Read the passage carefully and answer the questions based on the passage:

Passage: Pollen pistil interaction involves all events from the landing of pollen grains on the stigma until the pollen tube enters the embryo sac (when the pollen is compatible). When a pollen tube grows through the style and enters into the ovules, it finally discharges two male gametes in one of the synergids.

Syngamy and triple fusion are two fusion events that occur in angiosperms. Thus, angiosperms exhibit double fertilization. The products of these fusions are the diploid zygote and triploid primary endosperm nucleus. Zygote develops into embryo and primary endosperm cell forms the endosperm tissue. The developing embryo passes through different stages before maturation.

Formation of diploid zygote is a result of:

The correct option is Syngamy.

Step-by-Step Explanation:

1. Understanding Double Fertilization:
As described in the passage, angiosperms (flowering plants) undergo a unique process called double fertilization. This process involves two distinct fusion events occurring within the embryo sac after the pollen tube releases two male gametes into one of the synergids.

2. Analyzing the Fusion Events:
Let us break down the two fusion events mentioned in the passage:
• Syngamy: This is the fusion of one haploid male gamete ($n$) with the haploid egg cell ($n$). Since it is the fusion of two haploid nuclei, it results in the formation of a diploid zygote ($2n$). The zygote subsequently develops into the embryo.
• Triple Fusion: This is the fusion of the second haploid male gamete ($n$) with the two polar nuclei (or the diploid secondary nucleus, $2n$) present in the central cell. This fusion involves three nuclei and results in the formation of the triploid primary endosperm nucleus (PEN, $3n$), which develops into the endosperm tissue.

3. Evaluating the Options:
• Emasculation: This is the removal of anthers from a bisexual flower before they dehisce, which is a technique used in artificial hybridization to prevent self-pollination, not a cellular fusion event.
• Triple fusion: As detailed above, triple fusion results in a triploid primary endosperm nucleus, not a diploid zygote.
• Syngamy: As detailed above, syngamy is the specific fusion event between a male gamete and an egg cell that directly results in the formation of the diploid zygote.
• Bagging: This is the protective covering of emasculated flowers with a bag (usually made of butter paper) to prevent contamination of the stigma with unwanted pollen, which is also an artificial hybridization technique.

Therefore, the formation of the diploid zygote is a direct result of Syngamy.