10th Grade Biology PPT 2017 PDF

unit 2 plants 2.1. Characteristics of plants  unique characteristics that belong to plants Plants are living things that can :  grow,  Reproduce  and respond to changes in the environment. Plants are multicellular  made up of many eukaryotic cells  have well-d...

unit 2 plants 2.1. Characteristics of plants  unique characteristics that belong to plants Plants are living things that can :  grow,  Reproduce  and respond to changes in the environment. Plants are multicellular  made up of many eukaryotic cells  have well-defined nuclei  and membrane-bound organelles.  In addition to the cell membrane,  plant cells have a rigid cell wall made primarily of cellulose. Plants are autotrophic (self–feeding).  Plant cells contain the green pigment chlorophyll which enables them to absorb sunlight and produce their own food Plants are sessile:-  They cannot move by themselves.  They remain fixed at one place,  firmly anchored to the soil by their root Plants practice asexual lower plants and sexual reproduction patterns.  lower plants such as mosses and liverworts, asexual reproduction through spores is the dominant form  higher and seed-bearing plants such as gymnosperms and angiosperms, sexual reproduction which involves the union of gametes or sex cells is the dominant and visible form  2.2 Flowering and non – flowering plants Non-flowering plants. Bryophyte– the mosses and liverworts Pteridophyta (also known as the Filicinophyta) – the ferns. Gymnospermae (also known as the Coniferophyta) – the conifers Flowering plants Angiosperm (also known as the Angiospermophyta) – the true flowering plants non –vascular tissue plants ( bryophta (mosses and lverwort))  i.e., do not have transporting system or conducting vessels( xylem and phloem ) , essential to transport water, nutrient and food needed for the plants  The non –vascular plants, are generally small with limited height and restricted to moist and shaded areas.  These lower plants are seedless and do not have flowers and fruits  They also have simple root-like structures called rhizoids that have slender filaments and attach the mosses to the soil but without any strength  The other example is the liverworts, which only grow in very wet places  Lack of true stem ,root and leave  rhizoid helps anchors them and absorb water and nutrients from soil  reproduction through alternation generation : sexual gametophyte ( haploid )  Antheridia - male gamete contain sperm  Archegonia – female gamete contain egg  sperm from antheridia need water to archegonia for fertilization  Asexulal by sporophte (diploid ); produce spore in the capsule which dispersed and germinate into new gamete gametophyte Cont….  Vascular plants have transporting system or conducting vessels( xylem and phloem , essential to transport water, nutrient and food needed for the plant the plants have true leaves, stems and roots. Pteridophyta (e.g. Ferns)  have true leaves, stems and roots.  Fern stems have rhizomes, which grow horizontally just below the surface of the soil.  Their stems contain vascular tissue and so do their roots.  They produce spore-forming bodies on the underside of the fronds called sori.  The spores are dispersed by wind still rely on water for reproduction  Most ferns live in damp, shady places.  They are very common in tropical rain forests  2.3 Structure and function of plant parts we will focus on the external and internal structure of a flowering plant (angiosperm) the external structure of a typical angiosperm has two major systems 1. The shoot system: plant part usually found above the ground and includes the organs such as  stem,  branches, ( node and internode  leaves,( petiole ,base and lamina (tip ,margin vein mid rib  buds,( apical and axillary bud  flowers  and fruits Node is specific points on the plant stem between where leave branch internode is section of plant stem b/n two node Apical bud ( terminal bud ) is located the tip plant stem which contain meristem tic cell responsible for vertical growth of plants Axillary bud located in the angle b/ n leaf and stem just above node potentially growth of lateral branch of leave and flower Cont…  2. The root system: This is the part of the plant that usually grows downward into the ground. It includes the primary or tap root, lateral or branch roots, root hairs and root cap root are distinguish from under ground stem in that they do not bear either leave or bud External structure of leaf with function The leaves:-use light energy, Co2 and H2o to make food by photosynthesis Leave contain : 1.Petiole 2.Base 3.Lamina ( leave blade)(apex, vein, midrib , margin ) Contain  Cont… 1.Lamina ( leaf blade ):-  main light collective structure , broad and flat surface  Provide large surface area which able to collect sunlight  thinness create short distance for gas exchange through stomata Midrib :  is main central vein running through the leaf blade  is harder and contain veins( transport vessels ) of leaf and supportive tissue with hard cell wall Vein :  smaller vascular structure branching from the midrib which transporting water, nutrients and food through leaf and help to maintain its structure leaf Apex: tip or outer ends of leaves Margin : edge or boundary of leaf blade 2. Base : leaf that attach to petiole or directly to stem Provided support and helps anchors the leaf to stem 3. Petiole :  the stalk that attach the leaf blade to stem  support leaf and helps in the maximum light absorption , transport water ,and nutrients food with in leaf  Types of root two types of roots namely 1.tap-roots a 2 fibrous roots 1.Tap root  consists of one large, primary vertical root  It has very few lateral roots that develop which grown from main root  By penetrating deep into the soil,  provide stability (anchorage) and absorb water located deep in the ground.  a feature of dicot plants  2. Fibrous root  thin, moderately branching roots growing from stems.  They are more or less similar size and length.  In grasses they develop as consists of fine hair – like root that. is very efficient for absorbing water and minerals close to soil surface.  It creates a thick network of roots that are good at holding soil together and protect soil from erosion.  Fibrous roots are features of monocot plants  2.3 Internal leaf structure components of the two internal layers of a leaf, namely; Outer layer and middle (inner) layer. A) Outer layer also known as the epidermis, a single layer of tightly packed cells that covers the upper and lower surface of the leaf. upper epidermis is usually covered by a waxy cuticle, which transmit sunlight for photosynthesis but restricts water loss by evaporation from the leaf tissue Lower epidermis usually contains bean shaped guard cells that leave open spaces known as stomata (singular stoma). Stomata are “little mouths” or “ little noses”, which regulate O2 release, CO2 intake and water loss. In most leaves, stomata are more abundant in the lower epidermis, reducing water loss due to direct sunlight.  Middle ( inner ) layer known as the mesophyll (“middle leaf”) layer. It lies between the upper and lower epidermis. It includes tissues that are directly or indirectly involved in photosynthesis. There are two regions in the mesophyll layer 1.The palisade layer  composed of regularly arranged and closely packed columnar (vertically elongated) cells  The cells contain the largest number of chloroplasts per cell.  As the layer is immediately beneath the upper epidermis,  it is in the best position to capture most of the sunlight and this enables it to carry out most of the photosynthesis.  The slight but precise separation of the columnar cells maximizes the diffusion of CO2 and capillary movement of H20.  2. Sponge mesophyll  lies below the palisade cells.  Spongy cells are irregularly shaped with fewer chloroplasts.  They are very loosely arranged with numerous airspaces.  These air spaces, which are very close to the stomata allow the diffusion of O2, water vapour and CO2 2.3.2 The internal structure of a dicot stems. epidermis is the outermost layer of the stem. The outer walls are greatly thickened with cuticles, cuticles :-  minimizes the rate of transpiration.  Moreover, the cells are compactly arranged, which in turn protect the underlying tissues from mechanical injury and  prevent the entry of harmful organisms  CONT…. Hypodermis lies below the epidermis. It is mainly composed of collencyma cells that are specially thickened at the corners due to the deposition of thick cellulose. collenchyma are living cell have thickened cells wall dueto pecto- cellulose and provides mechanical support to stem This enables the layer to give mechanical strength to the stem. 3.Cortex consists of few layers of thin-walled, large, round, or oval cells, having intercellular space and serving for storage of food. 4. Endodermis is the innermost layer of the cortex that separates the cortex from the vascular bundles. The cells are compactly arranged and usually contain starch grains. Thus, the endodermis serves as a food reserve and may be termed as a starch sheath.  