Mollo Lorenzo, Petrini Alice, Norici Alessandra, Ferrante Antonio, Cocetta Giacomo
Laboratory of Algal and Plant Physiology, Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, Ancona 60131, Italy.
Department Agricultural and Environmental Sciences, Università degli Studi di Milano, Via Celoria 2, Milano 20133, Italy.
Plant Sci. 2025 Oct;359:112643. doi: 10.1016/j.plantsci.2025.112643. Epub 2025 Jul 4.
Foliar spraying is a simple and efficient technique that enables targeted delivery of biostimulants directly onto plant surfaces, minimizing losses and environmental dispersion. Among biostimulant categories, microalgae-based formulations represent an eco-friendly solution to improve crop productivity, thanks to their richness in bioactive compounds and rapid growth in low-input systems. In this study, the crude extract of three green microalgae with high commercial value and broad biotechnological potential-Auxenochlorella protothecoides, Tetradesmus obliquus and Chlamydomonas reinhardtii-along with their consortium, was tested as foliar biostimulants for the first time on wild rocket (Diplotaxis tenuifolia L.) at an early vegetative stage. Plants received three sequential treatments, and physiological and biochemical responses were evaluated at 24, 48, and 72 h after the final application. Biostimulation led to up to 32 % increases in fresh biomass and significantly enhanced photosynthetic efficiency (F/F, PI), particularly in consortium-treated plants. The multi-step application also triggered a late and transient rise in antioxidant compounds (carotenoids and phenolics), potentially improving post-harvest quality. Remarkably, these effects were observed even in the absence of abiotic stress, highlighting the intrinsic biostimulant potential of the treatments. Notably, when the consortium crude extract was applied, higher chlorophyll content, nitrate accumulation, and enhanced nitrogen assimilation (indicated by lower δ¹⁵N values) were also observed. These results suggest a compositional and functional uniqueness of the consortium, likely due to interspecies interactions. Overall, early-stage, multi-step foliar biostimulation with selected microalgal species or consortia represents a promising and sustainable strategy to improve crop performance and modulate quality traits in leafy vegetables.
叶面喷施是一种简单有效的技术，能够将生物刺激剂直接精准施用于植物表面，最大限度地减少损失和环境扩散。在生物刺激剂类别中，基于微藻的配方是一种生态友好的解决方案，有助于提高作物产量，这得益于其丰富的生物活性化合物以及在低投入系统中的快速生长。在本研究中，首次对三种具有高商业价值和广泛生物技术潜力的绿色微藻——原壳小球藻、斜生栅藻和莱茵衣藻——及其混合体的粗提物，在野生火箭菜（细叶双行芥）营养生长早期作为叶面生物刺激剂进行了测试。植株接受了三次连续处理，并在最后一次施用后24、48和72小时评估了生理和生化反应。生物刺激使新鲜生物量增加了32%，并显著提高了光合效率（F/F，PI），特别是在混合体处理的植株中。多步骤施用还引发了抗氧化化合物（类胡萝卜素和酚类）的后期短暂增加，可能改善了收获后的品质。值得注意的是，即使在没有非生物胁迫的情况下也观察到了这些效果，突出了这些处理的内在生物刺激潜力。值得注意的是，当施用混合体粗提物时，还观察到了更高的叶绿素含量、硝酸盐积累以及增强的氮同化作用（以较低的δ¹⁵N值表示）。这些结果表明混合体具有组成和功能上的独特性，可能是由于种间相互作用。总体而言，用选定的微藻物种或混合体进行早期、多步骤的叶面生物刺激是一种有前景的可持续策略，可用于改善叶菜类作物的性能并调节品质性状。
