Chalaza
Appearance
This article needs additional citations for verification. (December 2009) |
The chalaza (nucellus within the larger structure.
In animals
In the eggs of most birds (not of the reptiles[1]), the chalazae are two spiral bands of tissue that suspend the yolk in the center of the white (the albumen). The function of the chalazae is to hold the yolk in place. In baking, the chalazae are sometimes removed in order to ensure a uniform texture.
In plants
In plant ovules, the chalaza is located opposite the
nucellus are joined. Nutrients from the plant travel through vascular tissue in the funiculus and outer integument through the chalaza into the nucellus. During the development of the embryo sac inside a flowering plant
ovule, the three cells at the chalazal end become the antipodal cells.
Chalazogamy
In most flowering plants, the pollen tube enters the ovule through the micropyle opening in the integuments for fertilization (porogamy). In chalazogamous fertilization, the pollen tubes penetrate the ovule through the chalaza rather than the micropyle opening.[2] Chalazogamy was first discovered in
monoecious plant species of the family Casuarinaceae by Melchior Treub, but has since then also been observed in others, for example in pistachio and walnut
.
Notes
- ^ Palmer, Brent David (10 April 1990). Functional morphology and biochemistry of reptilian oviducts and eggs : implications for the evolution of reproductive modes in tetrapod vertebrates.
- ^ Pratiyogita Darpan (September 2006). Competition Science Vision. Pratiyogita Darpan.