Defense Mechanism & Pollination pattern in plants ppt
- 1. A PRESENTATION ON “ DEFENSE MECHANISM” & "POLLINATION PATTERN” IN PLANTS Presented By : Sunil Kumar Sahoo Enrolment No-CUSB1703132020 SECOND Semester, Msc Life science (L.Sc.-552)
- 2. DEFENSE MECHANISM IN PLANTS INTRODUCTION – - Plants represent a rich source of nutrients for many organisms including fungi, bacteria, virus, nematodes, insects, and vertebrates. - Plant lacking an immune system comparable to animals. - Plants have developed a stunning array of structural, chemical, and protein based defenses designed to detect invading organisms and stop them before they are able to cause extensive damage. - Each plant species is affected by approximately 100 different kinds of fungi, bacteria, mollicutes, viruses and nematodes.
- 3. FLOW CHART -
- 4. I) STRUCTURAL DEFENSE MECHANISM -The surface of the plant or host is first line of defense against the pathogen. -The pathogen must adhere to the surface and penetrate, if it is to cause infection. Structural defense mechanism are mainly two type:- 1. Pre-existing structural defense mechanism 2. Post-infectional or induced structural defense mechanism Pre-existing structural defense 1.Wax 2.Thick cuticle 3.Thickness and toughness of the outer wall of epidermal cells 4.Stomata 5.Sclerenchyma cells 6.Lenticel
- 5. i)Induced structural defense – 1. Cellular defense structure -Hyphal sheathing 2. Histological defense structure - Formation of cork layer -Formation of abscission layer - Formation of tyloses -Deposition of gums A) PRE-EXISTING STRUCTURAL DEFENSE – It includes: - Amount and quality of wax and cuticle. -Shapes, size and locations of natural openings (stomata and lenticels). - Presence of thick walled cells in the tissues of the plant that hinder the advance of pathogen.
- 6. Wax- It is the mixture of long chain of apolar lipid. -It forming a protective coating on plant leaves and fruit. -Synthesized by epidermis. - Extremely hydrophobic. Cuticle & Epidermal cell – -Ex: Disease resistance in Barberry species infected with Puccinia graminis tritici has been attributed to the tough outer epidermal cells with a thick cuticle. -In linseed, cuticle acts as a barrier against Melampsora lini. -Silicification and lignifications of epidermal cells offers protection against Pyricularia oryzae and Streptomyces scabies in paddy and potato, respectively.
- 7. B)POST-INFECTIONAL/INDUCED STRUCTURAL DEFENSE MECHANISM- -Most pathogen manage to penetrate their hosts through wounds and natural opening and to produce various degree of infection. - Pathogen penetration through the host surface induced the structural defense mechanism in the host cells. These may be regarded as:- -Histological defense barriers (cork layer, abscission layers and tyloses formation) -Cellular defense structures (hyphal sheathing). HISTOLOGICAL DEFENSE STRUCTURES- Cork layer :- - Infection by fungi, bacteria, some viruses and nematodes induce plants to form several layers of cork cells beyond the point of infection. - These cork cells inhibits the further invasion by the pathogen beyond the initial lesion and also blocks the spread of toxin substances secreted by the pathogen. Abscission layers:- -An abscission layer consists of a gap formed between infected and healthy cells of leaf surrounding the locus of infection. - Due to the disintegration of middle lamella of parenchymatous tissue. - Gradually, infected area shrivels, dies, and sloughs off, carrying with it the pathogen -Abscission layers are formed on young active leaves of stone fruits infected by fungi, bacteria or viruse
- 8. TYLOSES- - Tyloses are the overgrowths of the protoplast of adjacent living parenchymatous cells, which protrude into xylem vessels through pits. -Tyloses have cellulosic walls. -It formed quickly ahead of the pathogen and may clog the xylem vessels completely blocking the further advance of the pathogen in resistant varieties. Ex: Tyloses form in xylem vessels of most plants under invasion by most of the vascular wilt pathogens. GUM DEPOSITION- -Various types of gums are produced by many plants around lesions after infection by pathogen or injury. -Generally these gums are exudated by plant under stressed condition.
