Hydrotropism
he root system is developed in the soil since soil can help establish their strand and protect the fragile roots from stressful conditions such as drought, nutrient deficiency, unfavourable temperature, etc. Hydrotropism is a directional growth response exhibited in terrestrial plants in which water or water vapour is the orienting stimulus. In hydrotropism the root caps perceive and respond to moisture gradient of the soil simultaneously which will then regulate the directional growth of the root towards or away from water. A tropism is termed “Positive” if growth is toward the signal and in this case higher moisture gradient and “Negative” if it is away from it. (John Z. Kiss, 2007). Tropisms normally interact between each other and in this case, plants must overcome gravitropism first, since it is dominant on earth. (Jaffe et al. 1985) Other tropisms, such as thigmotropism, in which touch is the stimulus, interfere with hydrotropism. The root system is developed in the soil since soil can help establish their strand and protect the fragile roots from stressful conditions such as drought, nutrient deficiency, unfavourable temperature, etc.(Darwin and Darwin, 1880; Takahashi, 1997) Tropism is one of the most important adaptation method plants have acquired. (Yutaka Miyazawa et al. 2008) However there have not been many studies done on hydrotropism and the mechanism underlying it, despite it's importance. A study by Akie Kobayashi, Akiko Takahashi, Yoko Kakimoto, Yutaka Miyazawa, Nobuharu Fujii, Atsushi Higashitani, and Hideyuki Takahashi that was published in 2007 examines the roosts of arabidopsis mutant Mizu-Kussei1 (Miz1) which are impaired in hydrotropism but show normal gravitropism and elongation growth. The results of this study suggest that hydrotropism takes and independent pathway from other tropisms, Since the roots of mutant Miz 1 and the wild type had similar root structures and morphology but the mutant showed reduced phototropism. in this