SAMACHEER CLASS 10 UNIT 12 NOTES

 UNIT 12

    SAMACHEER SCIENCE 
CLASS 10

BIOLOGY

PLANT ANATOMY & PLANT PHYSIOLOGY

 

INTRODUCTION

·         Plants exhibit varying degrees of organization

·         Atoms à Molecules à Organelles àCells à Tissues à Organs

·         Internal structure of plants – published by Nehemiah Grew – Father of Plant Anatomy

·         Anatomy – Greek Ana = as under; Temnein = to cut

·         Plant Anatomy – study of internal structure of plants

 

TISSUES

·         Tissues – group of cells – similar or dissimilar in structure & origin – but perform similar function

·         Plant tissues – 2 types – based on their ability to divide

·         (i) Meristematic tissue

·         (ii) Permanent tissue

 

TISSUE SYSTEM

·         Sachs (1875) – classified Tissue System – 3 types

·          (i) Dermal or Epidermal tissue system

·          (ii) Ground tissue system

·          (iii) Vascular tissue system

 

DERMAL OR EPIDERMAL TISSUE SYSTEM

·         Epidermis, stomata & epidermal out growths

·         Epidermis – outermost layer

·         Stomata – minute pores in epidermis

·         Cuticle – present on outer wall of epidermis – checks evaporation

·         Epidermal outgrowths – Trichomes & root hairs

 

FUNCTIONS OF DERMAL TISSUE SYSTEM

·         Epidermis – protects inner tissues

·         Stomata – helps in transpiration

·         Root hairs – absorption of water & minerals

 

GROUND TISSUE SYSTEM

·         Includes all the plant tissues – except epidermis & vascular tissues

·         (i) Cortex

·          (ii) Endodermis

·          (iii) Pericycle

·         (iv) Pith 

 

VASCULAR TISSUE SYSTEM

·         Consists of Xylem & Phloem

·         Present as bundles – called Vascular bundles

·         Xylem – conducts water to different parts

·         Phloem – conducts food materials to different parts

·         3 types of vascular bundles

·         (i) Radial (ii) Conjoint   (iii) Concentric

 

(I) RADIAL BUNDLES

·         Xylem & Phloem – present in different radii – alternating

·         Example: Roots

 

(II) CONJOINT BUNDLES

·         Xylem & Phloem – lie on same radius

·         2 types

·         (a) Collateral       (b) Bicollateral

o   COLLATERAL

–     Xylem – centre; Phloem – Periphery

–     Open – when cambium is present

–     Closed – when cambium is absent

–     Example: Monocot stem  

o   BICOLLATERAL

–     Phloem – present on both outer & inner side of xylem

–     Example: Cucurbita

 

 

(III) CONCENTRIC BUNDLES

·         Xylem – completely surrounds phloem or vice versa

·         2 types

·         (i) Amphivasal – Xylem surrounds Phloem

·         Example: Dracaena

·         (ii) Amphicribal – Phloem surrounds Xylem

·         Example: Ferns

 

ENDARCH & EXARCH

·         ENDARCH

–     Protoxylem – centre; Metaxylem – periphery. Example: Stem

·         EXARCH

–     Protoxylem – Periphery; Metaxylem – centre. Example: Roots

  

    ENDARCH XYLEM                                            EXARCH XYLEM

TISSUE SYSTEM & ITS FUNCTIONS

INTERNAL STRUCTURE OF DICOT ROOT (BEAN)

·         T.S of DICOT ROOT shows the following

 

(i) EPIBLEMA

·         Outer most layer

·         Cuticle & stomata – absent

·         Unicellular root hairs – present

·         Also known as – Rhizodermis or Piliferous layer

 

 (ii) CORTEX

·         Multilayered large zone – has thin walled parenchyma cells

·         Has intercellular spaces

·         Stores food and water

 

(iii) ENDODERMIS

·         Innermost layer of cortex

·         Cells – barrel shaped, closely packed

BARREL SHAPED CELLS

·         Cell – thickenings on their radial & tangential walls – Casparian strips

·         Helps in – movement of water & dissolved salts – from cortex to xylem  

 