CONT… 5. Vascular bundles are longitudinal strands of conducting tissues or transporting vessels, consisting essentially of xylem and phloem arranged in a ring around the central pith. Each bundle has a patch of xylem towards the pith and a patch of phloem towards the endodermis and a strip of actively dividing young cells (cambium) in between them. 6. Pith – occupies the central portion of the stem, composed of thin walled cells, which are rounded or polygonal, with or without intercellular space. It stores food and helps in the internal translocation of water.  2.3.3 The internal structure of a root transverse section of the dicot root shows the following plan of arrangement of tissues from the periphery to the center 1. Peliferous layer is the outermost layer made up of single-layer cells. The cuticle is absent. It consists the single-celled root hairs. 2. Cortex is a multi-layered large zone made of thin- walled oval or rounded loosely arranged cells with intercellular spaces. It stores food and water. 3. Endodermis is the innermost layer of the cortex, made of barrel shaped closely packed cells. The layer helps the movement of water and dissolved nutrients from the cortex into the xylem. 4. Pericycle is a single layer inner to endodermis. It is the site of origin of lateral roots. 6. Vascular bundles consist of xylem and phloem with meristematic (cambium) or actively dividing cells between them 7. Pith is present in young roots while absent in old roots CONT…  Gymnosperm Characteristics of gymnosperm  They have well-developed roots, stem and leaves.  They have well-developed vascular tissues.  The male gametes are contained within pollen grains  The product of fertilization in sexual reproduction is a seed that not be enclosed in a fruit.  Their reproductive organ is cone,( naked seeds ) instead of flowers.  one third of the world’s forests are coniferous  dominant vegetation in cold and mountainous regions  developed relatively fleshy tissue around their seeds (e.g juniper and yew),  They are evergreen maintain their leaves throughout the year, even in temperate climates.  they shed and replace a few leaves all the time rather than spending part of the year leafless and dormant  They have small needle-shaped leaves.  Leaves are thick with a waxy cuticle that reduces water loss and minimizes damage by excess heat or cold.  A conifer tree produces two different types of cones  The male cone forms huge numbers of pollen grains that are blown by wind to a female cone  Fertilization results in a small winged seed  E.g  Podocarpus falcatus ( zigba)  Junipers  Yew  Pine tree  cradus  Reproductive structure and life cycle of 1. Cone formation gymnosperm Reproductive through structure are found in the cone ( strobili's ) Two types of cone : 1 male cone ( microsporangiate ) 2 female cone ( megasporangiate Male produce pollen contain male gamete female cone contain ovule which developed into seed if fertilized 2. Pollination is pollen from female cone transferred to female cone by wind Pollen from male cone reaches to the ovule to form pollen tube Pollen tube( microspore) helps the sperms moves to egg in the archegonium the pollen tube develop slowly and generative cell of pollen grain divided into two sperm cell from two sperm cell only one used in the reproduction the remain one sperm cell degenerate and either reabsorbed with without further use in reproduction female cone contain two ovule per scale Each ovule undergoes meiosis and produce four egg cell ( megaspore ) only one egg cell survive which developed into female gametophyte which produce egg cell in archegonium the remain three egg cell degenerate cell do not have any further role in the reproduction Simple breakdown within the tissue to ensuring that resource are focused on development viable gamete  Cont.. 3. fertilization single egg cell fused with one sperm cell form zygote 4. seed formation zygote developed into seed embryo inside the ovule which be come seed 5. seed dispersal ad germination matured seed release from female cone when it dry and open then dispersed( scattered away from parents plant by wind germinate into seedling (young plants ) up on getting favarouable condition seedling plants which growth into matured gymnosperm with both male and female cone Reproductive structure and lifecycle of angiosperm  Their reproductive structures are carried in flowers.  They have their seeds enclosed in a fruit.  