Nucleus endosperm

Samen-haar, n. (Bot.) seed hair, coma, -hefe, /. seed yeaat. -keim, m. germ, embryo, -kem, m. seed kernel (Bot.) endosperm Physiol.) spermatic nucleus, -lappen, m. seed lobe, cotyledon, -ol, n. seed oil. -pflan-zen, /.pi. seed plants, Spermatophyta. -probe, /. seed test or sample, -saift, m. seminal fluid, -staub, m. pollen, -tierchen, n. sp< rmatozoon. -zelle, /. seminal cell, spertpatozoon. -zucker, m. quercitol, quer-cite. ... 

Experiment 5. Observation under transmission electron microscope We compared the TEM ultrastructure of the seed coat and endosperm of control and rue-treated seeds The palisade layer of treated seed appears thicker than in the control (Figs 6A and 7A), while comparison between aleuronic cells of the control and treated cells (Figs. 6B and 7B), reveals that the cells of the control are healthy with some evident organelles such as the nucleus and the rough endoplasmic reticulum and other structures, the plastid, the plasmodesmata, conspicous constrictions, protein bodies and... 

XENIOPHYTE The triploid tissue found in the endosperm of the angiosperms formed as the result of the fusion of a sperm nucleus with two polar nuclei in the embryo sac, at the same time the egg is fertilized. 

The embryo develops from a zygote formed by fusion of a sperm nucleus originating from the pollen and an egg cell. The fertilized egg is surrounded in the gynmosperms by a nutritive layer or endosperm which is haploid and is derived from the same game-tophyte tissue that produced the egg. In angiosperms two sperm nuclei form one of these fertilizes the egg, while the other fuses with two haploid polar nuclei derived from the female gametophyte. (The polar nuclei are formed by the same mitotic divisions that formed the egg.) From this develops a 3n triploid endosperm. 

Fig. 97.—A, Immature angiospermous ovule B, same, after embryo-sac e.s). has matured to form the female gametophyte nucellus nuc) outer integument (0. int) inner integument (t. int) embryo sac e.s.) micropyle mic) chalaza ch) funiculus (/) synergids s) ovum (0) polar nuclei p) antipodals a) C, fertilized and matured angiospermous ovule (seed). Note that the nucellus nuc) has been pushed out by the encroachment of the embryo sac, in which endosperm has formed by the fusion of the two polar nuclei with the second sperm nucleus from the pollen tube which has later divided to form numerous nuclei scattered about in the protoplasm of the embryo sac and accumulated protoplasm and laid down walls, within which nourishment was stored embryo em) from fertilized ovum testa t) from outer integument tegmen te) from maturation of inner. integument micropyle mic) hilum or scar (h), after funiculus became detached.

In by far the greater number of Angiosperms, the endosperm nucleus, after double fertilization, divides and redivides, giving rise to numerous nuclei imbedded in the protoplasm of the embryo sac, outside of the developing embryo. Gathering protoplasm about themselves and laying down cell walls they form the endosperm tissue outside of the embryo. Into this tissue food is passed constituting the Endospermic albumen. 

Genomic imprinting is a genetic phenomenon that occurs in the placenta of mammals and in the endosperm of angiosperms, in which a set of alleles that reside in the same nucleus and share the same DNA sequence is expressed in a parent-of-origin manner. Imprinting is an... 

As mentioned above, the true endosperm is derived from two polar nuclei of the ovule and one male nucleus. It is therefore at least a triploid tissue. 

Fertilization is twofold. One of the two sperm cells fuses with the diploid, secondary embryo sac nucleus to form the triploid endosperm nucleus. The endosperm nucleus divides to form many nuclei each of which combines with cytoplasm to form a cell. In this way the multicellular endosperm emerges. Subsequently it can be enriched with reserve materials, vitamins, phytohormones, and other factors that are necessary for development before and, in part, also after germination. In some cases such as the coconut and pumpkin plants the endosperm is wholly or partially fluid. 

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