OM) • Excess carbohydrates stored as starch (coiled, branched polymer of glucose) • Cell walls of cellulose = fibrous (not branched) polysaccharide = accounts for the relative rigidity of the cell wall • Cell division by formation of cell plate • Most extant plant species are terrestrial (many characteristics that are adapted for terrestrial life) • Separated from cyanobacteria by chloroplasts • Separated from green algae by various adaptations to 16 Read this later…. terrestrial life

Plants were the first organisms to move onto land • Occurred about 475 mya • Very different conditions from former marine habitat • Many new traits emerged in adaptation to life on dry land • Extensive adaptive radiation into many new ecological niches 17

Four major groups of plants have emerged since plants took to land Diagram – phylogeny of land plants; same on next slide 18

We will focus on angiosperms Next semester in 211 you will learn more about the transition from water to land, and the evolution of reproductive strategies in all plants 19

Angiosperms – the flowering plants: 90% of the Earth’s modern flora Images – flowering plants 20

Basic Structure of the Plant Cell – what’s unique? ? ? Diagram – plant cell; same on next slide 21

Basic Structure of the Plant Cell 22

Critical Thinking • Do all plant cells have chloroplasts? ? ? • How can you tell? ? ? 23

Critical Thinking • Do all plant cells have chloroplasts? ? ? • How can you tell? ? ? 24

Critical Thinking • Do all plant cells have chloroplasts? ? ? • How can you tell? ? ? Image – chloroplast free white bracts on white-top sedge 25

More on the cell wall: • All cell walls are produced by the cell membrane, outside • Primary wall is produced first Diagram – primary and secondary cell walls; same on next slide Ø Mostly cellulose • Secondary walls are produced later Ø Lignified, so ? ? ? • Secondary walls are interior to primary walls 26

More on the cell wall: • All cell walls are produced by the cell membrane • Primary wall is produced first Ø Mostly cellulose • Secondary walls are produced later Ø Lignified, so • Secondary walls are interior to primary walls 27

Five Major Plant Cell Types Micrographs – plant cell types • Parenchyma • Collenchyma • Sclerenchyma • Xylem elements • Phloem elements 28

Parenchyma • • Thin primary wall No secondary wall Many metabolic and storage functions Bulk of the plant body Micrographs – parenchyma cells 29

Collenchyma • Thick primary wall • No secondary wall Micrograph – collenchyma cells; same on next slide ØImplications? ? ? • Support growing tissues 30

Collenchyma • Thick primary wall • No secondary wall ØImplications? ? ? • Support growing tissues 31

Sclerenchyma • Thick secondary wall • Secondary walls are lignified Micrograph – sclerenchma cells; same on next slide ØImplications? ? ? • Support mature plant parts • Often dead at maturity 32

Sclerenchyma • Thick secondary wall • Secondary walls are lignified ØImplications? ? ? • Support mature plant parts • Often dead at maturity 33

Collenchyma vs. Sclerenchyma • • Both provide structural support Both have thick walls Collenchyma = thick primary wall, no lignin Sclerenchyma = thick secondary wall, lignified Micrographs – collenchyma and sclerenchyma cell comparison 34

Xylem Elements • Lignified secondary walls • Always dead at maturity (open) • Function to transport water and dissolved nutrients, and to support the plant • Tracheids and vessel elements Diagrams and micrograph – tracheids and vessel elements 35

Critical Thinking • Vessel elements and the convergent evolution of rings • What else looks like this? ? • What is the function? ? Micrograph – rings of lignin in developing vessel element; same on next slide 36

Critical Thinking • Vessel elements and the convergent evolution of rings • What else looks like this? ? • What is the function? ? 37

Phloem Elements • Sieve tube members + companion cells • STM lack nucleus, ribosomes – their metabolism is controlled by the companion cells Micrograph – phloem elements • Function to transport the products of metabolism • Non-angiosperms have more primitive phloem elements 38

Critical Thinking • What might be the functional advantage of a cell with no nucleus? ? ? Diagram – phloem elements 39

Critical Thinking • What might be the functional advantage of a cell with no nucleus? ? ? 40

Plants are Simple Only Five Major Cell Types Micrographs – plant cell types • Parenchyma • Collenchyma • Sclerenchyma • Xylem elements • Phloem elements 41

Tissue Systems • • Diagram – plant tissue types Epidermis Vascular Ground Meristem 42

Epidermis Tissue: • Covers the outer surface of all plant parts • Shoot surfaces covered with waxy cuticle Micrograph and diagram – epidermis ØHelps to protect the plant and prevent desiccation • Usually a single, transparent cell layer • Tight joints; stomata allow for gas exchange 43

