Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Double fertilization is a unique characteristic of angiosperms, first discovered by Nawaschin in and .
It involves two types of nuclear fusions: Syngamy and Triple Fusion.
Syngamy: One male gamete () fuses with the egg cell () to form a diploid zygote (), which eventually develops into the embryo.
Triple Fusion: The second male gamete () fuses with the two polar nuclei () or the secondary nucleus () in the central cell to produce a triploid Primary Endosperm Nucleus ( or ).
The pollen tube enters the embryo sac through the micropylar end, guided by the filiform apparatus of the synergids.
The central cell after triple fusion becomes the Primary Endosperm Cell () and develops into the endosperm, which provides nutrition to the developing embryo.
The total number of nuclei involved in double fertilization is five (two male gametes, one egg cell, and two polar nuclei).
📐Formulae
💡Examples
Problem 1:
If an angiospermic plant has chromosomes in its root cells, calculate the number of chromosomes present in the following: (a) Synergids (b) Endosperm (c) Pollen grain.
Solution:
(a) , (b) , (c) .
Explanation:
Root cells are somatic and diploid (), so the haploid number . (a) Synergids are haploid (), thus . (b) Endosperm is triploid (), so . (c) Pollen grains contain male gametes which are haploid (), thus .
Problem 2:
How many nuclei are involved in the process of Triple Fusion specifically?
Solution:
nuclei.
Explanation:
Triple fusion involves the fusion of one male gamete () and two polar nuclei () located in the central cell, resulting in a nucleus.