- 9. II)BIOCHEMICAL DEFENSE MECHANISM- Pre-existing chemical defense – 1. Inhibitors- -Released by plant in it’s environment. -Present in plant cells before infection. 2.Phenolics- -Tannins - Glucanases -Dienes -Chitinase Induced chemical defense – Hypersensitivity response (HR) Production of Antimicrobial substances -Phytoalexins -Plantibodies
- 10. INHIBITORS RELEASED BY THE PLANT IN IT’S ENVIRONMENT – -Plants exude a variety of substances through the surface of their aboveground parts as well as through the surface of their roots. -Inhibitory substances directly affect micro-organisms or encourage certain groups to dominate the environment which may act as antagonists to pathogens. Ex 1: Root exudates of marigold contain α-terthinyl which is inhibitory to nematodes. Ex 2: In Cicer arietinum (chickpea), the Ascochyta blight resistant varieties have more glandular hairs which have maleic acid which inhibit spore germination. Ex 3:Red scales of red onion contain the phenolic compounds, protocatechuic acid and catechol.
- 11. INHIBITORS PRESENT IN PLANT CELLS BEFORE INFECTION- -It is becoming increasingly apparent that some plants are resistant to disease caused by certain pathogens of an inhibitory compound present in the cell before infection. -It stored in vacuoles of plant cells. Phenolics – onion (catechol and protocatechuic acid ). Tannins, and some fatty acid-like compound such as dienes,which are present in high concentrations in cells of young fruits, leaves or seeds. These compounds are potent inhibitors of many hydrolytic enzymes. Ex: Chlorogenic acid in potato inhibits common scab bacteria, Streptomyces scabies,and to wilt pathogen, Verticillium alboatrum Saponins:- - It have antifungal membranolytic activity. Ex: Tomatine in tomato and Avenacin in oats. Lactins:- - They are protiens. Bind specifically to certain sugars and occur in large concentrations in many types of seeds, cause “lysis” and growth inhibition of many fungi. Hydrolytic enzymes:- -“Glucanases” and “chitinases” enzymes. -It may cause breakdown of pathogen cellwall.
- 12. INDUCED CHEMICAL DEFENSE – Phytoalexins:- (Phyton = plant; alexin = to ward off) -Muller and Borger (1940) first used the term phytoalexins for fungistatic compounds produced by plants in response to injury (mechanical or chemical) or infection. - Phytoalexens are toxic antimicrobial substances. - It produced in appreciable amounts in plants only after stimulation by phytopathogenic micro-organisms or by chemical or mechanical injury. -Phytoalexins are not produced during compatable reaction. Characteristics of phytoalexins:- - Fungitoxic and bacteriostatic at low concentrations. -Produced in host plants in response to stimulus (elicitors) and metabolic products. -Absent in healthy plants. - Remain close to the site of infection. -Produced in quantities proportionate to the size of inoculum. - Produced in response to the weak or
- 13. CONCLUSION – -Both the host and pathogen evolve in nature side by side. -Disease development depends upon successful host-pathogen interaction. - Susceptibility and resistance of a host against various pathogens is predominantly decided by the gene. -Different types of chemical and structural defense mechanism provide plant defenses response to the pathogens. -Defense mechanism will not work ,when compatible reaction occurs between host and pathogen.
