Reproduction in Plants

Reproduction in plants with diagrams

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  • Created by: bethedoc
  • Created on: 04-04-12 09:52

Reproduction in Plants

  • Asexual reproduction involves one parent. The offspring are identical to the parent
  • Sexual reproduction involves the joining of two special sex cells or gametes. The offspring are not identical to the parents
  • Plants can reproduce sexually and asexually
  • Pollen needs to be carried from one flower to another. Flowers can be pollinated by wind or insects

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  • After pollination a pollen tube grows down into the ovary to carry the male nucleus to the ovules
  • Fertilisation is the fusing of the male and female gametes. After this, seeds and fruits form
  • Seeds need warmth, water and oxygen to germinate
  • Seeds use their stored food as they germinate until the new leaves open and photosynthesise
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Asexual Reproduction in Plants

  • Plants can reproduce asexually to form identical offspring in many different ways, e.g. runners
  • Asexual reproduction is the result of mitosis
  • People can encourage plants to reproduce asexually by taking cuttings


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Sexual Reproduction in Plants

  • Flowers are the sex organs of plants. 
  • They contain pollen grains, which are the male gametes, and the ovules, which are the female gametes
  • Pollen is formed in the anthers of the stamens. Ovules are formed in the ovaries
  • The gametes are formed by meiosis. They contain half the number of chromosomes of the normal plant cells
  • For the gametes to meet, pollination must take place. Pollen grains are transferred from the anthers of a flower to the stigma.
  • Flowers which rely on insects to pollinate them have different features from flowers that are pollinated by wind
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Insect-pollinated Flower

  • The stamens and stigma are inside the petals so insects come into contact with them
  • The stigma is sticky so the pollen grains attach
  • The petals are large to attract insects and are often brightly coloured
  • There are nectaries to attract the insects
  • The pollen grains are big and stick to insects
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Insect-pollinated Flower

IMAG0064-1.jpg

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Wind-pollinated Flower

  • The stamens and stigma are outside the petals so wind can blow the pollen away and to catch pollen blowing in the wind
  • The stigma is feathery and sticky to catch the pollen
  • The petals are small and usually green
  • There are no nectaries
  • The pollen grains are small, smooth and light to carry in the wind
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Wind-pollinated Flower

IMAG0065-1.jpg

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Fertilisation

  • After pollination the nucleus of the pollen grain must fuse with the nucleus of the ovule for fertilisation to take place
  • A pollen tube grows out of the pollen grain and down the style into the ovary into the ovule
  •  grain and fuses with the female egg nucleus in the ovule to form a zygote
  • The male nucleus travels down this tube from the pollen
  • This then develops to form a seed
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Seeds and Fruit

  • Each seed contains the embryo plant, which has a root (radicle) and a shoot (plumule), the seed leaves (cotyledons) which act as a food store for the young plant while the seed germinates, and the seed coat (testa)
  • The ovary wall becomes the fruit coat
  • Each type of fruit is adapted to disperse the seeds as far away from the parent plant as possible.
  • They can be dispersed by animals, wind or water
  • Dispersal is important because it avoid compertition for resources (water, minerals and light) 
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Germination

  • Germination is the process by which the embryo plant in the seed starts to grow to the point where it photosynthesises independently
  • The radicle breaks through the testa and grows downwards into the soil (positive geotropism)
  • The plumule grows upwards towards the light (negative geotropism)

The conditions needed for germination are:

  • warmth for maximum enzyme efficiency
  • water to soften the testa and for chemical reactions in the seed to take place in solution
  • oxygen for respiration to provide energy
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Germination

(http://visual.merriam-webster.com/images/plants-gardening/plants/plant/germination.jpg)

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Comments

Ellie Oliver

Brilliant!

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