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

Calyx flowers-digieduco

on
Calyx flowers is the lowermost whorl of the flower. Calyx, in some flowers (Hibiscus sp. of Malvaceae), is subtended below by an epicalyx. Normally sepals are green in colour. The function of the calyx is to protect flower in bud condition and they can also perform photosynthesis.
Calyx flowers-digieduco

Like the flower, the calyx may be regular or irregular. The sepals may be free from one another, known as polysepalous, or they may be partially or entirely united which is tennedgamosepalous forms of gamosepalous regular calyx may be tubular (e.g. Datum),bell-shaped (Hibiscus rosa-sinensis), urceolate (e.g. Hyoscyamus sp. etc.; irregularly gamosepalous calyx may be bilabiate (e.g. Leonurus sp., Leucas sp. etc . In some genera e.g. species of Delphinium, Heleborus of Ranunculaceae and Mirabilis sp. of Nyctaginaceae, sepals are coloured and they look like corolla.

Calyx flowers-digieduco
A petal with limb and claw

Modifications of calyx are of various types, such as :

(a) Pappus-when modified into few hairy or scaly or feathery structures as seen in most species of Compositae  and some members of the family Valerianaceae.

(b) Spinous-as seen in Trapa bispinosa (Onagraceae)

(c) Spurred-when prolonged into tubular or bcaklike structures as seen in Impatiens balsamina (Balsaminaccae), Delphinium sp. (Ranunculaceae) etc.

(d) Hood-like enlarged sepals are also noted in some members of Ranunculaceae (Aconitum sp.), Duration of calyx varies in different flowers-it may be:
(a) Caducous or fugacious-when calyx falls off before the complete opemng of flowers, e.g.Argemone sp. (Papaveraceae).

(b) Deciduous-when calyx falls off at the same time with corolla after fertilization. e.g. Brassica sp. (Cruciferae).

(c) Persistent-when calyx is attached with the fruit and become permanent ', this is again of two types such as
(i) Marcescent-when persistent sepals shows shrivelled and Withered appearance, e.g. Psidium guajava (Myrtaceae).
(ii)Accrescent--when persistent calyx grows in size along With the fruit , e.g. Dillenia indica (Dilleniaceae), Physalis sp. of Solanaceae.






Comments

Post a Comment