Do all plants have both an adroecium and a gynoecium (both male and female parts) or do some have one gender?

I thought I heard that some plants require insects to pollinate each other. So in my mind that would seem that some plants are male and the bees must deliver pollen to the female plants. If the plants all have both, then why why are insects necessary for pollination? Thanks so much!!! all help is appreciated.

Do all plants have both an adroecium and a gynoecium (both male and female parts) or do some have one gender?
1) In flowering plants there are two types of flowers =



A ) Flowers with both androecium and gynoecium in one and same flower . Such flowers are called bisexual flowers.



Examples of bisexual flowers are = Hibiscus, Mallow or Abutilon and , Rose .



click the link for photo=

http://extension.oregonstate.edu/mg/bota...



http://plant-life.org/Malvaceae/malva_fl...



http://bellevuecollege.edu/ArtsHum/mater...



B) Flowers with the sex organs mentioned above located in separate flowers . Such flowers are unisexual flowers .( male and female flowers separate .)



examples of unisexual flowers are = cucumbers , squashes and watermelons .



http://www.beeculture.com/content/pollin...



2) From pollination point of view there are again two types of plants / flowers =



A) Self pollinating plants / Flowers =These plants are bisexual ( Ref. above ) AND the stamens ( Male ) and carpels ( Female ) reach maturity simultaneously.



In such cases the pollen from the anthers gets transferred to the stigma OF THE SAME FLOWER without any aid from any agent .



http://cache.eb.com/eb/image?id=95387%26amp;re...



http://ecs.lewisham.gov.uk/youthspace/ca...



B ) Cross pollinating plants / Flowers = Unisexual flowers , by perforce , are pollinated by agents as they have no alternative .



http://plantandsoil.unl.edu/croptechnolo...



http://www2.dpi.qld.gov.au/images/3521.g...



BUT



Even in bisexual flowers there are many that require help from agents like insects .



This is because , even though bisexual , the sex organs ( Stamens and carpels ) DO NOT MATURE simultaneously!!!



When pollen is ready , it is taken away by bees to another flower which is older and has shed its pollen and now stigma is mature to receive pollen from another flower!!!



Thus , inspite of the fact that a particular flower is bisexual ,it still requires help from insects for pollination !!!!
Reply:Thanks for the honor! Thank you very much for the comments !! Report It
Reply:yes there are indeed separate male and female plants... cycas is one example of plants with separate gender.

also in some plants, the time at which the androecium and gynoecium mature are different, so insects are required for pollination.

structurally too, some flowers have a higher gynoecium which is situated at a higher level than the androecium. so pollination becomes an up-hill task. for these reasons, insects are a necessary force for effective pollination.
Reply:Some plants have both male and female organs, and some have only one or the other. That is life.



Bees also help by cross pollinating plants so that you get some genetic diversity, instead of plants just pollinating themselves.

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