Q.Describe the structure of megasporangium.

The hilum is the junction between the ovule and its funicle (stalk).

An ovule is attached to the placenta of the ovary by a stalk called the funicle. The point of attachment of the ovule body to the funicle is called the hilum, and it marks the boundary between the funicle and the ovule proper. Other parts named in the options are elsewhere on the ovule: the micropyle is a pore at the opposite end (near the tip) through which the pollen tube usually enters; the i …

An anatropous ovule is completely inverted along its funicle, bringing the micropyle and chalaza close to each other near the base, with the raphe marking the fused stalk.

Diagram (labelled description to draw):

Draw an oval outer body (the ovule, made of the nucellus surrounded by integuments) turned upside-down (180°) relative to its stalk. Label the following parts:

1. Funiculus — the stalk attaching the ovule to the placenta.
2. Hilum — the point where the funiculus joins the ovule body.
3. Raphe — the ridge running along the ovule body, formed because the funiculus is fused lengthwise with the body of the inverted ovule.
4. Chalaza — the basal region of the ovule where the integuments and nucellus merge (this ends up close to the hilum in an anatropous ovule).
5. Micropyle — the small pore in the integuments through which the pollen tube enters; in an anatropous ovule it lies close to the funiculus, at the same end as the hilum/chalaza. …

Pollen-tube entry through the micropyle is porogamy; through the chalaza is chalazogamy; through the integuments/funicle is mesogamy.

After reaching the ovary, the pollen tube grows towards the ovule to deliver the male gametes. Depending on the point of entry into the ovule it is named:

• Porogamy - entry through the micropyle (the normal and most common route).
• Chalazogamy - entry through the chalaza (e.g. Casuarina). …

The orthotropous ovule occurs in Polygonum.

In an orthotropous (atropous) ovule, the body of the ovule is erect and straight so that the micropyle, chalaza and the point of attachment (hilum/funicle) all lie in one straight line. This primitive type is found in plants such as Polygonum and Piper (Piperaceae, Polygo …

The micropyle is the small apical pore left by the integuments of the ovule; it is the usual entry point for the pollen tube and later for water during germination.

Structure of the ovule

An ovule develops from the placenta and consists of a central mass of nucellus (megasporangium) enclosed by one or two protective layers called integuments. The integuments do not close completely at the apex — they leave a narrow canal-like opening called the micropyle.

Why the other options are wrong

• Nucellus is the nutritive tissue inside the integuments, not an opening.
• Funiculus is the stalk that attaches the ovule to the placenta.
• Hilum is simply the junction/region where the funiculus meets the body of the ovule. …

The mass of cells enclosed within the integuments of an ovule is the nucellus.

An ovule is the structure in flowering plants that, after fertilisation, develops into a seed. It consists of: the funicle (stalk attaching the ovule to the placenta), the integuments (protective outer layer(s) that later become the seed coat), the micropyle (a small pore in the integuments), the chalaza (the basal part where the integuments and nucellus are attached), and the nucellus — a mass of nutritive, undifferentiated cells enclosed within the integuments, occupying the main body of the ovule. It provides nutrition to the developing embryo sac, and the embryo sac (megagametophyte, containing the egg cell) is e …