Final answer:
Geotropism affects overall plant growth by causing roots to grow downward (positive gravitropism) and stems to grow upwards (negative gravitropism), guided by the plant hormone auxin.
Step-by-step explanation:
Geotropism, also known as gravitropism, significantly affects a plant's growth by dictating the direction in which different parts of the plant grow in response to gravity. Plant roots exhibit positive gravitropism, meaning they will grow downward into the soil, which is beneficial for absorbing water and nutrients. In contrast, stems and leaves usually demonstrate negative gravitropism, by growing upwards, away from the earth's gravitational pull, ensuring that they grow toward sunlight which is essential for photosynthesis.
The plant hormone auxin plays a crucial role in this process. In stems, auxin accumulates on the lower side when a plant is tipped, causing those cells to grow faster and the stem to bend upwards. In roots, however, a higher concentration of auxin inhibits cell extension, thus causing roots to grow downwards.
In conclusion, geotropism ensures that the roots of a plant are firmly anchored into the soil and capable of nutrient uptake, while the shoots can reach for light necessary for their growth and development.