POSITIVE GEOTROPISM Meaning and
Definition
-
Positive geotropism, also known as positive gravitropism or orthogravitropism, refers to a plant's natural response to grow or bend in the direction of gravity. This phenomenon occurs when the plant's roots grow downwards into the soil and its stems grow upwards towards the light. Positive geotropism is an essential adaptive mechanism that helps plants establish a stable position in the soil, ensuring maximum exposure to light for photosynthesis.
In positive geotropism, plant hormones called auxins play a crucial role. The concentration of auxins is higher on the lower side of a plant. When the roots, which are more sensitive to gravity, sense this imbalance in auxins, they exhibit growth inhibition, causing them to elongate and grow towards the downward gravitational force. Conversely, the stems sense the higher concentration of auxins on their lower side and subsequently experience growth stimulation, leading them to elongate in the opposite direction, against gravity, towards the source of light.
Positive geotropism is particularly noticeable in seedlings and young plants, as it helps them anchor firmly in the soil and grow upwards for optimum light absorption. However, as plants mature, the effect of gravity becomes less significant, especially in the stems, which may exhibit negative geotropism or grow in random directions instead. Positive geotropism is a vital characteristic for plant survival and growth, enabling them to establish a strong foundation, maximize light capture, and optimize their photosynthetic capabilities.
Etymology of POSITIVE GEOTROPISM
The word "positive geotropism" is composed of two components: "positive" and "geotropism".
1. Positive: The term "positive" originated from the Latin word "positivus", which means "placed, set, laid down" or "expressing affirmation". It has evolved through Old French and Middle English. In the context of plant biology, "positive" refers to a response or growth movement towards a stimulus, such as light or gravity.
2. Geotropism: The term "geotropism" is formed by combining the prefix "geo-", meaning "earth" or "ground", and the Greek word "tropism", which means "a turning or bending movement". Geotropism specifically refers to the growth or movement of an organism in response to gravity.