 (iv) STELE

·         All cells inside endodermis – constitute stele

·         Includes Pericycle, Vascular bundle & Pith

 

PERICYLE

·         Inside endodermis – single layer – Pericycle

·         Origin of Lateral roots

 

VASCULAR BUNDLE

·         It is radial

·         Xylem – exarch & tetrarch

·         Conjunctive tissue – made of parenchyma cells

 

PITH

·         Young root contains pith

·         Older roots – pith is absent

 

INTERNAL STRUCTURE OF MONOCOT ROOT (MAIZE)

·         T.S of MONOCOT ROOT shows the following

 

(i) EPIBLEMA  OR RHIZODERMIS

·         Outermost layer

·         Single layer – thin walled – parenchyma cells

·         Stomata & Cuticle – absent

·         Root hairs – helps absorption of water & minerals

·         Protects inner tissues

 (ii) CORTEX

·         Multilayered large zone

·         Composed of parenchyma cells

·         Has intercellular spaces

·         Stores water & food material

 

(iii) ENDODERMIS

·         Innermost layer of cortex

·         Has casparian strips & passage cells

·         Casparian strips – based of thickening made of suberin

 

(iv) STELE

·         All cells inside endodermis – constitute stele

·         Includes Pericycle, Vascular bundle & Pith

 

o   (a) PERICYLE

–     Single layer of Pericycle – thin walled cells

–     Site of origin of lateral roots

 

o   (b) VASCULAR BUNDLE

–     Contains many patches of Xylem & Phloem – arranged radially

–     Xylem – exarch & polyarch

–     Conjunctive tissue – made of Sclerenchyma cells

o    (c) PITH

–     Present at the center

–     Made of parenchyma cells

–     Has intercellular spaces

–     Contains abundant amount of starch grains

–     It stores food

 

DIFFERENCE BETWEEN DICOT & MONOCOT ROOT

INTERNAL STRUCTURE OF DICOT STEM (SUNFLOWER)

·         T.S of DICOT STEM shows the following

 

(i) EPIDERMIS

·         Outermost layer

·         Single layer of Parenchyma cells

·         Outer wall – covered with cuticle

·         Protective in function

 

(ii) CORTEX - 3 distinct regions

 

(a) HYPODERMIS

·         3 TO 6 layers of Collenchyma cells

·         Gives mechanical support

 

(b) MIDDLE CORTEX

·         Few layers of Chlorenchyma cells

·         Involved in Photosynthesis – due to presence of chloroplast

 

(c) INNER CORTEX

·         Few layers of parenchyma cells

·         Helps in gaseous exchange & stores food

 

(iii) ENDODERMIS

·         Innermost layer of cortex

·         Single layer – barrel shaped cells

·         Cells – contains starch grains

·         Also called starch sheath

 

(iv) STELE

·         Central part – inner to endodermis

·         Consists of Pericycle, Vascular bundles & pith

 

o   (a) PERICYCLE

–     Occurs between endodermis & vascular bundle

–     Multilayered – parenchyma cells, alternating sclerenchyma patches

 

o    (b) VASCULAR BUNDLE

–     Conjoint, collateral, endarch & open

–     Arranged as a ring around the pith

o   (c) PITH

–     Large central zone

–     Parenchyma cells

–     With intercellular spaces

–     Helps in storage of food 

 

INTERNAL STRUCTURE OF MONOCOT STEM (MAIZE)

·         T.S of MONOCOT STEM shows the following

 

(i) EPIDERMIS

·         Outermost layer

·         Single layer – Parenchyma cells

·         Covered with thick cuticle

·         Multicellular hairs

·         Stomata – less in number

 

(ii) HYPODERMIS

·         few layers of Sclerenchyma – interrupted by Chlorenchyma

·         Sclerenchyma – provide mechanical support

 

(iii) GROUND TISSUE

·         Parenchyma cells – next to hypodermis

·         Extends to the centre

·         Not differentiated into Endodermis, Cortex, Pericycle & Pith

 

(iv) VASCULAR BUNDLE

·         Skull shaped – scattered in ground tissue

·         Conjoint, Collateral, endarch  & closed  

·         Each Vascular bundle – surrounded by a layer of sclerenchyma cells – ‘Bundle Sheath’

