With respect to diagram, answer the following :[Figure: L.S. of an inverted ovule. The rounded body of the ovule has the chalaza at the top and the micropylar end facing downwards; the funicle runs up alongside the body of the ovule from the placenta…

Answer: (a) Anatropous (inverted) ovule. (b) Functional megaspore. (c) A – micropyle; B – secondary nucleus (fused polar nuclei).

(a) The ovule is anatropous: its body is inverted through 180°, so the micropyle comes to lie close to the funicle (hilum), while the micropyle and chalaza still lie in one straight line. The funicle runs alongside the body of the ovule. This is the most common type of ovule in angiosperms.

(b) The first cell of the embryo sac (female gametophyte) is the functional megaspore (the surviving chalazal megaspore of the linear tetrad formed by meiosis of the megaspore mother cell).

(c)

• A – Micropyle: the small opening left at the tip of the integuments. Function: the pollen tube usually enters the ovule through it (porogamy) to deliver male gametes; in the seed it allows entry of water and oxygen at germination.
• B – Secondary nucleus (definitive nucleus): the diploid nucleus of the central cell formed by fusion of the two polar nuclei. Function: it fuses with the second male gamete (triple fusion) to form the triploid primary endosperm nucleus, which develops into the endosperm that nourishes the embryo.