刺梨(Rosa roxburghii)是原产中国西南地区的特色经济树种, 贵州将其作为喀斯特山区重点发展的果树。迄今, 刺梨能否适应喀斯特地区高钙生境尚不清楚。明确刺梨的适钙类型及其对高钙生境的适应性, 旨在为刺梨种植区域的确定提供科学依据。该研究对贵州喀斯特地区不同钙生境下50个野生刺梨植株的不同器官和立地土壤进行取样, 测定土壤的pH、交换性钙、镁含量和植株不同器官中总钙、草酸钙及叶中的钙和镁的含量, 明确不同器官中草酸钙含量占总钙含量的比例, 分析土壤交换性钙、镁含量与不同器官总钙、叶片钙和镁含量的相关性关系, 观察低钙和高钙生境下不同器官中及叶表面草酸钙晶体的分布。对土壤的分析结果表明: 喀斯特地区野生刺梨立地土壤的pH高, 交换性钙、镁的含量高且差异大。在不同钙生境下, 野生刺梨不同器官中的总钙含量与土壤中交换性钙含量呈显著正相关关系, 叶片中总钙和镁的含量与土壤中交换性钙、镁含量的相关性也是如此。刺梨枝、叶是富集钙最多的器官, 根和果实中钙的含量相对较少, 所有样本叶片中总钙和镁的含量在1.71%-2.73%之间, 枝和叶中草酸钙含量占总钙含量的比例分别为55.81%和52.76%, 而根和果实中只占29.34%和34.30%。在高钙生境中, 野生刺梨枝、叶中和叶片气孔边缘有大量草酸钙棱晶, 果实中有少量针晶; 而在低钙生境中, 野生刺梨的根和果实中及叶片气孔边缘均无草酸钙晶体分布。该研究明确了刺梨的适钙类型属于中间型, 对喀斯特地区不同钙生境均有较强的适应性, 枝、叶中大量储存草酸钙和通过叶片气孔排钙的生理特性, 对降低刺梨体内钙离子浓度和缓解高钙胁迫对自身的伤害具有重要作用。研究结果对喀斯特地区刺梨种植区域的确定具有重要指导意义。

Aims Rosa roxburghii is a special economic tree species native to southwest China, and it has been taken as a key fruit tree in karst mountainous areas of Guizhou Province. However, it is unclear whether R. roxburghii can adapt to high-calcium habitats in the karst areas. To provide scientific evidence for determining the potential planting sites of R. roxburghii, the calcium-tolerance type and adaptability to high-calcium habitats of R. roxburghii were needed to be clarified.

Methods In this study, different organs from 50 R. roxburghii individuals and different calcareous soils where R. roxburghii grew were sampled in karst areas of Guizhou. The pH, exchangeable calcium and magnesium contents in the soil, total calcium and calcium oxalate contents in the plant organs, and calcium and magnesium contents in the leaves were determined, and the proportion of calcium oxalate in different organs to total calcium content was calculated. Then, the correlations between the exchangeable calcium and magnesium content in the soil with total calcium in different organs, and calcium and magnesium content in the leaves were analyzed. In addition, the distribution of calcium oxalate crystals in different organs as well as on the leaf surface was observed in samples collected from low-calcium and high-calcium habitats.

Important findings The soil at R. roxburghii sites in karst areas had a high pH, and the content of exchangeable calcium and magnesium was abundant and varies greatly. In different calcareous habitats, the total calcium content in different organs of R. roxburghii was significantly and positively correlated with the exchangeable calcium content in the soil. Similarly, the contents of total calcium and magnesium in the leaves were correlated with those in the soil. The branches and leaves were the organs that accumulated the most calcium, whereas the calcium enrichment in the roots and fruit were relatively low. The total calcium and magnesium contents of all the sample leaves ranged from 1.71% to 2.73%, among which, the proportions of calcium oxalate in branches and leaves were 55.81% and 52.76% of the total calcium, respectively; while only 29.34% and 34.30% were in roots and fruit. In samples from a high-calcium habitats, calcium oxalate prismatic crystals were abundant in the branches, leaves, and around stomatal pores, while few needle crystals were observed in the fruits. However, in samples from a low-calcium environment, no calcium oxalate crystals were observed in the roots, fruit, and leaf stomatal pores. In this study, we clarified that the R. roxburghii is an intermediate type of calcium-tolerance, which has strong adaptability to different calcium habitats in karst areas. The physiological characteristics of storing abundant calcium oxalate crystals in branches and leaves, and excreting calcium through leaf stomata play important roles in reducing the calcium concentration in R. roxburghii tissues and alleviating damages from high-calcium stress. The results of this study provide important guidance for the determination of suitable planting sites for R. roxburghii in karst areas.