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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Structure of Monocotyledonous Exalbuminous Seeds-digieduco

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Structure of Monocotyledonous Exalbuminous Seeds : This type is seen in Sagittaria sagittifolia, Alisma plantago (Alismaceae) and almost in all the genera of Orchidaceae .


In Alisma. the seed consisting of a seed coat (only testa) and a large curved embryo ; the embryo consists of one cotyledon, and a radicle.
Structure of Monocotyledonous Exalbuminous Seeds-digieduco

Structure of some Special Monocotyledonous Seeds : 

(a) COCONUT (Cocos nucifera, Palmae)-
It is really an one-seeded fruit. The epicarp and mesocarp are fibrous. The hard shell-like structure, called endocarp is the part of the fruit. Beneath this, there lies dark brown seed coat attached to white kernel. The embryo is embedded on the top of the thick white cartilage, the centre is occupied by water ; white cartilage and water together constitute the endosperm. The embryo consists of a large cotyledon, major part of which is attached to the endosperm and functions as sucker. The axis is very short and slender, almost invisible and is within the lower portion of the sheath which elongates.
Structure of Monocotyledonous Exalbuminous Seeds-digieduco

(b) DATE SEED (Phoenix sylvestris, Palmae)-The seed coat is the brownish testa which covers the stony seed. The embryo is small and located laterally on one side of the copious horny endosperm consisting of reserved cellulose-the other side of the endosperm bears longitudinal groove.

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