Q.3 Entry of pollen tube into the ovule through funiculus or integuments is referred as:
- Mesogamy
- Porogamy
- Xenogamy
- Chalazogamy
Correct Answer: Mesogamy
The entry of the pollen tube into the ovule through the funiculus or integuments is Mesogamy. This process occurs when the pollen tube penetrates the ovule laterally via its protective layers or stalk, rather than the standard opening.
Option Explanations
Porogamy: The pollen tube enters through the micropyle, the small pore at the ovule’s apex; this is the most common type in angiosperms like lilies. It directly accesses the embryo sac efficiently.
Mesogamy: Pollen tube entry happens through the middle of the integuments (after piercing tissues) or funiculus; seen in plants like Cucurbitaceae (e.g., pumpkins). This lateral path distinguishes it from direct micropylar access.
Xenogamy: Refers to cross-pollination between different plants, involving pollen from another individual; unrelated to pollen tube entry path into the ovule.
Chalazogamy: Pollen tube enters via the chalaza, the ovule’s basal end opposite the micropyle; occurs in species like Casuarina.
Pollen tube entry into ovule through funiculus or integuments defines mesogamy, a key fertilization variant in angiosperms. This process ensures male gametes reach the embryo sac despite indirect paths. Understanding it aids botany students in exams on double fertilization.
Types of Pollen Tube Entry
Pollen tube pathways vary by plant species, optimizing reproduction.
Type Entry Route Examples Notes Porogamy Micropyle (apical pore) Most angiosperms Common, direct access Mesogamy Integuments or funiculus Cucurbits, Pistacia Lateral, tissue-piercing Chalazogamy Chalaza (basal end) Casuarina Opposite micropyle Xenogamy, often confused, describes cross-pollination source, not entry route.
Biological Significance
In mesogamy, the pollen tube pierces integument tissues midway or travels the funiculus stalk before micropylar entry to the embryo sac. This adapts to ovule structure in families like Cucurbitaceae, ensuring syngamy and triple fusion. Porogamy suits simpler ovules, while chalazogamy aids chalazal-dominant species.
These mechanisms highlight angiosperm diversity, crucial for seed formation and crop breeding. For life sciences students, mastering them clarifies reproductive barriers in exams.
