Flowers and reproductive structures of
Cactus and Succulents ... 2/2

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Flower Types:
Imperfect Flower - A flower that has either all male parts or all female parts, but not both in the same flower. Examples: cucumbers, pumpkin, and melons.
Perfect Flower - A flower that has both the male parts and female parts in the same flower. Examples: roses, lilies, and dandelion.

Reproduction

Pollen must fertilize an ovule to produce a viable seed. This process is called pollination, and is often aided by animals like bees, humming birds, bats, moths etc, which fly from flower to flower collecting sweet nectar and in the process, they transfer pollen around, depositing it on some stigmas on a subsequent flower. After a male's pollen grains have landed on the stigma, pollen tubes develop within the style, burrowing down to the ovary, where the sperm fertilizes an ovum (an egg cell), in the ovule. After fertilization, the ovule develops into a seed in the ovary.

Cactus

In cacti the ovary is inferior, that is the flower is located above the ovary, sometimes with an elongated tube. The flower is usually regular or symmetrical, that is it forms equal halves whichever plane it is sliced across. Some are asymmetrical or zygomorphic, that is it only has one plane of symmetry eg Cleistocactus, Borzicactus and Schlumbergera.

Most species are self-incompatible i.e. they need another plant from the same species (but not a cutting) to form viable seed, some are self-compatible ie seed is formed by self pollination. Still others are cleistogamous whereby the flower does not even have to open to be pollinated and form seed - eg Frailea genera.

Flowers may be either diurnal (day opening) and pollinated by Bees and other insects, and birds, or they may be nocturnal (night) and pollinated by moths and bats. Diurnal flowers are usually colourful, whereas nocturnal are usually larger, and white as well as being often highly perfumed to entice the pollinator in the dark. Nocturnal flowers open at dusk and usually by the next morning are finished not to open again, whereas diurnal can open and close (at night) over a few days.

The end result - seed