- 14. POLLINATION PATTERN IN PLANTS • The transfer of pollen grains from an anther to the stigma in angiosperms or from the microsporangium to the micropyle in gymnosperms is called as pollination. • Two types of pollination are generally found like 1. Self-pollination 2. Cross-pollination
- 15. ABIOTIC AGENCIES- i)ANEMOPHILY- - It is a mode of cross pollination or transfer of pollen grains through the agency of wind. -Example: Coconut Palm, Date Palm, Maize, many grasses, Cannabis. Characterstics : -The flowers are colourless, odourless & nectarless. - Pollen grains are light, small and winged or dusty, dry smooth, nonsticky and unwettable. - Stigma is hairy, feathery or branched to catch the wind-borne pollen grains. - Pollen grains are produced in very large number.
- 16. ii)HYDROPHILY- - It is the mode of pollination or transfer of pollen grains through the agency of water. - Example - Zoostera , Vallisneria, Ceratophyllum, Hydrilla ,Lemna. Characters: -Flowers are small and inconspicuous. - Nectar and odour are absent. -Pollen grains are light and unwettable due to presence of mucliage cover. - Stigma is long, sticky but unwettable.
- 17. BIOTIC AGENCIES- i)ENTOMOPHILY- • -The pollen grains are transferred to a mature through the agency of insects like moths, butterflies, wasps, bees, beetles, etc. • -Examples of insect pollinated flowers are Jasmine,Bougainvillea ,Sunflower ,Cestrum ,Amorphophallus. Characters : - They are showy or brightly coloured. - Most insect pollinated flowers have a landing platform. -The pollen grains are spiny, heavy and surrounded by a yellow oily sticky substance called pollenkit. - Stigmas are often inserted and sticky. -Some flowers provide safe place to insects for laying eggs, e.g., Yucca.
- 18. • Some flowers that mimic female bees or wasps. • Look like females. • Smell like females: chemical mimicry. One study showed flower more attractive than real female. • Example – Sexual mimic orchids ii) ORNITHOPHILY- -It is the mode of allogamy performed by birds. Only a few types of birds are specialised for this. They usually have small size and long beaks. Example : Salmalia &Erythrina (by Crows & Mynas) Characters : - Ornithophilous flowers are usually brightly coloured— red, orange, yellow or blue. - The floral parts are commonly leathery.
- 19. iii) CHIROPTEROPHILY – -Pollination carried out by bats is descried as chiropterophily. -The common examples of chiropterophilous flowers are durio, kigella pinnata, anthocephalus (kadamb), adansonia (baobab tree), bauhinia etc. Characters : 1.The flowers are freely exposed, large and tough so that bats can hold on to them. 2. The flowers open in the evening since bats are nocturnal animal. 3. The flowers give off a strong scent like that of rotting fruits to attract bats. 4. Bats feed on nectar and pollen produced in very large amounts by these flowers.
- 20. POLLINATION AS MUTUALISM – - Most flowering plants are pollinated by animals.This usually viewed as mutualism (where both species benefit). - Plant gets pollen transferred & Animal gets “reward”. - The rewards may be 1. Pollen (high in protein, Also has lipids, minerals, starch) 2. Nectar (sugary fluid produced by nectar glands (nectaries) in flower) 3. Oils/Resins: some used as construction materials, “cologne” (male solitary bee uses oil as female attractant), food for larvae (Krameria) 4. Edible petals e.g.(pineapple guava: New Zealand) Krameria wax gland: wasp food
- 21. ARTIFICIAL POLLINATION - - This technique is used for the purpose of Hybridization. - It involves pollination of desired female parents with pollen from the desired male parent, taking all precautions to prevent contamination of stigma with undesired pollen. - In unisexual plants the procedure is simple but its complicated in bisexual ones. - 2 processes that takes place in bisexual flower : Emasculation & Bagging
- 22. CONCLUSION – -Pollination is a vital process of nature that isn’t very well known, but is extremely important in the food growing processes, and without it, we would be in trouble. - For the fruit seeds to develop, pollen has to be transferred between two flowers of the same species, which then fertilizes the flower and allows the production of healthy seeds on the plant.
- 23. REFERENCES 1. Pollination friendly gardening : by Rhonda Fleming Hayes 2. Pictures from google.co.in