Module: | Pollination & Outbreeding Devices
Q36: Consider the following statements regarding the pathways of pollen tube entry:
1. Porogamy is the standard condition where the pollen tube enters the ovule directly through the micropyle.
2. Chalazogamy, famously observed in Casuarina, involves the pollen tube penetrating the ovule through the basal chalazal tissues.
3. Regardless of the entry point into the ovule, the pollen tube always enters the embryo sac through the chalazal end.
Which of the above statements is/are correct?
2. Chalazogamy, famously observed in Casuarina, involves the pollen tube penetrating the ovule through the basal chalazal tissues.
3. Regardless of the entry point into the ovule, the pollen tube always enters the embryo sac through the chalazal end.
Which of the above statements is/are correct?
✅ Correct Answer: A
The correct option is A. Statements 1 and 2 are correct, whereas Statement 3 is strictly incorrect.
After navigating down the style, the pollen tube must breach the ovule to deliver its male gametes.
Botanists classify this entry into three types based on the structural entry point.
Porogamy is the most common, where entry is through the micropylar opening.
Chalazogamy (seen in Casuarina and walnut) occurs when the tube digests its way through the chalaza.
A third type, mesogamy (seen in cucurbits), involves entry through the integuments or funicle.
However, Statement 3 presents a major physiological trap.
No matter how the pollen tube enters the broader ovule, its final target is the egg apparatus.
Therefore, it must causally bend and ALWAYS enter the female gametophyte (embryo sac) through the micropylar end, specifically via the filiform apparatus of one of the synergids.
After navigating down the style, the pollen tube must breach the ovule to deliver its male gametes.
Botanists classify this entry into three types based on the structural entry point.
Porogamy is the most common, where entry is through the micropylar opening.
Chalazogamy (seen in Casuarina and walnut) occurs when the tube digests its way through the chalaza.
A third type, mesogamy (seen in cucurbits), involves entry through the integuments or funicle.
However, Statement 3 presents a major physiological trap.
No matter how the pollen tube enters the broader ovule, its final target is the egg apparatus.
Therefore, it must causally bend and ALWAYS enter the female gametophyte (embryo sac) through the micropylar end, specifically via the filiform apparatus of one of the synergids.