Plant Form and Function (IVLE) 4-1

8/2/2019 Plant Form and Function (IVLE) 4-1

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1. Introduction2. Flower structure and function3. The plant body4. Vegetative organs5. How do plants acquire nutrients?6. How do plants transport water

and minerals?7. How do plants transport sugars?8. Concluding remarks

Plant Form and Function

8th

EdChapter 21 (section21.1)

Chapter 42 (relevantsections)

Chapter 43 (section43.3)

Reference(Skim through for relevant info, you may use other text books)

7th Ed

Chapter 21 (section 21.2)


Chapter 25 (sections25.2, 25.3 & 25.4)

9th Ed




Taxus brevifolia

Pacific yewTaxol

Ovarian cancer, breast cancer

Pharmaceuticals

1. Introduction

Why learn about plants?

Catharanthus roseus

PeriwinkleVincristine, Vinblastine

Leukemia

Food

Industrial and building materials

Source of oxygen

Removal of carbon dioxide. Old trees lock up much carbon intheir tree trunks

Main features

1. Photosynthesis chlorophyll

2. Cellulose in cell wall3. Alternation of generations between

haploid and diploid forms

Plants = Members of plant kingdom(Kingdom Plantae)

What are plants?


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Plant types

FloweringPlants

What are flowers?

2. Flower structure and function


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Complete flower

has 4 sets ofmodified leaves:

Sepals

Petals

Stamens(filaments andanthers)

Carpels (stigma,

style and ovary)

Incomplete flowers

lack one or more of the 4 floral parts

Eg plants of the squash family (e.g.zucchinis, cucumber) flowers haveseparate male flowers (lack carpels) andfemale flowers (lack stamens)

Incomplete flowers may also lack sepals

or petals

Each anther contains hundreds tothousands of pollen grains .Pollen is the male gametophyte (haploidstage).

In many species, each immature pollen grainconsists of a large tube cell and a smallergenerative cell

In more mature pollen grain: generative celldivides into 2 sperm cells


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-Ovary is deep-seeded in the flower.

-In the ovary are the ovules. polar nuclei withincentral cell

egg cell

Each ovule is

surrounded byprotective layers ofintegument (a).

Each ovule containsan embryo sac (b).

Embryo sac is thefemale gametophyte.

Each embryo saccontains 7 cells, one ofthem is the egg cell.

The egg cell is locatednear the opening ofthe ovule (c).

a

b

c

How a sperm cell fertilizes an egg cell?

Pollen grains land on stigma of a flower ofa same species.

The pollen grain absorbs water from thestigma.

The tube cell elongates, the pollen tubegrows along the style towards the ovules.

If all goes well, pollen tube reaches theopening of the ovule and breaks into theembryo sac.


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The tip of the tube ruptures releasing the 2

sperm cells.

One sperm fertilizes the egg cell, thefertilized egg cell will develop into anembryo.

The other sperm fuses with two other cellsin the embryo sac, this triploid (3n) celldivides repeatedly and developed intoendosperm, a food storage tissue.

The embryo + endosperm + seed coat(developed from integument) = the seed

3. The plant body

Seeds germinate and grow into plants

The plant body is modular, it is made up ofmodules

All modules are produced by the shootapical meristems

Each module: Node (axillary bud, leaf) +internode


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Shoot systemInternode

NodeAxillary budBranchFlowerInflorescenceLeaf

Root systemRoot

MainBranch

Basically 3 tissue systems

Vascular

Xylem

Phloem

Ground

Parenchyma

Collenchyma

Sclerenchyma Dermal

- Epidermal tissues

Tissue = Agroup of(normallysimilar) cellsthat togethercarry out aspecificfunction and ofsimilar origin.