 

o   (a) XYLEM

–     Metaxylem & protoxylem – present

–     Xylem vessels – arranged in V or Y shape

–     Mature Vascular bundle – lower most protoxylem disintegrates & forms a cavity – called Protoxylem Lacuna

o   (b) PHLOEM

–     consists of sieve tube elements & companion cells

–     Phloem parenchyma & Phloem fibres – absent

(v) PITH

·         Not differentiated in Monocot stems

 

 

DIFFERENCE BETWEEN DICOT & MONOCOT STEM

 

INTERNAL STRUCTURE OF DICOT OR DORSIVENTRAL LEAF (MANGO)

·         T.S of DICOT LEAF shows the following

 

(i) UPPER EPIDERMIS

·         Outermost layer

·         Single layer – Parenchyma cells

·         No intercellular spaces

·         Outer wall – has cuticle

·         Stomata – less in number

 

(ii) LOWER EPIDERMIS

·         Single layer – Parenchyma cells

·         Thin cuticle present

·         Stomata – numerous

·         Chloroplasts – present only in guard cells

·         Lower epidermis – helps in – exchange of gases

·         Water loss – facilitated through this chamber

 

 (iii) MESOPHYLL

·         Tissue between upper & lower epidermis

·         Differentiated into – Palisade & Spongy Parenchyma

 

o   PALISADE PARENCHYMA

–     Found below upper epidermis

–     Cells – elongated

–     Cells – have more number of Chloroplasts

–     Donot have intercellular spaces

–     Take part in Photosynthesis

 

o   SPONGY PARENCHYMA

–     Found below Palisade Parenchyma

–     Cells – almost spherical or oval

–     Irregularly arranged

–     Have intercellular spaces

–     Helps in gaseous exchange

 

(iv) VASCULAR BUNDLES

·         Vascular Bundle of midrib – larger

·         Conjoint, Collateral & Closed

·         Each Vascular bundle – surrounded by a sheath of parenchymatous cells – bundle sheath

·         Xylem – lying towards upper epidermis

·         Phloem – Lying towards the lower epidermis

 

INTERNAL STRUCTURE OF MONOCOT OR ISOBILATERAL LEAF (MANGO)

·         T.S of MONOCOT LEAF reveals the following

 

(i) EPIDERMIS

·         Has upper & lower epidermis

·         Made of Parenchyma cells

·         Cuticle – present on outer wall

·         Stomata – present on both upper & lower epidermis

·         Upper epidermis – some cells – large & thin walled – Bulliform cells

 

(ii) MESOPHYLL

·         Ground tissue – present between both epidermis

·         Not differentiated into Palisade & spongy Parenchyma

·         Cells – irregularly arranged with inter cellular spaces

·         Cells contain chloroplasts

 

(iii) VASCULAR BUNDLES

·         Large number of vascular bundles are present

·         Some vascular bundles – small & some are large

·         Each vascular bundle – surrounded by parenchymatous bundle sheath

·         Conjoint, Collateral & Closed

·         Xylem – towards upper epidermis

·         Phloem – towards lower epidermis 

 

DIFFERENCE BETWEEN DICOT & MONOCOT LEAF

 

 

PLASTIDS

·         Plastids – double membrane bound organelle – found in plants & some algae

·         Responsible for – preparation & storage of food

·         3 types

o   (i) Chloroplast – Green coloured plastids

o   (ii) Chromoplast – Yellow, red, orange coloured plastids

o   (iii)Leucoplast – colourless plastids

 

STRUCTURE OF CHLOROPLAST

·         Chloroplast – green plastids – contain green pigment – Chlorophyll

·         Chloroplasts – oval shaped organelles

·         Diameter – 2 to 10 micrometer

·         Thickness – 1 to 2 micrometer

 

(i) ENVELOPE

·         Envelope – has outer & inner membrane – separated by intermembrane space

 

(ii) STROMA

·         Matrix – inside the membrane – called stroma

·         Contains DNA, 70 S ribosomes, other molecules – required for protein synthesis