They have well-developed xylem and phloem tissue  They have well-developed roots, stem and leavesa  typical flower has four floral parts, namely Sepals, Petals, Stamen, and Pistil. Sepals ( calyx) – usually green leaf-like structure protecting the lower part of female and male parts Petals (corolla) – mostly brightly coloured and attract pollinating agents like insects Stamen (Androecium) – is the male part, consisting of the filament and bilobed anther that function to produce pollen grain Pistil ( Gynoecium or carpel) – is the female part, consisting of the ovary with ovules, style and stigma. Cont…  Cont…. filaments is the long cylindrical tendril parts of stamen that support the anther to position it for pollen transfer anther is sac that sit at top of filaments where the pollen grain is produced and released stigma is located in the gynoecium of flower its main functions is to attract the pollen grain from the air its stick tip for reproduction Style is long tube like slender stalk that structure which connect the stigma and the ovary passage for pollen to travel from stigma to ovary Ovary : house ovule and developed into fruit after fertilization Receptacle is parts of flower stalk where the parts of flower are attached and under nearth the main portion of flower Support the flower structure Peduncle : the stalk that holds the flower up rigtht  Complete vs incomplete flower Complete flower Flower contain all four whorls present those are sepals , petals, both male(stemen and female( pistil ) productive structure Can perform self-pollination since they have both male and female E.g rose lilies hibiscus incomplete flower missing one of their four whorls example missing one of those parts or more (may lack petal ,sepal ,stamen or pistil Often unisexual meaning they are either male or female, which can cross-pollination with other flower e.g most grass and corn an imperfect flower is one that only has male or female imperfect flower are always incomplete ,but incomplete flower may or may not be imperfect It making unisexual b/c lack either male or female parts and usually require cross –pollination Prefect flower has both stamens and carpels it either complete or incomplete Pollination Pollination is a method where pollen grains are picked from an anther, which is the male part of a flower and transferred to the flower’s female part called the stigma Self-pollination The transfer can be between stamen and pistil on one flower or between flowers on one plant E.g wheat ,barley, oat ,rice , tomatoes, potatoes ,sunflowers and etc  Self –pollination  Transfer pollen grains from the anther to the stigma of the same flower.  It occurs in the flowers which are genetically identical  increases genetic uniformity and decreases genetic variation. Causes inbreeding. both the stigma and anther simultaneously mature Transfers a limited number of pollens.. No need for pollinators to transfer pollen grains. Pollen grains are transferred directly to a flower’s stigma. Less wastage of pollen grain  Cross pollination cross –pollination the transfer of pollen grains from the anther of a stamen to the stigma of the pistil between two flowers on different plants by pollinating agents such as insects , water or wind e.g apples ,plums, runner beas.maize Tabaco ,Cotton sorghum and etc.  Cont…  process can take place between two flowers present on different plants.  occurs between flowers which are genetically different.  decreases genetic uniformity and increases genetic variation. Causes outbreeding. Produces large amounts of pollen grains. both the stigma and anther mature at different times. Transfers large numbers of pollen. For to happen, the flower should be open. Require pollinators to transfer pollen grains. Pollen grains are carried via wind, insects, animals, water, etc.  pollination stages of flowering plants pollination, a flowering plant passes through distinct stages described as follows : 1. Pollen tube formation Pollen grains landing on the stigma will form pollen tubes that grow down in the style and form the male gamete as it approaches the ovule 2. Fertilizations  This is the union of the male gamete and the female gamete, occurring in the ovule within the ovary.  As a result, a zygote that develops into a seed embryo will be formed 3.Seed and fruit formation  Following fertilization and formation of seed embryo, the ovule matures into seed while the ovary matures into a fruit.  Thus seed is a matured ovule while the fruit is a matured ovary 4.Seed dispersal This is a mechanism of scattering seeds around or away from the parent plant. Seed dispersal like pollination requires agents such as animals water , insect or wind. 5. Seed dormancy /Seed germination A dormant seed is inactive and waiting for the favorable condition to start germination. If there is enough water and nutrients the seed will break dormancy and the seed embryo starts to develop into a seedling (Young and new plant). This process is called seed germination Cont….  