Critical Thinking • Do roots have a waxy cuticle? ? ? • Why or why not? ? ? 44

Critical Thinking • Do roots have a waxy cuticle? ? ? • Why or why not? ? ? Never forget the importance of natural selection!!!!! 45

Vascular Tissue: • Transports water, solutes, and metabolic products throughout the plant • Confers structural support • Includes xylem elements, phloem elements, parenchyma and sclerenchyma fibers Micrograph – vascular bundle in cross section 46

Critical Thinking • Why does vascular tissue give structural support to a plant? ? ? 47

Critical Thinking • Why does vascular tissue give structural support to a plant? ? ? 48

Ground Tissue: • Bulk of the plant body – pith, cortex and mesophyll • Mostly parenchyma • Most metabolic, structural and storage functions Micrograph and diagram – ground tissues in stems and leaves 49

Critical Thinking • Is this what the inside of a tree looks like? ? ? Micrograph – herbaceous dicot stem 50

Critical Thinking • Is this what the inside of a tree looks like? ? ? Micrograph of herbaceous eudicot stem; image of woody stem; diagram of woody stem tissue organization 51

Meristem Tissue: • How the plant grows • Cells divide constantly during the growing season to make new tissues • More details later Image – new growth at tip of stem 52

Plants are Simple Only Four Major Tissue Types • • Diagram – plant tissue systems Epidermis Vascular Ground Meristem 53

Tissues Make Organs: • Roots – anchor the plant, absorb water and nutrients • Stems – support the leaves • Leaves – main site of photosynthesis • Reproductive organs (flowers, cones, etc – more later) All organs have additional functions – hormone synthesis, transport, etc… 54

Plant Organ Systems Diagram – root and shoot systems 55

Modern molecular evidence indicates four classes of angiosperms paleoherbs magnoliids eudicots monocots ancestral 56

Paleoherbs and Magnoliids comprise about 3% of angiosperms Paleoherbs • Aristolochiaceae, Nymphaeaceae, etc Magnoliids • Magnoliaceae, Lauraceae, nutmeg, black pepper, etc Images – water lily and magnolia 57

Modern evidence indicates 4 classes of angiosperms paleoherbs magnoliids eudicots monocots ~ 97% of angiosperms ancestral 58

Monocots include grasses, sedges, iris, orchids, lilies, palms, etc…. . Images – monocots 59

Eudicots include 70+% of all angiosperms: • Most broadleaf trees and shrubs • Most fruit and vegetable crops • Most herbaceous flowering plants Images – eudicots 60

Monocots vs. Eudicots Monocots • Flower parts in multiples of 3 • Parallel leaf venation • Single cotyledon • Vascular bundles in complex arrangement • ~90, 000 species Eudicots • Flower parts in multiples of 4 or 5 • Netted leaf venation • Two cotyledons • Vascular bundles in a ring around the stem • Modern classification indicates 2 small primitive groups + eudicots • 200, 000+ species 61

Root System Tissue Organization Eudicots Monocots Micrographs – cross sections of eudicot and moncot roots; same on next 3 slides Epidermis, ground, endodermis, pericycle, vascular tissues 62

Eudicot root – closeup Epidermis Cortex Endodermis Pericycle Vascular tissues – in solid core 63

Monocot root – closeup Epidermis Cortex Endodermis Pericycle Vascular tissues – in ring Pith in the very center 64

Critical Thinking • Where do branch roots form? ? ? 65

Critical Thinking • Where do branch roots form? ? ? Micrograph – root emerging from pericycle 66

Stem System Tissue Organization Eudicots Monocots Micrograph – eudicot and monocot stem tissue organization; same on next 4 slides Epidermis, ground, vascular tissues 67

Eudicot stem – closeup Epidermis Cortex Vascular tissues – bundles in a ring Pith 68

Monocot stem – closeup Epidermis Cortex Vascular tissues – bundles are scattered 69

Wood forms from a meristem that links the vascular bundles: 70

Stem System Tissue Organization Eudicots Monocots cannot make wood More on wood formation later 71

Leaf Tissue Arrangement Micrograph – cross-section of leaf tissue arrangement Epidermis, ground, vascular tissues 72

Leaf closeup Epidermis Diagram – leaf tissue arrangement Cortex – palisade mesophyll Cortex – spongy mesophyll Vascular tissues 73

Stomata – pores to allow for gas exchange and transpiration Micrograph – epidermis tissue showing stomata 74

See, plants really are simple • 5 cell types • 4 tissue types • 4 organ types Diagram – shoot and root systems 75

Plant Growth • Remember, most plants are anchored by roots • They can’t move to escape or take advantage of changes in their environment • Plants adjust to their environment • Simple structure + lots of developmental flexibility allow plants to alter when and how they grow Developmental flexibility comes from meristems 76

