Among all living organisms, flowers, which are the reproductive structures of angiosperms, are the most varied fertilization in plants pdf and show a correspondingly great diversity in methods of reproduction. Dioicous gametophytes of the liverwort Marchantia polymorpha.
In this species, gametes are produced on different plants on umbrella-shaped gametophores with different morphologies. Plants have complex lifecycles involving alternation of generations. One generation, the sporophyte, gives rise to the next generation asexually via spores. For example, a sporophyte that produces spores that give rise only to male gametophytes may be described as “male”, even though the sporophyte itself is asexual, producing only spores. Each carpel in Ranunculus species is an achene that produces one ovule, which when fertilized becomes a seed. If the carpel contains more than one seed, as in Eranthis hyemalis it is called a follicle. Alnus serrulata has unisexual flowers and is monoecious.
Shown here: maturing male flower catkins on the right, last year’s female catkins on the left. A “perfect” flower has both stamens and carpels, and may be described as “bisexual” or “hermaphroditic”. A “unisexual” flower is one in which either the stamens or the carpels are missing, vestigial or otherwise non-functional. Each plant produces either functionally male flowers or functionally female flowers. In extreme cases, all of the parts present in a complete flower may be missing, so long as at least one carpel or one stamen is present. A species such as Fraxinus excelsior, the common ash of Europe, demonstrates one possible kind of variation. Ash flowers are wind-pollinated and lack petals and sepals.
Like Amborella, some plants undergo sex-switching. The complexity of the morphology of flowers and its variation within populations has led to a rich terminology. Androdioecious: having male flowers on some plants, bisexual ones on others. Androgynomonoecious: having male, female, and bisexual flowers on the same plant, also called trimonoecious. Andromonoecious: having both bisexual and male flowers on the same plant. Bisexual: each flower of each individual has both male and female structures, i.
Flowers of this kind are called perfect, having both stamens and carpels. This promotes outcrossing by limiting self-pollination. Dioecious: having either only male or only female flowers. No individual plant of the population produces both pollen and ovules. From the Greek for “two households”. Gynodioecious: having hermaphrodite flowers and female flowers on separate plants. Gynomonoecious: having both bisexual and female flowers on the same plant.
Monoecious: In the commoner narrow sense of the term, it refers to plants with unisexual flowers which occur on the same individual. In the broad sense of the term, it also includes plants with bisexual flowers. Polygamodioecious: mostly dioecious, but with either a few flowers of the opposite sex or a few bisexual flowers on the same plant. Or, mostly monoecious, but also partly polygamous. Polygamous: having male, female, and bisexual flowers on the same plant. Or, with bisexual and at least one of male and female flowers on the same plant.