Q.Draw a longitudinal section of pistil of a flower showing growth of the pollen tube. Label the part :

Concept: Post-pollination events — path of the pollen tube through the pistil to reach the female gametophyte.

Reasoning:

1. After landing on the stigma, the pollen grain germinates and produces a pollen tube. This tube grows down through the style (the elongated part of the pistil) to reach the ovary.
2. Inside the ovary, the pollen tube enters the ovule through the micropyle and finally discharges its two male gametes into the embryo sac (specifically, into one of the synergid cells).

Diagram (longitudinal section of pistil):

        Stigma
          |
        Style  ← (a) Pollen tube moves down through the style …

The key here is to visualise the female reproductive structure of a flower — the pistil — and trace the path of the pollen tube after a pollen grain lands on the stigma. You are not just drawing a diagram; you are showing a biological process in motion.

The pistil has three main parts: the sticky stigma at the top, the long style in the middle, and the swollen ovary at the base. Inside the ovary are ovules, each containing an embryo sac (the female gametophyte). When a pollen grain germinates, it produces a pollen tube that must travel through the style to reach the ovule. The tube does not simply drill through cells — it grows between the cells of the style, often digesting its way through the transmitting tissue.

Once the pollen tube reaches the ovule, it enters through a small opening called the micropyle. Inside the embryo sac, the tube tip bursts open and releases two male gametes (sperm cells). This release happens inside one of the synergid cells — the two specialised cells flanking the egg cell. The synergid degenerates to allow this entry.

Let us now build the diagram step by step.

1. Draw the pistil outline. Start with a vertical, flask-shaped structure. At the top, draw a slightly expanded, lobed stigma. Below it, draw a long, narrow style (this is the part labelled (a)). At the base, draw a rounded, hollow ovary. Inside the ovary, draw one or two small oval ovules attached to the ovary wall by a short stalk (the funicle).

2. Show the pollen tube path. From the stigma surface, draw a thin, wavy line (the pollen tube) moving downward through the centre of the style. This line should pass through the style tissue and then curve toward one ovule. The tube enters the ovule through a tiny gap at its tip — the micropyle. Label the entire path through the style as (a) style.

3. Draw the embryo sac inside the ovule. Inside the ovule, draw a large oval cell — this is the embryo sac. At its micropylar end (the end near the micropyle), draw two small cells side by side: these are the synergids. The pollen tube tip should be shown entering the embryo sac and touching one of these synergids. Label that synergid as (b) synergid (or, more generally, "the cell wherein the pollen tube releases its contents"). …