Seed The seed (fertilized ovule) contains three parts:  1.the seed embryo,  2. cotyledon/endosperm (reserve food)  3. and seed coat 1.the seed embryo The seed embryo, in turn, consists of the radicle (future root), epicotyl, hypocotyl and the plumule (future shoot plumule : its is the primary embryonic shoot which develops into the stem and leaves Radicle : it is primary embryonic root which form the root system of the seedling Epicotyl ( epi: upon ,over ) which is the region above the cotyledons and which will become the stem and leaves Hypocotyl ( hypo : under , beneath ) which is the region under the cotyledons. The lower ends of the hypocotyl , which become the root system is called the radical  Cont… Cotyledon and endosperm are food storing tissues, essential for the seed embryo (future plant) until it forms leaf and starts manufacturing its own food. monocot the main food store is endosperm and embryo remains very small a parts of the seed in dicot the endosperm move food into the cotyledons which become the main food store. testa : the seed coat , which may be thin and papery like the covering on the groundnuts or very strong and hard like shell of nuts Helps protect the embryo from the mechanical injury , predators and drying out Cont… Cont… Cont… 2.6 Seed dispersal and germination 2.6.1 Seed dispersal However, plants at their seed stage display long-distance mobility and they do so with the help of seed dispersal agents like animals, water or winds Seed dispersal is an adaptive mechanism of plants that ensures seed will be separated from the parent plants distributed over a large area to safeguard the germination and survival of the seeds to adult plants, there by :-  minimizing overcrowding at one place.  Preventing competition  Promote genetic diversity  Colonization of new area  Cause out breeding  Reduce risk of predators and disease  balance of ecosystem For instance, fleshy fruits that have seeds in them can be ingested by birds and due to hard seed coats, the seeds escape digestion and are dropped at a distance upon defecation. Seeds that have additional hairy or winged structures can be dispersed by wind or float in water and taken away to a new habitat  2.6.2 Germination of seed germinations is the process by which a plants growth from seed into seedling The life of a flowering plant starts with a tiny seed embryo that stays dormant until the essential conditions for active growth are fulfilled. The resumption of active growth of the embryo after a period of dormancy is known as germination There are three essential conditions for seed germination. Water (moisture) Water is important for the germinating seed because the hydration of the seed coat increases its permeability to O2. Water is essential for the enzymatic hydrolysis of organic food and acts as an agent of transport in the translocation of soluble substances. Oxygen ( Aeration) Oxygen is necessary for aerobic respiration by which the seeds get energy for the growth of the embryo. Temperature (warmth) Seeds require optimum temperature for germination  Types germinations 1. epigeal germination hypocotyl is elongate and forms the hooks as germination continues the hypocotyl straightens and carries the cotyledon and plumule above the soil surface. This types of germination ,where the cotyledons are carried above the soils is called epigeal germination e.g most dicot plants such as castor oil seed , groundnut, cotton , bean , Bambara nut and few monocot such as onion and lilies  Hypogeal germination  the cotyledons remains underground  the plumule its away out of soil while the cotyledons remains under ground  where the epicotyl elongate and , forms the hooks and the cotyledons stay underground where eventually decompose.  e.g most monocot are wheat , sorghum , millet and few dicot seed such kidney beans , mango , peas  2.7 Photosynthesis  it occurs in organisms bearing chlorophyll such as green algae and higher plants(green plants) which enables them to trap solar energy and transform it into chemical energy. This process is known as photosynthesis  Photosynthesis is the process by which green plants and certain other organisms transform light energy into chemical energy.  During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds  Cont….  Photosynthesis is a series of chemical reactions that use light energy to assemble CO2 into glucose (C6H12O6)  The plant uses water (H2O) in the process and releases oxygen gas (O2) as a by product.  the vast consumers known as heterotrophs (feeding on plants and on one another).  The basic source of energy that sustains life begins with sunlight.  In turn, sunlight is absorbed by a green pigment known as chlorophyll. 2.7.1 The photosynthetic apparatus  the internal structure of the chloroplast, which is termed as photosynthetic apparatus.  