The structural organization of orchid embryos: a functional interpretation

Yeung E.C., . (2005) The structural organization of orchid embryos: a functional interpretation. [Proceedings Paper]

Compared to other flowering plants orchid embryos are unique in that they are minute in size. In addition orchid embryo structures such as a cotyledon and apical meristems are usually not present in fully mature embryos. After fertilization the first division of the zygote is unequal giving rise to a smaller terminal cell and a larger basal cell. The smaller terminal cell gives rise to the embryo proper whereas the basal cell often divides further giving rise to a short-lived embryonic organ known as the suspensor. Forms of suspensor morphologies found in orchids are rarely found in other flowering plants. The suspensor cells of orchids are vacuolated having thin primary cell walls and are tightly pressed against the inner surface of the seed coat. The embryo proper has a simple structure. Distinct tissues such as the meristems and procambium are not present. However cells at the future shoot pole tend to be smaller suggesting that a distinct polarity is present within the embryo. Storage food reserves are present in mature embryos mainly in the form of protein and lipid bodies. A layer of cuticular material covers the surface of the embryo proper and is absent from the suspensor cell wall. The cuticle-like structure may function to prevent desiccation during the course of embryo development and the early stages of protocorm formation. A mature orchid seed is devoid of endosperm and the embryo is protected by a thin seed coat.

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Abstract

Compared to other flowering plants orchid embryos are unique in that they are minute in size. In addition orchid embryo structures such as a cotyledon and apical meristems are usually not present in fully mature embryos. After fertilization the first division of the zygote is unequal giving rise to a smaller terminal cell and a larger basal cell. The smaller terminal cell gives rise to the embryo proper whereas the basal cell often divides further giving rise to a short-lived embryonic organ known as the suspensor. Forms of suspensor morphologies found in orchids are rarely found in other flowering plants. The suspensor cells of orchids are vacuolated having thin primary cell walls and are tightly pressed against the inner surface of the seed coat. The embryo proper has a simple structure. Distinct tissues such as the meristems and procambium are not present. However cells at the future shoot pole tend to be smaller suggesting that a distinct polarity is present within the embryo. Storage food reserves are present in mature embryos mainly in the form of protein and lipid bodies. A layer of cuticular material covers the surface of the embryo proper and is absent from the suspensor cell wall. The cuticle-like structure may function to prevent desiccation during the course of embryo development and the early stages of protocorm formation. A mature orchid seed is devoid of endosperm and the embryo is protected by a thin seed coat.

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Item Type:	Proceedings Paper
Additional Information:	Summary En
AGROVOC Term:	ORCHIDACEAE
AGROVOC Term:	PLANT EMBRYOS
AGROVOC Term:	SEED STORAGE
AGROVOC Term:	GERMINATION
AGROVOC Term:	ENDOSPERM
AGROVOC Term:	SEED
Geographical Term:	MALAYSIA
Depositing User:	Ms. Norfaezah Khomsan
Last Modified:	24 Apr 2025 05:27
URI:	http://webagris.upm.edu.my/id/eprint/16539

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