Tropizmus

Tropizmus refers to the movement or growth of a plant in response to an external stimulus. This response can be either towards the stimulus, which is called positive tropism, or away from it, known as negative tropism. These movements are crucial for a plant's survival, enabling it to access necessary resources like light and water, and to anchor itself in the soil.

There are several types of tropisms, each corresponding to a specific stimulus. Phototropism is the growth in response to light. Stems typically exhibit positive phototropism, bending towards the light source to maximize photosynthesis. Gravitropism, also known as geotropism, is the response to gravity. Roots usually show positive gravitropism, growing downwards into the soil, while shoots exhibit negative gravitropism, growing upwards.

Thigmotropism is the directional growth in response to touch. This is commonly observed in climbing plants, where tendrils coil around supports, allowing the plant to ascend. Hydrotropism is the growth in response to water. Roots will grow towards areas of higher moisture content, which is vital for water absorption. Lastly, chemotropism is growth in response to chemical stimuli, such as the growth of pollen tubes towards the ovule during fertilization. Tropisms are mediated by plant hormones, primarily auxins, which influence cell elongation differently on opposite sides of a growing organ.