What is Orthotropous ovule?
An orthotropous [atropous] ovule is one in which no curvature takes place during development; the micropyle is positioned opposite the funiculus base. (An ovule somewhat intermediate in curvature between anatropous and orthotropous is sometimes termed hemitropous or hemianatropous.)
What is Anatropous ovule example?
, Orthotropous ovules are the ovules that grow straight so that micropyle is at the end opposite the stalk. For example, Piper, Polygonum, Cycas. Anatropous ovules are the ovules that are completely inverted on its stalk. For example, Helianthus and Tridax.
Why do we call Anatropous ovules?
The ovules where micropyle come to lie close to the funiculus due to unilateral growth of the ovule are called anatropous. This is the most common type of ovule in angiosperms where the curvature of the ovule also affects the nucellus so that the later becomes horse shoe-shaped. The ovule is called amphitropous.
Is Anatropous ovule inverted?
– Anatropous: In this type ovule is entirely inverted, where micropyle lies close to hilum( hilum is where the seed is attached to the fruit by funicle).
What is Circinotropous ovule?
Circinotropous ovule is a type of ovulewhere the funicle is long creating nearly a full circle around the ovulewith micropyle pointing to upward direction. Here female reproductive cells are created and kept which eventually after fertilization develops into a seed.
How many types of ovules are found in angiosperms?
There are categorically six types of ovules. These are orthotropous or anatropous ovules, anatropous ovule, hemi-anatropous ovule or hemitropous ovule, campylotropous ovule, amphitropous ovule, and circinotropous ovule.
What are Integuments in plants?
An integument is a protective layer of cells surrounding the ovule. Gymnosperms typically have one integument (unitegmic) while angiosperms typically have two integuments (bitegmic).
How do you identify Anatropous ovules?
The characteristic of anatropous ovule is (1) Occurrence of hilum near the micropyle (2) Presence of raphe (3) Body of the ovule is inverted (3) All the above. The most common form of ovules is anatropous ovule, which occurs in more than 80% of angiospermic families.
Which of the following is example of Circinotropous type of ovule?
6. Circinotropous ovule-opuntia.
What is Tenuinucellate ovule?
Definition. The presence of no cells or a single cell layer between the megasporophyte and the epidermal cells in the early development of the megasporophyte. The megasporophyte develops into the embryo sac which contains an egg that, if fertilized and the conditions are right, will develop into an embryo.
Where is Anatropous ovule found?
The most common form of ovules is anatropous ovule, which occurs in more than 80% of angiospermic families. The ovule body is turned 180 ° and micropyle comes close to the funiculus. Chalaza and micropyle lie in the straight line but hilum is at 90 °to the micropyle. The micropyle, then, is close to funiculus.
What are integuments in ovule?
A mature ovule consists of a food tissue covered by one or two future seed coats, known as integuments. A small opening (the micropyle) in the integuments permits the pollen tube to enter and discharge its sperm nuclei into the embryo sac, a large oval cell in which fertilization and development occur.