Bupleurum tenuissimum is a rare species in Spain, which became extinct in recent decades in many localities, including protected areas. In the study area, the 'Albufera' Natural Park (SE Spain), the species was present in Limonietalia grasslands, a priority and endangered habitat, but has not been observed in the last 40 years. At present, it is included in conservation programmes aimed at its reintroduction in this territory. This study's primary objective was to establish the limits of tolerance of this species to salt and water stress under controlled greenhouse conditions. A congeneric species, B. fruticousm, was included as comparative material to get insights into its stress response mechanisms. Analysis of changes in growth parameters (stem length, number of leaves, root length, fresh weight and water content of roots and leaves) in response to the applied stress treatments confirmed that B. tenuissimum behaves as a facultative (moderate) halophyte susceptible to drought stress, whereas B. fruticosum is not severely affected by water stress but is sensitive to salinity, even at low NaCl concentrations. The stress-induced changes in several biochemical parameters (contents of photosynthetic pigments, ions, osmolytes, oxidative stress markers, and non-enzymatic antioxidant compounds, and specific activities of relevant antioxidant enzymes) explained the differential behaviour of the investigated Bupleurum species. In addition to the novelty of these findings in a genus that has rarely been studied from this perspective, these results will be relevant for implementing and managing B. tenuissimum conservation programmes, guiding the selection of reintroduction sites. The study also provides valuable information on the stress tolerance of B. fruticosum, with great potential for the ecological restoration of Mediterranean dry forest vegetation and riparian thickets.

Bupleurum tenuissimum是西班牙的一种稀有物种，近几十年来在包括保护区在内的许多地方已经灭绝。在研究区域“Albufera”自然公园（西班牙东南部），该物种存在于Limonietalia草原，这是一个优先和濒危的栖息地，但在过去 40 年中没有被观察到。目前，它已被纳入旨在将其重新引入该领土的保护计划。本研究的主要目的是确定该物种在受控温室条件下对盐分和水分胁迫的耐受限度。同属物种，B. fruticousm，作为比较材料被包括在内，以深入了解其压力反应机制。响应施加压力处理的生长参数（茎长、叶数、根长度、根和叶的鲜重和含水量）变化的分析证实，B. tenuissimum表现为对干旱敏感的兼性（中度）盐生植物压力，而B. fruticosum不受水分胁迫的严重影响，但对盐度敏感，即使在低 NaCl 浓度下也是如此。几种生化参数（光合色素、离子、渗透物、氧化应激标记物和非酶抗氧化化合物的含量，以及相关抗氧化酶的比活性）的应激引起的变化解释了所研究的柴胡属物种的不同行为。除了这些发现在很少从这个角度研究的属中的新颖性之外，这些结果将与实施和管理B. tenuissimum保护计划相关，指导重新引入地点的选择。该研究还提供了有关B. fruticosum胁迫耐受性的宝贵信息，对地中海干旱森林植被和河岸灌丛的生态修复具有巨大潜力。