the manner in which the Plantae are distributed in the ovary is called Placentation and it is helpful in classification.
in a simple ovary (Formed of one carpel) there is only one type of placentation.
In compound ovaries, the placentation may be parietal, axile, free central, basal, or superficial.
vertical section of flower refers to its having been cut vertically in a median plane. it furnishes the following information.
A floral formula is a short symbolic representation of the various features of a flower. it furnishes information about:
the various symbols used in floral formulas are as under:-
2. Symmetry of flower
3. number and conditions for sepals
Calyx
Epicalyx, if present, is represented by the Letter “Epi K” and is mentioned before K. The fused nature of floral parts is shown by enclosing the numbers in the breast, e.g. K(5) indicates a calyx comprising five fused sepals.
If sepals, petals, and stamens are present in two whorls, then the number of constituent parts in the outer whorl is mentioned first, and then the sign of plus (+) is put before mentioning the number of constituent parts comprising the second whorl.
For example, suppose a calyx consists of four sepals, of which two are present in the inner whorl and two in the inner whorl then„ in the floral formula, such a condition is represented as K2 +2.
The superior nature of the ovary is indicated by putting a small straight line below the number of carpels; e.g., G(3) The inferior nature of the ovary is indicated by putting a small straight line above the number of carpels, e.g., (G3).
In Brassica:
The floral formula of such a flower will be as follows:-
A ground plan showing the relation of floral leaves to each other and to the axis is called a Floral Diagram. It explains the number and positional Arrangement of the floral leaves in one view. The axis on which the flower is borne is known as the Mother Axis. The side of the flower towards the mother axis is Posterior, and that towards the bract or away from the mother axis, Anterior.
A line is drawn across the flower, passing through the mother axis and the Centre of the flower indicates the Antero-Posterior or Median Plane. A line at right angles to this, also passing through the center of the flower, indicates the Lateral Plane.
The planes which bisect the angles formed by the median and lateral planes are called Diagonal Planes, while all other planes are said to be oblique. The mother axis is indicated by a dot or a small circle in the
anteroposterior plane above the diagram. No dot is shown in the case of a terminal flower.
The sepal or petal lying just opposite the mother- axis is the odd Sepal or Odd Petal. The floral leaves usually alternate with one another. If a sepal is odd, the mother will be lying between the two petals.
Beginning with the odd sepal, or odd petal, the exact number of sepals and petals are represented by brackets which are broader in the middle and taper towards the end. The sepals are shown in the outer circle and the petals are in the inner. Gamosepalous and gamopetalous condition is shown by linking the ends of the brackets.
The stamens are indicated by small kidney-shaped ‘figures, if the androecium is epipetalous, the stamen figures are linked by radial lines to the petal brackets.
If the stamens are united, the stamen figures are connected with each other by an arc or circle. If there are two or more alternating whorls of stamens, their number and position are indicated accordingly. The gynoecium is shown in the Centre of the diagram in the transverse section.
The ovary is drawn in a double line and the number of carpels is indicated by as many constrictions. The septa are shown by radial lines meeting in the Centre and the ovules are represented by small rounded figures attached to the placentas.
Homologies | |
Carpel | Megasporophyll |
Ovule | Mega sporangium |
Embryo Sac | Female Gametophyte |
Egg | Female Gamete |
Stamen | Microsporophyll |
Anther | Microsporangium |
Pollen grain | Microspore |
Germinating Pollen grain | Male gametophyte |
Ovule | Seed |
Funicle | Stalk |
Integuments | seed coat |
Hilum, raphe | Hilum, raphe |
Chalaza & Micropyle | Chalaza & Micropyle |
Nucellus | Perisperm |
Embryo Sac | Embryo |
Egg cell | Endosperm |
Endosperm nucleus | Disintegate |
Synergids | Disintegrate |
Antipodal cells | |
The following facts may be cited to prove that the Thalamus is a modified branch; Sepals, Petals, Stamens, and Carpels are modified vegetative leaves; and the Flower as a whole is a modified leaf-bud. Placentation
In Pineapple, the inflorescence axis ends in one or more buds (bulbils) for vegetative propagation of the plant. These organs thus show a reversion of ancestral forms, i.e. the forms from which they had been derived. Placentation
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