Today we are doingthe function of the reproductive parts of the plant so we will be looking at the structure of the flower and the functions of its partsThe processes of pollination and fertilizationI thought we’d start with a quick ident.
I have some gapped hand-outs of this slide which I will pass out to you once we’ve gone through the diagram.We’ll then go through it more slowly so you can fill in the blanks.The RHS specify you must be able to describe the structure of a dicotelydon flower so don’t use a lily or any other monocot.Basically the flower can be divided into 3 parts – generally! We’ll go into the differences in a minute.Perianth Stamen (male) Pistil (female)These 3 grouping names are not required for your exam but I find them useful to divide the structure.Hand out gapped handouts.Now we’ll fill out the forms and go through the functions of each part.Get filled out copy ready for myself.
Choose your own variety of Iris, Lilium or Phalaenopsis orchid as an example.
As I said earlier the general rule is that flowers have both male and female sex parts.
Tulipa – add your own cultivar
Birch (Betula) and hazel (Corylus) are also monoecious
People usually grow one male plant with a few female plants so they get more berries.Those who are short of space grow the hermaphrodite Skimmia japonica subsp. reevesiana and its cultivars.Holly too is USUALLY a dioecious plant. Unfortunately ‘Golden Queen’ is a male plant and ‘Golden King’ is a female plant!Garrya and Pernettya are also dioecious.Are we all clear on the structure now? We’ll dissect some real flowers now to put the theory into practice.
Bees like nectar and pollen
Flowers pollinated by bats and moths, for example, are strongly scented at night, such as night-scented Stocks, Eryngiumgiganteum, Evening primrose, Globe Artichoke, Honeysuckle (egLonicera ‘Graham Thomas'), Jasmine (Jasminumofficinale), Tobacco plant (Nicotianasylvestris) and Verbena bonariensis.
Bats dispersing fruit seeds. Many tropical plant species depend entirely on bats for the distribution of their seeds
Birches and sweet chestnut. The pollen of this plant group frequently brings out symptoms of hayfever among those sensitive to the pollens. pollination by water occurs in aquatic plants which release their pollen directly into the surrounding water. Water can carry pollen from one plant to another. This often takes place with pond plants, such as pondweed. Water surface-pollinated pollen grains are spherical or reniform and large, while subaquatic-pollinated pollen grains are filiform. eelgrass (Zostera).
For fertilization to take place, pollen of the right type must join up with the ovules. The pollen is contained within pollen sacs in the anther which open when the pollen is ripe. Some pollen is only ripe for a couple of days, some last much longer. The stigma is only able to receive the pollen for a limited time. When it is ready the tip is sticky to help the pollen grains stay in place.When pollen with the right chemical password lands on the stigma a pollen tube grows down the style to reach the ovules. The male sperm nuclei follows the tube down to the female ovules where they fuse together. The ovules grow on to become seeds. The ovary expands and becomes the fruit.Once the ovules have been fertilized by the pollen, any pollen which is left falls off the stigma. The flower no longer needs the stamens or the petals so these drop off.in gymnosperms the pollen is directly applied to the ovule itself
Flower structure, pollination, fertilization
RHS Level 2 in the Principles of HorticultureThe Function of the Reproductive Parts of the Plant Echinacea Caryopteris x clandonensis angustifolia ‘Arthur Simmonds’ Peacock Butterfly Monarch Butterfly www.hdwallpapers.in www.commons.wikimedia.org
Structure of a Dicotyledon Flower Corolla (All the petals together) Nectaries (At base of Perianth) http://www.osovo.com/diagram/flowerpartsdiagram.htm
The Role of Each Component within the Perianth• All the Sepals (usually green) together form the Calyx and protect the young flower bud• All the Petals together form the Corolla and attract pollinators with colour and shape• The Nectaries are at the base of the Perianth and produce nectar to attract pollinators
Tepals in Monocotyledon Flowers• In most monocots the Sepals look like Petals• The Petals & the Sepals alternate around the rim of the flower and both are called Tepals
The Role of Each Male Component within the Stamen• The Anther produces pollen which consists of grains containing the male gametes (reproductive cells).• The Filament is the stalk of the stamen and supports the Anther.
The Role of Each Female Component within the Carpel• The Stigma is a receptive surface for pollen grains and is usually sticky.• The Style joins the Stigma to the Ovary and the pollen tube grows through it.• The Ovary contains the Ovule(s) and becomes the fruit.• The Ovule carries female gametes (reproductive cells) and become a seed on fertilization.
The Sexual VariationsThe sex of a flower can be described in 3 ways1) Hermaphrodite Flowers: these are complete and bear both male and female sex parts.2) Male Flowers: bear only male sex parts.1) Female Flowers: bear only female sex parts.
