8 public questions tagged with this topic.
In gymnosperms, the endosperm, which is haploid, provides nourishment to the developing embryo.
Ref: NCERT Class 11 Biology Chapter 3: Plant Kingdom Gymnosperms - Characteristics and Life Cycle
The radicle develops into the root, while the plumule forms the shoot.
Ref: NCERT Class 11 Biology chapter - Morphology of flowering plants
Monocot seeds such as maize have an endosperm, which stores food for the developing embryo.
Ref: NCERT Class 11 Biology chapter - Morphology of flowering plants
The seed coat provides protection to the embryo, preventing damage and desiccation.
Ref: NCERT Class 11 Biology chapter - Morphology of flowering plants
Micropyle originates from narrow gap between integuments of ovule persisting in mature seed coat as minute pore near hilum. During germination it serves as primary portal for water imbibition initiating metabolic reactivation, enzyme synthesis like amylases, respiration increase and radicle expansion through testa. It previously allowed pollen tube entry into embryo sac during fertilization. Gas exchange occurs through general testa porosity and hilum, food storage in endosperm or cotyledons, protection by testa and tegmen. Micropylar function is critical for dormancy break demonstrated by increased germination after micropylar scarification in hard-seeded species.
Ref: NCERT Class 12 Biology Chapter 2, Ovule micropyle and germination imbibition; Raven Plant Biology
Endospermic or albuminous seeds retain persistent endosperm at maturity as nutritive tissue for embryo derived from triple fusion forming triploid tissue that nourishes developing embryo. In such seeds cotyledons thin, food storage extracellular, seen in castor, coconut and cereals like wheat. Non-endospermic exalbuminous seeds consume endosperm during embryogenesis and store reserves in fleshy cotyledons as in pea and gram. Retaining only testa or lacking reserves not viable. Endosperm persistence thus distinguishes monocot albuminous grains from dicot exalbuminous legumes and correlates with germination strategies and seedling establishment ecology.
Ref: NCERT Class 11 & 12, Seed structure albuminous vs exalbuminous; Campbell Biology 12th, Endosperm
Gymnosperm diaspore organization comprises three components integrated: diploid embryo new sporophyte derived syngamy, haploid megagametophyte food reserve preformed, and diploid testa seed coat from integuments maternal. Conspicuously absent pericarp derived from ovary wall developed from carpel because carpel absent ovules naked on scales bracts. Taxus fleshy red aril enveloping seed, Ginkgo orange foul sarcotesta resemble fruit attracting vertebrate dispersal but develop from funiculus or outer integument rather than ovary, hence not true fruit wall botanically. Seed coat present fully enclosing, embryo present well differentiated with cotyledons, food reserve abundant, only fruit wall missing defining naked condition diagnostic gymnospermae.
Ref: NCERT Class 11 Biology, Chapter 3: Gymnosperm seed lacks fruit wall pericarp absence naked
Gymnosperm reproductive investment invests heavily in haploid female gametophyte tissue prior to fertilization serving as nutritive reserve analogous functionally to angiosperm triploid endosperm but genetically different haploid maternal only. Megaspore mitotic divisions produce bulky tissue packed with oils lipids starch proteins containing archegonia each with egg. After fertilization proembryo consumes surrounding gametophyte, remainder stored supporting germination. Unlike angiosperms where triploid endosperm induced by second fertilization of central cell, gymnosperm reserve haploid from gametophyte generation, demonstrating alternate evolutionary strategy for parental provisioning without double fertilization dependence and without genomic imprinting.
Ref: Campbell Biology, 12th ed., Chapter 30: Gymnosperm haploid female gametophyte nutritive reserve
