Cell membrane function and difference-digieduco

on
  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 this p
0

MIXED INFLORESCENCE AND ITS TYPES- DIGIEDUCO

on
MIXED INFLORESCENCE

Besides the typical racemose and cymose intiorescences, several mixed types are often found. Here the combinations of a racemose type and cymose type or of two racemose types e.g. raceme with spike, raceme with umbel etc. are noted. In sunflower, Dahlia, etc. the individual
inflorescence is racemose, but with respect to the opening of the inflorescence the top apical inflorescence opens first and the lateral ones lower down opens later like cymose.


MIXED INFLORESCENCE AND ITS TYPES- DIGIEDUCO

(a) Mixed panicle-It is a compound type and the combination of racemose and cymose or irregularly arranged floWers. The primary axis bears flowers in racemose manner and secondary axes bear flowers irregularly though terminal flowers open first like cymose. Example-Ligustrum vulgare (Oleaceae).

(b) Mixed spadix-Here cymosely arranged flower-groups are racemosely arranged on the thick fleshy primary axis in acropetal manner and each flower group is subtended by a spathe, e.g. Musa paradisiaca (Musaceae).

(c) Cymose umbel-This is seen in Allium cepa (Onion, Liliaceae), Calotropis sp. (Asclepiadaceae) etc. where cluster of cymose inflorescences are developed in “umbel” type.
MIXED INFLORESCENCE AND ITS TYPES- DIGIEDUCO

(d) Cymose corymb or Corymbose cyme-Here clusters of cymose inflorescences are arranged in corymbose manner e.g. Ixora sp., Oldenlandia corymbosa (Rubiaceae), Holarrhena antidysenterica (Apocynaceae) etc.

There is a special type of cymose corymb known as fascicle. Here the successive
axes of a polychasial inflorescence are of equal lengths so that flowers are arranged to the same level in a corymbose manner-e.g. Garcinia of the family Guttiferae and some species of Catyopbyllaceae.

(e) Thyrsus-In this form,several cymose clusters are arranged acropetally forming the shape of a double cone on a raceme type of primary axis. Example-inflorescence of Vitis vinifera ( vitaceae )


Comments

Post a Comment