Meristem Tissues • Actively dividing cells that generate all other cells in the plant body • Cause indeterminate growth ØStems and roots elongate throughout the plant’s life (indeterminate primary growth) ØTrees continually expand in diameter (indeterminate secondary growth) ØBranches form in roots and stems 77

Not all plant parts have indeterminate growth patterns Indeterminate: Roots and Stems Determinate: Leaves Flowers Fruits These parts grow throughout the life of the plant, exploring new environments or responding to damage These parts grow to a genetically +/predetermined size and shape and then stop – cannot repair 78 damage

Some mature cells can de -differentiate to become meristematic once more!!! • Primarily occurs in the indeterminate parts ØStems and roots • A process that very seldom occurs in other kingdoms • Allows stems and roots to repair damage and form branches and sprouts 79

Critical Thinking • Can all plant cells de-differentiate? ? ? • What would control this? ? ? 80

Critical Thinking • Can all plant cells de-differentiate? ? ? • What would control this? ? ? 81

Critical Thinking • Can all plant cells de-differentiate? ? ? • What would control this? ? ? 82

Growth in Plants: an irreversible increase in size due to metabolic processes (processes that use ATP energy) • Cell division produces new cells = function of meristem • Cell expansion increases the size of the new cells = up to 80% of size increase • Cell differentiation occurs during and after expansion 83

The plane of cell division contributes to morphogenesis Diagram – planes of cell division and the effect on morphogenesis Division in 2 planes forms sheets of cells 84

Critical Thinking • What tissues are files of cells? ? ? • What tissues are sheets of cells? ? ? • What tissues are 3 -D bulky? ? ? 85

Critical Thinking • What tissues are files of cells? ? ? • What tissues are sheets of cells? ? ? • What tissues are 3 -D bulky? ? ? 86

Growth in Plants: an irreversible increase in size due to metabolic processes (processes that use ATP energy) • Cell division produces new cells = function of meristem • Cell expansion increases the size of the new cells = up to 80% of size increase • Cell differentiation occurs during and after expansion 87

Auxin-mediated cell expansion Diagram – how auxin works to promote cell expansion ATP is used 88

The direction of cell expansion depends on cellulose orientation, and contributes to morphogenesis Diagram – cellulose orientation in primary wall and the effects on morphogenesis 89

Growth in Plants: an irreversible increase in size due to metabolic processes (processes that use ATP energy) • Cell division produces new cells = function of meristem • Cell expansion increases the size of the new cells = up to 80% of size increase • Cell differentiation occurs during and after expansion 90

Expansion and differentiation occur in an overlapping zone in all plant parts Diagram – patterns of growth in roots 91

REVIEW: Growth in Plants: an irreversible increase in size due to metabolic processes (processes that use ATP energy) • Cell division produces new cells = function of meristem • Cell expansion increases the size of the new cells = up to 80% of size increase • Cell differentiation occurs during and after expansion 92

Location of the meristems determines the pattern of plant growth Diagram – location of meristems on the plant body; next slide also Most common meristems: apical, axillary and lateral 93

Apical meristems cause elongation of roots and stems 94

Micrograph – longitudinal section showing distribution of tissues in root 95

Images – root cap and mucigel 96

Root Cap • Protects the meristem • Secretes mucigel ØEases movement of roots through soil ØSecretes chemicals that enhance nutrient uptake • Constantly shedding cells ØMechanical abrasion as roots grow through soil • Constantly being replenished by meristem 97

Primary Growth in Roots Diagram – longitudinal section of root showing zones of growth; same on next 2 slides 98

Primary Growth in Roots 99

Primary Growth in Roots 100

Root Hairs • Form as the epidermis fully differentiates • Extensions off epidermal cells Ø NOT files of cells Ø Part of an epidermal cell Micrograph – root hairs extending from epidermis; same on next few slides • Hugely increase the surface area of the epidermis • 10 cubic cm (double handful) of soil might contain 1 m of plant roots Ø Mostly root hairs 101

Critical Thinking • What is the selective advantage of root hairs? ? ? 102

Critical Thinking • What is the selective advantage of root hairs? ? ? 103

Root Hairs • By contrast, 10 cc of soil may contain up to 1000 m of fungal hyphae (1 km!) Ø These serve a similar function for the fungus Ø Ramify throughout the substrate for maximum absorption Ø Some fungi form symbiotic associations with plant roots and both organisms benefit from this huge absorptive surface area! Ø More in 211…. . 104

Apical meristems cause elongation of roots and stems Diagram – location of apical meristems 105

Apical Meristems in Shoots Micrograph – longitudinal section of stem showing apical and axillary meristems 106

