Question

Double fertilization was discovered by Nawaschin (1898) in
A. Lilium and Fritillaria
B. Mango and sugarcane
C. Papaya and pea
D. Brassica and Candytuft

Answer 1

Double fertilization is the most distinguishing feature of flowering plants. In this process, one male gamete fertilizes the egg resulting in the formation of the zygote and the other male gamete combines with the two polar nuclei present in the ovary to form the endosperm. It was first discovered in a genus of herbaceous flowering plants.

Complete step by step answer: The process of double fertilization was discovered by Nawaschin in 1898 by conducting experiments in flowers of Lilium and Fritillaria. In the experiment, it was found that the two male gametes from the pollen tube upon penetration into the embryo sac, one fuses with the egg cell and the other fuses with the polar nuclei, which result in a diploid (2n) zygote and a triploid (3n) primary endosperm nucleus (PEN) respectively exhibiting double-fertilization. Since endosperm is a product of the fusion of three haploid nuclei, it is called triple fusion. Eventually, the primary endosperm nucleus develops into the primary endosperm cell (PEC) and then into the endosperm. Once the fertilization is completed, embryonic development starts and no more sperm can enter the ovary. The fertilized ovule develops into a seed, and ovary tissues develop as fleshy fruit which encloses the seed. The observed event was independently confirmed by Guignard in 1899.
Hence, the correct answer is option A.

Note: Significance of double-fertilization includes:
i. It increases the viability of the seeds.
ii. It results in polyembryony, as a result of which plants have better chances of survival.
iii. It gives rise to an endosperm that nourishes the developing embryo.