草坪系统的生物刺激剂和植物健康产品。当前和未来的使用趋势

What are Biostimulants? In the purest sense the word, a biostimulant can be defined as any material when applied to a plant that stimulates “life” (e.g. bio). Numerous materials fall this simple definition and it could even be argued that applying water to a plant is one example of a biostimulant since it “promotes life”. Research and use of plant biostimulants in turf systems is nothing new and work has been ongoing for over three decades. An early pioneer in biostimulant research was Dr. Richard E. Schmidt from Virginia Tech. His program pioneered many basic and applied aspects of biostimulants for many plants. A great deal of that research focused on exogenous applications of various natural and synthetic plant hormones with the intent of helping to optimize rooting (Liu et al. 1998), superior tolerance to soil-borne pests like nematodes (Sun et al., 1997), mitigate the effects of stresses like intense ultra-violet light (Schmidt and Zhang, 2001), heat-drought (Wang et al., 2012, 2013, 2014; Zhang and Schmidt, 1999,2000; Zhang et al., 2012,2013), salinity (Yan, 1993; Nabati et al. 1994), improving winter survival (Schmidt and Chalmers. 1993; Zhang et al., 2013), optimizing nutritional efficiency (Schmidt et al., 1999; Wang et al., 2011), or enhancing recovery from routine stressful mechanical cultural management practices (Bigelow et al., 2010).
Dr. Schmidt and with Dr. Xunzhong Zhang coined an initial operating definition for describing these various plant growth substances they were exploring that promoted plant growth without being nutrients, soil improvers or pesticides. They defined biostimulants as “materials that, in minute quantities, promote plant growth”. The use of the word minute in this definition was important and intended to differentiate the fact that these substances compared to traditional nutrients and/or soil amendments elicited a measurable and beneficial response at much lower application rates. They explained the plant biostimulation by way of hormonal effects and often plant protection against abiotic stress through various antioxidant production. Later, the term “metabolic enhancers” was also used but the important aspect was that something positive was happening to the plant beyond what mineral nutrition supplied.
More recently, the definition of biostimulants has been continually refined. In 2015, Patrick duJardin published the paper, “Plant biostimulants: Definition, concept, main categories and regulation”. In this article a plant biostimulant is defined as “any substance or microorganism applied to plants with the aim to enhance nutritional efficiency, abiotic stress tolerance and/or crop quality traits, regardless of its nutrient content.” The main categories of biostimulants proposed were: Humic and fulvic acids, protein hydrolysates and other N-containing compounds, seaweed extracts and botanicals, chitosan and other biopolymers, inorganic compounds, beneficial fungi and bacteria. These categories were important to define not only traditional biostimulants but also including the beneficial organisms that may elicit a positive plant health response while also helping to guide policymakers who might want to regulate these materials.
In the turf market segment, particularly in the USA, research into the biostimulant was continued at a high level by Drs. Ervin and Zhang who explored numerous aspects of biostimulant materials and their effect on turf physiology from the 2000’s to present. These projects included previously explored materials while including an expanded view of how various synthetic, non-mineral nutritional materials might also promote growth. It was postulated that these materials when applied in conjunction to the naturally biostimulants may produce additive and/or synergistic effect on turf plant growth. In addition to the categories named previously, Ervin (2013) described and suggested mechanisms for a wider range of additional products and chemistries commonly being applied to turf. For example, secondary plant hormones (e.g. salicylic acid) which can induce systemic acquired resistance (SAR) in response to plant pathogens (e.g. fungi, bacteria, insects, nematodes), similarly compounds like phosphites (PO3) that may stimulate phytoalexins (stress induced antimicrobial compounds) for health/diseases suppression. Additional products that could protect tissues from ultra-violet light injury like green pigments or compounds containing titanium dioxide and zinc oxide. Acibenzolar, which mimics salicylic acid effects to induce SAR. Synthetic fungicides like propiconazole had been previously explored by Dr. Schmidt with positive plant responses, but newer chemistries like pyraclostrobin was shown in a number of University research trials to slow down plant respiration and boost antioxidants under heat and drought stress. One interesting find was that pyraclostrobin naturally degrades to the amino acid tryptophan which is a precursor to the plant rooting hormone auxin. Amino acids like proline and glycine-betaine are often suggested for use as osmoregulators or dehydration avoidance compounds. The practice of supplementing amino acids via foliar applications in summer months is a long-standing suggested approach to improve plant health that might be experiencing energy depletion during stressful environmental conditions (e.g. the aim of mitigating seasonal summer decline for cool-season grasses). Lastly, the long standing well researched biostimulants like humic substances, auxin, seaweed and cytokinins are listed. A large fraction of biostimulant products marketed to the turf industry contain seaweed extract (SWE), or seaplant/kelp extract. SWE is naturally high in cytokinin (Crouch and VanStaden, 1993) and research by Schmidt, Ervin and Zhang has shown that SWE was similar to a synthetic cytokinin applications and that monthly application of SWE boosted antioxidant levels, less loss of root viability and improved heat/drought tolerance. Further, Ervin and Zhang showed that combining HA + SWE can provide better plant health during stressful conditions than using either alone. The turf industry contains a vast array of products that claim positive plant or soil health benefits, particularly under stress conditions. Choosing the right material for the intended specific plant benefit is truly important.

摘要：正确管理草皮系统可以成为一种巨大的环境资产。茂密、健康的草皮提供了许多美学、娱乐和环境方面的好处，最明显的是可以固定城市土壤和过滤城市水径流中的污染物。然而，它们是多年生植物系统，需要一定程度的营养和水的投入来保持活力和持久性。如果目标是用更少的传统投入来更可持续地管理它们，并使它们对环境压力更有弹性，那么生物刺激剂和其他植物健康产品就是实现这一目标的工具。研究生物刺激剂对草坪草的影响，可以使草坪营养的可持续发展方法取得进展。在适当的植物营养中，草地生理学的有机方面与矿物方面同样重要。同一栽培品种的植物在不同的生长反应下，其矿物质含量的差异相对较小。此外，矿物质营养与对压力的耐受性关联不大。然而，了解生物活性物质对草皮代谢的影响，可以使草皮管理者更好地调节草皮，使其能够承受环境压力。对矿物质功能和新陈代谢影响的了解，可以加强营养方面的最佳管理措施，以减轻许多草皮压力。利用这些知识，在不利环境下生长时，为生产高质量、有弹性的草皮提供了额外的工具"。
随着人们对养分和水的投入的关注和不断增加的审查，再加上有时严重的草皮压力，如因日益不可预测的气候条件而导致的长期干旱，将生物刺激剂应用于传统上不太受关注的领域，如草坪，可能会成为一种更主流的做法。无论哪种生物刺激剂/植物健康产品或计划，重要的是要指出，生物刺激剂不能替代健全的植物矿物营养计划。此外，如果目的是将生物刺激剂作为整体植物健康计划的一部分，草坪系统的研究表明，它们必须在环境压力之前应用，以优化其效益。在这一领域有令人振奋的创新，基于证据的努力将引导人们更好地理解这些材料将如何帮助维护和改善植物健康。