Critical Thinking • There is no “shoot cap” – why not? ? ? 107

Critical Thinking • There is no “shoot cap” – why not? ? ? 108

Axillary meristems allow for branching – similar in structure and function to apical meristems Diagram – meristem locations Remember, pericycle in roots has same function 109

Axillary Meristems in Shoots Micrograph – longitudinal section of stem showing apical and axillary meristems; same on next two slides 110

Primary Growth in Shoots • Apical meristem • Leaf primordia • Axillary buds 111

As with roots – cell division occurs first; zones of expansion and differentiation overlap Axillary buds may activate to make branches, or may remain dormant 112

Primary growth of a shoot – elongation from the tip Diagram – how stems elongate during primary growth 113

Lateral meristems cause diameter expansion Diagram – meristem locations Roots also expand in diameter, but it’s more complicated – we’ll save that for BIOL 300 114

Lateral Meristems = Cambiums Diagram – lateral meristems 115

Remember: Diagram – primary vs. secondary growth Elongation is primary growth Diameter expansion is secondary growth 116

Secondary growth – diameter expansion Images – cross section of wood and whole tree 117

Eudicot Stem – recall the arrangement of vascular bundles Micrograph – cross section of a eudicot stem; same on next 2 slides 118

Eudicot Stem – recall the arrangement of vascular bundles Vascular cambium forms here: 119

Eudicot Stem – recall the arrangement of vascular bundles Vascular cambium forms here: a cylinder of meristem tissue between the xylem to the interior and the phloem to the exterior 120

Secondary xylem and phloem form through cell division by the vascular cambium Diagram – location of the vascular cambium relative to other tree tissues 121

During primary growth the vascular tissues form in bundles from the apical meristem Diagram – transition from primary growth to secondary growth; same on next slide During secondary growth the vascular tissues form in cylinders from the vascular cambium 2 o xylem to the inside 2 o phloem to the outside 122

Secondary xylem accumulates 123

Secondary Xylem = Wood! Micrograph – cross section of woody plant showing secondary tissues; same on next slide 124

Annual growth rings are accumulating rings of secondary xylem 125

Critical Thinking • Why do eudicot trees taper? ? ? Diagram – pattern of accumulation of secondary xylem as a tree grows; same on next slide 126

Critical Thinking • Why do eudicot trees taper? ? ? 127

Bark • All tissues external to the vascular cambium • Diameter expansion splits original epidermis ØBark structurally and functionally replaces epidermis • Inner bark ØFunctional secondary phloem • Outer bark ØComposition varies as tree matures 128

Bark Formation Micrograph – cross section of a tree showing bark formation 129

Cork Cambium • Meristematic tissue • Forms in a cylinder during 2 o growth • Divides to produce cork cells ØCells filled with waxy, waterproof suberin • Eventually cork cambium becomes cork itself 130

More on cork cambium • First layer develops from cortex ØDe-differentiation!!! • Second layer forms from cortex – same process • Third layer forms from cortex…. . • Cortex eventually runs out • Then what? ? ? 131

More on cork cambium • First layer develops from cortex ØDe-differentiation!!! • Second layer forms from cortex – same process • Third layer forms from cortex…. . • Cortex eventually runs out • Then what? ? ? 132

More on cork cambium • First layer develops from cortex ØDe-differentiation!!! • Second layer forms from cortex – same process • Third layer forms from cortex…. . • Cortex eventually runs out • Then what? ? ? 133

More on cork cambium • First layer develops from cortex ØDe-differentiation!!! • Second layer forms from cortex – same process • Third layer forms from cortex…. . • Cortex eventually runs out • Then what? ? ? 134

Critical Thinking • What is the next available layer of tissue? ? ? Diagram – lateral meristems and the secondary tissues in a tree; same on next slide 135

Critical Thinking • What is the next available layer of tissue? ? ? 136

More on cork cambium • First layer develops from cortex ØDe-differentiation!!! • Second layer forms from cortex – same process • Third layer forms from cortex…. . • Cortex eventually runs out • Then what? ? ? 137

More on cork cambium • First layer develops from cortex ØDe-differentiation!!! • Second layer forms from cortex – same process • Third layer forms from cortex…. . • Cortex eventually runs out • Then what? ? ? 138

Stem Tissue Derivations and Fates: Diagram – how undifferentiated cells develop into the tissues of the plant body Cells divide, expand differentiate 139

Review: Key Concepts: • • What is a kingdom? Why study plants? What makes a plant? The hierarchy of structure – plant cells, tissues and organs Growth Primary growth – elongation Secondary growth – diameter expansion Morphogenesis occurs during growth 140

Monocots, Palmetto Trees, Ft. Moultrie and the SC State Flag Various images and a micrograph of a monocot stem – an example of one influence of plants on American history 141