Plant reproduction and pollination and stuff

what is reproduction and why is reproduction existing

• the process of producing new organisms

• it ensures the continuity of a species

what is asexual reproduction

the process resulting in the production of genetically identical offspring (clones) from one parent, without the fusion of gametes

what is sexual reproduction

the process involving the fusion of toe gametes to form the zygote. it produces genetically dissimilar offspring

differences between asexual and sexual reproduction

• number of parents: one, two (opposite sex)

• sex cells involved (no, yes)

• zygote formed (no, yes)

• offspring (genetically identical to each other and to parents, genetically dissimilar to each other and parents)

• genetic variation (no, yes)

• survival rate in unfavourable conditions (low, high)

• population growth rate (fast, slow)

• organisms involved (unicellular, flowering plants and animals)

advantages of asexual reproduction

1. one parent only

2. if parent can survive well in a particular environment, genetically identical offspring should be well suited to the same environment

3. relatively certain method of reproduction

4. offspring are produced in large numbers, quick and with known characteristics

5. does not depend on pollinators for reproduction

disadvantages of asexual reproduction

1. identical offspring lack in genetic variation, preventing evolution

2. characteristics are identical to parents. if environment changes and parents cant adapt, daughter will also not adapt

3. overcrowding and competition for resources such as water, air, food

what is a sepal

a modified leaf that protects the flower in the bud stage

what is a petal and what are its functions

1. modified lea that forms the most obvious part of a flower

2. function

   1. brightly coloured to attract insects for pollination

   2. large petals provide a landing platform for insects

whats the receptacle and the pedicel

the enlarged end of the flower stalk that bears parts of the flower

the pedicel is the flower stalk

what does the filament do

holds anther in a suitable position to disperse pollen grains

what does the anther do and what is its structure

It produces pollen grains, and is made up of two lobes, each containing two pollen sacs. also contains a vascular bundle made up of a phloem and a xylem

what does pollen grain cells consist of

1. haploid set of chromosomes

2. each pollen grain has 2 nuclei

   1. generative nucleus

   2. pollen tube nucleus / vegetative nucleus

what sex is the carpel

female

what sex is the stamen

male

what is a stigma and what is its function

1. stigma → the swollen structure that receives pollen grains. a mature stigma secretes sugary fluid to stimulate the germination of pollens

what is a style and what is its function

1. style → connects the stigma to the ovary and holds the stigma in a suitable position to trap pollen grains

what does the ovary contain of

one or more ovules

tell me more about the ovules

ovule container ovum, which has a haploid set of chromosomes

ovule is attaches to the placenta by a stalk called the funicle

what is pollination and what is its function

• the transfer of pollen grains from the anther to the stigma

• important to help bring together the male and female gametes to enable fertilisation to take place

what is self-pollination

the transfer of pollen grains from the inter to the stigma of the same flower or a different flower on the same plant

adaptations to promote self pollination and discourage cross pollination

• flowers are bisexual with anthers and stigmas maturing at the same time

• stigma is situated directly below the anther

• certain flowers in bisexual plants never open and only self-pollination can happen

benefits of self-pollination

1. only one parent needed

2. beneficial qualities are passed down from parent plant to offspring

3. not dependent on external factors for pollination

4. more likely to take place since stigmas are closer to anthers

5. less pollen and energy wasted

disadvantages of self-pollination

1. offspring produced are genetically similar to parents causing fewer varieties of offspring

2. probability of harmful recessive alleles being expressed in offspring Is higher as compared with cross-pollination

what is cross-pollination

involves the transfer of pollen grains from anther to stigma of a flower of another plant of the same species

how to promote cross-pollination?

