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1.1 TROPISM


1.Phototropism

❤Plants tend to grow either toward or away from light.


Positive tropism: the shoot that grows towards the light

Negative tropism: the root that grows away from the light


❤Cells on the different sides of the shoot grow at different rates. Cells on the opposing side lengthen more rapidly causing the bend of the shoot towards the light. The cells on the shade side develop rapidly than those on the lit side.







2. Gravitropism


❤To maintain an effective photosynthesis and gas exchange of the leaf, shoots develop upward and roots develop downward.


Positive: roots that develop downward

Negative: shoots that develop upward


❤Gravitropism is important for the roots to anchor the plant and absorb water and mineral ions from the soil and for the shoots to move towards the sunlight to ensure enough sunlight is supplied to the plant.





❤Statoliths are starch-granule-containing plastids that move downwards in reaction to gravity.


❤Statoliths are located in the root cap's specialized cells as well as in the shoots. 


❤Starch grains, which are free and moveable and hence fall to the cell's bottom end, are thought to fulfill the role of statoliths.


❤Auxin inhibits elongation by moving to larger quantities on the root's bottom side. Asymmetry in auxin distribution causes unequal root tissue development, leading the root to bend and follow gravity stimuli.



Then how do the shoots grow?


As the auxin moves towards the bottom of the shoot, the bottom cells continue to develop curvedly and stretch their cells upward, away from gravity's pull.



3. Thigmotropism


❤Movement of plants due to touch


❤Two types:


a. Tendrils


🍀A tendril is a thread-like structure required to provide assistance in climbing plants. Coiling is a kind of thigmotropism that occurs in a modified leaf, stem, or petiole.


🍀Tendrils begin by bending in seeking of a surface on which to develop. When they discover it, the section of the tendon that is in contact with the surface releases a hormone called auxin, that encourages the growth of a significant portion of the tendon which is not in contact with the surface.

 


b. Clinging roots


🍀The epiphytes are where the clinging roots may be discovered. These roots anchor the plant to the tree's bark while simultaneously absorbing nutrients from the bark.

Comments

  1. deerMay 24, 2021 at 8:31 AM

    usually learning about plants is not that easy but this blog makes it seem effortless. points are precise and concise.

    ReplyDelete
  2. UnknownMay 24, 2021 at 8:54 AM

    Very precise and good reference to make revision everywhere.👏👏👏🤩

    ReplyDelete
  3. Marzlan Che OmarMay 24, 2021 at 8:58 PM

    Good for reference . Good information

    ReplyDelete
  4. UnknownMay 24, 2021 at 10:21 PM

    Artistic and cute drawings with simple short notes to understand.What more could anybody ask hehe.Goodjob!!

    ReplyDelete

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