"Negative geotropism" refers to a plant's growth or movement in the direction opposite to the force of gravity. In other words, when a plant exhibits negative geotropism, it grows or moves away from the center of the Earth, against the force of gravity, rather than toward it (which is known as positive geotropism).
Negative
geotropism is observed in certain plant responses and behaviors. One of the
most common examples of negative geotropism is the growth of plant roots. Plant
roots typically exhibit positive geotropism, as they grow downward into the
soil, following the direction of gravity, in search of water and nutrients.
However, when roots encounter obstacles or toxic substances in the soil, they
may exhibit negative geotropism by growing away from the source of the obstacle
or toxicity.
For
instance, if a plant's roots encounter a large rock in the soil, they may grow
laterally or curve away from the rock to avoid it. Similarly, if roots
encounter a zone with high salinity or toxins, they may grow away from that
area in a negative geotropic response.
Negative
geotropism in roots allows plants to navigate and adapt to their environment,
avoiding physical barriers or unfavorable conditions that could hinder their
growth and survival.
It's
important to note that geotropism, whether positive or negative, is just one of
many tropic responses in plants. Tropic responses refer to the ways in which
plants grow or move in response to environmental stimuli, including light
(phototropism), gravity (geotropism), and touch (thigmotropism), among others.
These responses help plants optimize their growth and interact with their
surroundings.