Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Denmark.
University of South Australia, Future Industries Institute, Mawson Lakes, South Australia, Australia.
Physiol Plant. 2022 Jul;174(4):e13761. doi: 10.1111/ppl.13761.
Foliar fertilization delivers essential nutrients directly to plant tissues, reducing excessive soil fertilizer applications that can lead to eutrophication following nutrient leaching. Foliar nutrient absorption is a dynamic process affected by leaf surface structure and composition, plant nutrient status, and ion physicochemical properties. We applied multiple methods to study the foliar absorption behaviors of manganese (Mn) and phosphorus (P) in nutrient-deficient spring barley (Hordeum vulgare) at two growth stages. Nutrient-specific chlorophyll a fluorescence assays were used to visualize leaf nutrient status, while laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to visualize foliar absorption pathways for P and Mn ions. Rapid Mn absorption was facilitated by a relatively thin cuticle with a low abundance of waxes and a higher stomatal density in Mn-deficient plants. Following absorption, Mn accumulated in epidermal cells and in the photosynthetically active mesophyll, enabling a fast (6 h) restoration of Mn-dependent photosynthetic processes. Conversely, P-deficient plants developed thicker cuticles and epidermal cell walls, which reduced the penetration of P across the leaf surface. Foliar-applied P accumulated in trichomes and fiber cells above leaf veins without reaching the mesophyll and, as a consequence, no restoration of P-dependent photosynthetic processes was observed. This study reveals new links between leaf surface morphology, foliar-applied ion absorption pathways, and the restoration of affected physiological processes in nutrient-deficient leaves. Understanding that ions may have different absorption pathways across the leaf surface is critical for the future development of efficient fertilization strategies for crops in nutrient-limited soils.
叶面施肥将必需的营养物质直接输送到植物组织中，减少了过量的土壤肥料施用量，从而避免了养分淋溶后导致的富营养化。叶面养分吸收是一个受叶片表面结构和组成、植物养分状况和离子物理化学性质影响的动态过程。我们应用多种方法研究了在两个生长阶段营养缺乏的春大麦（Hordeum vulgare）中锰（Mn）和磷（P）的叶面吸收行为。营养特异性叶绿素 a 荧光测定法用于可视化叶片养分状况，而激光烧蚀-电感耦合等离子体质谱法（LA-ICP-MS）用于可视化 P 和 Mn 离子的叶面吸收途径。在 Mn 缺乏的植物中，相对较薄的角质层、蜡质含量低和较高的气孔密度促进了快速的 Mn 吸收。吸收后，Mn 积累在表皮细胞和光合作用活跃的叶肉中，使 Mn 依赖的光合作用过程能够快速（6 小时）恢复。相比之下，P 缺乏的植物形成了较厚的角质层和表皮细胞壁，这减少了 P 穿过叶片表面的渗透。叶面喷施的 P 积累在叶脉上方的毛状体和纤维细胞中，而没有到达叶肉，因此没有观察到 P 依赖的光合作用过程的恢复。本研究揭示了叶片表面形态、叶面施用离子吸收途径与营养缺乏叶片中受影响生理过程恢复之间的新联系。了解离子在叶片表面可能具有不同的吸收途径对于未来开发在养分有限土壤中提高作物施肥效率的策略至关重要。
