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Hyphal Elongation Questions

Question 1

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Answer 1

Wall precursors are delivered to the hyphal tip, probably in vesicles carried by the cytoskeleton. The vesicles are deposited in the plasmamembrane at the tip, where the action of the contents may be to reduce the solidity of the existing wall, or to provide wall precursors for subsequent construction.

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Question 2

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Answer 2

Simply by marking the wall with an agent which does not move. By using a marker, it has been observed that the wall, once laid down, then progressively moves away from the hyphal tip, but is constant in relation to its background.

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Question 3

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Answer 3

The cytoplasm is at a higher turgor that the exterior of the cell. Thus, if you cut a hypha, cytoplasm will spurt out until repair is effected, or the pore of the septum is closed. By having the cytoplasm at a higher turgor pressure, any weakening of the hyphal tip will result in a "bulge" of the wall at that point. The cytoskeleton ensures movement of materials to the tip during elongation. Hyphal elongation is currently presented as a balancing act between turgor pressure pushing the tip out, and the need to prevent the cytoplasm from being lost through rupture of the tip. Thus the role of turgor pressure is likely to be most important where the hypha is penetrating a substrate or tissue, but ultimately elongation is regulated by movement of solutes into the hypha and materials to the tip.

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Question 4

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In agar, staling products and secondary metabolites remain after the digestion of materials at the hyphal tip. Hyphae appear unable to continue growing through staling products, and hyphae from within the agar appear at the surface in front of the staling zone. The formation of concentric patterns of hypha on agar plates is thought to indicate pattern of hyphal growth in response to staling.

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Question 5

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Question 6

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Question 7

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