The stem of a plant is growing upward while the roots grow downward
This directional growth of the stem and roots is known as geotropism or gravitropism. Geotropism is the ability of plant parts to respond to gravity, leading to the upward growth of the stem and downward growth of the roots.
The upward growth of the stem is called positive geotropism or positive gravitropism. The cells in the stem detect gravity and respond by elongating more on the upper side, causing the stem to grow upwards against the force of gravity.
On the other hand, the downward growth of the roots is called negative geotropism or negative gravitropism. The cells in the root tip also detect gravity, but they respond by elongating more on the lower side, causing the roots to grow downwards towards the force of gravity.
This geotropic response is crucial for the proper orientation and positioning of plant parts. The upward growth of the stem allows the plant to reach light for photosynthesis, while the downward growth of the roots helps in anchoring the plant in the soil and absorbing water and nutrients from the ground.