Kiyoshi Yamazaki
While it is well known that plants show hydrotropism, gravitropism, and phototropism, there has until now been no experimental evidence to demonstrate tropism towards nutrients. Yamazaki et al. (on pp. 546–553) have discovered that rice lateral roots exhibit tropic responses toward nutrient sources. Moreover, directional changes in lateral roots were stimulated by a nitrogen nutrient (NH4+) gradient, thus providing the first evidence that plant roots have the ability to move toward nutrients. Nutritropism enables plants to seek out nutrients that are unevenly distributed in the natural environment, and should therefore offer the adaptive advantage of nutrient acquisition.