Anatomy of Reproductive Parts: Flower, Fruit,Seed

Anatomy of Reproductive Parts: Flower, Fruit,Seed

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  Submitted to: SirGulam Sarwar Submitted by:Alisha Fatima Class:Bs hons Botany Smester:5th Evening Roll no:46 The Islamia university bahawalpur
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   A flower,sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Magnoliophyta, also called angiosperms). The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs. Flowers may facilitate outcrossing (fusion of sperm and eggs from different individuals in a population) or allow selfing (fusion of sperm and egg from the same flower). Some flowers produce diaspores without fertilization (parthenocarpy). Flowers contain sporangia and are the site where gametophytes develop. Flowers give rise to fruit and seeds. Many flowers have evolved to be attractive to animals, so as to cause them to be vectors for the transfer of pollen.
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   Vegetative (Perianth) Collectively the calyx and corolla form the perianth.  Calyx: the outermost whorl consisting of units called sepals; these are typically green and enclose the rest of the flower in the bud stage, however, they can be absent or prominent and petal-like in some species.  Corolla: the next whorl toward the apex, composed of units called petals, which are typically thin, soft and colored to attract animals that help the process of pollination.
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   Androecium :Thewhorl sometimes multiplied into several whorls consisting of units called stamens.A stalk called a filament topped by an anther wherepollen is produced by meiosis and eventually dispersed.  Gynoecium: The innermost whorl of a flower, consisting of one or more units called carpels. The carpel or multiple fused carpels form a hollow structure called an ovary, which produces ovules internally. Ovules are megasporangia and they in turn produce megaspores by meiosis which develop into female gametophytes. These give rise to egg cells.The relationship to the gynoecium on the receptacle is described as hypogynous (beneath a superior ovary), perigynous (surrounding a superior ovary), or epigynous (above inferior ovary).
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   Fruit anatomyis the internal structure of fruits.  Fruits are the mature ovary or ovaries of one or more flowers. In fleshy fruits, the outer layer (which is often edible) is the pericarp, which is the tissue that develops from the ovary wall of the flower and surrounds the seeds.  But in some seemingly pericarp fruits, the edible portion is not derived from the ovary. For example, in the fruit of the ackee tree the edible portion is an aril, and in the pineapple several tissues from the flower and stem are involved.  The outer covering of a seed is tough because the parent plant needs to protect the plant growing.
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   In berriesand drupes, the pericarp forms the edible tissue around the seeds. In other fruits such as Citrus stone fruits (Prunus) only some layers of the pericarp are eaten. In accessory fruits, other tissues develop into the edible portion of the fruit instead, for example the receptacle of the flower in strawberries.
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   The pericarpis typically made up of three distinct layers: the epicarp, which is the outermost layer; the mesocarp, which is the middle layer; and the endocarp, which is the inner layer surrounding the ovary or the seeds. In a citrus fruit, the epicarp and mesocarp make up the peel.  Epicarp:  Epicarp is a botanical term for the outermost layer of the pericarp (or fruit). The epicarp forms the tough outer skin of the fruit, if there is one. The epicarp is sometimes called the exocarp, or, especially in Citrus, the flavedo.  Flavedo:  Flavedo is mostly composed of cellulosic material but also contains other components, such as essential oils, paraffin waxes,steroids and triterpenoids, fatty acids, pigments (carotenoids, chlorophylls, flavonoids), bitter principles (limonene), and enzymes.
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  Mesocarp:  The mesocarpis the fleshy middle layer of the pericarp of a fruit; it is found between the epicarp and the endocarp. It is usually the part of the fruit that is eaten. For example, the mesocarp makes up most of the edible part of a peach, and a considerable part of a tomato. "Mesocarp" may also refer to any fruit that is fleshy throughout. Endocarp:  Endocarp is a botanical term for the inside layer of the pericarp (or fruit), which directly surrounds the seeds. It may be membranous as in citrus where it is the only part consumed, or thick and hard as in the stone fruits of the family Rosaceae such as peaches, cherries, plums, and apricots.  In nuts, it is the stony layer that surrounds the kernel of pecans, walnuts, etc., and that is removed prior to consumption.
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  The grains ofgrasses are single-seed simple fruits wherein the pericarp (ovary wall) and seed coat are fused into one layer. This type of fruit is called a caryopsis. Examples include cereal grains, such as wheat, barley, and rice.
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   A seedis an embryonic plant enclosed in a protective outer covering known as the seed coat.  It is a characteristic of spermatophytes (gymnosperm and angiosperm plan ts) and the product of the ripened ovule which occurs after fertilization and some growth within the mother plant. The formation of the seed completes the process of reproduction in seed plants (started with the development of flowers and pollination), with the embryo developed from the zygote and the seed coat from the integuments of the ovule.  Seeds have been an important development in the reproduction and spread of gymnosperm and angiosperm plants.
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   Seeds consistof three genetically distinct constituents:  (1) the embryo formed from the zygote,  (2) the endosperm, which is normally triploid,  (3) the seed coat from tissue derived from the maternal tissue of the ovule. In angiosperms, the process of seed development begins with double fertilization, which involves the fusion of two male gametes with the egg cell and the central cell to form the primary endosperm and the zygote.
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   The Ovule: Gymnosperm ovule on left, angiosperm ovule (inside ovary) on right  After fertilization the ovules develop into the seeds. The ovule consists of a number of components:  The funicle (funiculus, funiculi) or seed stalk which attaches the ovule to the placenta and hence ovary or fruit wall, at the pericarp.  The nucellus, the remnant of the megasporangium and main region of the ovule where the megagametophyte develops.  The micropyle, a small pore or opening in the apex of the integument of the ovule where the pollen tube usually enters during the process of fertilization.  The chalaza, the base of the ovule opposite the micropyle, where integument and nucellus are joined together).
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   A typicalseed includes two basic parts:  an embryo  a seed coat