Presentation on theme: "Sexual reproduction in plants"— Presentation transcript:
1 Sexual reproduction in plants A flower is a leafy shoot containing the sexual organs of a flowering plant.It is adapted for sexual reproduction.It is a modified terminal bud typically composed of four sets of modified leaves.
6 Diagram of a wind-pollinated flower BractAntherFilamentOvaryStigma
7 Functions of parts of the flower sepalspetalsAnthersfilamentStigmastyleovariesProtects the flower during the bud stageAttracts insect pollinators by colour and scentproduce and release pollen grainspositions the anther for effective pickup of pollen by the pollinating agentcollects the pollen from the pollinating agentpositions the stigma for pollen collectionsite of fertilisation, protects the developing seeds, aids in seed dispersal
8 .. . . thinking of you!In a form of a table, compare the different structural adaptations of insect-pollinated and wind-pollinated flowers 
9 structural adaptations of insect-pollinated and wind-pollinated flowers Insect-pollinated flowersWind-pollinated flowersPetals large & brightly coloured to attract insectsStigma located inside the flower where the insects have to brush past itAnthers inside the flower where the insects have to brush past themStigma usually small & sticky so that pollen grains can attach from insect bodyFlower often strongly scentedLarge sticky or spiky pollen grains which stick to insectsPetals small or absent, if present, not brightly colouredStigma exposed to catch pollen grains blowing in the windAnthers exposed outside the flower so that wind can easily blow the pollen grains awayStigma large & feathery to catch pollen grains blowing in the windFlowers have no scentLight & smooth pollen that can be blown in the wind
10 Pollinationthe transfer of pollen grains from the male part of the plant (anther of stamen) to the female part of the plant (stigma).
11 Agents of pollination. . . the means that moves the pollen grains from the anther to the stigma.Agents of pollination include: wind; insects; birds; water & rodents.
12 Photomicrograph of pollen grains: Note the spikes that attach pollen grains to insect’s body.
13 What happens after pollination? pollen grains germinates forming pollen tubethe pollen tube grows down style digesting the style tissuethe e pollen tube enters ovule through micropylemale nucleus moves into ovulemale nucleus (male gamete) fuses with the ovum or egg cell (female gamete) i.e. fertilisation occursovule becomes seedovule wall becomes seed coat or testaovary becomes fruitstigma and the style weathers and dry up
14 Seed and fruit dispersal This is spread of seeds & fruits some distance away from the parent plantDispersal allow seeds to spread out to colonise new areas so that the new plants do not compete with parent plant for light, water and mineral saltsmeans of seeds & fruits are:animalswindwaterself dispersal
15 Seed and fruit dispersal by Wind Wind dispersed seeds such as sycamore & dandelion:are light so that they can easily be blown by windhave wing –like outgrowth or feathery hair projections which increase the surface area so that the seeds can ‘float’ in air for some time so they are carried over long distance from the parent plantSycamore seedDandelion seeds
16 Seed and fruit dispersal by Animals Animal dispersed seeds includes: tomato & burr grass.Tomato fruits:they are fleshy (succulent), brightly coloured & scented to attract animalsHave tough seed coat to protect the seeds from being digested in the animals' gutBurr grass:Are covered with stiff, hooked spines which catch onto the animals’ fur to be carried long distance before dropping off
17 Advantages of seed dispersal There is less competition, with parent plant & among seedlings for same resources such as; light, water , nutrients & spaceDispersal allow plants to colonise new areas since plants are stationary i.e. don’t move from place to place
18 Structure of a Seed plumule radicle micropyle cotyledon testa (seed coat)
20 Testa; protects the embryo from physical damage & attack from pathogens Micropyle; a hole in the testa that allow water & oxygen to enter into the seedCotyledons; stores nutrients (starch, protein & lipids) required during germinationPlumule; grows into shoot after germinationRadicle; grows into root after germination
21 Conditions for seed germination Seed germination is the process in which a plant emerges from a seed & begins growConditions needed for seeds germination are:Suitable temperature; for enzymes to work effectivelyOxygen; for aerobic respiration to provide energy to growing embryoWater; for chemical reactions to occur in solution, dissolve nutrients for transportation, activate enzymes & soak testa
22 Design & carry out an experiment to investigate the conditions necessary for germination of mung bean seeds.
23 I am willing to answer questions on sexual reproduction in plants I am willing to answer questions on sexual reproduction in plants. Thank you folks! You are such a wonderful group of students.