In plants, the highest density of chloroplasts is found in the mesophyll cells of leaves.  two distinct parts in chloroplasts: Granum and Stroma. i) Granum:  consists of stacks of flattened sacks, each of which is called thylakoid.  The granum contains the chlorophyll, enzymes and cofactors that participate in the light trapping phase of photosynthesis.  It is here that the light reaction takes place  Cont… Within thylakoids is the photosynthetic pigment called chlorophyll. The interior of a thylakoid is called the thylakoid lumen.. The grana are stacks of up to 100 disc-like structure res called thylakoids where the light-dependent stage of photosynthesis takes place  Stroma  a gel-like colorless matrix, which is a site for sugar (carbohydrate) synthesis through carbon fixation.  It is from the sugar produced in the stroma that is directly or indirectly converted to all organic compounds (including amino acids, proteins and lipids) virtually found in all organisms.  the narrow intermembrane space from the aqueous interior of the chloroplast, called the stroma.  The stroma is a fluid-filled matrix where the light-independent stage of photosynthesis takes place  2.7.2 The light absorbing system in chloroplast the role of light absorbing pigments, mainly chlorophyll and sunlight absorbed serves as agent of photochemical reaction in food synthesis (photosynthesis). the light absorbing pigments of chloroplasts absorb most of the visible light ,ranging from 400 – 700 nm. Maximum light absorption occurs at wavelengths from 400 – 500 nm and 600 – 700 nm, blue and red light respectively. Light ranging from 500 to 600nm that includes green light is not absorbed, it is rather reflected. This is the reason why leaves look green Only absorbed light (largely blue and red) is useful in photosynthesis. Absorption spectra of photosynthetic pigments Chlorophyll a, Chlorophyll b, and the carotenoids. Chlorophyll a absorbs violet blue and reddish orange-red wavelengths. Chlorophyll b absorbs mostly blue and yellow light. Both Chlorophyll a and Chlorophyll b also absorb light of other wavelengths with less intensity 2. Carotenoid  are usually red, orange, or yellow pigments, and they include the familiar compound carotene, which gives carrots their color.  cannot transfer sunlight energy directly to the photosynthetic pathway, but must pass their absorbed energy to chlorophyll.  They absorb in the blue-green region of the solar spectrum and transfer the absorbed energy to chlorophylls  For this reason, they are called accessory pigments.  2.7.3Mechanism of photosynthesis Photosynthesis consists of a number of photochemical and enzymatic reaction two sub types of photosynthesis reactions 1. Light reaction  this is also known as the light dependent stage,  It takes place in the granum, where the light absorbing system – mainly chlorophyll occurs.  Here, the granum is organized as Photosystems and Electron Transporting System.  The photosystem consists of chlorophyll that absorbs sunlight maximally at blue and red range of light spectrum.  The light absorbed by the chlorophyll will split of water molecules (H2O) into H+ and O2. This is known as photolysis  Cont…  The O2 is released to the atmosphere through leaf stomata.  excite some electrons in the chlorophyll molecule to higher energy level which pass down the ETS and generate high energy ATP molecule.  The ATP and H+ harvested during light reaction will be used as an input in the Stroma where conversion of CO2 to carbohydrate takes place  Cont… 1. Electrons in photosystem II are excited by the energy in photons and become more energetic as extra energy.  They escape from the chlorophyll and pass to primary electron acceptor. 2. Energy from sunlight split water molecule in chloroplast, photolysis. H2O →1/2 O2 + 2H+ + 2e–,  Where electrons replace those lost from the chlorophyll molecule. 3. Primary electron acceptor passes electrons to the next first ETC1 (plastoquinone or ‘Pq’), Cytochrome and to last carrier plastocyanin (Pc) respectively.  Electrons lose energy as they are pass from one carrier to the next, this empower the pump from outer stroma to inner thylakoid membrane. 4. In the cytochrome complex of ETC there is a proton pump between stroma and inner thylakoid.  This creates protons accumulation inside the thylakoid, which drives the chemiosmosis synthesis of ATP. 5. Electrons in photosystem I excited as absorbs photons and escape from chlorophyll molecule. They are replaced by the electrons that have passed down ETC from photosystem II. 6. Electrons then pass along a second ETC2 involving ferredoxin (Fd) and NADP reductases.  