 

(iii) THYLAKOIDS

·         Consists of thylakoid membrane – encloses thylakoid lumen

·         Forms  a stack of disc like structures – grana (singular-Granum)

 

(iv) GRANA 

·         Thylakoids – arranged in the form of discs – stacked one above the other – grana

·         Grana – interconnected to each other -  by membranous lamellae – Fret Channels

 

FUNCTIONS OF CHLOROPLAST

·         Photosynthesis

·         Storage of Starch

·         Synthesis of fatty acids

·         Storage of lipids

 

PHOTOSYNTHESIS

·         Photo = light; synthesis = to build

·         Process – by which autotrophic organisms (green plants, algae, chlorophyll containing bacteria) – utilize energy from sunlight – synthesize their own food

·         Carbondioxide + Water à Presence of Sunlight & Chlorophyll  form Carbohydrates

·         Oxygen – released as by product

·         Carbondioxide + Water à Glucose + Water + Oxygen

 

WHERE DOES PHOTOSYNTHESIS OCCUR?

·         Photosynthesis – Green parts of plants – leaves, stems & floral buds

PHOTOSYNTHETIC PIGMENTS

·         Pigments involved in Photosynthesis

·         2 classes of Photosynthetic pigments

o   (i) Primary pigments

o   (ii) Accessory pigments

 

PRIMARY & ACCESSORY PIGMENTS

·         Chlorophyll – primary pigment – traps solar energy – converts into electrical & chemical energy – thus called as reaction centre

·         Other pigments – chlorophyll b & Carotenoids – accessory pigments – they pass on the absorbed energy to chl. a molecule

·         Reaction centre (chl. a) & accessory pigments (harvesting centre) – together called Photosystems

 

ROLE OF SUNLIGHT IN PHOTOSYNTHESIS

·         Entire process of Photosynthesis – takes place inside chloroplast

·         Structure of chloroplast is such that – light dependent & light independent reaction takes place at different sites in the chloroplast

o   Light dependent – Light reaction

o   Light independent – Dark reaction

 

I. LIGHT DEPENDENT PHOTOSYNTHESIS (HILL REACTION/LIGHT REACTION)

·         Discovered by Robin Hill (1939)

·         Reaction takes place – presence of light energy – in thylakoid membranes (grana) – chloroplasts

·          Photosynthetic pigments – absorb light energy – convert to chemical energy (ATP & NADPH₂)

·         These products of light reaction – move out from thylakoid à stroma of the chloroplast

·         ATP – Adenosine Tri Phosphate

·         ADP – Adenosine Di Phosphate

·         NAD – Nicotinamide Adenine Dinucleotide

·         NADP – Nicotinamide Adenine Dinucleotide Phosphate

·         Cell – cannot get energy directly from glucose – in respiration – energy released from glucose – used to make ATP

 

II. LIGHT INDEPENDENT REACTIONS (BIOSYNTHETIC PHASE)

·         Dark reaction / biosynthetic pathway – carried out in stroma

·         During this reaction – CO₂ à reduced to carbohydrates  with the help of light generated ATP & NADPH₂

·         Also called Calvin Cycle – carried out in the absence of light

·         In Calvin Cycle – inputs are – CO₂ from atmosphere & ATP, NADPH₂ – produced from light reaction

 

CALVIN CYCLE

·         Melvin Calvin – American biochemist – discovered chemical pathway for Photosynthesis

·         The cycle is named as Calvin Cycle

·         He was awarded Nobel Prize - 1961

MELWIN CALVIN

 

FACTORS AFFECTING PHOTOSYNTHESIS

(A) INTERNAL FACTORS

·         Pigments

·         Leaf age

·         Accumulation of carbohydrates

·         Hormones

 

(B) EXTERNAL FACTORS

·         Light

·         Carbon dioxide

·         Temperature

·         Water

·         Mineral elements

ARTIFICIAL PHOTOSYNTHESIS

·         Artificial Photosynthesis – Method for producing renewable energy – using sunlight 

·         Indian Scientist – C.N.R. Rao – working on similar technology – to produce Hydrogen Fuel  (Renewable Energy)