1. plants bear either male or female flowers making self-fertilisation impossible

2. in bisexual plants:

   1. anthers and stigmas mature at different times

   2. stigmas of plants are situated at a distance away from the anthers

advantages of cross-pollination

1. more genetic variation in offspring / increased probability of offspring being heterozygous

2. seeds produced are capable of surviving longer before germination

3. probability of harmful recessive alleles being expressed offspring is lower as compared with self-pollination

4. offspring can inherit beneficial qualities from both parents

disadvantages of cross-pollination

1. two different pants of the same species are required

2. dependant on external factors for pollination

3. less likely to occur as compared to self-pollination

4. more energy and pollen are wasted

what is the calyx and epicalyx

• the calyx consists of five green sepals

• the base of the calyx is enclosed by the epicalyx consisting of two leaves

function of keel petal

enclose reproductive organs of the flower

what kinds of petals are there in the corolla of an insect pollinated flower

1. keel petal

2. wing petal

3. standard petal

what are the nectar guides and what is it used for

1. lines on the standard petals

2. guide insects to where the nectar is located

where is the nectar located in the clitoria flower and how can it be reached?

1. collects at the bottom of the stamen trough

2. can be reached only by insects with long tubular mouth (proboscis)

process of insect pollination

1. insects land on the standard petal

2. it follows the nectar guide into the flower

3. in order to collect the nectar, insect forces its way in between the two wing petals

4. insects back forces the keel petal upwards to expose the anthers and stigma

5. pollen grains from the anther stick onto the back of the insect and get transferred to a stigma

6. when insects leaves flower, the keel petals spring back into its original position

]what does the non-flowering bracts of the ischaemum muticum do

• protect the two flowers in the spikelet

what does the lodicules do in ischaemum muticum

when ready to reproduce, the lodicules swell and force the two flowering bracts apart

adaptations of the stamens of a wind-pollinated flower and why

1. mature stamens have long filaments that ang downwards and can swing freely / pendulous

2. this is so that

   1. when filaments sway, the pollen is shaken free and carried by the wind

adaptations of the stigma of a wind-pollinated flower and why

a mature stigma is large, extended and feathery to provide a large surface area for the capture of pollen floating in the air

difference between petals of insect and wind pollinated flower

Insect: large with brightly-coloured petals

Wind: small, dull-coloured and without petals

take note: if exam questions asks you to refer to a non-coloured diagram, dont talk about colour

difference between nectar of insect and wind pollinated flower

Insect: nectar present

Wind: nectar absent

difference between scent of insect and wind pollinated flower

Insect: sweet scent, fragrant

Wind: scent absent

take note: if exam questions asks you to refer to a non-coloured diagram, dont talk about scent

difference between stigmas of insect and wind pollinated flower

insect: small, compact and do not protrude out of flower

wind; large, feathery and protrude out of flower

difference between stamens of insect and wind pollinated flower

insect: not pendulous and do not protrude out of flowers

wind: long, pendulous filaments with protruding anther. sway freely

difference between pollen of insect and wind pollinated flower

insect: fairly abundant. pollen grains are large with rough surfaces (to cling onto insect hairs easier)

wind: more abundant, pollen grains are tiny with smooth surfaces

difference between nectar guides of insect and wind pollinated flowers

insect: present

wind: absent

process of fertilisation in a flowering plant

1. after pollination, pollen grain germinates in response to sugary fluid secreted by mature stigma

2. a pollen tube grows out from the pollen grain. growth pollen tube is controlled by the pollen tube nucleus

3. the cytoplasm and the two nuclei pass into the pollen tube

4. the pollen tube secretes enzymes to digest the surrounding tissue of stigma and style

5. pollen tube enters the ovule through the micropyle

6. the generative nucleus divides into two male gametes, while the pollen tube nucleus disintegrates

7. when the pollen tube reaches the ovule, its tip absorbs sap at the micropyle and bursts, releasing the two male gametes

   

8. one male gamete fuses with the ovum to form zygote. the other male gamete fuses with the definitive nucleus to form the endosperm nucleus

9. zygote divides and develops into the embryo and the endosperm nucleus will give rise to an endosperm

what happens to plant parts after fertilisation?

1. ovule develops into a seed

2. ovary develops into a fruit

3. zygote develops into an embryo