Govt. Exams
Entrance Exams
Angiosperm life cycle: diploid sporophyte (2n) → haploid spores (n) → haploid gametophyte (n) → diploid zygote (2n) after fertilization, and triploid endosperm (3n) after double fertilization.
Pollen dimorphism is associated with heterostyly, where plants like Primula produce different-sized pollen grains corresponding to different floral forms to promote cross-pollination.
Many orchids have seeds without endosperm (lacking nutritious reserve tissue). They require mycorrhizal fungal associations to obtain nutrients from the soil for germination and growth.
Most angiosperms release pollen at the binucleate stage (containing generative and vegetative nuclei). Some release at the trinucleate stage after generative nucleus division.
Pollen dormancy refers to the reduced metabolic activity of pollen that allows it to maintain viability over extended storage periods in dry, cool conditions.
The endothecium contains fibrous thickenings on cell walls that help in anther dehiscence by creating tension during drying, aiding pollen dispersal.
The correct sequence is: Microsporocyte undergoes meiosis to form microspores, which undergo mitosis to form mature pollen grain (male gametophyte).
Anaphase I involves separation of homologous chromosomes, which along with crossing over in Prophase I ensures genetic variation in resulting microspores.
Monoecious plants have both male and female flowers on the same plant (e.g., maize, coconut). Dioecious plants have them on different plants.
Apomixis is asexual reproduction through seeds, occurring without meiosis and fertilization, producing clones of the parent.
