Vincent Christopher, Pierre Myrtho, Li Jinyun, Wang Nian
Citrus Research and Education Center, Horticultural Sciences Department, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States.
Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States.
Front Plant Sci. 2019 Jan 30;10:41. doi: 10.3389/fpls.2019.00041. eCollection 2019.
Huanglongbing is an economically devastating disease of citrus in Florida and around the world. This study was undertaken to assess two grower-used therapies, heat treatment, and foliar anti-bacterial application. Specifically, there was an industry claim that heat treatment improved subsequent systemic uptake of foliar-applied anti-bacterial compounds. We hypothesized that new vegetative growth induced by heat treatment could lead to increased foliar delivery because of a greater number of new leaves in which cuticles would be more permeable. The study included two factors (1) heat treatment (with or without) and (2) pruning, in which all new leaves, all mature leaves, or no leaves were removed. A commercial formulation of oxytetracycline (OTC) was applied to plants with a non-ionic penetrant surfactant, but one branch on each tree was covered to assess direct versus systemic delivery. The study was repeated twice, destructively assessing whole-plant leaf area and dry weights, as well as OTC content in directly applied and covered leaves. Heat treatment and defoliation treatments reduced growth, but did not affect systemic delivery of OTC. OTC was detected in nearly all covered leaf samples in both repetitions, though at lower concentrations than in directly applied leaves. We conclude that neither heat treatment nor leaf age strongly affect systemic OTC delivery. Implications of this study for leaf age effects on foliar delivery and for phloem delivery of foreign compounds through foliar application are discussed.
黄龙病是佛罗里达州乃至全球柑橘产业面临的一种极具经济破坏力的病害。本研究旨在评估种植者使用的两种疗法：热处理和叶面抗菌剂施用。具体而言，业界有一种说法，即热处理能提高随后叶面施用抗菌化合物的系统吸收。我们推测，热处理诱导的新梢营养生长可能会因新叶数量增加而导致叶面输送增加，因为新叶的角质层通透性更高。该研究包括两个因素：（1）热处理（有或无）和（2）修剪，其中分别去除所有新叶、所有成熟叶或不进行去叶处理。将土霉素（OTC）的一种商业制剂与一种非离子渗透表面活性剂一起施用于植株，但每棵树上的一个枝条进行覆盖，以评估直接施用与系统输送情况。该研究重复进行了两次，对全株叶面积和干重进行破坏性评估，以及对直接施用和覆盖叶片中的OTC含量进行评估。热处理和去叶处理降低了生长，但不影响OTC的系统输送。在两次重复实验中，几乎所有覆盖叶片样本中都检测到了OTC，不过其浓度低于直接施用的叶片。我们得出结论，热处理和叶龄对OTC的系统输送影响都不大。本文讨论了该研究对于叶龄对叶面输送的影响以及通过叶面施用外来化合物的韧皮部输送的意义。
