Silicon (Si) efficiently controls Podosphaera xanthii in melon by affecting epidemic components related to the infection and colonization processes. Root amendments of Si prime melon defences, but its mode of action when sprayed on the leaves is unknown. The effects of potassium silicate (PS) on the development of the pathogen were observed by scanning electron microscopy. Both forms of PS application reduced conidial germination and delayed colony development. At 120 h after inoculation (hai), differentiation of the conidiophores was inhibited only by the root treatment and at 144 hai visual differences between PS treatments accentuated. Comparison of foliar PS with compounds of contrasting pH and ionic strength (KOH, KCl and PEG) showed that only PS and PEG inhibited conidial germination ruling out these variables as inhibitory factors. Alteration of the leaf surface tension was also excluded since it was affected by all compounds. The results indicate that foliar-applied PS affects P. xanthii conidial germination of and colony development by modifying the osmotic potential of the leaf surface.

硅（Si）有效控制黄单孢菌通过影响与感染和定殖过程有关的流行病成分来改善甜瓜中的抗性。Si主要甜瓜防御系统的根系改良剂，但其喷洒在叶子上时的作用方式尚不清楚。通过扫描电子显微镜观察了硅酸钾（PS）对病原体发育的影响。两种形式的PS施用均可减少分生孢子萌发并延迟菌落发育。接种后120 h（hai），分生孢子的分化仅受根处理抑制，而144 hai时PS处理之间的视觉差异加剧。将叶面P​​S与具有不同pH和离子强度的化合物（KOH，KCl和PEG）进行比较表明，只有PS和PEG抑制了分生孢子萌发，排除了这些变量作为抑制因子。还排除了叶片表面张力的变化，因为它受所有化合物的影响。结果表明，叶面施胶会影响P. xanthii分生孢子的萌发和菌落发育通过改变叶表面的渗透势来实现。