Henningsen Jon Niklas, Bahamonde Héctor Alejandro, Mühling Karl Hermann, Fernández Victoria
Institute of Plant Nutrition and Soil Science, Kiel University, Hermann-Rodewald-Straße 2, 24118 Kiel, Germany.
Facultad de Ciencias Agrarias y Forestales, Universidad Nacional de La Plata, Diagonal 113 N_469, La Plata 1900, Argentina.
Plants (Basel). 2023 May 29;12(11):2152. doi: 10.3390/plants12112152.
Foliar fertilisation is an application technique that is increasingly being used in agriculture and offers the possibility of providing nutrients directly to the site of highest demand. Especially for phosphorus (P), foliar application is an interesting alternative to soil fertilisation, but foliar uptake mechanisms are poorly understood. To gain a better understanding of the importance of leaf surface features for foliar P uptake, we conducted a study with tomato () and pepper () plants, which have different leaf surface traits. For this purpose, drops of 200 mM KHPO without surfactant were applied onto the adaxial or abaxial leaf side or to the leaf veins and the rate of foliar P absorption was evaluated after one day. Additionally, leaf surfaces were characterised in detail by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), estimating also leaf surface wettability and free energy, among other parameters. While the leaves of pepper hardly contained any trichomes, the abaxial side and the leaf veins of tomato leaves were densely covered with trichomes. The cuticle of tomato leaves was thin (approximately 50 nm), while that of pepper was thick (approximately 150-200 nm) and impregnated with lignin. Due to the fact that trichomes were most abundant in the leaf veins of tomato, dry foliar fertiliser drop residues were observed to be anchored there, and the highest P uptake occurred via tomato leaf veins, resulting in 62% increased P concentration. However, in pepper, the highest rate of P absorption was recorded after abaxial-side P treatment (+66% P). Our results provide evidence that different leaf parts contribute unequally to the absorption of foliar-applied agrochemicals, which could potentially be useful for optimising foliar spray treatments in different crops.
叶面施肥是一种在农业中越来越多地被使用的施肥技术，它提供了将养分直接供应到需求最高部位的可能性。特别是对于磷（P）而言，叶面施肥是土壤施肥的一种有趣替代方法，但叶面吸收机制却鲜为人知。为了更好地理解叶片表面特征对叶面磷吸收的重要性，我们对具有不同叶片表面特征的番茄（）和辣椒（）植株进行了一项研究。为此，将不含表面活性剂的200 mM KHPO液滴施用于叶片的正面或背面或叶脉上，并在一天后评估叶面磷吸收速率。此外，通过透射电子显微镜（TEM）和扫描电子显微镜（SEM）对叶片表面进行了详细表征，还估算了叶片表面润湿性和自由能等参数。辣椒叶片几乎不含任何毛状体，而番茄叶片的背面和叶脉则密布着毛状体。番茄叶片的角质层较薄（约50纳米），而辣椒的角质层较厚（约150 - 200纳米）且含有木质素。由于番茄叶脉中的毛状体最为丰富，观察到干的叶面肥料滴残留附着在那里，并且通过番茄叶脉的磷吸收最高，导致磷浓度增加了62%。然而，在辣椒中，背面施磷后记录到的磷吸收速率最高（磷增加66%）。我们的结果表明，不同的叶片部位对叶面施用的农用化学品的吸收贡献不均等，这可能有助于优化不同作物的叶面喷施处理。