Vascular tissuesystem

Xylem Phloem

Xylem Tissue

For transport ofmainly waterand mineralnutrients fromroots to rest ofthe plant

Tubeso Tracheido Vessel

element


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Tracheids

thin, slanting ends,stacked atop oneanother, pitted at ends

Vessel elements

larger, perforation atends or completely open

Phloem Tissue

For transport of sugars(and amino acids,hormones) in solution

Phloem cell typeso Sieve tube elemento Companion cell

(with each sieve-tube element, both

connected,regulates sugars inand out of sievetubes)

Ground tissuesystem (the in-betweens or fillers)

All-purpose Parenchyma (thin-

walled, alive at maturity)

Support Collenchyma (living,

elongated, thick-walled butflexible, support younggrowing stem)

Sclerenchyma (deadwhen differentiated, hardenedcell wall, permanent, fibers insome plants)

Ground Tissue System


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Dermal TissueSystem

Epidermis

Epidermis

Outermost cell layer Protects the plant

body from theenvironment

Epidermis cell typesoGround epidermal

cellsoGuard cellsoHairs (reduce water loss)oRoot hairs (increase

absorptive surface)

Basically 3 tissue systems

Vascular ( Xylem, Phloem)

Ground (Parenchyma,

Collenchyma, Sclerenchyma)

Dermal (Epidermal tissues)

+

+

4. Vegetative organs

Root =-normally underground

-provides anchorage-absorbs water anddissolved nutrients and

transports them to the stem-produces some hormones-in some plants serves as astorage site forcarbohydrates


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Stem =

-normally located

above ground

-bears leaves andreproductivestructures such asflowers and fruit

Apical meristem

Leaf =

-An outgrowth ofa stem, normallyflattened andphotosynthetic.

-Produced bythe apicalmeristem,initiallymicroscopic.

Tissues ofthe leaf

oUpperepidermis

oMesophyll(green)

-palisade-spongyoLower

epidermis-stoma


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5. How do plants acquire nutrients

Plant nutrients needed for plants to surviveand complete their life cycle.

Nutrientso From air : carbon (from CO2), O2

o From soil:o Phosphoruso Nitrogeno Potassiumo Magnesiumo Calciumo Trace elements (iron, chlorine, copper,

manganese, zinc, boron, molybdenum)Copyright 2011 Pearson Education, Inc.

Thro porous wall

Cross plasmamembrane (Active)

Throplasmodesmata

9th Ed

1. Minerals dissolved in soil water fill the porouswalls between cells. The Casparian strip ofendodermis blocks water and minerals frommoving between cells into the vascular cylinder.

2. Minerals are actively transported acrossplasma membranes of the cells.

3. Minerals diffuse from cell to cell throughplasmadesmata.

4. Minerals either diffuse or are activelytransported across plasma membranes ofendodermal and pericyle cells into extra cellularspace of vascular tissues.

5. Minerals and water enter vascular cylinder.

Symbiotic relationships help plants acquire nutrients.

Eg. Nitrogen-fixing bacteria


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Eg. Fungal mycorrhizae (converts rock-bound

minerals into simple compounds)

6. How do plants transport water and

minerals?99% of the water absorbed by the roots isevaporated through the leaves by a processcalled transpiration.

Hydrogen bonds among water moleculesprovide the cohesion that holds a long chain ofwater within the xylem.

Transpiration from the leaves caused theconcentration in the leaves to drop, created atension and pull the water chain up.

Mechanism(cohesion-tensiontheory) fortransport ofwater in the

stem

http://www.youtube.com/watch?v=At1BJJDcXhk&feature=related

7. How do plants transport sugars?

Sugars are producedin the leaves throughphotosynthesis.

Sugars are moved toother non-green parts

of the plant such asroots, flowers, fruits.

Sugars are moved insolution.

Mechanism of sugarmovement explainedby pressure-flowtheory.


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The Pressure-Flow Theory

Source: Any part of the plant thatsynthesizes more sugar than it uses

Sink: Any part that use more sugar than itproduces

1. Sugar produced by source cell isactively transported into phloem sieve tube

2. Water from nearby xylem follows byosmosis, creating higher pressure in cellbecause of the rigid cell wall

3. Water pressure drives fluid to region oflower pressure

4. Cells of a sugar sink actively transportsugar out

8. Concluding remarks

Flowering plants are highly evolved, highlyorganized

Developmental processes are well

regulated Understand the functioning of plants

enable us to utilize them eg cultivate themfor food or for medicine

Documents

Plant Form and Function (IVLE) 4-1