Phaseolus vulgaris L. plants were irradiated with different doses (0.3, 10, 50 and 100 Gy) of X-rays in order to obtain a reference curve of response to ionizing radiations for this species. Growth analysis, gas exchange and chlorophyll a fluorescence measurements were performed to estimate the radio-resistance of bean plants. Specifically, there was a negative influence of X-rays on the net photosynthesis rate at 50 and 100 Gy, already on the day of irradiation. Experimental data showed a recovery over time in the gas exchange while the theoretical maximum photochemical efficiency of the photosystem II (Fv/Fm) was fairly constant throughout the period of measurements (20 days) and for all the experimental conditions. On the other hand, the quantum yield of PSII linear electron transport (ΦPSII) and non-photochemical quenching (NPQ) were deeply influenced over time by X-ray dose, suggesting a decrease in the functionality of the photosynthetic apparatus at the highest radiation doses. The growth was affected only at the highest doses of radiation with a significant and severe reduction of leaf expansion and number of leaves per plant. Despite the arrest in growth, X-ray exposure seems to trigger an increased photochemical activity probably signifying that P. vulgaris plants have a fairly elevated resistance to this kind of ionizing radiation. Our current results will provide a complete analysis of the photosystem II (PSII) response of P. vulgaris to different doses (0.3, 10, 50 and 100 Gy) of X-rays, providing sound references for both space-oriented and radioecology questions.

中文翻译：

---

气体交换和叶绿素a荧光测量作为菜豆中X射线抗性的代理。

用不同剂量（0.3、10、50和100 Gy）的X射线照射过菜豆植物，以获得该物种对电离辐射的响应的参考曲线。进行了生长分析，气体交换和叶绿素a荧光测量，以估计豆类植物的抗辐射性。具体而言，在照射当天，X射线对50和100 Gy的净光合作用速率有负面影响。实验数据表明，随着时间的推移，气体交换得到恢复，而光系统II的理论最大光化学效率（Fv / Fm）在整个测量期间（20天）和所有实验条件下都相当恒定。另一方面，随着时间的推移，X射线剂量对PSII线性电子传输（ΦPSII）和非光化学猝灭（NPQ）的量子产率产生了深远的影响，这表明在最高辐射剂量下光合装置的功能降低了。生长仅在最高剂量的辐射下受到影响，并且叶片的膨胀和单株叶片的数量大大减少。尽管生长受到抑制，但X射线照射似乎触发了光化学活性的增强，这可能表明寻常型百日草植物对这种电离辐射具有相当高的抵抗力。我们当前的结果将提供对寻常假单胞菌对不同剂量（0.3、10、50和100 Gy）的X射线光系统II（PSII）反应的完整分析，为面向空间和放射生态学的问题提供可靠的参考。