About 350,000 plant species are currently known. Of this total, over 250,000 are angiosperms.
The word angiosperm comes from Greek. angels, which means 'purse', and sperma, 'seed'. These plants represent the most varied group of species among the components of the kingdom Plantae or Metaphyta.
Flowers and Fruits: Evolutionary Acquisitions
Angiosperms produce root, stem, leaf, flower, seed and fruit. Considering these structures, note that, in relation to gymnosperms, angiosperms present two "novelties": flowers and the fruits.
Passion flower and fruit
Flowers can be eye-catching in color and shape; often also give off a pleasant odor and produce a sugary liquid - the nectar - which serves as food for bees and other animals. There are also flowers that do not have colorful pieces, are not fragrant and do not produce nectar.
Colorful and fragrant or not, it is from the flowers that angiosperms produce seeds and fruits.
The flower parts
Flower supporting organs such as:
- peduncle - binds the flower to the rest of the branch.
- receptacle - dilation in the terminal area of the peduncle, where the remaining floral pieces are inserted.
Organs that surround the reproductive parts themselves, protecting them and helping to attract pollinating animals. The set of protection organs is called perianth. A flower without perianthus is said to be naked.
- Cup - Set of sepals, the most floral parts of leaves, as they are usually green. Its function is to protect the flower when in bud. The flower without sepals is said to be asepal. If the whole perianth looks the same (tepals), and is similar to sepals it is called sepaloid. In this case the perianth is said to be undifferentiated.
- corolla - Set of petals, usually colorful and fragrant floral pieces, with nectar-producing glands at their base, to attract animals. The flower without petals is called the petal. If all the perianth is equal (tepals), and is similar to petals, it is called petaloid. In this case too, the perianth is called undifferentiated.
Modified fertile leaves, located more in the center of the flower and designated sporophils. The male fertile leaves form the outer ring and the female fertile leaves the inner.
- androceu - male part of the flower, is the set of stamens. Stamens are modified leaves, or sporophils, as they support sporangia. They consist of a fillet (corresponds to the leaf petiole) and the anther (corresponds to the leaf limb);
- gyno - feminine part of the flower, is the set of carpels. Each carpel, or female sporophyll, consists of an enlarged hollow lower zone called the ovary, which contains eggs. After fertilization, the walls of the ovary form the fruit. The carpel extends over a narrow area, the stiletto, and ends in an enlarged area that receives pollen grains, called stigma. Usually the stigma it is taller than the anthers, so as to make self-pollination difficult.
The fruits contain and protect seeds and aid in dispersal in nature. Often they are colorful, succulent and attract various animals, which uses them as food. The seeds swallowed by the animals usually pass through the digestive tract intact and are eliminated in the environment with the feces, usually in distant places of the mother plant, by the wind, for example. This favors the species in the conquest of new territories.