Cell membrane function and difference-digieduco

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  Functions of cell membrane : (a) The proteins and enzymes present in the cell membrane helps in the transport of certain substances like sugar, sodium and other ions etc. across the cell membrane. (b) Cell membrane protects the internal structures of the cell and different organelles of the cytoplasm. (c) It maintains the shape of the cell. (d) It acts as a selective permeable membrane because it allows to pass certain substances while others are not, hence it helps in the transport of selective materials from and to the cells. (e) The membranes on the cytoplasmic organelles and nucleus most probably formed from the plasma membrane. (f) Other important functions of cell membrane of the cells are endocytosis and exocytosis . Endocytosis is the process by which materials are transported into the cells by the formation of vesicles. It includes two processes-phagocytosis (cell eating) and pinocytosis (cell drinking). The reverse process of endocytosis is exocytosis. During th...
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Union of stamens-digieduco

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Union of Stamens : Union of stamens may be with other unlike members such as petals or gynoecium which is termed adhesion, or union may be among themselves-either free member of stamens or their parts are united together which is termed cohesion.

Union of stamens-digieduco

A. ADHESION OF STAMENS

(a) Epipetalous-When stamens are adnate to corolla i. e. petals. Examples-flowers
of many families like Acanthaceae, Scrophulariaceae, Verbenaceae, Labiatae etc., in almost all flowers having gamopetalous corolla.

(b) Epiphyllous-When stamens are adnate to perianth leaves as seen in monocotyledonous families e.g. Liliaceae, Amaryllidaceae (Polyanthes tuberosa), etc.

(c) Gynandrous-This is adhesion between stamens and carpel. In Aristolochiaceac (Aristolochia sp.), Orchidaceae and Asclepiadaceae stamens and carpels unite completely forming gynostemium or gynostegium . In Asclepiadaceae (Calotropis sp.). the adnation between stamens and carpels is greater forming a column.
Union of stamens-digieduco

B. COHESION OF STAMENS-Here stamens may either be united by their filaments (adelphy) or by their anthers (syngeny).

(a) Monadelphous-Here all the stamens are united together by their filaments to
form one bundle while the anthers are free as in Malvaceae, Sterculiaceae, Meliaceae, few species of Euphorbiaceae, and Papilionaceae etc.

(b) Diadelphous-When put of ten stamens nine are united forming one bundle and the posterior one remains free as second bundle (9 + 1), or stamens are united in two distinct bundles of 5 + 5 (Smithia sp., Papilionaceae), the androecium is called diadelphous. Examples are found in most members of Papilionaceae.

(c) Polyadelphous-When in an androecium the stamens are united by their filaments to form several bundles, androecium is called polyadelphous. This type is found in Hypericum sp. (Guttiferae).

(d) Syngenesious-Sometimes in an androecium the filaments are free but anthers are united to form a tubular structure round the style, such condition is known as syngenesious. This is found in all the members of the family Compositae, e.g. Helianthus annuus (Sunflower)

(e) synandrous- when stamens are united by filaments as well as by anthers to form a compact body. This is seen in male flowers of cucurbita sp .

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