Finally, electron reacts with protons and NADP in the stroma of the chloroplast to form reduced NADP  Chemiosmosis is the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient  Summary of light reaction of photosynthesis In summary, the steps of the light reactions of photosynthesis produce three chemical products: O2 NADPH, and ATP: 1. O 2 is produced in the thylakoid lumen by the oxidation of water by photosystem II. 2. NADPH is produced in the stroma using high- energy electrons that start in photosystem II and are boosted a second time in photosystem I. – Two high-energy electrons and one H+ are transferred to NADP+ to produce NADPH. 3. ATP is produced in the stroma via ATP synthase that uses an H+ electrochemical gradient 2. Light independent reaction ( Dark reaction ) occurring independent of light are called dark reactions. It takes place in the stroma of the chloroplast. The dark reaction is purely enzymatic and it is slower than the light reaction. Dark reaction does not require light. In a dark reaction, the sugars are synthesized from CO2. use stored chemical energy from the light- dependent reactions to “fix” CO2 and create a product that can be converted into glucose The energy-poor CO2 is fixed by ATP, NADPH2 The process is called carbon fixation or carbon assimilation  Three stage of light independent reaction 1. carbon fixation, 2. reduction, and 3. regeneration.  1. Carbon fixation is the process by which inorganic carbon dioxide from the atmosphere is converted into organic compounds like glucose,  carbon dioxide enters the chloroplast and is attached to a five-carbon sugar molecule called ribulose-1,5-bisphosphate (RuBP) By enzyme of ribulose 1,5 bisphosphate carboxylase/ oxygenase  The resulting six-carbon intermediate is unstable and quickly splits into two molecules of 3-phosphoglycerate (3-PGA), a three-carbon compound 3. Reduction to G3P:  Using energy from ATP and NADPH (produced in the light-dependent reactions), 3-PGA is converted into glyceraldehyde-3- phosphate (G3P).  Some G3P molecules exit the cycle to be used in synthesizing glucose and other carbohydrates 3. Regenerati OF RUBP FROM G3P Some G3P molecules go to make glucose, while others must be recycled to regenerate the RuBP acceptor. Regeneration requires ATP Hint Calvin cycle needs six turns to produce two G3P (TP, Triose phosphate) which is enough to make one glucose molecule. One turn of Calvin cycle needs 3ATP and 2 NADP to produce one glucose molecule  Summer light dependent and light independent reaction Light-dependent reactions Goal Convert light energy into chemical energy Location Chloroplasts—thylakoids Input Sunlight, H2O, NADP+, ADP Output NADPH, ATP, O2 Light-independent reactions Goal Use stored chemical energy to “fix” CO2 and create a product that can be converted into glucose Location Chloroplasts—stroma Input CO2, NADPH, ATP Output NADP+, ADP, G3P (Two G3P can be made into C6H12O6) Contt…  2.8 TRANSPORT IN PLANTS the main route through which the raw materials, water and minerals, move from roots to leaves and the food manufactured from the leaves reach the rest of the plant are called vascular bundle ( xylem and phloem ) xylem Water and minerals are transported from the root to the leaf via the stem through conducting vessel  consists of elongated dead cells, joined end to end to form continuous vessels  no active transport take place in xylem  movement of water in xylem due to transpiration pull phloem  organic matter (food) manufactured in the leaf is transported to the rest of as opposed to xylem  consists of living cells arranged end to end and allows transport of food (sucrose and amino acids) up and down the plant. This is called translocation.  it happens between where these substances are made (Sources) and where they are used or stored (the sinks).  use energy to move substance ( active transport )  2.7.4. Testing a leaf for starch  A simple way of demonstrating food synthesis in leaves is testing a leaf for starch.  if you put iodine solution on powdered starch, piece of bread or potato slice a blue-black colour will develop confirming the presence of starch.  However, the cuticle of the leaf is impermeable to iodine.  Moreover, the leaf has green pigment chlorophyll that interferes with the coloring effect of iodine  2. Transport in plants  the main route through which the raw materials, water and minerals, move from roots to leaves and the food manufactured from the leaves reach the rest of the plant are called vascular bundle ( xylem and phloem ) xylem Water and minerals are transported from the root to the leaf via the stem through conducting vessel  consists of elongated dead cells, joined end to end to form continuous vessels  no active transport take place in xylem  movement of water in xylem due to transpiration pull phloem  organic matter (food) manufactured in the leaf is transported to the rest of as opposed to xylem  consists of living cells arranged end to end and allows transport of food (sucrose and amino acids) up and down the plant. This is called translocation.  