Atmospheric humidity, defined as the vapor pressure deficit (VPD), is an important factor affecting plant transpiration and nutritional status. Previous work has focused on the relationship between VPD and nitrogen metabolism; however, little is known about potassium (K) responses to VPD. Here, we investigated the effects of VPD and K supply on root morphology, potassium uptake, and plant growth with tomato ( Solanum lycopersicum L . , cv. Jinpeng). Experiments were conducted in greenhouses under low and high VPD conditions and featured three levels of K nutrient solution supply (2, 4, and 8 mmol/L). Characteristics of root morphology were significantly promoted by low VPD, including root length, root volume, root diameter, root surface area, number of fine roots, and proportion of fine roots, which combined were more conducive to the absorption of nutrients; low VPD reduced the transpiration rate, but the K accumulation by plants showed an increasing trend, indicating increased root morphology parameters could compensate for the impact of reduced transpiration-driven mass flow on K uptake. Meanwhile, higher biomass also promotes the accumulation of potassium. Photosynthesis is promoted due to increased potassium accumulation in the leaves, which in turn increases plant biomass, especially with moderate K supply. Furthermore, low VPD increases biomass allocation in leaves and reduces biomass allocation in stems but, in contrast, relatively more potassium is allocated to stems and roots but less to foliage. In summary, low VPD promotes K uptake by facilitating root system development in summer greenhouses. This result provides new knowledge for enhancing potassium utilization efficiency and reducing the use of chemical fertilizers.

中文翻译：

---

蒸气压不足和钾供应对番茄幼苗根系形态、钾吸收和生物量分配的影响

大气湿度，定义为蒸汽压差 (VPD)，是影响植物蒸腾作用和营养状况的重要因素。以前的工作主要集中在 VPD 与氮代谢之间的关系上；然而，人们对钾 (K) 对 VPD 的反应知之甚少。在这里，我们研究了 VPD 和钾供应对番茄（Solanum lycopersicum L.，cv. Jinpeng）根系形态、钾吸收和植物生长的影响。实验在温室中在低 VPD 和高 VPD 条件下进行，并提供三个水平的 K 营养液供应（2、4 和 8 mmol/L）。低VPD显着促进了根系形态特征，包括根长、根体积、根直径、根表面积、细根数和细根比例，两者结合更利于营养物质的吸收；低 VPD 降低了蒸腾速率，但植物的钾积累呈增加趋势，表明根系形态参数的增加可以补偿蒸腾驱动的质量流量减少对钾吸收的影响。同时，较高的生物量也促进钾的积累。由于叶片中钾的积累增加，光合作用得到促进，这反过来又增加了植物生物量，尤其是在适度的钾供应的情况下。此外，低 VPD 增加了叶中的生物量分配并减少了茎中的生物量分配，但相比之下，分配给茎和根的钾相对较多，但分配给叶的钾较少。总之，低 VPD 通过促进夏季温室根系发育来促进 K 吸收。