DataSheet1_Synergistic effects of SAP and PGPR on physiological characteristics of leaves and soil enzyme activities in the rhizosphere of poplar seedlings under drought stress.pdf

Super absorbent polymers (SAP) provide moisture conditions that allow plant growth-promoting rhizobacteria (PGPR) to enter the soil for acclimatization and strain propagation. However, the effects of SAP co-applied with PGPR on the physiological characteristics of leaves and rhizosphere soil enzyme activities of poplar seedlings are not well understood. Here, a pot experiment using one-year-old poplar seedlings with five treatments, normal watering, drought stress (DR), drought stress + SAP (DR+SAP), drought stress + Priestia megaterium (DR +PGPR) and drought stress + SAP + P. megaterium (DR+S+P), was performed to analyze the contents of non-enzymatic antioxidants, osmotic regulators and hormones in leaves, as well as rhizosphere soil enzyme activities. Compared with normal watering, the DR treatment significantly decreased the contents of dehydroascorbate (DHA; 19.08%), reduced glutathione (GSH; 14.18%), oxidized glutathione, soluble protein (26.84%), indoleacetic acid (IAA; 9.47%), gibberellin (GA) and zeatin (ZT), the IAA/abscisic acid (ABA), GA/ABA, ZT/ABA and (IAA+GA+ZT)/ABA (34.67%) ratios in leaves, and the urease and sucrase activities in the rhizosphere soil. Additionally, it significantly increased the soluble sugar, proline and ABA contents in leaves. However, in comparison with the DR treatment, the DR+S+P treatment significantly increased the DHA (29.63%), GSH (15.13%), oxidized glutathione, soluble protein (29.15%), IAA (12.55%) and GA contents, the IAA/ABA, GA/ABA, ZT/ABA and (IAA+GA+ZT)/ABA (46.85%) ratios in leaves, and the urease, sucrose and catalase activities in rhizosphere soil to different degrees. The soluble sugar, proline and ABA contents markedly reduced in comparison to the DR treatment. The effects of the DR+SAP and DR+PGPR treatments were generally weaker than those of the DR+S+P treatment. Thus, under drought-stress conditions, the simultaneous addition of SAP and P. megaterium enhanced the drought adaptive capacities of poplar seedlings by regulating the non-enzymatic antioxidants, osmotic regulators, and endogenous hormone content and balance in poplar seedling leaves, as well as by improving the rhizosphere soil enzyme activities.

高吸水性树脂（Super absorbent polymers, SAP）可提供适宜的水分条件，助力植物促生根际细菌（plant growth-promoting rhizobacteria, PGPR）进入土壤定殖并增殖。然而，SAP与PGPR配施对杨树幼苗叶片生理特性及根际土壤酶活性的影响尚不明确。为此，本研究以一年生杨树幼苗为材料开展盆栽试验，设置5组处理：正常浇水组、干旱胁迫（drought stress, DR）组、干旱胁迫+SAP（DR+SAP）组、干旱胁迫+PGPR（DR+PGPR）组以及干旱胁迫+SAP+巨大芽孢杆菌（Priestia megaterium, DR+S+P）组，分别测定叶片中非酶促抗氧化剂、渗透调节物质及激素含量，以及根际土壤酶活性。与正常浇水组相比，干旱胁迫组显著降低了叶片中脱氢抗坏血酸（dehydroascorbate, DHA；19.08%）、还原型谷胱甘肽（reduced glutathione, GSH；14.18%）、氧化型谷胱甘肽、可溶性蛋白（26.84%）、吲哚乙酸（indoleacetic acid, IAA；9.47%）、赤霉素（gibberellin, GA）及玉米素（zeatin, ZT）的含量，同时下调了叶片中IAA/脱落酸（abscisic acid, ABA）、GA/ABA、ZT/ABA及（IAA+GA+ZT）/ABA（34.67%）的比值，并显著降低了根际土壤脲酶与蔗糖酶活性。此外，干旱胁迫组显著提升了叶片中可溶性糖、脯氨酸及脱落酸的含量。与干旱胁迫组相比，DR+S+P组显著提升了叶片中DHA（29.63%）、GSH（15.13%）、氧化型谷胱甘肽、可溶性蛋白（29.15%）、IAA（12.55%）及GA的含量，同时上调了叶片中IAA/ABA、GA/ABA、ZT/ABA及（IAA+GA+ZT）/ABA（46.85%）的比值，还不同程度提升了根际土壤脲酶、蔗糖酶及过氧化氢酶（catalase）活性。与此同时，该组叶片中可溶性糖、脯氨酸及脱落酸含量较干旱胁迫组显著降低。DR+SAP与DR+PGPR处理的效果总体弱于DR+S+P处理。综上，在干旱胁迫条件下，同时配施高吸水性树脂与巨大芽孢杆菌，可通过调控杨树幼苗叶片中非酶促抗氧化剂、渗透调节物质及内源激素的含量与平衡，同时改善根际土壤酶活性，从而增强杨树幼苗的干旱适应能力。