The upward and downward growth of a plant is due to which of the following tropisms? 

The correct answer is Geotropism.

Key Points

• Geotropism is the growth of plant organs in response to gravity.
• Roots exhibit positive geotropism, growing downward towards gravitational pull.
• Shoots exhibit negative geotropism, growing upward away from gravitational pull.
• This response helps plants to anchor in soil and obtain necessary nutrients and water.
• The hormone auxin plays a significant role in geotropic responses by redistributing growth in plant cells.

Additional Information

• Phototropism
  • It is the growth of plant organs in response to light.
  • Shoots usually show positive phototropism by growing towards light sources.
• Hydrotropism
  • It refers to the growth of plant roots towards moisture or water.
  • This response helps plants maximize water uptake from the soil.
• Chemotropism
  • It involves growth or movement in response to a chemical stimulus.
  • An example is the growth of pollen tubes towards ovules during fertilization.
• Plant Hormones
  • Plant hormones like auxins, gibberellins, cytokinins, ethylene, and abscisic acid regulate various growth responses.
  • Auxins are key in phototropic and geotropic responses, influencing cell elongation.