·         Bharat Ratna - 2013

 

·                 MITOCHONDRIA

·         Mitochondria – filamentous or granular cytoplasmic organelles – present in cell

·         First discovered by Kolliker (1857) – as granular structures – in striated muscles

·         Singular – Mitochondrion

·         Organelles – within eukaryotic cells – produce ATP – energy currency of the cell

·         Hence Mitochondria – called ‘Power House of the Cell’

·         Vary in size – 0.5 µm  to 20 µm

·         It contains 60 – 70 % protein, 25 – 30% lipids, 5 – 7% RNA & small amount of DNA & minerals

 

STRUCTURE OF MITOCHONDRIA

(i) MITOCHONDRIAL MEMBRANES

·         Consists of 2 membranes – inner & outer membrane

·         Each membrane – 60 to 70 Å thick

 

OUTER MITOCHONDRIAL MEMBRANE

·         Smooth & freely permeable – to most small molecules

·         Contains enzymes, proteins & lipids

·         Has porin molecules (proteins) – form channels – passage of molecules

 

INNER MITOCHONDRIAL MEMBRANE

·         Semi -permeable membrane – regulates passage of materials – into & out of mitochondria

·         Rich in enzymes & carrier proteins

·         Consists of 80% proteins & lipids

 

 (ii) CRISTAE

·         Inner mitochondrial membrane – gives rise to finger like projections – cristae

·         Cristae – increase the inner surface area of mitochondria – hold variety of enzymes

 

(iii) OXYSOMES

·         Inner mitochondrial membrane – bears minute regularly spaced tennis racket shaped particles – Oxysomes (F1 particle)

·         They involve in ATP synthesis

 

(iv) MITOCHONDRIAL MATRIX

·         Complex mixture of proteins & lipids

·         Matrix contains enzymes for Kreb’s Cycle, Mitochondrial ribosome (70 S), tRNAs & Mitochondrial DNA

 

FUNCTIONS OF MITOCHONDRIA

·         Main organelle of Cell respiration

·         Produce large number of ATP molecules

·         Called as Power House of the Cell

·         Helps to maintain normal calcium ion concentration in cells

·         Regulates – metabolic activity of the cell

 

TYPES OF RESPIRATION

·         Respiration – exchange of gases between the organism & the external environment

·         Plants – obtain O₂ – from environment; Release – CO₂ & water vapour

·         Exchange of gases – external respiration – Physical process

·         Within cells – Biochemical process – where food is oxidised à energy – called cellular respiration

 

AEROBIC RESPIRATION

·         Type of Cellular respiration – organic food – completely oxidised – with the help of O₂ à CO₂, water & energy

·         Occurs in most plants & animals

 

STAGES OF AEROBIC RESPIRATION

(a) GLYCOLYSIS (Glucose Splitting)

·         One molecule of glucose (6C) à 2 molecules of Pyruvic acid (3C)

·         Takes place in Cytoplasm

·         First step in both aerobic & anaerobic respiration

 

(b) KREBS CYCLE

·         Occurs in mitochondria matrix

·         End of glycolysis – 2 molecules of Pyruvic acid – enter into mitochondria

·         Through this cycle – Oxidation of Pyruvic acid à CO₂ + Water

·         Also Called TCA Cycle (TriCarboxylic Acid Cycle)

 

 (c) ELECTRON TRANSPORT CHAIN

·         ETC – located on inner membrane of the mitochondria – system of electron carrier complex

·         NADH₂ & FADH₂ (formed during glycolysis & Kreb’s Cycle) à oxidised à NAD⁺  & FAD⁺ à to release energy via electrons

·         Electrons – as they move through the system – release energy – trapped by ADP – synthesize ATP

·         Called Oxidative Phosphorylation

·         O₂ (ultimate acceptor of electrons) – reduced to water

 

ANAEROBIC RESPIRATION

·         Takes place without oxygen

·         Glucose à ethanol (in plants)

·         Glucose à lactate (in some bacteria)

 

RESPIRATORY QUOTIENT (R.Q)

·         The ratio of volume of CO₂ liberated & the volume of O₂ consumes – during respiration