Jing Jianyuan, Zhang Shuiqin, Yuan Liang, Li Yanting, Chen Chengrong, Zhao Bingqiang
Key Laboratory of Plant Nutrition and Fertilizer, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China.
School of Environment and Science, Australian Rivers Institute, Griffith University, Nathan, QLD, Australia.
Front Plant Sci. 2022 May 19;13:885156. doi: 10.3389/fpls.2022.885156. eCollection 2022.
Humic acid-enhanced phosphate fertilizer (HAP) is widely applied in Chinese agriculture due to its high efficiency. Although the structural composition and physicochemical properties of humic acid (HA) are significantly altered during HAP production, a clear understanding of the mechanisms underlying the biological effects of HA extracted from HAP fertilizer (PHA) on plant growth is still lacking. In the current study, we extracted PHA from HAP and assessed its effects on the dry biomass, phosphorus (P) and nitrogen (N) uptake, and P absorption rate of maize seedlings when supplied at different concentrations (2.5, 5, 10, and 25 mg C L) in the hydroponic culture. The root vigor, root plasma membrane H-ATPase activity, and root nitrate reductase activity were also determined as the representative indicators of the root capacity for nutrient absorption, and used to clarify the mechanism by which PHA affects the maize growth and nutrient absorption. The results showed that the dry biomass, phosphorus uptake, nitrogen uptake, and average phosphorus absorption rates were significantly higher by 14.7-27.9%, 9.6-35.1%, 17.9-22.4%, and 22.1-31.0%, respectively, in plants treated with 2.5-5 mg C L PHA compared to untreated controls. Application of 10-25 mg C L raw HA resulted in similar stimulatory effects on plant growth and nutrient absorption. However, higher levels of PHA (10-25 mg C L) negatively impacted these indicators of plant growth. Furthermore, low PHA or high raw HA concentrations similarly improved root vigor and root plasma membrane H-ATPase and nitrate reductase (NR) activities. These results indicate that lower concentrations of PHA can stimulate maize seedling growth and nutrient absorption to an extent that is comparable to the effect of higher concentrations of raw HA. Thus, the proportion of HA incorporated into HAP could be lower than the theoretical amount estimated through assays evaluating the biological effects of raw HA.
腐植酸增效磷肥（HAP）因其高效性而在中国农业中广泛应用。尽管在HAP生产过程中腐植酸（HA）的结构组成和理化性质发生了显著变化，但对于从HAP肥料中提取的HA（PHA）对植物生长的生物学效应的潜在机制仍缺乏清晰的认识。在本研究中，我们从HAP中提取了PHA，并在水培条件下以不同浓度（2.5、5、10和25 mg C L）供应时，评估了其对玉米幼苗干生物量、磷（P）和氮（N）吸收以及P吸收速率的影响。还测定了根系活力、根细胞质膜H-ATPase活性和根硝酸还原酶活性，作为根系养分吸收能力的代表性指标，以阐明PHA影响玉米生长和养分吸收的机制。结果表明，与未处理的对照相比，用2.5 - 5 mg C L PHA处理的植物干生物量、磷吸收、氮吸收和平均磷吸收速率分别显著提高了14.7 - 27.9%、9.6 - 35.1%、17.9 - 22.4%和22.1 - 31.0%。施用10 - 25 mg C L的原始HA对植物生长和养分吸收产生了类似的刺激作用。然而，较高水平的PHA（10 - 25 mg C L）对这些植物生长指标产生了负面影响。此外，低浓度的PHA或高浓度的原始HA同样提高了根系活力、根细胞质膜H-ATPase和硝酸还原酶（NR）活性。这些结果表明，较低浓度的PHA可以刺激玉米幼苗生长和养分吸收，其程度与较高浓度的原始HA相当。因此，掺入HAP中的HA比例可能低于通过评估原始HA生物学效应的测定法估计的理论量。
