Ferrarezi Rhuanito Soranz, Lin Xiongjie, Gonzalez Neira Andres C, Tabay Zambon Flavia, Hu Hanqing, Wang Xianda, Huang Jing-Hao, Fan Guocheng
Department of Horticulture, University of Georgia, Athens, GA, United States.
Horticultural Sciences Department, Indian River Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Fort Pierce, FL, United States.
Front Plant Sci. 2022 May 13;13:856937. doi: 10.3389/fpls.2022.856937. eCollection 2022.
The substrate pH directly affects nutrient availability in the rhizosphere and nutrient uptake by plants. Macronutrients such as nitrogen, potassium, calcium, magnesium, and sulfur are highly available at pH 6.0-6.5, while micronutrients become less available at higher, alkaline pH (pH > 7.0). Recent research has indicated that low pHs can enhance nutrient uptake and improve sweet orange () tree health. We designed a study to understand the influence of a wide range of substrate pH values on plant size and biomass, nutrient availability, leaf gas exchange, and rhizosphere microbiome of grapefruit () affected by Huanglongbing (HLB). Two-year-old "Ray Ruby" grapefruit plants grafted on sour orange () rootstock were cultivated indoors in 10-cm wide × 40-cm tall pots with peat:perlite commercial substrate (80:20 v/v). We tested two disease statuses [HLB-free or healthy (negative, HLB-) and HLB-affected (positive, HLB+)] and six substrate pH values (4, 5, 6, 7, 8, 9) in a 2 × 6 factorial arranged on a complete randomized design with four replications. The canopy volume of HLB+ plants was 20% lower than healthy plants, with pHs 7 and 9 resulting in 44% less canopy volume. The root and shoot ratio of dry weight was 25.8% lower in HLB+ than in healthy plants. Poor root growth and a decrease in fibrous roots were found, especially in pH 5 and 6 treatments in HLB+ plants ( < 0.0001). The disease status and the substrate pHs influenced the leaf nutrient concentration ( < 0.05). High substrate pH affects nutrient availability for root uptake, influencing the nutrient balance throughout the plant system. pH values did not affect plant photosynthesis, indicating that pH does not recover HLB+ plants to the photosynthetic levels of healthy plants-even though high pH positively influenced internal CO. There were collectively over 200 rhizobacterial identified by the 16S rRNA gene sequencing in individual phylogenetic trees. Most rhizobacteria reads were identified in pH 9. Our results indicated no effect of substrate pHs on the plant disease status induced by enhanced nutrient uptake.
基质pH值直接影响根际养分有效性和植物对养分的吸收。氮、钾、钙、镁和硫等大量元素在pH值6.0 - 6.5时有效性高，而微量元素在较高的碱性pH值（pH > 7.0）下有效性降低。最近的研究表明，低pH值可以提高养分吸收并改善甜橙树的健康状况。我们设计了一项研究，以了解广泛的基质pH值对受黄龙病（HLB）影响的葡萄柚的植株大小和生物量、养分有效性、叶片气体交换和根际微生物群落的影响。将嫁接到酸橙砧木上的两年生“雷·鲁比”葡萄柚植株种植在室内10厘米宽×40厘米高的花盆中，花盆中装有泥炭：珍珠岩商业基质（80:20 v/v）。我们测试了两种病害状态[无HLB或健康（阴性，HLB-）和受HLB影响（阳性，HLB+）]以及六个基质pH值（4、5、6、7、8、9），采用2×6析因设计，完全随机排列，重复四次。HLB+植株的冠层体积比健康植株低20%，pH值7和9时冠层体积减少44%。HLB+植株干重的根冠比比健康植株低25.8%。发现根系生长不良且须根减少，尤其是HLB+植株中pH值5和6的处理（< 0.0001）。病害状态和基质pH值影响叶片养分浓度（< 0.05）。高基质pH值影响根系吸收养分的有效性，影响整个植物系统的养分平衡。pH值不影响植物光合作用，这表明即使高pH值对内部CO有积极影响，pH值也不能使HLB+植株恢复到健康植株的光合水平。通过16S rRNA基因测序在个体系统发育树中总共鉴定出200多种根际细菌。在pH值9中鉴定出的根际细菌读数最多。我们的结果表明，基质pH值对因养分吸收增强引起的植物病害状态没有影响。