Hermaphrodite Plants• Most plants have bisexual flowers containing both male and female reproductive organs• They may pollinate themselves or be pollinated by another plant of the same species or genus
Monoecious Plants• Other plants produce unisexual flowers• On a Monoecious plant male & female flowers are borne separately on the same plant so you only need one plant for pollination Begonia ‘Illumination Apricot’
Dioecious Plants• These also produce unisexual flowers but on different plants so two are needed for pollination Skimmia japonica ‘Rubella’(male) Skimmia japonica Bowles Dwarf Female
Different Types of Pollination• Self pollination: the transfer of pollen from the anther to the stigma of the same flower or another flower on the same plant.• Cross pollination: the transfer of pollen from the anther of a flower on one plant to the stigma of a flower on another plant.
Animal Pollinators - Insects• Pollination is aided by insects: butterflies, bees, flies, beetles, moths, wasps and ants.• The insects transport the pollen as a consequence of using the flowers for feeding, breeding or hiding.• The pollen adheres to insects body parts such as face, legs and mouthparts and then gets brushed off by the stigma.• Slugs are also known to transport pollen from
Insect Pollinated Plants - Characteristics• Have adapted their petal sizes, shapes and colours in different ways to attract particular pollinators.• Produce various scents and types of nectar to attract their pollinators.• Their reproductive structures (Stamen and Pistil) are ideally positioned to enable pollen to be easily transferred to and from visiting insects.• Their pollen grains have a coarse surface or are covered by a sticky oily fluid so they can attach themselves to the pollinator.
Insect Pollinated Plants - Variations• Butterflies like scent, bright colours such as red, yellow, orange and wide flowers to land on.• Bees prefer bright blue and violet colours and are attracted by patterns called ‘nectar guides’ that are visible only in ultraviolet light.• Flies are attracted to carrion odours.• Beetles prefer wide flowers with less nectar and more pollen.• Moths prefer white petals and a strong scent.
Insect Pollination - ExamplesHelianthus pollinated by Amorphophallus titanum Yucca pollinated bybutterfly pollinated by flies Yucca mothwww.landcareresearch.co.nz www.greendiary.com www.ces.ncsu.edu Orchid pollinated by beetle www.education.ezinemark.com Lavatera pollinated by bee www.sciencephotolibrary
Animal Pollinators – Birds, Reptiles & Mammals• In the tropics birds like hummingbirds and honeyeaters feed off nectar.• They prefer red, pink or purple flowers with long narrow tubes leading to the nectar.• Bats are an important pollinator and are attracted by scent.• Pollen has been found on the hairs of monkeys, lemurs, possums and rodents and on lizards and geckos.
Bird, Mammal & Reptile Pollination Numbat feeding on insect on Banksia attenuata www.michaelmorcombe.com.au Gecko www.greendiary.com Geckos pollinatingBat www.gesneriads.ca/paliav08.htm www.photomazza.com
Wind Pollinated Plants & their CharacteristicsConifers, palms, grasses & many deciduous trees• Inconspicuous, colourless flowers without petals or nectar that are clustered in large groups e.g. catkins.• Most pollen grains are small, dry and dust-like with a smooth surface and produced in massive quantities.• Larger grains like Pinus are kept lighter with air bags.• Male flowers have long filaments exposing the anthers and their pollen to the wind.• Female flowers have long, feather-like stigmas, which protrude outside the flowers to capture as much of the wind-blown pollen as possible.
The Fertilization Process1. Pollen grains land on thesticky stigma.2. A pollen tube growsdown the style, followed bymale sperm nuclei.3. The sperm nuclei fusewith the female ovules.4. The ovules develop intoseeds and the ovarydevelops into fruit. www.buzzaboutbees.net/plant-pollination-process.html
The Fertilization Process - Terms• Gametes are either male or female reproductive cells that unite during sexual reproduction to form a new cell called a Zygote.• Pollen has to be Compatible with the pistil it lands on in order for fertilization to take place.• If the pollen is Incompatible the process of pollen germination, pollen tube growth, ovule fertilization and embryo development is halted at one of its stages and no seeds are produced.
Reasons for Incompatibility• It happens when a pollen grain produced in a plant reaches a stigma of the same plant or another plant with a similar genetic make-up.• It prevents self-fertilization and thus encourages outcrossing.• It prevents selfing (in-breeding) and promotes the generation of new genetic make-ups in angiosperm plants.
Today we looked at• The structure of a dicotyledon flower• The role of each component of a flower• The meaning of the words monoecious, dioecious and hermaphrodite• The process of pollination• The characteristics of wind and animal pollinated plants• The process of fertilization