Given below are two statements
Statement (I) : Double fertilization involves the fusion of two sperm cells with two egg cells.
Statement (II) : In double fertilization, one sperm cell fuses with the egg cell, while the other sperm cell fuses with the two polar nuclei.
In light of the above statements, choose the most appropriate answer from the options given below:
नीचे दो कथन दिए गए हैं
कथन (I) : द्विनिषेचन (Double fertilization) में दो शुक्राणु कोशिकाओं (नर युग्मकों) का दो अंड कोशिकाओं के साथ संलयन शामिल है।
कथन (II) : द्विनिषेचन में, एक शुक्राणु कोशिका (नर युग्मक) अंड कोशिका के साथ संलयित होती है, जबकि दूसरी शुक्राणु कोशिका दो ध्रुवीय केंद्रकों (polar nuclei) के साथ संलयित होती है।
उपरोक्त कथनों के आलोक में, नीचे दिए गए विकल्पों में से सबसे उपयुक्त उत्तर चुनिए:
Double Fertilization in Angiosperms:
- Discovered by S.G. Nawaschin in Lilium and Fritillaria.
- The pollen tube discharges two non-motile male gametes (sperm cells) into the embryo sac:
- Syngamy (Generative fertilization): One haploid sperm cell ($n$) fuses with the haploid egg cell ($n$) to form the diploid zygote ($2n$), which develops into the embryo.
- Triple Fusion (Vegetative fertilization): The second haploid sperm cell ($n$) migrates to the central cell and fuses with the two haploid polar nuclei ($n + n$) to produce the triploid primary endosperm nucleus (PEN, $3n$), which forms nutritive endosperm tissue.
- Statement (I) is FALSE: Double fertilization does NOT involve two egg cells (an angiosperm embryo sac contains only one single egg cell).
- Statement (II) is TRUE: Accurately describes syngamy and triple fusion.
Therefore, Statement (I) is false but Statement (II) is true.
Correct Answer: Option 4.
विस्तृत व्याख्या:
Double Fertilization in Angiosperms (आवृतबीजी में द्विनिषेचन - Nawaschin, 1898):
- Discovered by S.G. Nawaschin in Lilium and Fritillaria.
- The pollen tube discharges two non-motile male gametes (sperm cells) into the embryo sac:
- Syngamy (Generative fertilization): One haploid sperm cell ($n$) fuses with the haploid egg cell ($n$) to form the diploid zygote ($2n$), which develops into the embryo.
- Triple Fusion (Vegetative fertilization): The second haploid sperm cell ($n$) migrates to the central cell and fuses with the two haploid polar nuclei ($n + n$) to produce the triploid primary endosperm nucleus (PEN, $3n$), which forms nutritive endosperm tissue.
- Statement (I) is FALSE: Double fertilization does NOT involve two egg cells (an angiosperm embryo sac contains only one single egg cell).
- Statement (II) is TRUE: Accurately describes syngamy and triple fusion.
Therefore, Statement (I) is false but Statement (II) is true.
Correct Answer: Option 4.
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