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Chapters 31 & 32: Plant Structure & Reproduction

Chapters 31 & 32: Plant Structure & Reproduction

Chapters 31 & 32: Structure &

1. Structure

2. & Development 1. Flowering Plant Structure “ & ” 2 basic parts of flowering : system • stems • • ,

system • taproot (dicots) • roots Plant Types 1) Dermal tissue • outer, protective covering of the plant

Dicot stem Monocot stem Vascular Vascular 2) bundle Cortex tissue • transport of fluids & Pith

Epidermis structural support

Xylem Vascular Phloem cylinder

Key 3) Ground Epidermis Dermal tissue tissue Cortex • everything Dicot root else! PHLOEM Vascular Tissue High concentration 1 High pressure sugar 2 Phloem water • transports products of Source cell () throughout plant from sugar sources to sugar sinks • driven by , SUGAR Sink SINK increased pressure due cell to more sugar solutes near source 3 sugar

4 Xylem water • transports water & Low sugar concentration Low water pressure minerals “upward” Low water pressure (towards shoots, leaves) How is water moved “upward”?

Xylem Water lost by Mesophyll cells

Air space within from leaves Outside air “pulls” water Adhesion Transpiration Cell upward wall Water through xylem molecule to replace what was lost.

Xylem Cohesion, Cohesion and cells by hydrogen Flow of water adhesion in the xylem bonding Depends on:

Root • cohesion due

Soil particle to H-bonding

Water • adhesion to Water uptake from soil xylem cells Leaf Structure epidermis

palisade mesophyll sheath xylem

spongy mesophyll phloem

guard cells stomata Epidermis • outer cell layer on both sides of leaf • secrete waxy to waterproof the leaf Mesophyll (ground tissue of leaf) • loosely packed photosynthetic cells • palisade or spongy arrangement Vascular Bundles • phloem & xylem • surrounding sheath Stomata (singular = “stoma”) • openings for , transpiration • regulated by guard cells Root Function Roots supply the plant with: CO2 • anchorage in the soil • water • mineral nutrients

• oxygen (O2)

• for respiration since O2 plants make ATP just as Minerals we do

• over-watering can H2O suffocate a plant! Importance of Nitrogen Fixation Plants require the element nitrogen in the form of + - ammonium (NH4 ) or nitrate (NO3 ) ions, however they CAN’T “fix” atmospheric nitrogen (N2) into these forms.

ATMOSPHERE

N2

Amino ammonium & nitrate acids, etc.

N2 Nitrogen-fixing ions taken up by roots bacteria NH + H+ 4 Soil + NO – NH3 NH4 3 (nitrate) (ammonium) Nitrifying bacteria Ammonifying bacteria Organic material Root Soil bacteria and some fungi CAN fix nitrogen, thus plants depend on these microbes for useable nitrogen. Monocots vs Dicots Flowering plants are of 2 basic types:

Seed Leaves Leaf veins Stems Flowers Roots MONOCOTS

One Vascular bundles Floral parts Fibrous cotyledon Main veins usually parallel in complex usually in root system arrangement multiples of three

DICOTS

Vascular bundles Floral parts arranged in ring usually in Two multiples of Taproot cotyledons Main veins usually branched four or five usually present Monocot vs Dicot Features Cotyledons (embryonic “ leaves”) • nourish the seedling: monocots have 1, dicots have 2 Roots • dicots have a central taproot, monocots do not Stems • dicots have a vascular structure organized into rings Leaves • monocots have narrow, smooth leaves w/parallel veins • dicots have broader leaves w/branched vein patterns Flowers • monocots – layered parts come in groups of 3 • dicots – layered flower parts come in groups of 4 or 5 2. Plant Reproduction & Development Basic Modes of Reproduction Plants reproduce in 2 basic ways:

Asexually: • piece of parent plant gives rise to new plant • involves mitotic cell division only • offspring are genetically identical to parent

Sexually: • fusion of haploid generates offspring • offspring are genetically unique Life Cycle of Plants (sexual)

• fertilization produces a that develops into a diploid

• haploid produced by in flowers grow into multicellular haploid , some cells of which are gametes The Plant Sexual Life Cycle The sexual life cycle of plants is unique, occurring by “Alternation of Generations”:

The sporophyte stage (diploid) • the plant is made of diploid cells • produces haploid spores by meiosis in the reproductive structures (e.g., flowers)

The stage (haploid)

• grows from haploid (via ) • produces gametes ( and/or egg) • fertilization then produces a new diploid sporophyte! ) n ( e ) t n y 2 h ( p e o t t y h me p a o r g o p s in more gametophyte prominent in more primitive plant species advanced plant species, the sporophyte prominant is more is much more Life Cycle in different Plant Phyla • • The Structure of Flowers

reproductive organ of angiosperms …more on Flower Structure Flowers have 4 main parts: • outermost structure (encloses flower ) • usually colored, inside sepals

Stamen (anther & filament) • male reproductive structure • anthers produce male gametophytes ( grains)

Carpel (, style & ) • reproductive structure • produces female gametophytes ( sacs) Fertilization in Angiosperms

• pollen grains adhere to the stigma ()

• tube cell in pollen elongates down style to penetrate in ovary

• 2 sperm are released to fertilize the egg & fuse with a special diploid cell in ovule Seed Production = nutrients for plant embryo

• zygote develops into embryo, triploid cell forms endosperm • seed coat derived fr. ovule wall encloses embryo, endosperm • develops from ovary wall to aid Seed Dispersal can be dispersed via fruits by:

Water • floating on water (e.g., coconuts)

Air • lightweight seeds can be transported by the wind (e.g., dandelion, maple)

Animal • edible fruits entice animals to eat them • “hitchhiker” fruits stick to animals Plant Growth Plant growth occurs in 2 basic ways:

Terminal bud Primary growth • growth in length of roots & shoots • due to special “stem cell” tissue called Axillary apical

Secondary growth • growth in width due

Arrows = to lateral meristem direction of growth • occurs in “woody” Root tips perennial plants o Apical Leaves Primary (1 ) Growth meristem

Vascular cylinder Cortex Root hair Epidermis

Zone of maturation 1o Root Growth

Zone of elongation Axillary bud ×

103 LM

1 o 2 Zone of 1 Shoot cell division Apical Growth meristem region

Key Root Dermal tissue system cap Ground tissue system Vascular tissue system Secondary (2o) Growth Due to lateral meristem tissue which consists of: Vascular Cambium (new phloem & xylem) (cork replaces the epidermis during 2o growth)

Year 1 Year 1 Year 2 Early Spring Late Summer Late Summer Key Dermal tissue system Ground tissue system Vascular tissue system Shed epidermis

wth wth wth Gro Gro Gro

Primary xylem Epidermis Secondary Cork Vascular xylem Cortex Cork Secondary xylem cambium () cambium Bark (2 years’ growth) Primary phloem Secondary phloem in Woody Plants Vascular cambium produces new phloem & xylem ea yr: • spring & summer growth look diff., producing an annual ring Sapwood

Rings

Wood rays Heartwood

Sapwood

Vascular cambium

Secondary phloem Heartwood Bark Cork cambium Cork Heartwood Sapwood • old, dead xylem from • new, functioning xylem previous years from most recent 2o growth Key Terms for Chapters 31 & 32

• mesophyll, stomata, phloem, xylem • asexual vs sexual, “alternation of generations” • sporophyte, gametophyte • , • – anther & filament (pollen, tube cell) • carpel – stigma, style, ovary (ovule, embryo sac) • monocot, dicot

Relevant Review Questions: Ch. 31 – 2-4, 6-11 Ch. 32 – 1, 3

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