117 public questions tagged with this topic.
Self-compatibility means that a plant can self-fertilize. While it offers reproductive assurance, it does not promote genetic diversity; in fact, cross-pollination is needed for increased variability.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Biology - Botany portion covering relevant concept, Topic: Plant structure, physiology and applications.
Antipodal lls are thought to help in nourishing the embryo sac and usually degenerate later in development. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Morphology and Anatomy of Flowering Plants, Topic: Plant structure and tissue systems.
In algae, asexual reproduction occurs by biflagellate, motile zoospores, which germinate to form new plants. This follows from NCERT principle where relation explains outcome clearly for students.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Biology - Botany portion covering relevant concept, Topic: Plant structure, physiology and applications.
Hydrophilous pollination occurs when water currents carry pollen, a mechanism seen in some aquatic plants. This follows from NCERT principle where relation explains outcome clearly for students.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Biology - Botany portion covering relevant concept, Topic: Plant structure, physiology and applications.
While wind, water, and insects are common vectors for pollen transfer, soil is not a pollination vector. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Morphology and Anatomy of Flowering Plants, Topic: Plant structure and tissue systems.
Anemophily is pollination by wind, typical in many grasses and some trees. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Morphology and Anatomy of Flowering Plants, Topic: Plant structure and tissue systems.
The fusion of one sperm with the two polar nuclei forms the triploid endosperm, which provides nutrition to the embryo. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Morphology and Anatomy of Flowering Plants, Topic: Plant structure and tissue systems.
Following double fertilization and early embryogenesis, embryo sac undergoes extensive remodeling via programmed cell death of unnecessary attraction cells. Two synergid cells that synthesized LURE peptides guiding pollen tube usually degenerate rapidly upon tube arrival preventing additional tubes via ethylene and FERONIA-mediated polyspermy block, and antipodal cells at chalazal pole degenerate quickly after fertilization, though persist longer in cereals providing transient nutrition support. Their coordinated degradation recycles valuable nutrients and eliminates residual attraction signals, efficiently allocating maternal resources to developing embryo and triploid endosperm within maturing seed for robust offspring production.
Ref: Mathew & Prasad, Bot Rev; Drews: synergids and antipodals degrade after fertilization via programmed cell death.
Embryo sac in Polygonum-type typical of approximately seventy percent angiosperms consists of seven cells organized around eight nuclei arising from three sequential free nuclear mitoses of functional megaspore without initial cytokinesis. Configuration comprises micropylar egg apparatus with two synergids flanking egg cell, large central cell with two polar nuclei occupying huge central vacuole, and chalazal three antipodal cells often ephemeral. This precise seven-celled eight-nucleate organization positions egg for fertilization, synergids for pollen tube attraction, central cell for endosperm initiation, and antipodals for transient support or signaling during early seed development stages.
Ref: Drews & Koltunow, Arabidopsis Book 2011: typical embryo sac seven cells eight nuclei Polygonum-type organization.
Angiosperm gametophytes develop from haploid spores produced within sporangia located in third and fourth floral whorls according to classical ABC model. Third whorl stamens produce microsporangia generating male gametophytes pollen grains, while fourth whorl carpels form megasporangia ovules generating female gametophytes embryo sac. First whorl sepals and second whorl petals are sterile protective and attractive structures aiding pollination and preventing desiccation. This organization directly links MADS-box floral organ identity patterning to gametophyte generation location, elegantly coordinating transition from diploid sporophyte to haploid gametophyte phase during sexual reproduction of flowering plants.
Ref: Coen & Meyerowitz, Nature; Goldberg: angiosperm gametophytes develop from third whorl anthers and fourth whorl carpels.
Tapetum is specialized innermost anther wall layer directly surrounding sporogenous tissue undergoing differentiation into secretory or amoeboid forms during anther development. Its functional role involves providing nourishment to developing microspores and pollen grains through synthesis and active secretion of enzymes, sporopollenin precursors, Ubisch bodies, pollenkitt, tryphine lipids, flavonoids, and self-incompatibility recognition proteins. It precisely regulates callose degradation via callase secretion and undergoes programmed cell death depositing materials onto exine forming protective pollen coat. Defects cause male sterility, highlighting essential nutritive and structural support ensuring viable pollen production.
Ref: Pacini et al., Can J Bot 1985; Goldberg: tapetum provides nourishment and sporopollenin to developing pollen grains.
Meiosis in microsporogenesis occurs specifically in diploid microspore mother cells also called pollen mother cells within anther locules surrounded by nutritive tapetum layer and middle layers. These cells undergo meiosis I with homologous chromosome separation and meiosis II with sister chromatid separation generating haploid tetrads of microspores encased in callose walls ensuring genetic recombination and chromosome reduction halving genome ploidy. Tetrads subsequently separate after enzymatic callase action secreted by tapetum. Resulting microspores differentiate into pollen grains via mitotic divisions establishing basis for haploid male gametophyte generation and genetic diversity.
Ref: Scott et al., Arabidopsis Book: meiosis in microsporogenesis occurs in microspore mother cells within anther.
