Q.26 In plants, the ovules are attached to the ovary by
(A) Placenta (B) Synergids (C) Embryo sac (D) Tube cells
In plants, ovules develop within the ovary and attach directly to its placental tissue, which nourishes them via a stalk called the funicle.
Option Analysis
Placenta: This is the correct specialized region of the ovary wall where ovules attach and receive nutrients. The funicle connects each ovule to the placenta, supporting its development into a seed.
Synergids: These are two short-lived cells flanking the egg cell inside the embryo sac of the ovule. They guide the pollen tube during fertilization but play no role in ovule attachment.
Embryo sac: Known as the female gametophyte, this structure forms within the ovule’s nucellus. It houses the egg and other cells for fertilization, not the attachment mechanism.
Tube cells: This likely refers to pollen tube cells, which grow from pollen grains through the style to deliver sperm to the ovule. They function in male gamete transport, unrelated to ovule-ovary attachment.
In plant reproduction, understanding how ovules are attached to the ovary by placenta proves essential for CSIR NET Life Sciences aspirants. The placenta serves as the key ovarian tissue anchoring ovules, ensuring nutrient supply for seed formation. This mechanism underpins angiosperm development, distinguishing it from unrelated structures like synergids or embryo sac.
Structure of Ovule Attachment
Ovules arise as outgrowths on the placenta, a placental ridge or cushion in the ovary wall. A stalk-like funiculus links the ovule body (at the hilum) to this placenta, facilitating vascular connections. Placentation types—marginal, axile, parietal—vary by species but all involve placental attachment.
Role of Other Options
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Synergids: Positioned in the embryo sac, these cells attract pollen tubes via chemical signals for double fertilization.
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Embryo sac: The ovule’s internal megagametophyte containing egg, synergids, and polar nuclei; not involved in external attachment.
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Tube cells: Pollen tube components delivering sperm; absent from ovary-ovule linkage.
Exam Relevance
For CSIR NET, recognize placenta as the direct attachment site, eliminating distractors focused on gametophytic or male elements. Master diagrams of ovule structure for visual questions.
