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 this p
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Corolla flowers and its types-digieduco

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Corolla flowers may be regular or irregular, usually variously coloured, sometimes green~ then they are called sepaloid. Sometimes petals are narrowed below into a stalk-like structure called claw or unguis, the actual expanded portion is called limb; petals having claw are called clawed.
Corolla flowers and its types-digieduco
Appendages of corolla


Appendages of the Corolla-Corolla may have various irregularities forming appendages of different types as follows :

(a) Saccate or Gibbous-When lower part of the corolla tube becomes dilated forming a sac, e.g. species of Valeriana (Valerianaceae), Antirrhinum (Scrophulariaceae) etc.

(b) Corona-When appendages in the form of scales, hair-like outgrowths of various types etc. are situated at the base of petals or in between claw and limb (i.e. corolla throat), e.g. species of Passiflora (Passifloraceae). Nerium (Apocynaceae). Lychnis (Caryophyllaceae), Narcissus and Pseudonarcissus (Amaryllidaceae), in many members of Acanthaceae, Boraginaceae etc.. .

(c) Spurred or Calcarate-When petal or petals, or corolla tube are prolonged downward forming spur, e.g. Aquilegia sp. (Ranunculaceae).
Corolla flowers and its types-digieduco
Forms of polypetalous corolla

Types of Corolla : These are of various types as follows :
A. Polypetalous regular corolla-
(a) CRUCIFORM OR CRUCIATE COROLLA-This is characteristic of mustard family i.e. Cruciferae. Here 4 petals, each of which is clawed, are arranged in one whorl in a diagonal cross.
(b) ROSACEOUS-Originally there are 5 petals (but many petals as in rose are due to reconversion of stamens into petals as a result of cultivation), each petal has outwardly spreading very wide limb and very short claw. Examples-Rosa sp. (Rosaceae), Camellia
sinensis (Theaceae) etc.
(C) CARYOPHYLLACEOUS-There are 5 clawed petals, the limbs ef whxch are at nght angles to the claws. Example-Dianthus sp. (Caryophyllaceae)

B. Polypetalous irregular corolla-
Only one kind i.e. PAPILIONACEOUS corolla of Papilionaceae. There are 5 petals, of which the odd fifth posterior is the outermost forming standard or vexillum, the 2 lateral petal wings are clawed covering almost the 2 anterior petals which are loosely connate to form a boat-shaped structure-the keel.
Corolla flowers and its types-digieduco
Forms of gamopetalous corolla

C. Gamopetalous regular corolla-
(a) TUBULAR COROLLA- All petals are united to form a more or less uniform tube. It is
found in the disc florets of Helianthus annuus (Compositae).

(b) CAMPANULATE OR BELL-SHAPED corolla is met with in Cucurbita maxima(Cucurbitaceae). In this type both tube and limb are almost of same dimension, the corolla resembles a bell.

(c) HYPOCRATERIFORM OR SALVER-SHAPED-In this kind the limb is very broad and it is placed at right angles to the slender tube, this is met with in Catharanthus roseus sp. of Apocynaceae.

(d)ROTATE OR WHEEL-SHAPED corolla is met with in flowers of Solanum sp. (Solanaceae), Nyctanthes arbor-tristis (Oleaceae) etc.-here the tube is short with spreading wheel Shaped limb.

(e) URCEOLATE OR URN-SHAPED-when the corolla is swollen in the middle and contracted at both ends (i.e. at both base and apex), Examples-Erica sp., Vaccinium myrtillus (Ericaeae), Bryophyllum calycinum (Crassulaceae) etc.

(f) INFUNDIBULIFORM OR FUNNEL-SHAPED corolla is found in Datura sp. (Solanaceae), Ipomoea reptans (Convolvuiaceae) etc. in which petals are united; corolla tube (wide upper portion) is speading like that of a funnel, the limb gradually tapers into tube.

D. Gamopetalous irregular corolla-

(a) BILABIATE OR TWO-LIPPED corolla is the characteristic of the flowers of Labiatae, Acanthaceae and many Scrophulariaceae. In this type, 5 petals are united to form bilabiate or two-lipped structure, the upper lip consists of two petals, the lower lip of three petals, the mouth remains open at the throat (i.e., the entrance gap leading to the tube inside).
(b) PERSONATE OR MASKED is a kind of bilabiate in which the throat of corolla is closed by a projection of the lower lip, known as palate. Examples are met within species of Antirrhinum, Lindenbergia (Scraphulariaceae) etc.
(c) LIGULATE OR STRAP-SHAPED corolla is met with in the marginal or ray-florets of the capitulum Composuae ; here 5 petals are connate to form strap or tongue-shaped structure.




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