Final answer:
The statement about microtropism is false, the correct term for plant growth in response to gravity is gravitropism, where shoots grow upward (negative gravitropism) and roots grow downward (positive gravitropism).
Step-by-step explanation:
The statement that microtropism is a process where plants grow upward against the downward force of gravity is false. The correct term for the plant growth response to gravity is gravitropism. Gravitropism is a growth movement by a plant in response to gravity. Shoots show negative gravitropism as they grow upward, away from the Earth's gravitational pull, and roots exhibit positive gravitropism by growing downward towards it. This response is due to the movement of amyloplasts, which are specialized plastids containing starch granules that settle in response to gravity, helping the plant orient its growth. For example, if a plant is tipped over, the amyloplasts will settle to the low side of the cells, signaling the plant to correct its growth direction. Additionally, plants also display phototropism, where they grow towards light, driven by the redistribution of the plant hormone auxin, which stimulates cell elongation on the darker side of the stem.