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 th...
0

Dispersal by animals-digieduco

on
Dispersal by animals such as grazing cattles, birds etc. is by no means infrequent. Various devices are found in the seeds and in dry indehiscent fruits. The common examples are the curved outgrowth of prickly bodies (hood-like) on the pericarp of Xanthium strumarium (Compositae), Urena lobata (Malvaceae) etc. One experiences difficulty in getting clothes freed from fruits when passing through Xanthium strumarium and Urena lobata plant growths.

The fruits of Chrysopogon aciculatus, Aristida sp. (Gramineae), etc are provided with stiff hairs so that they stick easily such fruits are means of the dispersal by animals including human beings. The fruits of Aerva aspera are sticky due to the presence of scarious bracts and perianths on them. We often get our clothes caught by those fruits when crossing a field. Another good example, found is the outgrowths in the form of recurved sharp  claws, in the fruits of Martynia diandra (Martyniaceae)-the fruits get attached to the bodies of grazing animals by means of the claws and can be carried to a distance. Sharp rigid spines on the fruits of Tribulus sp. (Zygophyllaceae) help in dispersal when those get embedded into the foot of hoofed animals. In Pupalia(Amaranthaceae) fruits, hooked bristles are present which help in dispersal in the same way. The fruits of Boerhaavia repens (Nyctaginaceae), Cleome viscosa
(Capparidaceae), etc. are provided with sticky glands so that they stick to the bodies of grazing animals and are thereby dispersed.
Dispersal by animals-digieduco

Special morphological elaboration for dispersal by birds, fIying foxes are found in succulent berries, syconus etc. The seeds of such fruits have resistant thick testa. The fruits are eaten by birds, the seeds remain undigested in the intestine and excreted off, where they germinate. The growth of Ficus benghalensis (Moraceae) in the old buildings is due to such mode of dispersal by birds. 

Comments

Post a Comment