Iodine uptake and "Akagare" disease of rice plants

在富碘土壤上种植的水稻植株，由于碘的毒性，大量积累碘，并表现出一种生理失调(Akagare病)。1.研究了水稻植株对碘的吸收机制。虽然碘对植物有害，但水稻对碘的吸收比溴更有选择性。为了解释这种选择性吸收，提出了如下假设：水稻植株通过其根部的氧化力氧化碘离子形成分子碘，并比碘离子更有选择性地吸收形成的分子碘。相比之下，溴只以离子的形式被水稻吸收。根据这一假设，水稻根系的氧化力与吸碘量之间应该有显著的相关性。然后，在水培条件下，以8个水稻品种为试材，研究了水稻根系氧化力与吸碘浓度的关系。根的氧化力与根吸收的碘浓度之间存在显著的相关性。但根的氧化力与吸溴量之间没有相关性。2.研究了土壤中可溶性碘与水稻赤霉病的关系。水稻幼苗萌发20天后，在富碘土壤中培养29天。1)水稻植株吸收的碘浓度与土壤可溶性碘浓度呈正相关。2)水稻株高和地上部干重随植株吸收碘浓度的增加而降低。3)当水稻植株(地上部)中碘含量超过200 mg/kg(干重)时，“赤霉病”症状明显。4)不同水稻品种对赤霉病的抗性存在显著差异。

Rice plants, cultivated in a soil with an abundance of iodine accumulate iodine in large quantities and take a physiological disorder ("Akagare" disease) due to the toxicity of iodine.1.The absorption mechanism of iodine by rice plants was studied. Although iodine is harmful to plants, rice plants absorbed iodine more selectively than bromine. To explain this selective absorption, the following hypothesis was proposed : rice plants oxidize iodide ion to form molecular iodine via the oxidizing power of their roots, and absorb the molecular iodine formed more selectively than iodide ion. Bromine, by contrast, is absorbed by rice plants only in the form of ion. According to this hypothesis, there should be a significant correlation between the oxidizing power of the rice roots and the amount of iodine absorbed. Then, the relationship between the oxidizing power of the roots and the concentration of iodine absorbed was studied in a water culture using 8 varieties of rice plants. A significant correlation was found between the oxidizing power and the concentration of iodine absorbed by the roots. However, no relationship was found between the oxidizing power of the roots and the amount of bromine absorbed.2.The relationship between soil soluble iodine and "Akagare" disease of rice plants was examined. Seedlings of rice plant 20 days after germination were cultivated in soils rich in iodine for 29 days. 1)The concentration of iodine absorbed by rice plants correlated positively with the concentration of soil soluble iodine. 2)Height and dry weight of shoot of rice plant decreased with the increase in the concentration of iodine absorbed by the rice plant. 3)The symptom of "Akagare" disease became remarkable, when the concentration of iodine in rice plant(shoot) was over 200 mg/kg(dry weight). 4)A remarkable difference in resistance to "Akagare" disease among varieties of rice plants was recognized.