Plant growth-promoting rhizobacteria (PGPR) are beneficial bacteria that survive within the range of plant rhizosphere and can promote plant growth. The effects of PGPR in promoting plant growth, activating soil nutrients, reducing fertilizer application, and improving the resistance of plant inducible system have been widely investigated. However, few studies have investigated PGPR as elicitors of tolerance to abiotic stresses, especially drought stress. In this study, the effects of Acinetobacter calcoaceticus X128 on the photosynthetic rate (P_n), stomatal conductance (G_s), intracellular CO₂ concentration (C_i), and total chlorophyll content [Chl(a+b)] of Sambucus williamsii Hance seedling leaves under moderate drought stress and drought-rewatering conditions were determined. Compared with those of uninoculated seedlings, the average P_n values during the entire drought stress of inoculated seedlings increased by 12.99%. As the drought duration was lengthened, C_i of uninoculated leaves continued to increase after rapidly declining, whereas G_s continuously decreased. Furthermore, their photosynthetic properties were simultaneously restricted by stomatal and non-stomatal factors. After X128 inoculation, C_i and G_s of S. williamsii Hance leaves continued to decrease, and their photosynthetic properties were mainly restricted by stomatal factors. At the end of the drought stress, water stress reduced [Chl(a + b)] of S. williamsii Hance leaves by 13.49%. However, X128 inoculation decreased this deficit to only 7.39%. After water supply was recovered, P_n, G_s, and [Chl(a+b)] in uninoculated leaves were reduced by 14.23%, 12.02%, and 5.86%, respectively, relative to those under well-watered conditions. However, C_i increased by 6.48%. Compared with those of uninoculated seedlings, P_n, G_s, and [Chl(a+b)] in X128-inoculated seedlings were increased by 9.83%, 9.30%, and 6.85%, respectively. Therefore, the inoculation of X128 under arid environments can mitigate the reduction of chlorophyll, delay the restriction caused by non-stomatal factors to P_n in plant leaves under water stress, and can be more conducive to the recovery of photosynthetic functions of leaves after water supply is recovered.

中文翻译：

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接种植物促生根际细菌对干旱胁迫下接骨木容器苗光合特性的影响

植物根际促生长细菌（PGPR）是在植物根际范围内生存并能促进植物生长的有益细菌。PGPR在促进植物生长、活化土壤养分、减少化肥施用、提高植物诱导系统抗性等方面的作用已被广泛研究。然而，很少有研究调查 PGPR 作为非生物胁迫（尤其是干旱胁迫）耐受性的引发剂。本研究研究了乙酸钙不动杆菌X128对接骨木光合速率( P _n )、气孔导度( G _s )、细胞内CO ₂浓度( C _i )和总叶绿素含量[Chl(a+b)]的影响。测定了中度干旱胁迫和干旱补水条件下的汉斯幼苗叶片。与未接种苗相比，接种苗在整个干旱胁迫过程中的平均P _{n值增加了12.99%。}随着干旱持续时间的延长，未接种叶片的C _i迅速下降后继续上升，而G _s不断下降。此外，它们的光合特性同时受到气孔和非气孔因素的限制。接种X128后，S. williamsii Hance叶片的C _i和G _s持续降低，其光合特性主要受气孔因素的限制。干旱胁迫结束时，水分胁迫使S. williamsii Hance叶片[Chl(a + b)]减少13.49%。然而，接种 X128 将这一缺陷减少至仅 7.39%。恢复供水后，未接种叶片的P _n、G _s和[Chl(a+b)]比浇水条件下的叶片分别降低了14.23%、12.02%和5.86%。然而，C _i增加了6.48%。与未接种苗相比，接种X128的苗P _n、G _{s和[Chl(a+b)]分别增加了9.83%、9.30%和6.85%。}因此，干旱环境下接种X128可以缓解叶绿素的减少，延缓水分胁迫下非气孔因素对植物叶片P _n的限制，更有利于水分后叶片光合功能的恢复。供应已恢复。