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#ovule

5 public questions tagged with this topic.

plant Development - 1

Pollen tube entry site in ovule:

Ovule integuments envelop nucellus and embryo sac leaving narrow canal micropyle at micropylar pole oriented toward placenta. Micropyle serves as specific entry site for pollen tube guiding sperm toward egg apparatus; synergid-secreted LURE peptides diffuse through this opening creating chemotropic gradient directing final guidance and reception of tube. Chalazal pole connects via funiculus to maternal vasculature providing nutrients, hilum marks detachment scar, chalaza opposite micropyle hosts vascular termination. Thus micropyle as pollen tube entry portal ensures precise delivery and positioning of male gametes immediately adjacent to egg and central cell.

Ref: Dresselhaus & Franklin-Tong, Nature Plants 2013: pollen tube enters ovule via micropyle guided by synergid LURE peptides.

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Plant Classification

Seed coat develops from

Ovule integuments maternal diploid sporophytic tissue origin undergo post-fertilization differentiation and sclerification: outer integument often forms testa outer seed coat providing mechanical protection impermeability dormancy, inner integument tegmen membranous thin often crushed. Both derived sporophyte, nucellus mostly consumed or persisting as perisperm in Caryophyllales beet family example, ovule overall refers to pre-fertilization structure including nucellus female gametophyte, endosperm triploid product after fertilization nutritive. Thus seed coat lineage directly traces to integument, explaining maternal inheritance of coat color texture patterns such as mottled beans studied by Mendel and imposing physical dormancy via phenolics cutin suberin layers.

Ref: NCERT Class 12 Biology, Chapter 2: Integument forms seed coat testa development origin

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