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Entry of Pollen Tube into the Embryo Sac
The pollen tube enters the embryo sac through the filiform apparatus of ong of the synergids. Generally, one of the synergids degenerates before the entry of pollen tube and the tube invariably enters through such synergids. In Plumbago, where synergids are absent and the egg has the filiform apparatus, the tube enters directly into the egg. In several taxa, however, both the synergids remain healthy until the entry of pollen tube and the one that receives the pollen tube starts degenerating. It has been proposed that the degeneration of synergid and also of pollen tube cytoplasm is essential to prevent male gametes from a rejection or antigen-antibody type of reaction.
The choice of the male gamete involved in syngamy and triple fusion has long been a subject of speculation. Embryologists were curious to know which of the two male gametes participated in syngamy. Transmission electron microscopy and scanning electron microscopy have revealed that in certain plants the two male gametes are unequal in size and in the number of plastids and mitochonoria they contain. The plastid rich sperm seems to be preferentially involved in syngamy and the one with poor plastids fuses with the secondary nucleus. However recent studies indicate that heteromorphic sperms are not seen in other plants.
Quaternary Structure (4 o Structure). Globular in structure. When two or more than two molecules of protein of tertiary structure are connected to each other through
define the pattern of cleavage i all aspects
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Explain the Occurrence of Nictoinic acid Nictoinic acid occurs widely in the animal and vegetable kingdom in free as well as in bound form (in enzymes). Several animal organs
proteins contain
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Erythropoietin (EPO) A. acts by increasing the production of red blood cells by cells in the bone marrow. B. is secreted by peritubular interstitial cells of the kidney cort
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The Environmental Disasters Are Classified Into Two Major Categories: 1. Natural Disasters like Earthquakes, Tsunami, Landslides, Cyclones, Floods, and Droughts Etc. 2.
All of the following illustrate why the bile acids are much better suited then cholesterol for use as emulsification agents for fats except: -cholesterol contains a hydroxyl gro
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