To tolerate phosphate (Pi) deficiency in the environment, plants alter their developmental and metabolic programs. In the past two decades, researchers have extensively used Petri dish-grown seedlings of the model plant Arabidopsis thaliana to study the molecular mechanisms underlying root developmental responses to Pi deficiency. A typical developmental response of the Petri dish-grown Arabidopsis seedlings to Pi deficiency is the inhibited growth of primary root (PR). This response is generally thought to enhance the production of lateral roots and root hairs, which increases the plant's ability to obtain Pi and is therefore regarded as an active cellular response. Here, we report that direct illumination of root surface with blue light is critical and sufficient for Pi deficiency-induced inhibition of PR growth in Arabidopsis seedlings. We further show that a blue light-triggered malate-mediated photo-Fenton reaction and a canonical Fenton reaction form an Fe redox cycle in the root apoplast. This Fe redox cycle results in the production of hydroxyl radicals that inhibit PR growth. In addition to revealing the molecular mechanism underlying Pi deficiency-induced inhibition of PR growth, our work demonstrated that this developmental change is not an active cellular response; instead, it is a phenotype resulting from root growth in transparent Petri dishes. This finding is significant because illuminated, transparent Petri dishes have been routinely used to study Arabidopsis root responses to environmental changes.

为了耐受环境中的磷酸盐（Pi）缺乏症，植物会更改其发育和代谢程序。在过去的二十年中，研究人员广泛使用了模型植物拟南芥的培养皿培养皿中的幼苗，以研究针对Pi缺乏的根系发育反应的分子机制。培养皿培养的拟南芥的典型发育反应幼苗缺磷是受抑制的主要根系（PR）的生长。人们普遍认为这种反应可增强侧根和根毛的产生，从而增加植物获得Pi的能力，因此被认为是活跃的细胞反应。在这里，我们报告说，用蓝光直接照射根表面至关重要并且足以抑制拟南芥中Pi缺乏诱导的PR生长抑制幼苗。我们进一步表明，蓝光触发的苹果酸介导的光芬顿反应和典型的芬顿反应在根质外体中形成Fe氧化还原循环。该Fe氧化还原循环导致抑制PR生长的羟基自由基的产生。除了揭示Pi缺乏引起的PR生长抑制的分子机制外，我们的工作还表明这种发育变化不是主动的细胞反应。相反，它是由于透明培养皿中的根生长而产生的表型。这一发现意义重大，因为通常使用照明透明的陪替氏培养皿来研究拟南芥对环境变化的根响应。