it happens between where these substances are made (Sources) and where they are used or stored (the sinks).  use energy to move substance ( active transport )  Cont… Do you know why the stem of sugar cane or stem tuber of sweet potato is so sweet? Sugars synthesized in the leaf is converted to starch and accumulated in the storage organs of plants, such as root and stem tubers, leaves seeds and fruits of a plant. Starch from plants is a good source of energy that we need in our diet  2.8.2 Mechanism of transport in plant  Uptake of water and minerals  Water from the soil first enters the root through root hairs.  These are elongated single cells that provide a large surface area allowing more water to enter into the root  Minerals also enter the root together with the water. This process is known as absorption  Water entering the root passes from cell to cell either by osmosis across the cell membrane and cytoplasm or freely flow by diffusion along the porous cell wall to reach the root xylem by passive transport  The roots are covered with special cells, which have tiny hair-like extensions called the root hairs..  Once water has moved into the root hair cells, the cytoplasm of the root hair cells is more dilute than the cytoplasm of the surrounding cells.  Water moves into the neighboring cells by osmosis.  These cells now have more dilute cytoplasm than the cells next to them, and the water moves on by osmosis until it reaches the xylem  Cont…  Water in the root xylem is pulled upward passively by transpiration pull it is the main force responsible for the water passing all the way from the root to the leaves through the xylem vessel . During transpiration water that evaporates from the leaves serve as a mechanism to pull or drag water from the root  Cont….  Trees are supported by their woody trunks. But many plants do not have woody tissue, and so they have no structural support.  They rely on having cells which are rigid and firm.  These firm cells are maintained by the movement of water into the cells by osmosis to create turgor  In the xylem, two physical forces help the water to move upwards.   These are:-  A. Adhesive forces  B. Cohesive  A. Adhesive force:- Forces of attraction between different types of molecule (Ex. Water & wall of xylem )  - It support the whole column of water  B. Cohesive force:- Forces of attraction between similar types of molecule( Ex. Between water molecules )  -The water molecules tend to stick together and get pulled upwards like a string of beads   When water reaches the xylem in the leaves, the concentration of water in the solution of xylem become higher than the solution in the mesophyll cells in the leaf   Water moves out from the xylem into the mesophyll cells and so across the leaf by osmosis   When it reaches a mesophyll cell which is surrounded by air, water evaporates from the surface into the air and diffuses out through the stomata along a concentration gradient.  Translocation food in plants  Translocation in plants is a shift or transport of food from the site of synthesis (source), which is the leaf, to the site of utilization or storage (sink), which can be either the stem or the root.  Translocation occurs through the phloem The ringing or girdling experiment  helps to identify the food conducting vessels. The experiment  involves removing the ring of bark with the phloem and the plant is placed in a beaker of water. Xylem will be the only vessel in the girdled area, which connects the upper and lower part of the plants  Cont… After few days, a swelling will be observed in the upper girdle. This is due to the accumulation of food materials, mainly sugar which was translocate from the photosynthesizing leaf towards the root The sugar can be sucked with syringe or using aphids and can be confirmed with food test. Aphids are soft – bodied insects that use piercing and suck in mouth parts to feed on phloem sap. Ringing will ultimately kill the plant, because of disruption of food transport through the phloem. The root dies first, because supply of food to the root will be discontinued. As the root dies, the upper part and finally the whole plant, which depends on root for water and minerals, will die Cont…. 2.9 Response in plants